Gasification of Algae

ENVE 645Water Chemistry

Woody ArnoldSpring 2014

Prof Temesgen Garoma

1

Table of Contents

Introduction pg 3

Discussion And Conclusion pg 4 ndash 5

References pg 6 ndash 7

Appendix pg 8 -19

2

Introduction

Through many decades humanity with the economic systems that are in place today have lead to the linear increase in the production of goods while not considering its impacts in the environment Over the past decade world energy consumption has increased progressively owing to the growing demand by burgeoning industrial societies in emerging markets and the rising world population The current global state of energy supply is highly dependent on fossil fuels Owing to finite nature of fossil fuels rapid increase in their prices and concerns about their environmental impact efforts around the world to develop and commercialize renewable transportation fuels and biobased chemicals have intensified (A Geraili P Sharma JA Romagnoli 2013) One example of a place that is highly independent on the oil industry and is a huge contributor to emissions is Iran Iran is the9th-largest emitter of total greenhouse gases in the world in 2010 CO2 has increased from 4923 million tons in 2007 to about 5324 million tons in 2010 showing a growth of 814 percent between these years However during the long period between 1990 until 2010 CO2 has a growth rate of 174 The power-generation sector alone has contributed to more than 291 percent of the total CO2 in 2010The bulk of Iranian greenhouse-gas emissions541come from power plants and domestic sectors mainly through the expansion of energy demand During this year emission from power plants was about 1548 million tons and emissions from industry and refinery sectors were about 886 and 172 million tons respectively In according to the average annual Growth rate of CO2 in power plants it is anticipated that CO2 from power plants and all sectors in 2025 will reach to 247 and 930 million tons respectively which are alarming figures (A Ghorbani HR Rahimpour YGhasemi S Zoughi MR Rahimpour 2014)

Because of this different methods of technologies have been created to help capture CO2 and positively contribute to the carbon cycle There are biological physical and chemical processes that can be effectively utilized for carbon sequestration but one possible way to help positively contribute to the carbon cycle is to gasify algae For example in the case of biofuel production it has been proposed as early as 1950s in the United States Algae are a single cell microorganism which is composed of lipids carbohydrates and proteins The algae biomass has potential to produce a variety of biofuels through not only the extraction of lipids and other methods but through gasification of the algal biomass by anaerobic digestion or thermal cracking to produce biogas (S J P Jegathese and M Farid 2014) Gasification is a process that converts organic or fossil based carbonaceous material into CO H2 and CO2 by reacting the material at temperatures at 700˚ C or above without combustion with a controlled amount of O2 or steam and produces synthetic gas or syngas which is mixture of CO H2 and CO2 and can be used for energy Gasification is an example of a physical process called Bio-Energy with Carbon Capture and Storage or BECCS for short There is promise in the use of algae in gasification because through gasification CO2 is produced and the capture of this CO2 can be used for the optimization of algae growth Hence collectively contributing to the recycle of CO2 in the carbon cycle positively

3

Discussion

In a study from Monash University in Australia the CO2 and the steam gasification reactivities of algal biomass (Chlorella sp) and wood were compared The algae were grown using a modified MLA medium of 0494 gL MgSO47H2O 17 gL NaNO3 014 gL K2HPO4 and 0029 gL CaCl22H2O and the wood was a commercial wood mix and the reactivities were evaluated at 800˚ 950˚ 1100˚ C in both CO2 and steam environments with structure of the char particles studied by scanning electron microscope imaging Based on the study algal and woody biomass chars prepared in similar conditions showed significant difference in structure and gasification reactivity Clinker like structure was observed for algal char prepared in entrained flowreactor and it showed the lowest reactivity in all cases studied Thealgal char obtained at a lower heating rate from TGA showed rigid structure despite its smaller particle size in comparison to the EFR char At temperatures below 950 degC the reactivity of algal char from TGA was similar to that of the commercial wood mix char derived from EFR inboth gasifying agents In the case of woody biomass high reactivity was observed for commercial wood mix char from EFR Woody chars from both EFR and TGA showed higher reactivity than the algal char at 1100 degC under both CO2 and steam It is likely that pyrolysis ofalgae at a lower heating rate would result in highly reactive char during low temperature gasification regardless of the gasifying agent For chars of both the species a temperature of 800 degC and time of around 20 min are found to be sufficient to accomplish most conversion (K Kirtania J Joshua MA Kassim S Bhattacharya 2013) Figures 1-6 show the general set up of the experiment the compositions of Chlorella sp and of the commercial wood mix from this study and the respective weight percentages and reactivities EFR stands for entrained flow reactor and TGA stands for thermogravimetric analysis Although this study shows the drawbacks of gasifying algal char compared to with commercial wood in regards to CO2

sequestration a couple of studies shows the effects of the gasification of algae in supercritical water

Gasifying biomass in supercritical conditions represent a promising alternative to treat humid biomasses saving the costs of preliminary drying In addition the high operative pressures allow either to consider the produced gas as an alternative to natural gas for civil and industrial use or a source of energy in expansion processes (A Molino M Migliori F Nanna 2013) A study from the University of Leeds shows that four macroalgae species from the experiments can be successfully gasified under supercritical conditions S latissima L digitata A esculenta L hypoborea In addition to the four macroalgae in this study Chlorella vulgaris a microalgae species showed promise and suitability of nutrient recycling from macroalgae gasification within the context of algae bio-refineries Higher gasification are shown with the presence of a ruthenium catalyst with the yield of combustible gases of the product gas increasing by 30 but sulfur adversely affected the yield due to a decrease in the yield of CH4 following the poisoning of the catalyst surface (R Cherad JA Onwudili U Ekpo PT Williams AR Lea-Langton M Carmargo-Valero AB Ross 2013) Figures 7-12 show the compositions of the macroalgae mentioned the percentages of the yield and gasification efficiencies the effects of the rubidium catalyst on S latissima and of C vulgaris and the growth effects on C vulgaris

4

respectively In addition to the study made by the University of Leeds on testing which algae is best for supercritical gasification a thermodynamic model can be used to predict the formation of compounds in biomass It can be concluded that microalgae samples could be a potential biomass for combustion applications The temperature needed to carry out the combustion process has been demonstrated to be lower than for other types of biomass feedstock Thisfact turns directly into low costs when implementing the process at a higher scale Furthermore the heat released during the combustion process was in the same order of magnitude than thatcalculated by other authors for lignocellulosic biomass (D Loacutepez-Gonzaacutelez M Fernandez-Lopez JL Valverde L Sanchez-Silva 2013) A multiphase thermodynamic equilibrium model based on the fundamentals of the Gibbs free energy minimization methodhas been developed to predict the equilibrium state compounds for the supercritical water gasification based biomass conversion systems The model is capable of performing calculations for various temperature pressure and dry matter conditions forboth subcritical and supercritical regions The validation of the model by comparing the results of others has been performed and the results of the model were found to be in agreementwith the results of others The model shows a very good performance in predicting the amount of gases in real biomass gasification processes and the solubility of salt mixtures insupercritical water (O Yakaboylu J Harinck K G Smit W de Jong 2014) The equations used in the Multiphase Thermodynamic Model are shown in the Appendix along with Figures 14 and 15 showing the results of gasification under supercritical conditions dependent on pressure temperature and percentages of dry mass content

Conclusion

Based on the findings of the gasification of algae in study where algae is being compared to commercial wood mix for carbon sequestration more carbon is released compared to with algae in this case Chlorella vulgaris was the algae in the study But under supercritical conditions via hydrothermal gasification since algae only requires lower temperatures to initiate the combustion process Therefore will cost less to capture CO2 from the algae In regards to the Multiphase Thermodynamic Model used to predict what compounds are released can be tracked and implemented in the design of algal biorefineries A biorefinery featuring hydrothermal liquefaction reaction conditions with relatively high temperatures and longer reaction times results in an aqueous phase containing a higher fraction of carbon in theinorganic form rather than organic Inorganic carbon is not available for energy recovery via catalytic hydrothermal gasification which is why the energy return on investment drops significantly as temperatures and reaction times are increased In addition to the drop in costs findings of E coli growth on the algae in aqueous phase boosts to the yield of oil per unit of algal mass by 10-20 without extra investment (ND Orfield AJ Fang PJ Valdez MC Nelson PE Savage XN Lin GA Keoleian 2014) With accurate tracking of the types of compounds that are released due to gasification we have a better solution to become more effective at carbon sequestration from algae and other biomass

5

References

Geraili A P Sharma and J A Romagnoli A modeling framework for design of nonlinear renewable energy systems through integrated simulation modeling and metaheuristic optimization Applications to biorefineries Computers amp Chemical Engineering 61 (2014) 102-117

Savage Phillip E and Jamie A Hestekin A perspective on algae the environment and energy Environmental Progress amp Sustainable Energy 324 (2013) 877-883

Ghorbani Afshin et al A Review of Carbon Capture and Sequestration in Iran Microalgal Biofixation Potential in Iran Renewable and Sustainable Energy Reviews 35 (2014) 73-100

Onwudili Jude A et al Catalytic hydrothermal gasification of algae for hydrogen production Composition of reaction products and potential for nutrient recycling Bioresource technology 127 (2013) 72-80

Du Yuying et al Cogasification of Biofermenting Residue in a Coal-Water Slurry Gasifier Energy amp Fuels 283 (2014) 2054-2058

Lane Daniel J et al Combustion Behavior of Algal Biomass Carbon Release Nitrogen Release and Char Reactivity Energy amp Fuels (2013)

Kirtania Kawnish et al Comparison of COlt subgt 2ltsubgt and steam gasification reactivity of algal and woody biomass chars Fuel Processing Technology 117 (2014) 44-52

Bagnoud-Velaacutesquez Mariluz et al Continuous catalytic hydrothermal gasification of algal biomass and case study on toxicity of aluminum as a step toward effluents recycling Catalysis Today 223 (2014) 35-43

Molino A M Migliori and F Nanna Glucose gasification in near critical water conditions for both syngas production and green chemicals with a continuous process Fuel 115 (2014) 41-45

Bai Xiujun et al Hydrothermal catalytic processing of pretreated algal oil A catalyst screening study Fuel 120 (2014) 141-149

Davis Ryan et al Integrated Evaluation of Cost Emissions and Resource Potential for Algal Biofuels at the National Scale Environmental science amp technology (2014)

Loacutepez-Gonzaacutelez D et al Kinetic analysis and thermal characterization of the microalgae combustion process by thermal analysis coupled to mass spectrometry Applied Energy 114 (2014) 227-237

6

Orfield Nolan D et al Life cycle design of an algal biorefinery featuring hydrothermal liquefaction effect of reaction conditions and an alternative pathway including microbial regrowth ACS Sustainable Chemistry amp Engineering 24 (2014) 867-874

Cherad Ramzi et al Macroalgae supercritical water gasification combined with nutrient recycling for microalgae cultivation Environmental Progress amp Sustainable Energy 324 (2013) 902-909

Jegathese Simon Jegan Porphy and Mohammed Farid Microalgae as a Renewable Source of Energy A Niche Opportunity Journal of Renewable Energy 2014 (2014)

Gong Jian and Fengqi You Optimal design and synthesis of algal biorefinery processes for biological carbon sequestration and utilization with zero direct greenhouse gas emissions Industrial amp Engineering Chemistry Research(2014)

Zhao Bingtao and Yaxin Su Process effect of microalgal-carbon dioxide fixation and biomass production A review Renewable and Sustainable Energy Reviews 31 (2014) 121-132

Kaewpanha Malinee et al Steam co-gasification of brown seaweed and land-based biomass Fuel Processing Technology 120 (2014) 106-112

Yakaboylu Onursal et al Supercritical Water Gasification of Biomass A Thermodynamic Model for the Prediction of Product Compounds at Equilibrium State Energy amp Fuels (2014)

7

Appendix

Figure 1 Experimental Flow Diagram comparing algae and commercial wood mix

8

Figure 2 Structure of Chlorella (less than 38 μm) mdash (a) raw (b) char obtained from TGA(left)

Figure 3 Structure of commercial wood mix (less than 38 μm) mdash (a) raw (b) char obtained from TGA(right)

Figure

4

Structu

re of Chlorella (150ndash250 μm) mdash (a) raw (b) char obtained from EFR (left)Figure 5 Structure of commercial wood mix (150ndash250 μm) mdash (a) raw (b) char obtained

from EFR (right)

9

Figure 6 Gasification characteristics of different types of char at 800 degC mdash (a) weight loss in 20 CO2 (b) weight loss in 20 steam (c) reactivity in 20 CO2 and (d) reactivity in

20 steam

10

Figure 7 Elemental compositions of the macroalgae

Figure 8 Experimental conditions and results for the hydrothermal gasification of macroalgae samples Tend = 500deg C Pend = 236-281 Holding time = 30 min Feed concentration = 666 wt 5 RuAl2O3 catalyst

Figure 9 Gas composition and yields of from supercritical gasification of S latissima Tend = 500deg C Pend = 236-281 Holding time = 30 min Feed concentration = 666 wt 5

RuAl2O3 catalyst

Figure 10 Gas composition and yields of from supercritical gasification of macroalgae Tend = 500deg C Pend = 236-281 Holding time = 30 min Feed concentration = 666 wt

5 RuAl2O3 catalyst

11

Figure 11 Nutrients and important metals in ppm from the process water of SCWG of S latissima Tend=500deg C Pend=236ndash281 bar Holding time=30 min Feed conc

5666 wt 5 RuAl2O3 catalyst compared with standard growth medium BBM

Figure 12 C vulgaris concentration (mgL) following 14-day cultivation in bioreactors Process water and dilutions SCWG of S latissima without catalyst (WC) with catalyst

(C)

12

Figure 13 Ternary diagram with different types of microalgae according to their maincomponents (lipid protein and carbohydrates)

Figure 14 The effect of temperature and pressure on the supercritical gasification of microalgae

13

Figure 15 The effect of temperature and dry matter content on the supercritical gasification of microalgae

Equations used for the creation of the Multiphase Thermodynamic Equilibrium Model to predict the behavior of gases and elements during supercritical gasification

Total Gibbs Free Energy

Chemical Potential based on Fugacity Coefficients

14

Peng-Robinson Equation of State

DebyeminusHuumlckel equations for molality based calculations in the model

15

The Equations of the Parameters of the DebyeminusHuumlckel equations

16

17

Equations used for the Activity of Water

Equations for the Aqueous Solution in Supercritical Region

18

19

3

Table of Contents

Introduction pg 3

Discussion And Conclusion pg 4 ndash 5

References pg 6 ndash 7

Appendix pg 8 -19

2

Introduction

Through many decades humanity with the economic systems that are in place today have lead to the linear increase in the production of goods while not considering its impacts in the environment Over the past decade world energy consumption has increased progressively owing to the growing demand by burgeoning industrial societies in emerging markets and the rising world population The current global state of energy supply is highly dependent on fossil fuels Owing to finite nature of fossil fuels rapid increase in their prices and concerns about their environmental impact efforts around the world to develop and commercialize renewable transportation fuels and biobased chemicals have intensified (A Geraili P Sharma JA Romagnoli 2013) One example of a place that is highly independent on the oil industry and is a huge contributor to emissions is Iran Iran is the9th-largest emitter of total greenhouse gases in the world in 2010 CO2 has increased from 4923 million tons in 2007 to about 5324 million tons in 2010 showing a growth of 814 percent between these years However during the long period between 1990 until 2010 CO2 has a growth rate of 174 The power-generation sector alone has contributed to more than 291 percent of the total CO2 in 2010The bulk of Iranian greenhouse-gas emissions541come from power plants and domestic sectors mainly through the expansion of energy demand During this year emission from power plants was about 1548 million tons and emissions from industry and refinery sectors were about 886 and 172 million tons respectively In according to the average annual Growth rate of CO2 in power plants it is anticipated that CO2 from power plants and all sectors in 2025 will reach to 247 and 930 million tons respectively which are alarming figures (A Ghorbani HR Rahimpour YGhasemi S Zoughi MR Rahimpour 2014)

Because of this different methods of technologies have been created to help capture CO2 and positively contribute to the carbon cycle There are biological physical and chemical processes that can be effectively utilized for carbon sequestration but one possible way to help positively contribute to the carbon cycle is to gasify algae For example in the case of biofuel production it has been proposed as early as 1950s in the United States Algae are a single cell microorganism which is composed of lipids carbohydrates and proteins The algae biomass has potential to produce a variety of biofuels through not only the extraction of lipids and other methods but through gasification of the algal biomass by anaerobic digestion or thermal cracking to produce biogas (S J P Jegathese and M Farid 2014) Gasification is a process that converts organic or fossil based carbonaceous material into CO H2 and CO2 by reacting the material at temperatures at 700˚ C or above without combustion with a controlled amount of O2 or steam and produces synthetic gas or syngas which is mixture of CO H2 and CO2 and can be used for energy Gasification is an example of a physical process called Bio-Energy with Carbon Capture and Storage or BECCS for short There is promise in the use of algae in gasification because through gasification CO2 is produced and the capture of this CO2 can be used for the optimization of algae growth Hence collectively contributing to the recycle of CO2 in the carbon cycle positively

3

Discussion

In a study from Monash University in Australia the CO2 and the steam gasification reactivities of algal biomass (Chlorella sp) and wood were compared The algae were grown using a modified MLA medium of 0494 gL MgSO47H2O 17 gL NaNO3 014 gL K2HPO4 and 0029 gL CaCl22H2O and the wood was a commercial wood mix and the reactivities were evaluated at 800˚ 950˚ 1100˚ C in both CO2 and steam environments with structure of the char particles studied by scanning electron microscope imaging Based on the study algal and woody biomass chars prepared in similar conditions showed significant difference in structure and gasification reactivity Clinker like structure was observed for algal char prepared in entrained flowreactor and it showed the lowest reactivity in all cases studied Thealgal char obtained at a lower heating rate from TGA showed rigid structure despite its smaller particle size in comparison to the EFR char At temperatures below 950 degC the reactivity of algal char from TGA was similar to that of the commercial wood mix char derived from EFR inboth gasifying agents In the case of woody biomass high reactivity was observed for commercial wood mix char from EFR Woody chars from both EFR and TGA showed higher reactivity than the algal char at 1100 degC under both CO2 and steam It is likely that pyrolysis ofalgae at a lower heating rate would result in highly reactive char during low temperature gasification regardless of the gasifying agent For chars of both the species a temperature of 800 degC and time of around 20 min are found to be sufficient to accomplish most conversion (K Kirtania J Joshua MA Kassim S Bhattacharya 2013) Figures 1-6 show the general set up of the experiment the compositions of Chlorella sp and of the commercial wood mix from this study and the respective weight percentages and reactivities EFR stands for entrained flow reactor and TGA stands for thermogravimetric analysis Although this study shows the drawbacks of gasifying algal char compared to with commercial wood in regards to CO2

sequestration a couple of studies shows the effects of the gasification of algae in supercritical water

Gasifying biomass in supercritical conditions represent a promising alternative to treat humid biomasses saving the costs of preliminary drying In addition the high operative pressures allow either to consider the produced gas as an alternative to natural gas for civil and industrial use or a source of energy in expansion processes (A Molino M Migliori F Nanna 2013) A study from the University of Leeds shows that four macroalgae species from the experiments can be successfully gasified under supercritical conditions S latissima L digitata A esculenta L hypoborea In addition to the four macroalgae in this study Chlorella vulgaris a microalgae species showed promise and suitability of nutrient recycling from macroalgae gasification within the context of algae bio-refineries Higher gasification are shown with the presence of a ruthenium catalyst with the yield of combustible gases of the product gas increasing by 30 but sulfur adversely affected the yield due to a decrease in the yield of CH4 following the poisoning of the catalyst surface (R Cherad JA Onwudili U Ekpo PT Williams AR Lea-Langton M Carmargo-Valero AB Ross 2013) Figures 7-12 show the compositions of the macroalgae mentioned the percentages of the yield and gasification efficiencies the effects of the rubidium catalyst on S latissima and of C vulgaris and the growth effects on C vulgaris

4

respectively In addition to the study made by the University of Leeds on testing which algae is best for supercritical gasification a thermodynamic model can be used to predict the formation of compounds in biomass It can be concluded that microalgae samples could be a potential biomass for combustion applications The temperature needed to carry out the combustion process has been demonstrated to be lower than for other types of biomass feedstock Thisfact turns directly into low costs when implementing the process at a higher scale Furthermore the heat released during the combustion process was in the same order of magnitude than thatcalculated by other authors for lignocellulosic biomass (D Loacutepez-Gonzaacutelez M Fernandez-Lopez JL Valverde L Sanchez-Silva 2013) A multiphase thermodynamic equilibrium model based on the fundamentals of the Gibbs free energy minimization methodhas been developed to predict the equilibrium state compounds for the supercritical water gasification based biomass conversion systems The model is capable of performing calculations for various temperature pressure and dry matter conditions forboth subcritical and supercritical regions The validation of the model by comparing the results of others has been performed and the results of the model were found to be in agreementwith the results of others The model shows a very good performance in predicting the amount of gases in real biomass gasification processes and the solubility of salt mixtures insupercritical water (O Yakaboylu J Harinck K G Smit W de Jong 2014) The equations used in the Multiphase Thermodynamic Model are shown in the Appendix along with Figures 14 and 15 showing the results of gasification under supercritical conditions dependent on pressure temperature and percentages of dry mass content

Conclusion

Based on the findings of the gasification of algae in study where algae is being compared to commercial wood mix for carbon sequestration more carbon is released compared to with algae in this case Chlorella vulgaris was the algae in the study But under supercritical conditions via hydrothermal gasification since algae only requires lower temperatures to initiate the combustion process Therefore will cost less to capture CO2 from the algae In regards to the Multiphase Thermodynamic Model used to predict what compounds are released can be tracked and implemented in the design of algal biorefineries A biorefinery featuring hydrothermal liquefaction reaction conditions with relatively high temperatures and longer reaction times results in an aqueous phase containing a higher fraction of carbon in theinorganic form rather than organic Inorganic carbon is not available for energy recovery via catalytic hydrothermal gasification which is why the energy return on investment drops significantly as temperatures and reaction times are increased In addition to the drop in costs findings of E coli growth on the algae in aqueous phase boosts to the yield of oil per unit of algal mass by 10-20 without extra investment (ND Orfield AJ Fang PJ Valdez MC Nelson PE Savage XN Lin GA Keoleian 2014) With accurate tracking of the types of compounds that are released due to gasification we have a better solution to become more effective at carbon sequestration from algae and other biomass

5

References

Geraili A P Sharma and J A Romagnoli A modeling framework for design of nonlinear renewable energy systems through integrated simulation modeling and metaheuristic optimization Applications to biorefineries Computers amp Chemical Engineering 61 (2014) 102-117

Savage Phillip E and Jamie A Hestekin A perspective on algae the environment and energy Environmental Progress amp Sustainable Energy 324 (2013) 877-883

Ghorbani Afshin et al A Review of Carbon Capture and Sequestration in Iran Microalgal Biofixation Potential in Iran Renewable and Sustainable Energy Reviews 35 (2014) 73-100

Onwudili Jude A et al Catalytic hydrothermal gasification of algae for hydrogen production Composition of reaction products and potential for nutrient recycling Bioresource technology 127 (2013) 72-80

Du Yuying et al Cogasification of Biofermenting Residue in a Coal-Water Slurry Gasifier Energy amp Fuels 283 (2014) 2054-2058

Lane Daniel J et al Combustion Behavior of Algal Biomass Carbon Release Nitrogen Release and Char Reactivity Energy amp Fuels (2013)

Kirtania Kawnish et al Comparison of COlt subgt 2ltsubgt and steam gasification reactivity of algal and woody biomass chars Fuel Processing Technology 117 (2014) 44-52

Bagnoud-Velaacutesquez Mariluz et al Continuous catalytic hydrothermal gasification of algal biomass and case study on toxicity of aluminum as a step toward effluents recycling Catalysis Today 223 (2014) 35-43

Molino A M Migliori and F Nanna Glucose gasification in near critical water conditions for both syngas production and green chemicals with a continuous process Fuel 115 (2014) 41-45

Bai Xiujun et al Hydrothermal catalytic processing of pretreated algal oil A catalyst screening study Fuel 120 (2014) 141-149

Davis Ryan et al Integrated Evaluation of Cost Emissions and Resource Potential for Algal Biofuels at the National Scale Environmental science amp technology (2014)

Loacutepez-Gonzaacutelez D et al Kinetic analysis and thermal characterization of the microalgae combustion process by thermal analysis coupled to mass spectrometry Applied Energy 114 (2014) 227-237

6

Orfield Nolan D et al Life cycle design of an algal biorefinery featuring hydrothermal liquefaction effect of reaction conditions and an alternative pathway including microbial regrowth ACS Sustainable Chemistry amp Engineering 24 (2014) 867-874

Cherad Ramzi et al Macroalgae supercritical water gasification combined with nutrient recycling for microalgae cultivation Environmental Progress amp Sustainable Energy 324 (2013) 902-909

Jegathese Simon Jegan Porphy and Mohammed Farid Microalgae as a Renewable Source of Energy A Niche Opportunity Journal of Renewable Energy 2014 (2014)

Gong Jian and Fengqi You Optimal design and synthesis of algal biorefinery processes for biological carbon sequestration and utilization with zero direct greenhouse gas emissions Industrial amp Engineering Chemistry Research(2014)

Zhao Bingtao and Yaxin Su Process effect of microalgal-carbon dioxide fixation and biomass production A review Renewable and Sustainable Energy Reviews 31 (2014) 121-132

Kaewpanha Malinee et al Steam co-gasification of brown seaweed and land-based biomass Fuel Processing Technology 120 (2014) 106-112

Yakaboylu Onursal et al Supercritical Water Gasification of Biomass A Thermodynamic Model for the Prediction of Product Compounds at Equilibrium State Energy amp Fuels (2014)

7

Appendix

Figure 1 Experimental Flow Diagram comparing algae and commercial wood mix

8

Figure 2 Structure of Chlorella (less than 38 μm) mdash (a) raw (b) char obtained from TGA(left)

Figure 3 Structure of commercial wood mix (less than 38 μm) mdash (a) raw (b) char obtained from TGA(right)

Figure

4

Structu

re of Chlorella (150ndash250 μm) mdash (a) raw (b) char obtained from EFR (left)Figure 5 Structure of commercial wood mix (150ndash250 μm) mdash (a) raw (b) char obtained

from EFR (right)

9

Figure 6 Gasification characteristics of different types of char at 800 degC mdash (a) weight loss in 20 CO2 (b) weight loss in 20 steam (c) reactivity in 20 CO2 and (d) reactivity in

20 steam

10

Figure 7 Elemental compositions of the macroalgae

Figure 8 Experimental conditions and results for the hydrothermal gasification of macroalgae samples Tend = 500deg C Pend = 236-281 Holding time = 30 min Feed concentration = 666 wt 5 RuAl2O3 catalyst

Figure 9 Gas composition and yields of from supercritical gasification of S latissima Tend = 500deg C Pend = 236-281 Holding time = 30 min Feed concentration = 666 wt 5

RuAl2O3 catalyst

Figure 10 Gas composition and yields of from supercritical gasification of macroalgae Tend = 500deg C Pend = 236-281 Holding time = 30 min Feed concentration = 666 wt

5 RuAl2O3 catalyst

11

Figure 11 Nutrients and important metals in ppm from the process water of SCWG of S latissima Tend=500deg C Pend=236ndash281 bar Holding time=30 min Feed conc

5666 wt 5 RuAl2O3 catalyst compared with standard growth medium BBM

Figure 12 C vulgaris concentration (mgL) following 14-day cultivation in bioreactors Process water and dilutions SCWG of S latissima without catalyst (WC) with catalyst

(C)

12

Figure 13 Ternary diagram with different types of microalgae according to their maincomponents (lipid protein and carbohydrates)

Figure 14 The effect of temperature and pressure on the supercritical gasification of microalgae

13

Figure 15 The effect of temperature and dry matter content on the supercritical gasification of microalgae

Equations used for the creation of the Multiphase Thermodynamic Equilibrium Model to predict the behavior of gases and elements during supercritical gasification

Total Gibbs Free Energy

Chemical Potential based on Fugacity Coefficients

14

Peng-Robinson Equation of State

DebyeminusHuumlckel equations for molality based calculations in the model

15

The Equations of the Parameters of the DebyeminusHuumlckel equations

16

17

Equations used for the Activity of Water

Equations for the Aqueous Solution in Supercritical Region

18

19

3

Introduction

Through many decades humanity with the economic systems that are in place today have lead to the linear increase in the production of goods while not considering its impacts in the environment Over the past decade world energy consumption has increased progressively owing to the growing demand by burgeoning industrial societies in emerging markets and the rising world population The current global state of energy supply is highly dependent on fossil fuels Owing to finite nature of fossil fuels rapid increase in their prices and concerns about their environmental impact efforts around the world to develop and commercialize renewable transportation fuels and biobased chemicals have intensified (A Geraili P Sharma JA Romagnoli 2013) One example of a place that is highly independent on the oil industry and is a huge contributor to emissions is Iran Iran is the9th-largest emitter of total greenhouse gases in the world in 2010 CO2 has increased from 4923 million tons in 2007 to about 5324 million tons in 2010 showing a growth of 814 percent between these years However during the long period between 1990 until 2010 CO2 has a growth rate of 174 The power-generation sector alone has contributed to more than 291 percent of the total CO2 in 2010The bulk of Iranian greenhouse-gas emissions541come from power plants and domestic sectors mainly through the expansion of energy demand During this year emission from power plants was about 1548 million tons and emissions from industry and refinery sectors were about 886 and 172 million tons respectively In according to the average annual Growth rate of CO2 in power plants it is anticipated that CO2 from power plants and all sectors in 2025 will reach to 247 and 930 million tons respectively which are alarming figures (A Ghorbani HR Rahimpour YGhasemi S Zoughi MR Rahimpour 2014)

Because of this different methods of technologies have been created to help capture CO2 and positively contribute to the carbon cycle There are biological physical and chemical processes that can be effectively utilized for carbon sequestration but one possible way to help positively contribute to the carbon cycle is to gasify algae For example in the case of biofuel production it has been proposed as early as 1950s in the United States Algae are a single cell microorganism which is composed of lipids carbohydrates and proteins The algae biomass has potential to produce a variety of biofuels through not only the extraction of lipids and other methods but through gasification of the algal biomass by anaerobic digestion or thermal cracking to produce biogas (S J P Jegathese and M Farid 2014) Gasification is a process that converts organic or fossil based carbonaceous material into CO H2 and CO2 by reacting the material at temperatures at 700˚ C or above without combustion with a controlled amount of O2 or steam and produces synthetic gas or syngas which is mixture of CO H2 and CO2 and can be used for energy Gasification is an example of a physical process called Bio-Energy with Carbon Capture and Storage or BECCS for short There is promise in the use of algae in gasification because through gasification CO2 is produced and the capture of this CO2 can be used for the optimization of algae growth Hence collectively contributing to the recycle of CO2 in the carbon cycle positively

3

Discussion

In a study from Monash University in Australia the CO2 and the steam gasification reactivities of algal biomass (Chlorella sp) and wood were compared The algae were grown using a modified MLA medium of 0494 gL MgSO47H2O 17 gL NaNO3 014 gL K2HPO4 and 0029 gL CaCl22H2O and the wood was a commercial wood mix and the reactivities were evaluated at 800˚ 950˚ 1100˚ C in both CO2 and steam environments with structure of the char particles studied by scanning electron microscope imaging Based on the study algal and woody biomass chars prepared in similar conditions showed significant difference in structure and gasification reactivity Clinker like structure was observed for algal char prepared in entrained flowreactor and it showed the lowest reactivity in all cases studied Thealgal char obtained at a lower heating rate from TGA showed rigid structure despite its smaller particle size in comparison to the EFR char At temperatures below 950 degC the reactivity of algal char from TGA was similar to that of the commercial wood mix char derived from EFR inboth gasifying agents In the case of woody biomass high reactivity was observed for commercial wood mix char from EFR Woody chars from both EFR and TGA showed higher reactivity than the algal char at 1100 degC under both CO2 and steam It is likely that pyrolysis ofalgae at a lower heating rate would result in highly reactive char during low temperature gasification regardless of the gasifying agent For chars of both the species a temperature of 800 degC and time of around 20 min are found to be sufficient to accomplish most conversion (K Kirtania J Joshua MA Kassim S Bhattacharya 2013) Figures 1-6 show the general set up of the experiment the compositions of Chlorella sp and of the commercial wood mix from this study and the respective weight percentages and reactivities EFR stands for entrained flow reactor and TGA stands for thermogravimetric analysis Although this study shows the drawbacks of gasifying algal char compared to with commercial wood in regards to CO2

sequestration a couple of studies shows the effects of the gasification of algae in supercritical water

Gasifying biomass in supercritical conditions represent a promising alternative to treat humid biomasses saving the costs of preliminary drying In addition the high operative pressures allow either to consider the produced gas as an alternative to natural gas for civil and industrial use or a source of energy in expansion processes (A Molino M Migliori F Nanna 2013) A study from the University of Leeds shows that four macroalgae species from the experiments can be successfully gasified under supercritical conditions S latissima L digitata A esculenta L hypoborea In addition to the four macroalgae in this study Chlorella vulgaris a microalgae species showed promise and suitability of nutrient recycling from macroalgae gasification within the context of algae bio-refineries Higher gasification are shown with the presence of a ruthenium catalyst with the yield of combustible gases of the product gas increasing by 30 but sulfur adversely affected the yield due to a decrease in the yield of CH4 following the poisoning of the catalyst surface (R Cherad JA Onwudili U Ekpo PT Williams AR Lea-Langton M Carmargo-Valero AB Ross 2013) Figures 7-12 show the compositions of the macroalgae mentioned the percentages of the yield and gasification efficiencies the effects of the rubidium catalyst on S latissima and of C vulgaris and the growth effects on C vulgaris

4

respectively In addition to the study made by the University of Leeds on testing which algae is best for supercritical gasification a thermodynamic model can be used to predict the formation of compounds in biomass It can be concluded that microalgae samples could be a potential biomass for combustion applications The temperature needed to carry out the combustion process has been demonstrated to be lower than for other types of biomass feedstock Thisfact turns directly into low costs when implementing the process at a higher scale Furthermore the heat released during the combustion process was in the same order of magnitude than thatcalculated by other authors for lignocellulosic biomass (D Loacutepez-Gonzaacutelez M Fernandez-Lopez JL Valverde L Sanchez-Silva 2013) A multiphase thermodynamic equilibrium model based on the fundamentals of the Gibbs free energy minimization methodhas been developed to predict the equilibrium state compounds for the supercritical water gasification based biomass conversion systems The model is capable of performing calculations for various temperature pressure and dry matter conditions forboth subcritical and supercritical regions The validation of the model by comparing the results of others has been performed and the results of the model were found to be in agreementwith the results of others The model shows a very good performance in predicting the amount of gases in real biomass gasification processes and the solubility of salt mixtures insupercritical water (O Yakaboylu J Harinck K G Smit W de Jong 2014) The equations used in the Multiphase Thermodynamic Model are shown in the Appendix along with Figures 14 and 15 showing the results of gasification under supercritical conditions dependent on pressure temperature and percentages of dry mass content

Conclusion

Based on the findings of the gasification of algae in study where algae is being compared to commercial wood mix for carbon sequestration more carbon is released compared to with algae in this case Chlorella vulgaris was the algae in the study But under supercritical conditions via hydrothermal gasification since algae only requires lower temperatures to initiate the combustion process Therefore will cost less to capture CO2 from the algae In regards to the Multiphase Thermodynamic Model used to predict what compounds are released can be tracked and implemented in the design of algal biorefineries A biorefinery featuring hydrothermal liquefaction reaction conditions with relatively high temperatures and longer reaction times results in an aqueous phase containing a higher fraction of carbon in theinorganic form rather than organic Inorganic carbon is not available for energy recovery via catalytic hydrothermal gasification which is why the energy return on investment drops significantly as temperatures and reaction times are increased In addition to the drop in costs findings of E coli growth on the algae in aqueous phase boosts to the yield of oil per unit of algal mass by 10-20 without extra investment (ND Orfield AJ Fang PJ Valdez MC Nelson PE Savage XN Lin GA Keoleian 2014) With accurate tracking of the types of compounds that are released due to gasification we have a better solution to become more effective at carbon sequestration from algae and other biomass

5

References

Geraili A P Sharma and J A Romagnoli A modeling framework for design of nonlinear renewable energy systems through integrated simulation modeling and metaheuristic optimization Applications to biorefineries Computers amp Chemical Engineering 61 (2014) 102-117

Savage Phillip E and Jamie A Hestekin A perspective on algae the environment and energy Environmental Progress amp Sustainable Energy 324 (2013) 877-883

Ghorbani Afshin et al A Review of Carbon Capture and Sequestration in Iran Microalgal Biofixation Potential in Iran Renewable and Sustainable Energy Reviews 35 (2014) 73-100

Onwudili Jude A et al Catalytic hydrothermal gasification of algae for hydrogen production Composition of reaction products and potential for nutrient recycling Bioresource technology 127 (2013) 72-80

Du Yuying et al Cogasification of Biofermenting Residue in a Coal-Water Slurry Gasifier Energy amp Fuels 283 (2014) 2054-2058

Lane Daniel J et al Combustion Behavior of Algal Biomass Carbon Release Nitrogen Release and Char Reactivity Energy amp Fuels (2013)

Kirtania Kawnish et al Comparison of COlt subgt 2ltsubgt and steam gasification reactivity of algal and woody biomass chars Fuel Processing Technology 117 (2014) 44-52

Bagnoud-Velaacutesquez Mariluz et al Continuous catalytic hydrothermal gasification of algal biomass and case study on toxicity of aluminum as a step toward effluents recycling Catalysis Today 223 (2014) 35-43

Molino A M Migliori and F Nanna Glucose gasification in near critical water conditions for both syngas production and green chemicals with a continuous process Fuel 115 (2014) 41-45

Bai Xiujun et al Hydrothermal catalytic processing of pretreated algal oil A catalyst screening study Fuel 120 (2014) 141-149

Davis Ryan et al Integrated Evaluation of Cost Emissions and Resource Potential for Algal Biofuels at the National Scale Environmental science amp technology (2014)

Loacutepez-Gonzaacutelez D et al Kinetic analysis and thermal characterization of the microalgae combustion process by thermal analysis coupled to mass spectrometry Applied Energy 114 (2014) 227-237

6

Orfield Nolan D et al Life cycle design of an algal biorefinery featuring hydrothermal liquefaction effect of reaction conditions and an alternative pathway including microbial regrowth ACS Sustainable Chemistry amp Engineering 24 (2014) 867-874

Cherad Ramzi et al Macroalgae supercritical water gasification combined with nutrient recycling for microalgae cultivation Environmental Progress amp Sustainable Energy 324 (2013) 902-909

Jegathese Simon Jegan Porphy and Mohammed Farid Microalgae as a Renewable Source of Energy A Niche Opportunity Journal of Renewable Energy 2014 (2014)

Gong Jian and Fengqi You Optimal design and synthesis of algal biorefinery processes for biological carbon sequestration and utilization with zero direct greenhouse gas emissions Industrial amp Engineering Chemistry Research(2014)

Zhao Bingtao and Yaxin Su Process effect of microalgal-carbon dioxide fixation and biomass production A review Renewable and Sustainable Energy Reviews 31 (2014) 121-132

Kaewpanha Malinee et al Steam co-gasification of brown seaweed and land-based biomass Fuel Processing Technology 120 (2014) 106-112

Yakaboylu Onursal et al Supercritical Water Gasification of Biomass A Thermodynamic Model for the Prediction of Product Compounds at Equilibrium State Energy amp Fuels (2014)

7

Appendix

Figure 1 Experimental Flow Diagram comparing algae and commercial wood mix

8

Figure 2 Structure of Chlorella (less than 38 μm) mdash (a) raw (b) char obtained from TGA(left)

Figure 3 Structure of commercial wood mix (less than 38 μm) mdash (a) raw (b) char obtained from TGA(right)

Figure

4

Structu

re of Chlorella (150ndash250 μm) mdash (a) raw (b) char obtained from EFR (left)Figure 5 Structure of commercial wood mix (150ndash250 μm) mdash (a) raw (b) char obtained

from EFR (right)

9

Figure 6 Gasification characteristics of different types of char at 800 degC mdash (a) weight loss in 20 CO2 (b) weight loss in 20 steam (c) reactivity in 20 CO2 and (d) reactivity in

20 steam

10

Figure 7 Elemental compositions of the macroalgae

Figure 8 Experimental conditions and results for the hydrothermal gasification of macroalgae samples Tend = 500deg C Pend = 236-281 Holding time = 30 min Feed concentration = 666 wt 5 RuAl2O3 catalyst

Figure 9 Gas composition and yields of from supercritical gasification of S latissima Tend = 500deg C Pend = 236-281 Holding time = 30 min Feed concentration = 666 wt 5

RuAl2O3 catalyst

Figure 10 Gas composition and yields of from supercritical gasification of macroalgae Tend = 500deg C Pend = 236-281 Holding time = 30 min Feed concentration = 666 wt

5 RuAl2O3 catalyst

11

Figure 11 Nutrients and important metals in ppm from the process water of SCWG of S latissima Tend=500deg C Pend=236ndash281 bar Holding time=30 min Feed conc

5666 wt 5 RuAl2O3 catalyst compared with standard growth medium BBM

Figure 12 C vulgaris concentration (mgL) following 14-day cultivation in bioreactors Process water and dilutions SCWG of S latissima without catalyst (WC) with catalyst

(C)

12

Figure 13 Ternary diagram with different types of microalgae according to their maincomponents (lipid protein and carbohydrates)

Figure 14 The effect of temperature and pressure on the supercritical gasification of microalgae

13

Figure 15 The effect of temperature and dry matter content on the supercritical gasification of microalgae

Equations used for the creation of the Multiphase Thermodynamic Equilibrium Model to predict the behavior of gases and elements during supercritical gasification

Total Gibbs Free Energy

Chemical Potential based on Fugacity Coefficients

14

Peng-Robinson Equation of State

DebyeminusHuumlckel equations for molality based calculations in the model

15

The Equations of the Parameters of the DebyeminusHuumlckel equations

16

17

Equations used for the Activity of Water

Equations for the Aqueous Solution in Supercritical Region

18

19

3

Discussion

In a study from Monash University in Australia the CO2 and the steam gasification reactivities of algal biomass (Chlorella sp) and wood were compared The algae were grown using a modified MLA medium of 0494 gL MgSO47H2O 17 gL NaNO3 014 gL K2HPO4 and 0029 gL CaCl22H2O and the wood was a commercial wood mix and the reactivities were evaluated at 800˚ 950˚ 1100˚ C in both CO2 and steam environments with structure of the char particles studied by scanning electron microscope imaging Based on the study algal and woody biomass chars prepared in similar conditions showed significant difference in structure and gasification reactivity Clinker like structure was observed for algal char prepared in entrained flowreactor and it showed the lowest reactivity in all cases studied Thealgal char obtained at a lower heating rate from TGA showed rigid structure despite its smaller particle size in comparison to the EFR char At temperatures below 950 degC the reactivity of algal char from TGA was similar to that of the commercial wood mix char derived from EFR inboth gasifying agents In the case of woody biomass high reactivity was observed for commercial wood mix char from EFR Woody chars from both EFR and TGA showed higher reactivity than the algal char at 1100 degC under both CO2 and steam It is likely that pyrolysis ofalgae at a lower heating rate would result in highly reactive char during low temperature gasification regardless of the gasifying agent For chars of both the species a temperature of 800 degC and time of around 20 min are found to be sufficient to accomplish most conversion (K Kirtania J Joshua MA Kassim S Bhattacharya 2013) Figures 1-6 show the general set up of the experiment the compositions of Chlorella sp and of the commercial wood mix from this study and the respective weight percentages and reactivities EFR stands for entrained flow reactor and TGA stands for thermogravimetric analysis Although this study shows the drawbacks of gasifying algal char compared to with commercial wood in regards to CO2

sequestration a couple of studies shows the effects of the gasification of algae in supercritical water

Gasifying biomass in supercritical conditions represent a promising alternative to treat humid biomasses saving the costs of preliminary drying In addition the high operative pressures allow either to consider the produced gas as an alternative to natural gas for civil and industrial use or a source of energy in expansion processes (A Molino M Migliori F Nanna 2013) A study from the University of Leeds shows that four macroalgae species from the experiments can be successfully gasified under supercritical conditions S latissima L digitata A esculenta L hypoborea In addition to the four macroalgae in this study Chlorella vulgaris a microalgae species showed promise and suitability of nutrient recycling from macroalgae gasification within the context of algae bio-refineries Higher gasification are shown with the presence of a ruthenium catalyst with the yield of combustible gases of the product gas increasing by 30 but sulfur adversely affected the yield due to a decrease in the yield of CH4 following the poisoning of the catalyst surface (R Cherad JA Onwudili U Ekpo PT Williams AR Lea-Langton M Carmargo-Valero AB Ross 2013) Figures 7-12 show the compositions of the macroalgae mentioned the percentages of the yield and gasification efficiencies the effects of the rubidium catalyst on S latissima and of C vulgaris and the growth effects on C vulgaris

4

respectively In addition to the study made by the University of Leeds on testing which algae is best for supercritical gasification a thermodynamic model can be used to predict the formation of compounds in biomass It can be concluded that microalgae samples could be a potential biomass for combustion applications The temperature needed to carry out the combustion process has been demonstrated to be lower than for other types of biomass feedstock Thisfact turns directly into low costs when implementing the process at a higher scale Furthermore the heat released during the combustion process was in the same order of magnitude than thatcalculated by other authors for lignocellulosic biomass (D Loacutepez-Gonzaacutelez M Fernandez-Lopez JL Valverde L Sanchez-Silva 2013) A multiphase thermodynamic equilibrium model based on the fundamentals of the Gibbs free energy minimization methodhas been developed to predict the equilibrium state compounds for the supercritical water gasification based biomass conversion systems The model is capable of performing calculations for various temperature pressure and dry matter conditions forboth subcritical and supercritical regions The validation of the model by comparing the results of others has been performed and the results of the model were found to be in agreementwith the results of others The model shows a very good performance in predicting the amount of gases in real biomass gasification processes and the solubility of salt mixtures insupercritical water (O Yakaboylu J Harinck K G Smit W de Jong 2014) The equations used in the Multiphase Thermodynamic Model are shown in the Appendix along with Figures 14 and 15 showing the results of gasification under supercritical conditions dependent on pressure temperature and percentages of dry mass content

Conclusion

Based on the findings of the gasification of algae in study where algae is being compared to commercial wood mix for carbon sequestration more carbon is released compared to with algae in this case Chlorella vulgaris was the algae in the study But under supercritical conditions via hydrothermal gasification since algae only requires lower temperatures to initiate the combustion process Therefore will cost less to capture CO2 from the algae In regards to the Multiphase Thermodynamic Model used to predict what compounds are released can be tracked and implemented in the design of algal biorefineries A biorefinery featuring hydrothermal liquefaction reaction conditions with relatively high temperatures and longer reaction times results in an aqueous phase containing a higher fraction of carbon in theinorganic form rather than organic Inorganic carbon is not available for energy recovery via catalytic hydrothermal gasification which is why the energy return on investment drops significantly as temperatures and reaction times are increased In addition to the drop in costs findings of E coli growth on the algae in aqueous phase boosts to the yield of oil per unit of algal mass by 10-20 without extra investment (ND Orfield AJ Fang PJ Valdez MC Nelson PE Savage XN Lin GA Keoleian 2014) With accurate tracking of the types of compounds that are released due to gasification we have a better solution to become more effective at carbon sequestration from algae and other biomass

5

References

Geraili A P Sharma and J A Romagnoli A modeling framework for design of nonlinear renewable energy systems through integrated simulation modeling and metaheuristic optimization Applications to biorefineries Computers amp Chemical Engineering 61 (2014) 102-117

Savage Phillip E and Jamie A Hestekin A perspective on algae the environment and energy Environmental Progress amp Sustainable Energy 324 (2013) 877-883

Ghorbani Afshin et al A Review of Carbon Capture and Sequestration in Iran Microalgal Biofixation Potential in Iran Renewable and Sustainable Energy Reviews 35 (2014) 73-100

Onwudili Jude A et al Catalytic hydrothermal gasification of algae for hydrogen production Composition of reaction products and potential for nutrient recycling Bioresource technology 127 (2013) 72-80

Du Yuying et al Cogasification of Biofermenting Residue in a Coal-Water Slurry Gasifier Energy amp Fuels 283 (2014) 2054-2058

Lane Daniel J et al Combustion Behavior of Algal Biomass Carbon Release Nitrogen Release and Char Reactivity Energy amp Fuels (2013)

Kirtania Kawnish et al Comparison of COlt subgt 2ltsubgt and steam gasification reactivity of algal and woody biomass chars Fuel Processing Technology 117 (2014) 44-52

Bagnoud-Velaacutesquez Mariluz et al Continuous catalytic hydrothermal gasification of algal biomass and case study on toxicity of aluminum as a step toward effluents recycling Catalysis Today 223 (2014) 35-43

Molino A M Migliori and F Nanna Glucose gasification in near critical water conditions for both syngas production and green chemicals with a continuous process Fuel 115 (2014) 41-45

Bai Xiujun et al Hydrothermal catalytic processing of pretreated algal oil A catalyst screening study Fuel 120 (2014) 141-149

Davis Ryan et al Integrated Evaluation of Cost Emissions and Resource Potential for Algal Biofuels at the National Scale Environmental science amp technology (2014)

Loacutepez-Gonzaacutelez D et al Kinetic analysis and thermal characterization of the microalgae combustion process by thermal analysis coupled to mass spectrometry Applied Energy 114 (2014) 227-237

6

Orfield Nolan D et al Life cycle design of an algal biorefinery featuring hydrothermal liquefaction effect of reaction conditions and an alternative pathway including microbial regrowth ACS Sustainable Chemistry amp Engineering 24 (2014) 867-874

Cherad Ramzi et al Macroalgae supercritical water gasification combined with nutrient recycling for microalgae cultivation Environmental Progress amp Sustainable Energy 324 (2013) 902-909

Jegathese Simon Jegan Porphy and Mohammed Farid Microalgae as a Renewable Source of Energy A Niche Opportunity Journal of Renewable Energy 2014 (2014)

Gong Jian and Fengqi You Optimal design and synthesis of algal biorefinery processes for biological carbon sequestration and utilization with zero direct greenhouse gas emissions Industrial amp Engineering Chemistry Research(2014)

Zhao Bingtao and Yaxin Su Process effect of microalgal-carbon dioxide fixation and biomass production A review Renewable and Sustainable Energy Reviews 31 (2014) 121-132

Kaewpanha Malinee et al Steam co-gasification of brown seaweed and land-based biomass Fuel Processing Technology 120 (2014) 106-112

Yakaboylu Onursal et al Supercritical Water Gasification of Biomass A Thermodynamic Model for the Prediction of Product Compounds at Equilibrium State Energy amp Fuels (2014)

7

Appendix

Figure 1 Experimental Flow Diagram comparing algae and commercial wood mix

8

Figure 2 Structure of Chlorella (less than 38 μm) mdash (a) raw (b) char obtained from TGA(left)

Figure 3 Structure of commercial wood mix (less than 38 μm) mdash (a) raw (b) char obtained from TGA(right)

Figure

4

Structu

re of Chlorella (150ndash250 μm) mdash (a) raw (b) char obtained from EFR (left)Figure 5 Structure of commercial wood mix (150ndash250 μm) mdash (a) raw (b) char obtained

from EFR (right)

9

Figure 6 Gasification characteristics of different types of char at 800 degC mdash (a) weight loss in 20 CO2 (b) weight loss in 20 steam (c) reactivity in 20 CO2 and (d) reactivity in

20 steam

10

Figure 7 Elemental compositions of the macroalgae

Figure 8 Experimental conditions and results for the hydrothermal gasification of macroalgae samples Tend = 500deg C Pend = 236-281 Holding time = 30 min Feed concentration = 666 wt 5 RuAl2O3 catalyst

Figure 9 Gas composition and yields of from supercritical gasification of S latissima Tend = 500deg C Pend = 236-281 Holding time = 30 min Feed concentration = 666 wt 5

RuAl2O3 catalyst

Figure 10 Gas composition and yields of from supercritical gasification of macroalgae Tend = 500deg C Pend = 236-281 Holding time = 30 min Feed concentration = 666 wt

5 RuAl2O3 catalyst

11

Figure 11 Nutrients and important metals in ppm from the process water of SCWG of S latissima Tend=500deg C Pend=236ndash281 bar Holding time=30 min Feed conc

5666 wt 5 RuAl2O3 catalyst compared with standard growth medium BBM

Figure 12 C vulgaris concentration (mgL) following 14-day cultivation in bioreactors Process water and dilutions SCWG of S latissima without catalyst (WC) with catalyst

(C)

12

Figure 13 Ternary diagram with different types of microalgae according to their maincomponents (lipid protein and carbohydrates)

Figure 14 The effect of temperature and pressure on the supercritical gasification of microalgae

13

Figure 15 The effect of temperature and dry matter content on the supercritical gasification of microalgae

Equations used for the creation of the Multiphase Thermodynamic Equilibrium Model to predict the behavior of gases and elements during supercritical gasification

Total Gibbs Free Energy

Chemical Potential based on Fugacity Coefficients

14

Peng-Robinson Equation of State

DebyeminusHuumlckel equations for molality based calculations in the model

15

The Equations of the Parameters of the DebyeminusHuumlckel equations

16

17

Equations used for the Activity of Water

Equations for the Aqueous Solution in Supercritical Region

18

19

3

respectively In addition to the study made by the University of Leeds on testing which algae is best for supercritical gasification a thermodynamic model can be used to predict the formation of compounds in biomass It can be concluded that microalgae samples could be a potential biomass for combustion applications The temperature needed to carry out the combustion process has been demonstrated to be lower than for other types of biomass feedstock Thisfact turns directly into low costs when implementing the process at a higher scale Furthermore the heat released during the combustion process was in the same order of magnitude than thatcalculated by other authors for lignocellulosic biomass (D Loacutepez-Gonzaacutelez M Fernandez-Lopez JL Valverde L Sanchez-Silva 2013) A multiphase thermodynamic equilibrium model based on the fundamentals of the Gibbs free energy minimization methodhas been developed to predict the equilibrium state compounds for the supercritical water gasification based biomass conversion systems The model is capable of performing calculations for various temperature pressure and dry matter conditions forboth subcritical and supercritical regions The validation of the model by comparing the results of others has been performed and the results of the model were found to be in agreementwith the results of others The model shows a very good performance in predicting the amount of gases in real biomass gasification processes and the solubility of salt mixtures insupercritical water (O Yakaboylu J Harinck K G Smit W de Jong 2014) The equations used in the Multiphase Thermodynamic Model are shown in the Appendix along with Figures 14 and 15 showing the results of gasification under supercritical conditions dependent on pressure temperature and percentages of dry mass content

Conclusion

Based on the findings of the gasification of algae in study where algae is being compared to commercial wood mix for carbon sequestration more carbon is released compared to with algae in this case Chlorella vulgaris was the algae in the study But under supercritical conditions via hydrothermal gasification since algae only requires lower temperatures to initiate the combustion process Therefore will cost less to capture CO2 from the algae In regards to the Multiphase Thermodynamic Model used to predict what compounds are released can be tracked and implemented in the design of algal biorefineries A biorefinery featuring hydrothermal liquefaction reaction conditions with relatively high temperatures and longer reaction times results in an aqueous phase containing a higher fraction of carbon in theinorganic form rather than organic Inorganic carbon is not available for energy recovery via catalytic hydrothermal gasification which is why the energy return on investment drops significantly as temperatures and reaction times are increased In addition to the drop in costs findings of E coli growth on the algae in aqueous phase boosts to the yield of oil per unit of algal mass by 10-20 without extra investment (ND Orfield AJ Fang PJ Valdez MC Nelson PE Savage XN Lin GA Keoleian 2014) With accurate tracking of the types of compounds that are released due to gasification we have a better solution to become more effective at carbon sequestration from algae and other biomass

5

References

Geraili A P Sharma and J A Romagnoli A modeling framework for design of nonlinear renewable energy systems through integrated simulation modeling and metaheuristic optimization Applications to biorefineries Computers amp Chemical Engineering 61 (2014) 102-117

Savage Phillip E and Jamie A Hestekin A perspective on algae the environment and energy Environmental Progress amp Sustainable Energy 324 (2013) 877-883

Ghorbani Afshin et al A Review of Carbon Capture and Sequestration in Iran Microalgal Biofixation Potential in Iran Renewable and Sustainable Energy Reviews 35 (2014) 73-100

Onwudili Jude A et al Catalytic hydrothermal gasification of algae for hydrogen production Composition of reaction products and potential for nutrient recycling Bioresource technology 127 (2013) 72-80

Du Yuying et al Cogasification of Biofermenting Residue in a Coal-Water Slurry Gasifier Energy amp Fuels 283 (2014) 2054-2058

Lane Daniel J et al Combustion Behavior of Algal Biomass Carbon Release Nitrogen Release and Char Reactivity Energy amp Fuels (2013)

Kirtania Kawnish et al Comparison of COlt subgt 2ltsubgt and steam gasification reactivity of algal and woody biomass chars Fuel Processing Technology 117 (2014) 44-52

Bagnoud-Velaacutesquez Mariluz et al Continuous catalytic hydrothermal gasification of algal biomass and case study on toxicity of aluminum as a step toward effluents recycling Catalysis Today 223 (2014) 35-43

Molino A M Migliori and F Nanna Glucose gasification in near critical water conditions for both syngas production and green chemicals with a continuous process Fuel 115 (2014) 41-45

Bai Xiujun et al Hydrothermal catalytic processing of pretreated algal oil A catalyst screening study Fuel 120 (2014) 141-149

Davis Ryan et al Integrated Evaluation of Cost Emissions and Resource Potential for Algal Biofuels at the National Scale Environmental science amp technology (2014)

Loacutepez-Gonzaacutelez D et al Kinetic analysis and thermal characterization of the microalgae combustion process by thermal analysis coupled to mass spectrometry Applied Energy 114 (2014) 227-237

6

Orfield Nolan D et al Life cycle design of an algal biorefinery featuring hydrothermal liquefaction effect of reaction conditions and an alternative pathway including microbial regrowth ACS Sustainable Chemistry amp Engineering 24 (2014) 867-874

Cherad Ramzi et al Macroalgae supercritical water gasification combined with nutrient recycling for microalgae cultivation Environmental Progress amp Sustainable Energy 324 (2013) 902-909

Jegathese Simon Jegan Porphy and Mohammed Farid Microalgae as a Renewable Source of Energy A Niche Opportunity Journal of Renewable Energy 2014 (2014)

Gong Jian and Fengqi You Optimal design and synthesis of algal biorefinery processes for biological carbon sequestration and utilization with zero direct greenhouse gas emissions Industrial amp Engineering Chemistry Research(2014)

Zhao Bingtao and Yaxin Su Process effect of microalgal-carbon dioxide fixation and biomass production A review Renewable and Sustainable Energy Reviews 31 (2014) 121-132

Kaewpanha Malinee et al Steam co-gasification of brown seaweed and land-based biomass Fuel Processing Technology 120 (2014) 106-112

Yakaboylu Onursal et al Supercritical Water Gasification of Biomass A Thermodynamic Model for the Prediction of Product Compounds at Equilibrium State Energy amp Fuels (2014)

7

Appendix

Figure 1 Experimental Flow Diagram comparing algae and commercial wood mix

8

Figure 2 Structure of Chlorella (less than 38 μm) mdash (a) raw (b) char obtained from TGA(left)

Figure 3 Structure of commercial wood mix (less than 38 μm) mdash (a) raw (b) char obtained from TGA(right)

Figure

4

Structu

re of Chlorella (150ndash250 μm) mdash (a) raw (b) char obtained from EFR (left)Figure 5 Structure of commercial wood mix (150ndash250 μm) mdash (a) raw (b) char obtained

from EFR (right)

9

Figure 6 Gasification characteristics of different types of char at 800 degC mdash (a) weight loss in 20 CO2 (b) weight loss in 20 steam (c) reactivity in 20 CO2 and (d) reactivity in

20 steam

10

Figure 7 Elemental compositions of the macroalgae

Figure 8 Experimental conditions and results for the hydrothermal gasification of macroalgae samples Tend = 500deg C Pend = 236-281 Holding time = 30 min Feed concentration = 666 wt 5 RuAl2O3 catalyst

Figure 9 Gas composition and yields of from supercritical gasification of S latissima Tend = 500deg C Pend = 236-281 Holding time = 30 min Feed concentration = 666 wt 5

RuAl2O3 catalyst

Figure 10 Gas composition and yields of from supercritical gasification of macroalgae Tend = 500deg C Pend = 236-281 Holding time = 30 min Feed concentration = 666 wt

5 RuAl2O3 catalyst

11

Figure 11 Nutrients and important metals in ppm from the process water of SCWG of S latissima Tend=500deg C Pend=236ndash281 bar Holding time=30 min Feed conc

5666 wt 5 RuAl2O3 catalyst compared with standard growth medium BBM

Figure 12 C vulgaris concentration (mgL) following 14-day cultivation in bioreactors Process water and dilutions SCWG of S latissima without catalyst (WC) with catalyst

(C)

12

Figure 13 Ternary diagram with different types of microalgae according to their maincomponents (lipid protein and carbohydrates)

Figure 14 The effect of temperature and pressure on the supercritical gasification of microalgae

13

Figure 15 The effect of temperature and dry matter content on the supercritical gasification of microalgae

Equations used for the creation of the Multiphase Thermodynamic Equilibrium Model to predict the behavior of gases and elements during supercritical gasification

Total Gibbs Free Energy

Chemical Potential based on Fugacity Coefficients

14

Peng-Robinson Equation of State

DebyeminusHuumlckel equations for molality based calculations in the model

15

The Equations of the Parameters of the DebyeminusHuumlckel equations

16

17

Equations used for the Activity of Water

Equations for the Aqueous Solution in Supercritical Region

18

19

3

References

Geraili A P Sharma and J A Romagnoli A modeling framework for design of nonlinear renewable energy systems through integrated simulation modeling and metaheuristic optimization Applications to biorefineries Computers amp Chemical Engineering 61 (2014) 102-117

Savage Phillip E and Jamie A Hestekin A perspective on algae the environment and energy Environmental Progress amp Sustainable Energy 324 (2013) 877-883

Ghorbani Afshin et al A Review of Carbon Capture and Sequestration in Iran Microalgal Biofixation Potential in Iran Renewable and Sustainable Energy Reviews 35 (2014) 73-100

Onwudili Jude A et al Catalytic hydrothermal gasification of algae for hydrogen production Composition of reaction products and potential for nutrient recycling Bioresource technology 127 (2013) 72-80

Du Yuying et al Cogasification of Biofermenting Residue in a Coal-Water Slurry Gasifier Energy amp Fuels 283 (2014) 2054-2058

Lane Daniel J et al Combustion Behavior of Algal Biomass Carbon Release Nitrogen Release and Char Reactivity Energy amp Fuels (2013)

Kirtania Kawnish et al Comparison of COlt subgt 2ltsubgt and steam gasification reactivity of algal and woody biomass chars Fuel Processing Technology 117 (2014) 44-52

Bagnoud-Velaacutesquez Mariluz et al Continuous catalytic hydrothermal gasification of algal biomass and case study on toxicity of aluminum as a step toward effluents recycling Catalysis Today 223 (2014) 35-43

Molino A M Migliori and F Nanna Glucose gasification in near critical water conditions for both syngas production and green chemicals with a continuous process Fuel 115 (2014) 41-45

Bai Xiujun et al Hydrothermal catalytic processing of pretreated algal oil A catalyst screening study Fuel 120 (2014) 141-149

Davis Ryan et al Integrated Evaluation of Cost Emissions and Resource Potential for Algal Biofuels at the National Scale Environmental science amp technology (2014)

Loacutepez-Gonzaacutelez D et al Kinetic analysis and thermal characterization of the microalgae combustion process by thermal analysis coupled to mass spectrometry Applied Energy 114 (2014) 227-237

6

Orfield Nolan D et al Life cycle design of an algal biorefinery featuring hydrothermal liquefaction effect of reaction conditions and an alternative pathway including microbial regrowth ACS Sustainable Chemistry amp Engineering 24 (2014) 867-874

Cherad Ramzi et al Macroalgae supercritical water gasification combined with nutrient recycling for microalgae cultivation Environmental Progress amp Sustainable Energy 324 (2013) 902-909

Jegathese Simon Jegan Porphy and Mohammed Farid Microalgae as a Renewable Source of Energy A Niche Opportunity Journal of Renewable Energy 2014 (2014)

Gong Jian and Fengqi You Optimal design and synthesis of algal biorefinery processes for biological carbon sequestration and utilization with zero direct greenhouse gas emissions Industrial amp Engineering Chemistry Research(2014)

Zhao Bingtao and Yaxin Su Process effect of microalgal-carbon dioxide fixation and biomass production A review Renewable and Sustainable Energy Reviews 31 (2014) 121-132

Kaewpanha Malinee et al Steam co-gasification of brown seaweed and land-based biomass Fuel Processing Technology 120 (2014) 106-112

Yakaboylu Onursal et al Supercritical Water Gasification of Biomass A Thermodynamic Model for the Prediction of Product Compounds at Equilibrium State Energy amp Fuels (2014)

7

Appendix

Figure 1 Experimental Flow Diagram comparing algae and commercial wood mix

8

Figure 2 Structure of Chlorella (less than 38 μm) mdash (a) raw (b) char obtained from TGA(left)

Figure 3 Structure of commercial wood mix (less than 38 μm) mdash (a) raw (b) char obtained from TGA(right)

Figure

4

Structu

re of Chlorella (150ndash250 μm) mdash (a) raw (b) char obtained from EFR (left)Figure 5 Structure of commercial wood mix (150ndash250 μm) mdash (a) raw (b) char obtained

from EFR (right)

9

Figure 6 Gasification characteristics of different types of char at 800 degC mdash (a) weight loss in 20 CO2 (b) weight loss in 20 steam (c) reactivity in 20 CO2 and (d) reactivity in

20 steam

10

Figure 7 Elemental compositions of the macroalgae

Figure 8 Experimental conditions and results for the hydrothermal gasification of macroalgae samples Tend = 500deg C Pend = 236-281 Holding time = 30 min Feed concentration = 666 wt 5 RuAl2O3 catalyst

Figure 9 Gas composition and yields of from supercritical gasification of S latissima Tend = 500deg C Pend = 236-281 Holding time = 30 min Feed concentration = 666 wt 5

RuAl2O3 catalyst

Figure 10 Gas composition and yields of from supercritical gasification of macroalgae Tend = 500deg C Pend = 236-281 Holding time = 30 min Feed concentration = 666 wt

5 RuAl2O3 catalyst

11

Figure 11 Nutrients and important metals in ppm from the process water of SCWG of S latissima Tend=500deg C Pend=236ndash281 bar Holding time=30 min Feed conc

5666 wt 5 RuAl2O3 catalyst compared with standard growth medium BBM

Figure 12 C vulgaris concentration (mgL) following 14-day cultivation in bioreactors Process water and dilutions SCWG of S latissima without catalyst (WC) with catalyst

(C)

12

Figure 13 Ternary diagram with different types of microalgae according to their maincomponents (lipid protein and carbohydrates)

Figure 14 The effect of temperature and pressure on the supercritical gasification of microalgae

13

Figure 15 The effect of temperature and dry matter content on the supercritical gasification of microalgae

Equations used for the creation of the Multiphase Thermodynamic Equilibrium Model to predict the behavior of gases and elements during supercritical gasification

Total Gibbs Free Energy

Chemical Potential based on Fugacity Coefficients

14

Peng-Robinson Equation of State

DebyeminusHuumlckel equations for molality based calculations in the model

15

The Equations of the Parameters of the DebyeminusHuumlckel equations

16

17

Equations used for the Activity of Water

Equations for the Aqueous Solution in Supercritical Region

18

19

3

Orfield Nolan D et al Life cycle design of an algal biorefinery featuring hydrothermal liquefaction effect of reaction conditions and an alternative pathway including microbial regrowth ACS Sustainable Chemistry amp Engineering 24 (2014) 867-874

Cherad Ramzi et al Macroalgae supercritical water gasification combined with nutrient recycling for microalgae cultivation Environmental Progress amp Sustainable Energy 324 (2013) 902-909

Jegathese Simon Jegan Porphy and Mohammed Farid Microalgae as a Renewable Source of Energy A Niche Opportunity Journal of Renewable Energy 2014 (2014)

Gong Jian and Fengqi You Optimal design and synthesis of algal biorefinery processes for biological carbon sequestration and utilization with zero direct greenhouse gas emissions Industrial amp Engineering Chemistry Research(2014)

Zhao Bingtao and Yaxin Su Process effect of microalgal-carbon dioxide fixation and biomass production A review Renewable and Sustainable Energy Reviews 31 (2014) 121-132

Kaewpanha Malinee et al Steam co-gasification of brown seaweed and land-based biomass Fuel Processing Technology 120 (2014) 106-112

Yakaboylu Onursal et al Supercritical Water Gasification of Biomass A Thermodynamic Model for the Prediction of Product Compounds at Equilibrium State Energy amp Fuels (2014)

7

Appendix

Figure 1 Experimental Flow Diagram comparing algae and commercial wood mix

8

Figure 2 Structure of Chlorella (less than 38 μm) mdash (a) raw (b) char obtained from TGA(left)

Figure 3 Structure of commercial wood mix (less than 38 μm) mdash (a) raw (b) char obtained from TGA(right)

Figure

4

Structu

re of Chlorella (150ndash250 μm) mdash (a) raw (b) char obtained from EFR (left)Figure 5 Structure of commercial wood mix (150ndash250 μm) mdash (a) raw (b) char obtained

from EFR (right)

9

Figure 6 Gasification characteristics of different types of char at 800 degC mdash (a) weight loss in 20 CO2 (b) weight loss in 20 steam (c) reactivity in 20 CO2 and (d) reactivity in

20 steam

10

Figure 7 Elemental compositions of the macroalgae

Figure 8 Experimental conditions and results for the hydrothermal gasification of macroalgae samples Tend = 500deg C Pend = 236-281 Holding time = 30 min Feed concentration = 666 wt 5 RuAl2O3 catalyst

Figure 9 Gas composition and yields of from supercritical gasification of S latissima Tend = 500deg C Pend = 236-281 Holding time = 30 min Feed concentration = 666 wt 5

RuAl2O3 catalyst

Figure 10 Gas composition and yields of from supercritical gasification of macroalgae Tend = 500deg C Pend = 236-281 Holding time = 30 min Feed concentration = 666 wt

5 RuAl2O3 catalyst

11

Figure 11 Nutrients and important metals in ppm from the process water of SCWG of S latissima Tend=500deg C Pend=236ndash281 bar Holding time=30 min Feed conc

5666 wt 5 RuAl2O3 catalyst compared with standard growth medium BBM

Figure 12 C vulgaris concentration (mgL) following 14-day cultivation in bioreactors Process water and dilutions SCWG of S latissima without catalyst (WC) with catalyst

(C)

12

Figure 13 Ternary diagram with different types of microalgae according to their maincomponents (lipid protein and carbohydrates)

Figure 14 The effect of temperature and pressure on the supercritical gasification of microalgae

13

Figure 15 The effect of temperature and dry matter content on the supercritical gasification of microalgae

Equations used for the creation of the Multiphase Thermodynamic Equilibrium Model to predict the behavior of gases and elements during supercritical gasification

Total Gibbs Free Energy

Chemical Potential based on Fugacity Coefficients

14

Peng-Robinson Equation of State

DebyeminusHuumlckel equations for molality based calculations in the model

15

The Equations of the Parameters of the DebyeminusHuumlckel equations

16

17

Equations used for the Activity of Water

Equations for the Aqueous Solution in Supercritical Region

18

19

3

Appendix

Figure 1 Experimental Flow Diagram comparing algae and commercial wood mix

8

Figure 2 Structure of Chlorella (less than 38 μm) mdash (a) raw (b) char obtained from TGA(left)

Figure 3 Structure of commercial wood mix (less than 38 μm) mdash (a) raw (b) char obtained from TGA(right)

Figure

4

Structu

re of Chlorella (150ndash250 μm) mdash (a) raw (b) char obtained from EFR (left)Figure 5 Structure of commercial wood mix (150ndash250 μm) mdash (a) raw (b) char obtained

from EFR (right)

9

Figure 6 Gasification characteristics of different types of char at 800 degC mdash (a) weight loss in 20 CO2 (b) weight loss in 20 steam (c) reactivity in 20 CO2 and (d) reactivity in

20 steam

10

Figure 7 Elemental compositions of the macroalgae

Figure 8 Experimental conditions and results for the hydrothermal gasification of macroalgae samples Tend = 500deg C Pend = 236-281 Holding time = 30 min Feed concentration = 666 wt 5 RuAl2O3 catalyst

Figure 9 Gas composition and yields of from supercritical gasification of S latissima Tend = 500deg C Pend = 236-281 Holding time = 30 min Feed concentration = 666 wt 5

RuAl2O3 catalyst

Figure 10 Gas composition and yields of from supercritical gasification of macroalgae Tend = 500deg C Pend = 236-281 Holding time = 30 min Feed concentration = 666 wt

5 RuAl2O3 catalyst

11

Figure 11 Nutrients and important metals in ppm from the process water of SCWG of S latissima Tend=500deg C Pend=236ndash281 bar Holding time=30 min Feed conc

5666 wt 5 RuAl2O3 catalyst compared with standard growth medium BBM

Figure 12 C vulgaris concentration (mgL) following 14-day cultivation in bioreactors Process water and dilutions SCWG of S latissima without catalyst (WC) with catalyst

(C)

12

Figure 13 Ternary diagram with different types of microalgae according to their maincomponents (lipid protein and carbohydrates)

Figure 14 The effect of temperature and pressure on the supercritical gasification of microalgae

13

Figure 15 The effect of temperature and dry matter content on the supercritical gasification of microalgae

Equations used for the creation of the Multiphase Thermodynamic Equilibrium Model to predict the behavior of gases and elements during supercritical gasification

Total Gibbs Free Energy

Chemical Potential based on Fugacity Coefficients

14

Peng-Robinson Equation of State

DebyeminusHuumlckel equations for molality based calculations in the model

15

The Equations of the Parameters of the DebyeminusHuumlckel equations

16

17

Equations used for the Activity of Water

Equations for the Aqueous Solution in Supercritical Region

18

19

3

Figure 2 Structure of Chlorella (less than 38 μm) mdash (a) raw (b) char obtained from TGA(left)

Figure 3 Structure of commercial wood mix (less than 38 μm) mdash (a) raw (b) char obtained from TGA(right)

Figure

4

Structu

re of Chlorella (150ndash250 μm) mdash (a) raw (b) char obtained from EFR (left)Figure 5 Structure of commercial wood mix (150ndash250 μm) mdash (a) raw (b) char obtained

from EFR (right)

9

Figure 6 Gasification characteristics of different types of char at 800 degC mdash (a) weight loss in 20 CO2 (b) weight loss in 20 steam (c) reactivity in 20 CO2 and (d) reactivity in

20 steam

10

Figure 7 Elemental compositions of the macroalgae

Figure 8 Experimental conditions and results for the hydrothermal gasification of macroalgae samples Tend = 500deg C Pend = 236-281 Holding time = 30 min Feed concentration = 666 wt 5 RuAl2O3 catalyst

Figure 9 Gas composition and yields of from supercritical gasification of S latissima Tend = 500deg C Pend = 236-281 Holding time = 30 min Feed concentration = 666 wt 5

RuAl2O3 catalyst

Figure 10 Gas composition and yields of from supercritical gasification of macroalgae Tend = 500deg C Pend = 236-281 Holding time = 30 min Feed concentration = 666 wt

5 RuAl2O3 catalyst

11

Figure 11 Nutrients and important metals in ppm from the process water of SCWG of S latissima Tend=500deg C Pend=236ndash281 bar Holding time=30 min Feed conc

5666 wt 5 RuAl2O3 catalyst compared with standard growth medium BBM

Figure 12 C vulgaris concentration (mgL) following 14-day cultivation in bioreactors Process water and dilutions SCWG of S latissima without catalyst (WC) with catalyst

(C)

12

Figure 13 Ternary diagram with different types of microalgae according to their maincomponents (lipid protein and carbohydrates)

Figure 14 The effect of temperature and pressure on the supercritical gasification of microalgae

13

Figure 15 The effect of temperature and dry matter content on the supercritical gasification of microalgae

Equations used for the creation of the Multiphase Thermodynamic Equilibrium Model to predict the behavior of gases and elements during supercritical gasification

Total Gibbs Free Energy

Chemical Potential based on Fugacity Coefficients

14

Peng-Robinson Equation of State

DebyeminusHuumlckel equations for molality based calculations in the model

15

The Equations of the Parameters of the DebyeminusHuumlckel equations

16

17

Equations used for the Activity of Water

Equations for the Aqueous Solution in Supercritical Region

18

19

3

Figure 6 Gasification characteristics of different types of char at 800 degC mdash (a) weight loss in 20 CO2 (b) weight loss in 20 steam (c) reactivity in 20 CO2 and (d) reactivity in

20 steam

10

Figure 7 Elemental compositions of the macroalgae

Figure 8 Experimental conditions and results for the hydrothermal gasification of macroalgae samples Tend = 500deg C Pend = 236-281 Holding time = 30 min Feed concentration = 666 wt 5 RuAl2O3 catalyst

Figure 9 Gas composition and yields of from supercritical gasification of S latissima Tend = 500deg C Pend = 236-281 Holding time = 30 min Feed concentration = 666 wt 5

RuAl2O3 catalyst

Figure 10 Gas composition and yields of from supercritical gasification of macroalgae Tend = 500deg C Pend = 236-281 Holding time = 30 min Feed concentration = 666 wt

5 RuAl2O3 catalyst

11

Figure 11 Nutrients and important metals in ppm from the process water of SCWG of S latissima Tend=500deg C Pend=236ndash281 bar Holding time=30 min Feed conc

5666 wt 5 RuAl2O3 catalyst compared with standard growth medium BBM

Figure 12 C vulgaris concentration (mgL) following 14-day cultivation in bioreactors Process water and dilutions SCWG of S latissima without catalyst (WC) with catalyst

(C)

12

Figure 13 Ternary diagram with different types of microalgae according to their maincomponents (lipid protein and carbohydrates)

Figure 14 The effect of temperature and pressure on the supercritical gasification of microalgae

13

Figure 15 The effect of temperature and dry matter content on the supercritical gasification of microalgae

Equations used for the creation of the Multiphase Thermodynamic Equilibrium Model to predict the behavior of gases and elements during supercritical gasification

Total Gibbs Free Energy

Chemical Potential based on Fugacity Coefficients

14

Peng-Robinson Equation of State

DebyeminusHuumlckel equations for molality based calculations in the model

15

The Equations of the Parameters of the DebyeminusHuumlckel equations

16

17

Equations used for the Activity of Water

Equations for the Aqueous Solution in Supercritical Region

18

19

3

Figure 7 Elemental compositions of the macroalgae

Figure 8 Experimental conditions and results for the hydrothermal gasification of macroalgae samples Tend = 500deg C Pend = 236-281 Holding time = 30 min Feed concentration = 666 wt 5 RuAl2O3 catalyst

Figure 9 Gas composition and yields of from supercritical gasification of S latissima Tend = 500deg C Pend = 236-281 Holding time = 30 min Feed concentration = 666 wt 5

RuAl2O3 catalyst

Figure 10 Gas composition and yields of from supercritical gasification of macroalgae Tend = 500deg C Pend = 236-281 Holding time = 30 min Feed concentration = 666 wt

5 RuAl2O3 catalyst

11

Figure 11 Nutrients and important metals in ppm from the process water of SCWG of S latissima Tend=500deg C Pend=236ndash281 bar Holding time=30 min Feed conc

5666 wt 5 RuAl2O3 catalyst compared with standard growth medium BBM

Figure 12 C vulgaris concentration (mgL) following 14-day cultivation in bioreactors Process water and dilutions SCWG of S latissima without catalyst (WC) with catalyst

(C)

12

Figure 13 Ternary diagram with different types of microalgae according to their maincomponents (lipid protein and carbohydrates)

Figure 14 The effect of temperature and pressure on the supercritical gasification of microalgae

13

Figure 15 The effect of temperature and dry matter content on the supercritical gasification of microalgae

Equations used for the creation of the Multiphase Thermodynamic Equilibrium Model to predict the behavior of gases and elements during supercritical gasification

Total Gibbs Free Energy

Chemical Potential based on Fugacity Coefficients

14

Peng-Robinson Equation of State

DebyeminusHuumlckel equations for molality based calculations in the model

15

The Equations of the Parameters of the DebyeminusHuumlckel equations

16

17

Equations used for the Activity of Water

Equations for the Aqueous Solution in Supercritical Region

18

19

3

Figure 11 Nutrients and important metals in ppm from the process water of SCWG of S latissima Tend=500deg C Pend=236ndash281 bar Holding time=30 min Feed conc

5666 wt 5 RuAl2O3 catalyst compared with standard growth medium BBM

Figure 12 C vulgaris concentration (mgL) following 14-day cultivation in bioreactors Process water and dilutions SCWG of S latissima without catalyst (WC) with catalyst

(C)

12

Figure 13 Ternary diagram with different types of microalgae according to their maincomponents (lipid protein and carbohydrates)

Figure 14 The effect of temperature and pressure on the supercritical gasification of microalgae

13

Figure 15 The effect of temperature and dry matter content on the supercritical gasification of microalgae

Equations used for the creation of the Multiphase Thermodynamic Equilibrium Model to predict the behavior of gases and elements during supercritical gasification

Total Gibbs Free Energy

Chemical Potential based on Fugacity Coefficients

14

Peng-Robinson Equation of State

DebyeminusHuumlckel equations for molality based calculations in the model

15

The Equations of the Parameters of the DebyeminusHuumlckel equations

16

17

Equations used for the Activity of Water

Equations for the Aqueous Solution in Supercritical Region

18

19

3

Figure 13 Ternary diagram with different types of microalgae according to their maincomponents (lipid protein and carbohydrates)

Figure 14 The effect of temperature and pressure on the supercritical gasification of microalgae

13

Figure 15 The effect of temperature and dry matter content on the supercritical gasification of microalgae

Equations used for the creation of the Multiphase Thermodynamic Equilibrium Model to predict the behavior of gases and elements during supercritical gasification

Total Gibbs Free Energy

Chemical Potential based on Fugacity Coefficients

14

Peng-Robinson Equation of State

DebyeminusHuumlckel equations for molality based calculations in the model

15

The Equations of the Parameters of the DebyeminusHuumlckel equations

16

17

Equations used for the Activity of Water

Equations for the Aqueous Solution in Supercritical Region

18

19

3

Figure 15 The effect of temperature and dry matter content on the supercritical gasification of microalgae

Equations used for the creation of the Multiphase Thermodynamic Equilibrium Model to predict the behavior of gases and elements during supercritical gasification

Total Gibbs Free Energy

Chemical Potential based on Fugacity Coefficients

14

Peng-Robinson Equation of State

DebyeminusHuumlckel equations for molality based calculations in the model

15

The Equations of the Parameters of the DebyeminusHuumlckel equations

16

17

Equations used for the Activity of Water

Equations for the Aqueous Solution in Supercritical Region

18

19

3

Peng-Robinson Equation of State

DebyeminusHuumlckel equations for molality based calculations in the model

15

The Equations of the Parameters of the DebyeminusHuumlckel equations

16

17

Equations used for the Activity of Water

Equations for the Aqueous Solution in Supercritical Region

18

19

3

The Equations of the Parameters of the DebyeminusHuumlckel equations

16

17

Equations used for the Activity of Water

Equations for the Aqueous Solution in Supercritical Region

18

19

3

17

Equations used for the Activity of Water

Equations for the Aqueous Solution in Supercritical Region

18

19

3

Equations used for the Activity of Water

Equations for the Aqueous Solution in Supercritical Region

18

19

3

19

3

3