Current and potential uses of thermally treated olive …htgomes/FCT115275/Ref10.pdf · Current and...

Original article

Current and potential uses of thermally treated olive oil waste

Ioannis S. Arvanitoyannis,1* Aikaterini Kassaveti2 & Stelios Stefanatos3

1 Department of Agriculture Animal Production and Aquatic Environment, School of Agricultural Sciences, University of Thessaly, Fytokou

Street, 38446 Nea Ionia Magnesias, Volos, Greece

2 Department of Agriculture Crop Production and Agricultural Environment, School of Agricultural Sciences, University of Thessaly, Fytokou

Street, 38446 Nea Ionia Magnesias, Volos, Greece

3 IVP Consulting, Lixourion 3, Anthoussa 15349, Athens, Greece

(Received 27 November 2005; Accepted in revised form 19 April 2006)

Summary The ongoing stricter policy rules on environmental issues, recent changes in consumer towards the

environmental effects of food production, and even stricter regulations voted by the European Union

towards reduction of the use of natural resources initiated a great amount of research towards improving the

thermal waste treatment methodology. The olive oil industry continues to be one of the most heavily

polluting ones among the food industries. Along this line, various thermal processes, such as pyrolysis,

combustion and gasification, were investigated. Another crucial issue is the fate of treated waste. This review,

apart from the presentation of various thermal treatment waste methodologies summarises the uses (either

currently ongoing or having potential in the future): biodiesel, activated carbon and briquette production.

Ten figures and four tables illustrated in this article provide comprehensive idea of the waste treatment

methodologies, their effectiveness and uses of thermally waste treated olive materials.

Keywords Activated carbon, biodiesel, briquette production, combustion, gasification, olive oil waste, pyrolysis.

Introduction

Strong public pressure in Europe and the United Stateshas pushed companies towards the awareness thatconsumers are strongly interested in the interactions ofbusiness operations with the environment. This trend, inconjunction with a steadily growing number of regula-tory requirements, has convinced companies to developtheir own environmental management systems (EMSs).An EMS considers a company’s organisation through athorough review of operations and analyses how theactions of a company affect environmental issues (Beg-ley, 1996). Organisations contemplating the implemen-tation of ISO 14000 have to evaluate the impact an EMSis anticipated to have on its internal structure and itsability to meet external expectations (Boudouropoulos& Arvanitoyannis, 1999).There are two main EMSs: the ISOs (International

Organization for Standardization) ISO 14000 and theEuropean Union’s Eco-Management and AuditScheme. The EMS is not prescriptive because it doesnot specify how environmental targets should be met –but rather provides a framework in which organisationscan examine their practices and then determines how

these can be more effectively managed (Boudouropoulos& Arvanitoyannis, 2000; http://www.chinacp.com/eng/cp_tools.html).Life-cycle assessment (LCA) is a process of evaluating

the effects that a product has on the environment overthe entire period of its life, thereby increasing resource-use efficiency and decreasing liabilities. It can be used tostudy the environmental impact of either a product orthe function the product is designed to perform (http://www.agrifood-forum.net/practices/lca.asp). Most LCAmeasurements are made by summing the amount ofenergy consumed in the extraction of raw materials,transport, manufacture, distribution and final disposalof a product or service and emissions to air, land orwater resulting from the creation and disposal of theproduct or service. LCA is also used to identify pointswithin a product’s life cycle where the greatest reductionin resource requirements and emissions can be achieved.(Gibson, 1997; http://www.chinacp.com/eng/cptools/cpt_lca.html).Olive (Olea europaea) is an evergreen tree traditionally

cultivated for olive oil and table fruit consumption.Although olive trees are distributed over all continents,97% of the world production of olive oil is concentratedin the Mediterranean Basin countries: Spain, Portugal,Italy, Greece, Turkey, Tunisia and Morocco (Lopez-Villalta, 1998). The production of olive oil in the

*Correspondent: Fax: +30 2421093137;

e-mail: [email protected]

International Journal of Food Science and Technology 2007, 42, 852–867852

doi:10.1111/j.1365-2621.2006.01296.x

� 2007 The Authors. Journal compilation � 2007 Institute of Food Science and Technology Trust Fund

European Union (EU), being Spain, Greece and Italythe three main producers, amounts to about 80% of theworld production. Spain produces more than 30% ofthe world’s total production (Bas et al., 2001). However,the olive oil industry is characterised by its greatenvironmental impact because of the production of ahighly polluted wastewater and/or a solid residue, oliveskin and stone (olive husk), depending on the olive oilextraction process (Baeta-Hall et al., 2005).Olive waste contains up to 60% water and high

concentrations of sugars, pectin, salts, acids, polyalcoh-ols and polyphenols (Borja et al., 2002). Olive millwastewater (OMW) is the main waste produced by thethree-phase extraction process of olive oil (Aktas et al.,2001). Approximately, 10 million m3 of OMW areannually produced in the Mediterranean region (FiestasRos De Ursinos & Borja-Padilla, 1996). Over the last20 years, several processes were introduced in anattempt to reduce the pollutant load of OMW (Peredeset al., 1987; Vassilev et al., 1997a,b; Kiritsakis et al.,1998) based on evaporation ponds, thermal concentra-tion and different physicochemical and biological treat-ments (Fig. 1).Olive oil residue is a renewable source of energy, with

a relatively high heating value – around 18 MJ kg)1

(IDAE, 2001). It can be effectively used in thermochem-ical conversion technologies, such as combustion, gasi-fication and pyrolysis, which use elevated temperaturesto convert the energy content of biofuel materials.During thermochemical conversion, the thermal degra-dation of the various components (cellulose, hemicellu-lose and lignin) of the organic fuel materials occurs. Fullunderstanding of the biofuel properties and its therm-ochemical behaviour are thus essential for the properdesign of thermochemical conversion systems (Mansaray& Ghaly, 1997; Lipska-Quinn et al., 1985).

Treatment methodology

The primary aim of waste legislation is the prevention ofwaste generation. Waste prevention refers to three typesof practical actions, i.e. strict avoidance, reduction atsource and product reuse. According to EuropeanEnvironmental Agency, waste minimisation can takeplace by means of the following methods: prevention,reduction at source, reuse of products for same orother purpose, on- or off-site recycling, source- orwaste-oriented waste quality and energy recovery(i.e. pyrolysis, combustion and gasification) (Riemer &Kristoffersen, 1999).

Olives Leafremoval

Leaves

Crushing

Mixing

Composting Soilamendment

Carbon dioxideand humidity

emmisions

WashingStone

removal

Stones

Washing Crushing-milling

Pastemalaxation

3-phase centrifugationVirgin oliveoil for directconsumption

Olivepomace

Oil extractionwith ethanol

Crudeantioxidants

Wastewater

Coagulation-Flocculation

Chemicaloxidation

Biologicaltreatment

Reed beds

Treatedwastewater for

irrigation

Harvestingplants

Burning

Chemicalsludge

Biologicalsludge

Olive oil to refining

Biogas

H2O2

FeSO4

Water

Figure 1 An integrated pollution prevention method for olive oil processing (adapted from Vlyssides et al., 2004; http://www.rirdc.gov.au/reports/

npp/00-187.pdf; http://www.laggonsonline.com/reedbebs.htm).

Uses of thermally treated olive oil waste I. S. Arvanitoyannis et al. 853

� 2007 The Authors. Journal compilation � 2007 Institute of Food Science and Technology Trust Fund International Journal of Food Science and Technology 2007

The preferred option concerning waste management,reflecting the EC waste hierarchy, is prevention andminimisation, followed by reuse, recycling and biologi-cal treatment, energy recovery and environmentallysound disposal, either by thermal treatment (withoutenergy recovery) or by landfill. Under this hierarchy,landfill should be a last resort after all the higher optionshave been exhausted (Department of the Environmentand Local Government, 2002). A key point concerningthis strategy is that irrespective of the amount of sourcereduction within an economy, there can never be a ‘zero’waste situation. The planned increased use of inciner-ation as a waste management strategy has howeverraised concerns about the generation and emission ofsubstances that are harmful to the environment and tohuman health, including the polychlorinated dibenzo-p-dioxins (dioxins) and the polychlorinated dibenzofurans(furans) (http://www.fsai.ie/publications/reports/waste_incineration.pdf).

Thermal processes

Since the 1970’s oil price crisis, increased interest wasdisplayed on the development of technologies using newand renewable sources of energy like biomass, geother-mal, solar power, wind and hydropower (Demirbas,2005). Moreover, because of the increase in worldpopulation and industries, acceptance of any new sourceof energy must be associated with its impact on theenvironment. Nowadays, various forms of biomassenergy are consumed all over the world. Bioenergy doesnot affect the climate change through emissions ofcarbon dioxide or other ‘green house gases’ to theatmosphere (Zanzi et al., 2002; Minowa et al., 1998;Demirbas et al., 2000). Biomass used for energy pro-duction occupies a special place among renewableenergy sources and is estimated to contribute 10–14%of the world’s total energy supply. Biomass energy canbe effectively used to generate electricity, and heat, oreconomically competitive liquid transportation fuels formotor vehicles (Bridgewater & Grassi, 1991; Chum &Overend, 2001; McKendry, 2002). Fernandez-Bolanoset al. (2002) pretreated alperujo, a wet solid waste fromthe three-phase decanters and presses, by adding acidic(H2SO4) and alkaline (NaOH) catalysts to this wasteand feed it in a flash hydrolysis laboratory pilot unit,where it was treated by steam in order to produce highlypurified hydroxytyrosol. Of 1000 kg of alperujo (70%humidity), 4.5–5 kg of hydroxytyrosol was produced,and after the purification process, using a new chroma-tographic system, 3 kg of hydroxytyrosol (90–95%purity) was obtained. Hydroxytyrosol displayed strongantioxidant properties in accelerated oxidation condi-tions.Agricultural residues were estimated to have a high

potential for the development of bioenergy industries in

numerous countries; in Europe alone, about 250 mt perannum is available (Di Blasi et al., 1997). Among theagricultural residue straws, nutshells, fruit shells, fruitseeds, plant stalks, stovers, green leaves and molasseswere shown to stand for renewable energy resources ofadded value (Zhang & Zhang, 1999). Biomass thermo-chemical conversion technologies, such as pyrolysis,gasification and combustion, are currently being usedfor the world’s bioenergy production.

PyrolysisPyrolysis offers efficient utilisation of biomass, which isof particular importance for agricultural countries withvastly available biomass by-products (Minkova et al.,2000). Pyrolysis is the thermochemical process thatconverts biomass into liquid (bio-oil or bio-crude),charcoal and non-condensable gases, acetic acid, acet-one and methanol by heating the biomass to about 450–550 �C in the absence of air (Demirbas & Gullu, 1998;Demirbas, 1998; http://www.pubs.acs.org/cgi-bin/abstract.cgi/iecred/asap/abs/ie050486y.html). The solid product(char) obtained from pyrolysis usually has a porousstructure and a surface area that is appropriate to use asactive carbon. The liquids obtained from pyrolysiscontain many chemical compounds that can be used asfeedstock for synthesis of fine chemicals, adhesives;fertilisers, etc. (Meier & Faix, 1999). The third productgas having a high calorific value may also be used as afuel (Bridgewater & Grassi, 1991; Williams & Besler,1993; Encinar et al., 2000) (Fig. 2).The effect of burned olive waste on soil properties

(unconfined compressive strength, swelling pressure andmaximum dry density) was studied by Attom &Al-Sharif (1998). The solid olive waste was burned at550 �C and then mixed with four soil samples withdifferent plastic index at four different percentages(0.0%, 2.5%, 5.0%, 7.5% w/w). The results showedthat the burned olive waste reduced the soil plasticity,especially when the plastic index was high. An additionof 2.5% of the burned olive waste by weight to soilresulted in an increase in the maximum dry density andthe unconfined compressive strength. However, employ-ment of higher percentages of burned olive waste led todecrease of both the maximum dry density and theunconfined compressive strength of the soil. The addi-tion of 7.5% of the olive ash by weight also decreasedthe soil-swelling pressure. It was concluded that theburned material can be effectively used as stabiliser, thusresolving many of the problems associated with itsaccumulation.Zabaniotou & Karabelas (1999) constructed a plant

for the pyrolysis of forestry biomass, and in particularArbutus unedo an evergreen broad-leaf tree in the area ofEvritania (Greece). Other agricultural wastes can also befed to this plant, among them are olive pits and cuttings.The pyrolysis was carried out in a laboratory ‘captive

Uses of thermally treated olive oil waste I. S. Arvanitoyannis et al.854

International Journal of Food Science and Technology 2007 � 2007 The Authors. Journal compilation � 2007 Institute of Food Science and Technology Trust Fund

sample’ reactor at 400–700 �C, with heating rates 120–165 �C s)1, at atmospheric pressure, under nitrogen.The pyrolysis products were pyrolytic gas, bio-oil andcharcoal. The calorific value of charcoal is similar tocommercial type, and via briquetting it can be furtherupgraded and distributed to the local market. In the caseof bio-oil, a highly oxygenated hydrocarbon mixture ofwater and organic acids, a further investigation for itsuse is required.Putun et al. (2005) pyrolysed olive residue in a

stainless steel fixed-bed reactor and three experimentswere carried out under different pyrolysis conditions.The first experiment was carried out under normalatmosphere and the final temperatures were in therange 400–700 �C; in the second, nitrogen was used asa sweeping gas with various flow rates 50–400 cm3 min)1; in the third steam was applied to theraw material with different air velocities (0.6–2.7 cm s)1). The pyrolysis products were char (Fig. 3),gas and a liquid (bio-oil), consisting of an aqueous

phase and an oil phase. The bio-oil productionincreased up to 19.13 wt% when the flow rate ofnitrogen was 100 cm3 min)1, the maximum bio-oil yieldwas reported when the olive residue was treated withsteam and the air velocity was 1.3 cm s)1, and oil yieldwas found to be 27.3% at final temperature 500 �C(Fig. 4). Char, gas and bio-oil can be effectively used asfuel, while the liquid product of pyrolysis can be addedto petroleum refinery feedstocks or upgraded bycatalysts to produce premium grade refined fuels, ormay have a potential as chemical feedstocks (Encinaret al., 2000; Williams & Besler, 1993; Bridgewater &Grassi, 1991).Olive bagasse is the solid residue obtained by pressing

the olives. Reuse of these residues could greatly reducepollution problems, as recovery of energy or valuablecompounds is possible with pyrolysis (Encinar et al.,1997). Olive bagasse with particle size 0.425–0.600 mmwas pyrolysed in a stainless steel tubular reactor with asweep gas (nitrogen), heating rates 10 or 50 �C min)1

and temperature at 350, 400, 450, 500 and 550 �C. The

Substrate preparation

Pyrolysis (550 ºC,no oxygen)

Cleaning (ifnecessary)

Gas separation

Possible residues /products

Power and/orheat

Cleaned gas

Start-up heat

Oil Char

Storage / Transport

Combustion in agas engine, gas

turbine or boilerFlue gas

Figure 2 The pyrolysis process (adapted from http://www.wastere-

search.co.uk/ade/efw/gassification.htm; http://www.esru.strath.ac.uk/

eande/web_sites/01-02/re_info/biomass.htm; http://www.intuser.net/6/

1/renew_37.php). * Flue gas: gas that exits to the atmosphere via a flue,

which is a pipe or channel for conveying exhaust gases for a fireplace,

furnace, boiler or generator (http://www.en.wikipedia.org/wiki/flue-

gas).

20

25

30

35

40

300 400 500 600 700 800 900 1000 1100Temperature (ºC)

Cha

r yi

eld

(%)

Olive residueOlive bagasse (heating rate 10 ºC/min)Olive bagasse (heating rate 50 ºC/min)Olive husk

Figure 3 Char yield of pyrolysis products at various pyrolysis tem-

peratures (adapted from Putun et al., 2005; Sensoz et al., 2005; Caglar

& Demirbas, 2002).

20

25

30

35

40

300 500 700 900 1100Temperature (ºC)

Bio

-oil

yiel

d (%

)

Olive residue

Olive bagasse (heating rate 10 ºC/min)

Olive bagasse (heating rate 50 ºC/min)

Olive husk

Figure 4 Bio-oil yield of pyrolysis products at various pyrolysis tem-

peratures (adapted from Putun et al., 2005; Sensoz et al., 2005; Caglar

& Demirbas, 2002).



obtained bio-oil was characterised by lower oxygencontent (21.9%) than that of the original feedstock(37.5%), presence of oxygenated fractions such ascarboxyl and carbonyl groups produced by pyrolysisof the cellulose and phenolic and methoxy groupsproduced by pyrolysis of the lignin. The bio-oil consis-ted of aromatic and aliphatic hydrocarbons, withheating value of 31.8 MJ kg)1 close to those of petro-leum fractions and was successfully used as a fuel andchemical feedstock (Sensoz et al., 2005).Vegetation water (VW), obtained from a traditional

extraction process and a continuous extraction system,was concentrated with evaporation. The condensedresidues with olive husk, coming from a traditionalextraction process, were both dried at 105 �C prior topyrolysis (200–550 �C). The final products were char(solid residue), tar (heavy organic fraction), a liquidphase (oil and water) and an uncondensed gaseousfraction (CO2, H2, CO, CH4, C2H6 from VW and CO2,H2, CO, CH4 from olive husk). The VW residues and theolive husk could be used as a fuel to provide heat in theevaporation stage (Vitolo et al., 1999).Olive husk samples were pyrolysed in a stainless steel

cylindrical reactor with or without the presence ofcatalysts, such as ZnCl2, Na2CO3 or K2CO3 at differenttemperatures (502, 577, 652, 702 and 752 �C). Apyrolytic gas (mixture of CO, CO2, olefins + O2,H2 + paraffin gases) was obtained and its yield in bothexperiments (with or without catalysts) enhanced withan increase in temperature. The highest hydrogen-richgas yield was 70.6% and was obtained using 13% ZnCl2at 752 �C, while hydrogen yields from the other catalystswere 62.9% and 62.6% by Na2CO3 and K2CO3,respectively. The hydrogen yield increased when ZnCl2was employed as catalyst, but the yield of pyrolytic gasdecreased when the yield of charcoal and liquid productsincreased. Hydrogen gas produced from olive husk bydirect catalytic pyrolysis can be used as fuel for internalcombustion engines in automobiles (Caglar & Demir-bas, 2002).

CombustionIncineration is the controlled burning of waste at hightemperatures. Combustion reduces the waste to 10% ofits original volume and 25% of its original weight. It isessential that incinerators operate at high temperatures,in the region of 800–900 �C (http://www.grc.cf.ac.uk/lrn/resources/waste/management/recovery/incineration.php; http://www.members.axion.net/�enrique/combus-tiontemperature.html) (Figs 5 and 6). Incineration is amethod widely used for the disposal of waste materialbut the problem with olive oil waste is that it contains upto 60% moisture and so is unable to sustain combustionwithout predrying. Another problem is that olive oilproduction is a seasonal activity, which means that if theincinerator is to be run throughout the year then other

fuels are also required (Cliffe & Patumsawad, 2001).Fluidised bed combustion has been shown to be aversatile technology capable of burning practically anywaste combination with low emissions (Anthony, 1995).Olive cake is a subproduct of the mechanical olive oil

extraction industry, which consists of pit and pulp of theolive fruit, olive oil and vegetable water (Akgun &Doymaz, 2005). The energy characteristics of theexhaust foot cake were investigated by Masghouni &Hassairi (2000). The solid waste was combusted in astatic furnace of a brick factory with an adapted burnerat 850 ± 10 �C, 570 Nm3 h)1 combustion airflow,23 �C combustion air temperature and 40% relativehumidity. The results suggested that the exhaust footcake can be used instead of heavy fuel No. 2 (http://www.dieselnet.com/standards/fuels/us.html), while thecost of the energy reduced up to 64%.The potential use of olive cake as a source of energy

was investigated by Alkhamis & Kablan (1999). Olivecake with initial moisture content 30% was dried in ageneral-purpose oven for 1 h at 105–110 �C, groundedin a mill for particle size reduction and mixed at differentpercentages, 0 ± 90%, weight with particles of oil shale.The results suggested that the olive cake can be used asan excellent source of renewable energy (average calor-ific value: 31.2 kJ g)1) and as a catalyst to oil shalecombustion because of the calorific value of the mixture(13.2–31.2 kJ g)1). In blends of high olive cake content(90 ± 100% olive cake), the occurring combustion was


Substrate

Boiler

Power and/orheat

Flue gas, residuesand ash

Oxidisersource

Start-up heat Hot gases

Steam

Engine or Turbine

Substrate combustion

Figure 5 The combustion process (adapted from http://www.esru.

strath.ac.uk/eande/web_sites/01-02/re_info/biomass.htm; http://

www.grc.nasa.gov/www/k-12/airplane/combst1.html).



complete, whereas in other samples of mixtures(10 ± 30% olive cake) combustion was not complete.It was therefore concluded that direct mixing of olivecake with oil shale without any further processing is notsuitable for direct combustion.Olive cake, a considerable waste of olive oil mill, can

be considered as alternative fuel, provided that nosulphur was present. Topal et al. (2003) burned olivecake and lignite coal in a circulating fluidised bed (CFB)at 900 �C under various excess air ratios (k ¼ 1.1–2.16)to investigate the combustion characteristics of thiswaste and compare them with coal. The analysis of fluegas showed that it contained O2, CO, CO2, SO2, NOx

and hydrocarbons. The combustion efficiency of olivecake ranged between 82.3% and 98.7%, while themaximum combustion efficiency of coal reached 98.3%.The calorific value of coal was 22 000 kJ kg)1, veryclose to the calorific value of olive cake. The ash formedduring the olive cake combustion contained Na2O, anon-harmful metal oxide, so can be used as fertiliser.

These results suggested that olive cake stand as apotential fuel that can be utilised for clean energyproduction in small-scale industries using CFB.Various mixtures of olive cake (25, 50 and 75 wt%)

and lignite coal were co-combusted at 700 �C in a CFBwith various excess air ratios (from 1.1 to 2.2). Thecombustion efficiency ranged between 96.3% and98.5%. The mixture of olive cake and lignite coal canbe used as fuel for cleaner energy production in small-scale industries by means of CFB. The mixing ratio ofolive cake to lignite coal should be below 50 wt% inorder to lie within the limits set for emissions by EU.The minimum emissions were observed when the excessair ratio reached the level of 1.5 (Atimtay & Topal,2004).The removal of toxic metals from wastewaters is an

issue of great interest in the field of water pollution,which is one of the most crucial worldwide environ-mental problems. Veglio et al. (2003) investigated thepotential use of solid olive mill residues as copper-

Air blower

Venturi-meter Flexible coupling

Motor

Glass hopper

Screw feeder

Air distributer plate

LPC distributer

Combustionchamber

Cooling air Hot air

Ash tank

Cyclone

Exhaust

Figure 6 Schematic of the combustion process of olive cake (adapted from Abu-Qudais, 1996).



biosorbing material. This waste after having been driedat atmospheric environment for a year was ground andsieved. The solid olive mill residues were found to be anappealing ‘low-cost’ biosorbing material and promisingcopper sorbents, which can be effectively used for thetreatment of metal-bearing effluents.

GasificationBiomass gasification is a new physicochemical method,especially for the de-oiled two-phase olive mill waste.This process transforms solid biomass into syntheticgas (called ‘syngas’), a mixture of CO and H2, at900–1200 �C in an oxygen-restricted environment. Syn-thetic gas is used for obtaining important chemicalproducts such as CH3OH or NH3 and for preparationof synthetic fuel (Roig et al., 2005; http://www.listserv.repp.org/pipermail/gasification/2005-february/007904.html). The temperature range of pyrolysis,combustion and gasification is presented in Table 1.However, gasification of agricultural residues is moredifficult because of bed transport, partial ash sintering,non-uniform flow distribution and the presence of amuddy phase in the effluents (Di Blasi et al., 1999)(Fig. 7).Olive mill wastewater and olive husk were thoroughly

mixed and the blend was fed to a rotary dryer to reducethe moisture from 69% to 15% and utilise the producedhot gases. The dried blend was then fed to a gasifier andthe released gas was fed to a combined gas-stream cycle,gas turbine cycle or internal combustion engine in orderto produce a low heating value gas (5860 kJ kg)1). Onthe contrary, another experiment was conducted and thedried mixture of OMW and olive husk was combustedin a boiling atmospheric fluidised bed combustor. Thereleased fumes were fed into a steam generator, wherethe produced steam could be effectively used for thegeneration of electric energy. Another combustionmethod was also proposed for the blend by using aconventional boiler and steam turbine cycle. The mix-ture was dried in a rotary dryer until the moisture wasreduced down to 10%, fed to a boiler and the resultingsteam was placed in a steam turbine cycle. The resultsindicated a considerable energy recovery by treating

both olive husk and OMW of olive mill industries(Caputo et al., 2003).Table 2 provides a synoptical presentation of olive oil

waste thermal treatment methods, physicochemicalcharacteristics of olive oil waste, substrate to be appliedand final product uses.

Final product/uses

Activated carbon production

Activated carbon remains the principal adsorbent infull-scale water treatment, and it is expected that theapplication of adsorption to control contamination ofwater, by toxic or carcinogenic compounds, will increasein the future (Walker, 1996). Recently, in order to lowercost and to promote application, carbon processed fromvarious residues or raw materials of little value (Marsh,2001), such as sawdust, straw, rice hull, shell of nuts orhazel, stone of seed or fruit and agricultural waste, hasbeen tested (Fig. 8).The sorption properties of activated carbon made

from olive cake and commercial activated carbon toremove aquatic pollutants such as heavy metal (HM),phenol (Ph), dodecylbenzenesulphonic acid–sodium saltdetergent (DBSNa) and methylene blue (MB) dye wereinvestigated by Cimino et al. (2005). The olive cake wasdried for 2 h at 105 �C in an air oven, then placed in amuffle furnace with increasing temperature up to 700 �Cand the produced activated carbon was treated withH2SO4, HCl and HNO3. Olive cake carbon showed a

Table 1 Temperature range of pyrolysis, combustion and gasification

(http://www.members.axion.net/�enrique/combustiontempera-

ture.html; http://www.pubs.acs.org/cgi-bin/abstract.cgi/iecred/asap/

abs/ie050486y.html; http://www.listserv.repp.org/pipermail/gasifica-

tion/2005-february/007904.html)

Thermal process Temperature range (�C)

Pyrolysis 450–550

Combustion 800–900

Gasification 900–1200


Gasifier(1200 ºC)

Gas cleaning (ifnecessary)

Combustion in gasengine, gas turbine

or boiler

Residues

Power and/orheat

Flue gas*, residuesand ash

Limited airor oxygen

Start-up heat

Cleaned gas

Figure 7 Activated carbon production (http://www.home.att.net/

�africantech/ghie/actcarbon.htm; http://www.norit.com/

activatedcarbon.asp?submenucat¼introduction; http://www.scielo.br/scielo.php?pid¼s0104-66322005000100005&script¼sci_arttext&tlng¼en).



Tab

le2Thermalprocesses:treatm

entmethodofoliveoilwasteandphysicochem

icalcharacteristics,substrate

tobeapplied

andfinalproduct

uses

Su

bstr

ate

tob

eap

pli

ed

Tre

atm

en

tm

eth

od

Ph

ysic

och

em

ica

lch

ara

cte

risti

cs

Fin

al

pro

du

ct/

uses

Refe

ren

ces

Pyro

lysi

s

So

lid

wast

es

Bu

rnin

gat

550

�CR

ed

uce

sp

last

icit

y,

2.5

%o

fb

urn

ed

oli

ve

wast

ein

crease

sm

axim

um

dry

den

sity

an

du

nco

nfi

ned

com

pre

ssiv

est

ren

gth

wh

ile

in

hig

her

perc

en

tag

es

itd

ecr

ease

s

bo

th,7.5

%o

fo

live

ash

min

imis

es

the

swell

ing

pre

ssu

re

So

ilst

ab

ilis

er

Att

om

&A

l-S

hari

f

(1998)

Oli

ve

pit

an

dcu

ttin

gs

Pyro

lysi

sat

400–7

00

�C,

wit

hh

eati

ng

rate

s120–1

65

�Cs)

1,

at

atm

osp

heri

c

pre

ssu

re,

un

der

nit

rog

en

Bio

-oil

,p

yro

lyti

cg

as

an

dch

arc

oal

Ch

arc

oal

bri

qu

ett

ing

new

lin

eFu

rth

er

invest

igati

on

of

bio

-oil

Zab

an

ioto

u&

Kara

bela

s(1

999)

Oli

ve

resi

du

es

Pyro

lysi

sin

ast

ain

less

steel

fixed

-bed

react

or

(400–7

00

�C)

un

der

dif

fere

nt

atm

osp

here

s(n

orm

al,

sweep

ing

gas

–N

2,

steam

)

Bio

-oil

pro

du

ctio

nFu

eln

ew

lin

eA

dd

ed

top

etr

ole

um

refi

nery

feed

sto

cksn

ew

lin

eU

pg

rad

ed

by

cata

lyst

sto

pro

du

cep

rem

ium

gra

de

refi

ned

fuels

new

lin

eU

seas

chem

ical

feed

sto

cks

Pu

tun

et

al.

(2005)

Oli

ve

bag

ass

eP

yro

lysi

sin

ast

ain

less

steel

tub

ula

r

react

or

wit

ha

sweep

gas

(nit

rog

en

)

at

350–5

50

�C

Pro

du

ctio

no

fb

io-o

il(m

ixtu

reo

f

ali

ph

ati

can

daro

mati

c

hyd

roca

rbo

ns)

wit

hlo

wo

xyg

en

con

ten

t,p

rese

nce

of

oxyg

en

ate

d

fract

ion

s(c

arb

oxyl

an

dca

rbo

nyl

gro

up

s)an

dh

eati

ng

valu

e

31.8

MJ

kg)

1

Fu

el

an

dch

em

ical

feed

sto

ckS

en

soz

et

al.

(2005)

OM

WE

vap

ora

ted

(un

der

vacu

um

or

atm

osp

heri

cp

ress

ure

),d

ried

at

105

�C,

an

dp

yro

lyse

d(2

00–5

50

�C)

Red

uct

ion

of

CO

D(9

8%

),o

rgan

ic

load

inth

ere

sid

ues

(98%

)an

d

ab

sen

ceo

fp

oly

ph

en

ols

Fu

el

top

rovid

eh

eat

inth

eevap

ora

tio

n

stag

e

Vit

olo

et

al.

(1999)

Oli

ve

hu

skD

irect

an

dca

taly

tic

(Zn

Cl 2

,N

a2C

O3,

K2C

O3)

pyro

lysi

s(4

77–7

52

�C)

ina

stain

less

steel

cyli

nd

rica

lre

act

or

Hyd

rog

en

pro

du

ctio

nFu

el

for

inte

rnal

com

bu

stio

nen

gin

es

in

au

tom

ob

iles

(H2

fro

md

irect

cata

lyti

c

pyro

lysi

s)

Cag

lar

&D

em

ibra

s

(2002)

Co

mb

ust

ion

So

lid

wast

es

(fo

ot

cake

)C

om

bu

stio

n(a

vera

ge

tem

pera

ture

850

±10

�C,

com

bu

stio

nair

tem

pera

ture

23

�C,fl

ow

of

com

bu

stio

n

air

570

Nm

3h

)1

an

dre

lati

ve

hu

mid

ity

40%

)

Co

mb

ust

ible

Su

bst

itu

teo

fn

o.

2h

eavy

fuel

Masg

ho

un

i&

Hass

air

i(2

000)

Oli

ve

cake

Dry

ing

ino

ven

(1h

,105–1

10

�C),

gro

un

ded

ina

mil

l(r

ed

uct

ion

part

icle

size

)an

dm

ixtu

rew

ith

oil

shale

Calo

rifi

cvalu

e31.2

kJg

)1

So

urc

eo

fen

erg

y–

fueln

ew

lin

eC

ata

lyst

too

ilsh

ale

com

bu

stio

n

Alk

ham

is&

Kab

lan

(1999)

Oli

ve

cake

Co

mb

ust

ion

ina

circ

ula

tin

gfl

uid

ised

bed

(900

�C–5

h)

Flu

eg

as

(O2,

SO

2,

CO

2,

CO

,N

Ox,

Cm

Hn,

ash

)

Fu

el

insm

all

scale

-in

du

stri

esn

ew

lin

eA

sh

use

das

soil

fert

ilis

er

To

pal

et

al.

(2003)

Oli

ve

cake

Co

-co

mb

ust

ion

wit

hli

gn

ite

coal

ina

circ

ula

tin

gfl

uid

ised

bed

(700

�C)

Co

mb

ust

ion

effi

cien

cy96.3

–98.5

%Fu

el

for

en

erg

yp

rod

uct

ion

insm

all

-sca

le

ind

ust

ries

Ati

mta

y&

To

pal

(2004)

So

lid

oli

ve

mil

lre

sid

ues

Dri

ed

,g

rou

nd

an

dsi

eved

‘Lo

w-c

ost

’b

ioso

rbin

gm

ate

rial,

cop

per

sorb

en

t

Tre

atm

en

to

fm

eta

l-b

eari

ng

effl

uen

tsV

eg

lio

et

al.

(2003)

Gasi

fica

tio

n

OM

Wan

do

live

hu

skG

asi

fica

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n/c

om

bu

stio

nH

eati

ng

valu

eE

nerg

yp

rod

uct

ion

Cap

uto

et

al.

(2003)



good sorption capacity to Ph and HM (Ag+, Cd+2,Cr+3) comparable to that of commercial activatedcarbon. Olive cake carbon displayed a slightly lowereffectiveness towards removal of MB and DBSNacompounds than that observed for commercial activatedcarbon.Bacaoui et al. (2001) prepared a mixture of olive pulp

and stone for the production of activated carbon andstudied the potential use as adsorbents in aqueoussolutions. The raw material was carbonised in a stainlesssteel autoclave and heated at 400 �C for 1 h under anitrogen flow, and activated in a thermolyne silicaelectric oven with a temperature control device linked toa thermocouple at 750–850 �C for 30–70 min. The

produced activated carbon was boiled for 30 min indistilled water, dried, ground, sifted and dried again at110 �C. The optimal conditions for the production ofactivated carbon suitable for the removal of pollutantsfrom liquid phase (water) were found to be activationtime and activation temperature, 68 min and 822 �C,respectively.Nowadays, there is a great need for the production of

new, effective and low-cost sorbents worldwide. Abu-El-Shar et al. (1999) fabricated activated carbon fromsolid residue from olive mill waste in an attempt toexamine the possibility towards dye removal fromaqueous solutions. The raw material was kiln-roastedin a rotating cylinder at 150 �C, and then sieved intodifferent sizes. The produced activated carbon withparticle size 0.5–1.0 mm was used in batch experimentsand the adsorbance of methylene blue (cationic dye) andmethyl orange (anionic dye) was determined. Activatedcarbon effectively removed methylene blue, whereas itshowed poor removal of methyl orange in comparisonwith commercial activated carbon capable of removingboth dyes. It can be concluded that the activated carbonproduced by solid residue from olive mill waste is acheap and effective material in removing cationic dyes,but not anionic dyes.Galiatsatou et al. (2002) produced activated carbon

from solvent-extracted olive pulp in an attempt toexamine its porosity development and its ability towardszinc removal from aqueous solutions. The raw materialwas carbonised with nitrogen, at 850 �C for 1 h and30 min, and then activated with steam/nitrogen mixtureat 800 �C for 40 min. The obtained activated carbondisplayed low oxygen content and efficient macroporousvolume, which result in higher adsorption capacity, andcan be effectively employed towards the removal ofaqueous zinc species.The ability of activated carbon, made from solid

residue of olive mill products, to remove NH3, totalorganic carbon and some organic compounds compri-sing heteroatoms like sulphur and halogens from awastewater treatment plant was examined by Gharaibehet al. (1998). Batch reactors were filled with wastewaterand activated carbon, and the materials have beenmixed for 20 h. Batch experiments were also conductedin parallel using commercial types of activated carbonmade from metallurgical grade coal and peat. Thepercentage removal of compounds from the threedifferent types of activated carbon (peat, metallurgicalgrade coals and solid residue of olive mill industries) isshown in Table 3. The latter activated carbon can beused for tertiary treatment, or mixed with influentwastewater after screening, sedimentation, etc. in theprimary treatment, or fed to the aeration tank in thesecondary treatment.Walid (2001) dried olive cake for 1 h at 100 �C, sep-

arated the seeds from the initial sample and carbonised

Raw carbon material

Crusher

Crushed andsized material

Dried material

Carbonisation

MoistureDrier

Carbonised material

Activation

Activated carbon

Crusher Tumbling machine

Powdered activatedcarbon (particle

size 1–150 micron)

Granular activatedcarbon (particlesize 0.5 – 4 mm)

Gases (H2, CO, CO2)Steam

(110 ºC)Boiler

Water

Distillateproduct

Samplepreparation

Samplecharacterisation

Activatedcarbon test

Figure 8 The gasification process (adapted from http://www.esru.

strath.ac.uk/eande/web_sites/01-02/re_info/biomass.htm; http://

www.wasteresearch.co.uk/ade/efw/gassification.htm).



them in a sealed crucible at various temperatures (400,600, 800 �C) for 1 h. Olive seed activated carbon wasmore effective at 800 �C than commercial type carbon,while the adsorption capacity of fresh activated carbonat 800 �C was found to be higher than the others,followed closely by regenerated activated carbon andcommercial type.El-Sheikh et al. (2004) used olive stones for the

production of activated carbon. The sample wascrushed, dried at 120 �C and carbonised in a horizontaltube furnace with the temperature ranging from 25 to850 �C under a constant-flowing nitrogen atmosphere.Activation was then carried out at the same temperatureand the end products were dried at 120 �C for 4 h. Thefinal products displayed high adsorptive capacity in thepresence of an aqueous medium.

Biodiesel

The diesel fuel consumption in developed countries hasbeen increasing continuously over the past decades andis expected to continue in the same direction in thefuture. A promising alternative to fossil fuels is the useof biodiesel (Strub, 1984). More than 100 years ago,Rudolph Diesel tested vegetable oil as the fuel for hisengine (Shay, 1993).Transesterification of vegetable oils constitutes an

efficient method for providing a fuel (biodiesel) withchemical properties similar to those of diesel fuel(Dorado et al., 2004). Transesterification is the generalterm describing the important class of organic reactionswhere an ester is converted into another through aninterchange of the alkoxy moiety. When the originalester reacts with an alcohol, the transesterification

process is called alcoholysis (http://www.scielo.br/sci-elo.php?pid¼S0103-50531998000300002&script¼sci_art-text&tlng¼en) (Fig. 9).Waste olive oil collected from hospital kitchens was

preheated at different temperatures, and then KOH (ascatalyst) and methanol were added. The transesterifi-cation process was conducted while heating and stirringthe above-mentioned mixture at 1100 r.p.m. After theblend settled, two separate phases were formed: theupper consisted of biofuel, which was extracted andpurified using distilled water and then dried overanhydrous Na2SO4 and the lower comprised of gly-cerol, catalyst and some impurities. The optimalconditions of transesterification for maximum esteryield (94%) were 1.3% KOH, 12% methanol, 1 min ofstirring with 90 min of pour-off time, 11.4% distilledwater at 25 �C and drying over 0.5% Na2SO4. A short-term engine performance test was carried out in a dieselengine and showed no differences between diesel fueland biodiesel from used olive oil (Dorado et al., 2004).A study comparing exhaust emissions from in-useheavy trucks fuelled with a biodiesel blend (35%biodiesel and 65% petroleum diesel) to those fromtrucks fuelled with petroleum diesel was conducted byWang et al. (2000)). The results showed that the fueleconomy (gallon per mile) and the oxides of nitrogen(NOx) emissions of the two fuels were the same, but theemission test results indicated that the heavy trucksfuelled by the biodiesel blend emitted significantlylower particulate matter and moderately lower CO andhydrocarbon than the same trucks fuelled by No. 2diesel. Dorado et al. (2003a) conducted emission test ofa diesel direct-injection engine fuelled with biodiesel,obtained from waste olive oil after transesterification

Table 3 Percentage removal of compounds from the three different types of activated carbon [peat, metallurgical grade coals, solid residue of olive

mill industries (adapted from Gharaibeh et al., 1998)]

Type of activated carbon % removal Compounds

Activated carbon made from peat 100 Benzothiazole, 1,2-dihydro-2,2,4-trimethylquinoline, N-dimorpholinyl

ketone, methylsulphyl benzothiazole, methyl-2-benzothiazole sulphone

94 Total organic carbon

82 NH3

50 Tetrachloroethane

Metallurgical grade coals activated

carbon

100 Benzothiazole, 1,2-dihydro-2,2,4-trimethylquinoline, N-dimorpholinyl

ketone, methylsulphyl benzothiazole, methyl-2-benzothiazole sulphone

87 NH3



Activated carbon made from solid

residue of olive mill industries

100 Benzothiazole, methylsulphyl benzothiazole, methyl-2-benzothiazole

sulphone

78 NH3

70 1,2-dihydro-2,2,4-trimethylquinoline


50 N-dimorpholinyl ketone




(Dorado et al., 2004), at several steady-state operatingconditions. The results suggested that when biodieselwas used as a fuel, low emissions of CO (58.9%), CO2

(8.6%), NO (37.5%) and SO2 (57.7%) were reported.Dorado et al. (2003b) used biofuel produced throughtransesterification (Dorado et al., 2004), within theframe a 50-h short-term performance test in a dieseldirect-injection Perkins engine of 8–15 kW and 1800–2100 r.p.m. Biodiesel properties were very similar tothose of heavy fuel diesel No. 2, while a slight powerloss (<8%) and an increase in brake-specific fuelconsumption (up to 26%) were recorded. Therefore,waste olive oil methyl ester can be effectively used as adiesel fuel substitute.Encinar et al. (2005) used a mixture of frying olive oil

and sunflower oil for the production of methyl estersthat can be used as biodiesels. The transesterificationprocess was carried out in a spherical reactor at 25–65 �C. When the reactor reached 65 �C, methanol andcatalysts (sodium hydroxide, potassium hydroxide,sodium methoxide and potassium methoxide) wereadded. At the end of the process, two layerswere formed: the upper containing methyl esters, whichwere further purified and the lower phase with glycerol,excess methanol, remaining catalyst together with thesoaps formed during the reaction and some entrainedmethyl esters and partial glycerides. The mainly pro-duced methyl esters were linoleate (40%), oleate (35%),

palmitate (9%) and stearate (5%). The biodieselendowed with the best properties was obtained using amethanol/oil molar ratio of 6:1, potassium hydroxide ascatalyst at 1% (wt) concentration and temperature at65 �C. Furthermore, a two-stage transesterificationimparted better properties to the final product thanthat of the single-stage transesterification. The producedbiodiesel had similar properties (density, viscosity,cetane index, but higher heating value) to those ofheavy fuel diesel No. 2, thus resulting in its use incompression ignition motors.Among liquid biofuels, biodiesel derived from veget-

able oils is gaining ground and market share as Dieselfuel in Europe and the United States. The direct use ofoil derived from olive kernel as a fuel for Diesel enginescaused serious problems because of the high fuelviscosity in compression ignition. Dilution, microemul-sification, pyrolysis and transesterification stand for thefour main techniques applied towards resolving theproblems encountered with the high fuel viscosity(Ziejewski et al., 1986). Pyrolysis produced more bio-gasoline than biodiesel fuel (Fig. 10), while soap pyro-lysis products can be used as alternative diesel enginefuel. The most important variables affecting the esteryield during the transesterification reaction were themolar ratio of alcohol to vegetable oil, reactiontemperature, reaction time, water content and catalyst(Demirbas, 2003).

Vegetable oils Methanol Catalyst

Reactor

Separator Methyl esters

Neutralisationand methanol

removal

Glycerol (50%)

Acidification snd freefatty acids separation

Methanol removal

Crude glycerol(85%)

Refining

Soap industry

Free fattyacids

Acid

Crude biodiesel Refining

Dryer

Finishedbiodiesel

Residue

Waterwashing

Water wash

Acid

Methanol / waterstandardisation

Methanol recovery

Water

Water

Figure 9 Process flow diagram for biodiesel production (adapted from Barnwal & Sharma, 2005; http://www.uidaho.edu/bioenergy/biodieseled/

publication/01.pdf; http://www.dft.gov.uk/stellent/groups/dft_roads/documents/graphic/dft_roads_024054-2.jpg).



Briquette production

In recent years, considerable attention has been focusedon the briquetting of coal fine, peat, charcoal, bio-wasteand other combustible wastes (Richard, 1990; Ramler &Metzner, 1989; Rahman et al., 1990). Biomass briquet-ting involves grinding and drying of agro wastes tomaintain uniform particle size and optimum moisturecontent. The processed agro waste is then subjected tohigh temperature and pressure using screw press/mouldto produce briquettes (http://www.zenithenergy.com/biobriq.html).Olive refuse is one of the considerable sources of

biomass and has been used as a domestic fuel. Briquettingexperiments were performed on olive refuse (moisturecontent 7.5%) using a hydraulic press under pressures of150, 200 and 250 MPa, and the produced briquettes werestored under ambient conditions for a week prior totesting their mechanical properties and water resistance.The results indicated that the maximal compressivestrength was recorded at 150 MPa. At 200 MPa, theshatter index reached the highest value, and the waterresistance further improved with an increase in briquet-ting pressure. A fibrous biomass material, such as papermill waste, was added to the olive refuse waste, in order toincrease the mechanical strength, and the mixture wasbriquetted under 200 MPa pressure. The shatter index ofthis briquette was found to be 4813, compressive strengthamounted to 319 kg cm)2 and water resistance time wasdetermined at 27 min. The produced briquettes were ofgood quality and can be used as an alternative energysource (Yaman et al., 2000).

Table 4 provides a synoptical presentation of finalproduct uses (thermal processes: treatment method ofolive oil waste and physicochemical characteristics,substrate to be applied).

Conclusions

Consideration of environmental issues is growing,bringing about the need for more sophisticated controlof industrial emissions and waste and faster and moreadvanced on-board diagnosis (Lloyd Spetz et al., 1998).The impact of Clean Air Act Amendments on foodprocessing waste operations identified vegetable oilproduction, among others, as a target industry requiringspecific regulations (Walsh et al., 1993). Olive oilindustry waste has attracted a tremendous amount ofresearch, several hundreds of publications over the last15 years. Although for a long time, no effective actionswere undertaken in order to reduce the disastrous effectof untreated/partially treated waste effluents accordingto which the incorporation of environmental manage-ment into process management is encouraged with theaim to lead to a comprehensive process managementconcept (Schiefer, 2002). A rather recent analysis of theolive oil industry waste showed that value of the latterfalls in agreement with the published results regardingthe perceived impact on environmental areas (solidwaste: 60.4%, energy consumption: 55.1% and waste-water: 36.8%) reported by Baumast (2001) within theframe of a quantitative survey carried out on behalf ofEuropean Business Environmental Barometer. Amongthe olive oil waste thermal treatment methods, pyrolysis

Vegetable oil tanker

Pyrolysischamber

Sweeping gas stream

Peristaltic pump

Packingmaterial

Condenser Cold trap

Gas volume measure

Tight gas tank

Electric furnace Electric furnaceIII

Figure 10 Simplified experimental setting for vegetable oil pyrolysis (adapted from Demirbas, 2003).



Tab

le4Other

finalproduct

uses(thermalprocesses:treatm

entmethodofoliveoilwasteandphysicochem

icalcharacteristics,substrate

tobeapplied)

Su

bstr

ate

tob

eap

pli

ed

Tre

atm

en

tm

eth

od

Ph

ysic

och

em

ical

ch

ara

cte

risti

cs

Fin

al

pro

du

ct/

uses

Refe

ren

ces

Act

ivate

dca

rbo

np

rod

uct

ion

Oli

ve

cake

Carb

on

isati

on

(2h

,105

�C)

an

d

act

ivati

on

(in

am

uffl

efu

rnace

700

�C)

an

daci

dic

treatm

en

t

(H2S

O4,

HC

l,H

NO

3)

So

rpti

on

pro

pert

ies

of

the

oli

ve

cake

act

ivate

dca

rbo

ns

Hig

hso

rpti

on

cap

aci

tyto

ph

en

ol

an

dh

eavy

meta

l,lo

wso

rpti

on

cap

ab

ilit

yto

meth

yle

ne

blu

ed

ye

an

dd

od

ecy

lben

zen

esu

lph

on

ic

aci

d–s

od

ium

salt

dete

rgen

t

Cim

ino

et

al.

(2005)

Oli

ve

pu

lpan

do

live

sto

ne

Carb

on

isati

on

ina

stain

less

steel

au

tocl

ave

at

400

�Cfo

r1

hu

nd

er

N2

flo

w,

act

ivati

on

ina

therm

oly

ne

sili

caele

ctri

co

ven

wit

ha

tem

pera

ture

con

tro

ld

evic

eli

nke

d

toa

therm

oco

up

leat

750–8

50

�Cfo

r30–7

0m

in

Hig

had

sorp

tio

nca

paci

ty,

hig

h

surf

ace

are

a

Act

ivate

dca

rbo

n

pro

du

ctio

nn

ew

lin

eA

bso

rpti

on

of

po

llu

tan

tsfr

om

liq

uid

ph

ase

s

(wate

r)

Baca

ou

iet

al.

(2001)

So

lid

resi

du

efr

om

oli

ve

mil

lw

ast

e

Kil

nro

ast

ed

ina

rota

tin

gcy

lin

der

at

150

�CS

ign

ifica

nt

meth

yle

ne

blu

ean

dp

oo

r

meth

yl

ora

ng

ere

mo

val

Tre

atm

en

to

fw

ate

rco

nta

min

ate

d

wit

hca

tio

nic

dyes

(lik

em

eth

yle

ne

blu

e),

no

teff

ect

ive

inre

mo

vin

g

an

ion

icd

yes

Ab

u-E

l-S

har

et

al.

(1999)

So

lven

textr

act

ed

oli

ve

pu

lp

Carb

on

isati

on

un

der

N2

at

850

�Cfo

r

1h

30

min

an

dact

ivati

on

wit

h

steam

/nit

rog

en

mix

ture

at

800

�Cfo

r40

min

Ad

sorp

tio

nca

paci

ty,

low

oxyg

en

con

ten

t,si

gn

ifica

nt

nu

mb

er

of

basi

cg

rou

ps,

alo

ng

wit

han

effi

cien

tm

acr

op

oro

us

vo

lum

e

Ad

sorb

en

tsfo

rth

ere

mo

valo

fw

ate

r

po

llu

tan

tsan

dco

nta

min

an

ts(Z

n+

2)

Gali

ats

ato

uet

al.

(2002)

So

lid

resi

du

efr

om

oli

ve

mil

lw

ast

e

Batc

hexp

eri

men

tsin

are

act

or

fed

wit

hact

ivate

dca

rbo

nm

ad

efr

om

soli

dre

sid

ue

fro

mo

live

mil

lw

ast

e

an

dco

mm

erc

ial

typ

eact

ivate

d

carb

on

Rem

oval

of

po

llu

tan

tsfr

om

wast

e

wate

reffl

uen

t:b

en

zoth

iazo

le,

meth

yls

ulp

hyl

ben

zoth

iazo

lean

d

meth

yl-

2-b

en

zoth

iazo

lesu

lph

on

e

100%

>N

H3

78%

>1,2

-

dih

yd

ro-2

,2,4

-tri

meth

ylq

uin

oli

ne

70%

>te

trach

loro

eth

an

e58%

>

N-d

imo

rph

oli

nyl

keto

ne

50%

>

tota

lo

rgan

icca

rbo

n37%

Ind

ust

rial

wast

ew

ate

rtr

eatm

en

t

(tert

iary

treatm

en

t,m

ixed

wit

h

infl

uen

tw

ast

ew

ate

raft

er

scre

en

ing

,se

dim

en

tati

on

,etc

.in

the

pri

mary

treatm

en

t,fe

dto

the

aera

tio

nta

nk

inth

ese

con

dary

treatm

en

t)

Gh

ara

ibeh

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appears to be the most popular and widespread method,followed by incineration and gasification. As regards theuses of treated olive oil waste, biodiesel seems to beamong the most promising, followed by activatedcarbon and briquette production.

References

Scientific references

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ab

le4(C

ontinued)

Su

bstr

ate

tob

eap

pli

ed

Tre

atm

en

tm

eth

od

Ph

ysic

och

em

ica

lch

ara

cte

risti

cs

Fin

al

pro

du

ct/

uses

Refe

ren

ces

Wast

eveg

eta

ble

oil

Tra

nse

steri

fica

tio

nLo

wp

rese

nce

of

free

gly

cero

l,to

tal

gly

cero

l2.1

%,

pre

sen

ceo

fso

me

un

react

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gly

ceri

des,

carb

on

resi

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e

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Do

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oet

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Mix

ture

of

fryin

go

live

oil

an

dsu

nfl

ow

er

oil

Tra

nse

steri

fica

tio

nb

ym

ean

so

f

meth

an

ol

usi

ng

sod

ium

hyd

roxid

e,

po

tass

ium

hyd

roxid

e,

sod

ium

meth

oxid

ean

dp

ota

ssiu

m

meth

oxid

eas

cata

lyst

s

Pro

pert

ies

sim

ilar

toth

ose

of

No

.2

die

sel

(den

sity

,vis

cosi

ty,

ceta

ne

ind

ex,

bu

th

igh

er

heati

ng

valu

e)

Bio

die

sel

for

com

pre

ssio

nig

nit

ion

mo

tors

En

cin

ar

et

al.

(2005)

Oli

ve

kern

el

Dil

uti

on

,m

icro

em

uls

ifica

tio

n,

pyro

lysi

san

dtr

an

sest

eri

fica

tio

n

Bio

die

sel

pro

du

ctio

nS

oap

pyro

lysi

sp

rod

uct

sca

nb

e

use

das

alt

ern

ati

ve

die

sel

en

gin

e

fuel

Dem

irb

as

(2003)

Bri

qu

ett

ep

rod

uct

ion

Oli

ve

refu

sean

dp

ap

er

mil

l

wast

e

Bri

qu

ett

ing

by

usi

ng

ah

yd

rau

lic

pre

ssu

nd

er

pre

ssu

res

of

150,

200

an

d250

MP

a

Sh

att

er

ind

ex

4813,

com

pre

ssiv

e

stre

ng

th319

kgcm

)2,

wate

r

resi

stan

ceti

me

27

min

Du

rab

lefu

el

bri

qu

ett

es

pro

du

ctio

n–

alt

ern

ati

ve

en

erg

yso

urc

e

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an

et

al.

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