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Optimizing the Anaerobic Digestion Process

Examining the different types of

anaerobic digestion technologies

Frank Hofmann

7th September 2011, South Baltic Gas Forum, Gdansk

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Table of contents

1. Examining the different types of anaerobic digestion technologies

� Completely stirred reactor

� Plug-flow reactor

� Batch wise operated systems

� Lagoon biogas plants

� Specialized reactors (like UASB, dry fermentation)

2. Advanced biogas utilization

� Biogas upgrading

� Injection in the gas grid

� Use for transportation purposes

� CHP integration and optimization

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Examining the different types of anaerobic digestion technologies

Completely stirred reactor

Source: Ecofys

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Completely stirred reactor I

Opportunities for optimization (biochemical process)

� Mesophilic – thermophilic conditions

� Separated stages

� Stages in a row - parallel

� External hydrolysis

� Biochemical optimization

� Enzymes

� Minerals

4

Completely stirred reactor II

Opportunities for optimization (technology)

� Gas yield

� Energy demand

� Operational hours

� Process

� Technology

� Efficient energy utilization

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Completely stirred reactor III

Gas yield

� Pre treatment of biomass

� Example: Thermo-pressure-hydrolysis

� >190°C

� 20 min

� Decomposition of long carbon hydrates

� Reduced retention time

� Higher gas yield

� Sanitation of the material

� Option to treat material that is more difficult to degrade (cheaper feedstock, like straw, sewage sludge)

� Combination with thermophilic digestion

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Completely stirred reactor IV, electricity demand

n=297

0

10

20

30

40

50

10 100 1.000 10.000

installierte Leistung [kWel]

Eig

enstr

om

bedarf

[%

]

Installed electrical capacity [kWel]

Ownelectricitydemand[%

of production]

Source: DBFZ

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Completely stirred reactor V, disturbances

Operational hours

Source: Weiland et. al. (2008): Biology: 5th main reason for disturbancesDBFZ

Relative frequency Working efforts

Wo

rkin

geff

ort

sh

ou

rsp

er

week

Rela

tive f

req

uen

cy

of

dis

turb

an

ces

in %

Waste

in

pu

tte

ch

no

log

ies

Mech

an

ical

Pre

treatm

en

t

Sep

ara

tio

n

of

imp

uri

ties

Hyg

ien

isati

on

Bio

log

ical

Pro

cess

Pu

mp

s

So

lid

su

bstr

ate

Feed

ing

Sti

rrin

g

Clo

gg

ing

s

Gas p

uri

ficati

on

CH

P u

nit

Co

ntr

ol

eq

uip

men

t

Gas lo

sses

Oth

ers

8

Completely stirred reactor VI, CHP

Source: Weiland et. al. (2008) and DBFZ

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Cumulated annual standstill of CHP units in 60 German biogas plants [d/a]

Re

lati

ve f

req

uen

cy

[%]

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Completely stirred reactor VII, heat utilization

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n=166

0

20

40

60

80

100

≤ 50 51 - 150 151 - 500 501 – 1.000 > 1.000

installierte elektr. Anlagenleistung [kWel]

Ante

il B

iogasanla

gen m

it ents

pre

chenden

Wärm

enutz

ungsgra

d [%

]

Biogasanlagen Wärmenutzungsgrad ≤50% [%] Biogasanlagen Wärmenutzungsgrad >50% [%]

Share

of pla

nts

with

giv

en

heat

utliz

ation

share

[%]

Installed electrical capacity [kWel]

Average heat utilization share < 50 % Average heat utilization share > 50 %

Source: DBFZ

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Other types of anaerobic digestion technologies

� Lagoon biogas plants

� Specialized reactors like

� UASB

� Plug flow digestion

� Dry fermentation

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Lagoon systems for (industrial) waste water

Source: Ecofys

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Reasons for Lagoon systems

� Relatively cheap investment costs

� Huge amount of water processable

� Energy production

� COD/BOD reduction

� Waste stabilization (pH, volatiles, vector attraction)

� Odour reduction

� Immobilization of Heavy Metals (sulphide binds heavy metals)

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Chemical oxygen demand, COD

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Examples of input material,COD

� Meat, dairy processing, beer, winery, sugar beet, starch 5-10 kg/m3

� Ethanol vinasse 28-31 kg/m3

� Piggery effluent 10-30 kg/m3

� POME, wool processing 50-100 kg/m3

� Distillery slops 40-200 kg/m3

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Best Project Checklist

� Site conditions

� Size: large volumes of waste (water)

� Waste strength & composition

(Biodegradability)

� Waste temperature

� Open lagoon emissions

� Climate conditions

� Processing season

� Energy demand by owner

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Waste composition (Biodegradability)

� Simple wastewaters (soluble):

� Sugar, soft-drink, beer/wine, vinasse, blanching/cannery, some pharmaceutical, chemical

� Complex wastewaters (fat, protein)

� Slaughterhouse, dairy, starch, POME, wool, fish

� ‘Difficult’ wastewater

� Pulp and paper, rendering, tannery, distillery slops

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Conclusions Lagoon systems

� Opportunities in agro-industry, palm oil, starch, ethanol, food processing, slaughterhouse waste, dairy waste, solid waste and many more

� Processes depending on waste and location

� Lagoon-based treatment is best practical option for wastewaters containing suspended solids, fats and/or proteins in areas where space availability is not a problem

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UASB technology

� Process / waste water treatment

� High investment costs

� Low space requirement

Source: Ecofys

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Operating principle of plug-flow digestion.

Kompogas system

Strabag-system

Source: Kompogas

Source: Strabag

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Combination of plug flow, thermal treatment and completely mixed reactors

System as developed by Company Eisenmann

Source: Eisenmann AG

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Dry fermentation

� Input material often > 25 %

� Moderate to high investment costs

� No need for pre-treatment and stable process

Biogas Plant München – Source: Bekon GmbH & Co K.G.

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Operating principle of batch wise digestion

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Upgraded Biogas

Source: Deutsches BiomasseForschungsZentrum gGmbH

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Overview: utilisation of biogas

Upgrading and feeding biogas into the natural gas grid offers the possibility to use the upgraded biogas at the location of demand for electricity, heat, cold or fuel.

Source: Ecofys

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Differences between biogas and natural H-gas

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Upgrading technologies for biogas

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• 41 running plants with about 25,000 m³/h biomethane

• Largest: 5,300 m³/h biomethane

• Mainly 4 Technologies

0

10

20

30

40

50

60

2005 2006 2007 2008 2009 2010*

An

lag

en

za

hl

[-]

0

5000

10000

15000

20000

25000

30000

35000

Au

fbe

reit

un

gs

ka

pa

zit

ät

Bio

me

tha

n

[Nm

³/h

]Schätzung Zubau 2.HJ

Anlagenzahl

Aufbereitungskapazität [Nm³/h]

Biogas upgrading in Germany

28 28

Biogas feed-in capacity in Europe sorted according to countries

Sources: dena, ISET, DVGW e.V.

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Conclusions biogas upgrading and gas grid connection

�The overall feed-in capacity of all European biogas feed-in projects in operation currently amounts to 28,000 Nm³/h or about 150 MW

�Locations: Sweden, Switzerland, Netherlands, France, Germany

�Main utilization as gas grid injection or car fuel

�Legal frameworks were responsible for the development in the mentioned countries

�In Europe ~8 technology suppliers of upgrading biogas technology

�Main technologies are pressurized water scrubbing, pressurizes swing absorption, chemical (water) scrubbing and membrane separation

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Gas utilisation, CHP and alternatives

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Combined Heat and Power (CHP)

� Application in Gen-Sets with adapted gas or diesel engines for electricity and heat production

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� Fuel Cell

� � el. efficiency is up to 48% (55%);

� 1 pilot plant in service, still quite expensive

� ORC-Modules

� converting waste heat into electricity� 10% raise in el. efficiency; 3 plants in operation,

� Is additional to standard gas engine if heat is not utilized otherwise

� Micro gas turbines

�less sensitive, low maintenance costs, high durability

�compared to gas engines low el. efficiency

(38% � 28%)

Source: Köhler & Ziegler

Source: MTU

Source: ISET

Electricity generation,

other technologies

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Summary I

�Biogas plants are state of the art technologies

�There has been a huge technical development in the last 10 years

�Optimizing potentials are in the

� biochemical process

� Reliability of the technology

�There are very different kind of AD technologies on the market which are adapted on the special biomass

�Most efficient gas utilization is still a challenge

� Annual operation time

� Heat utilization

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Summary II

�There are very different types of biogas technologies on the market, optimized for different boundary conditions

�Biowaste treatment plants have a huge potential and some special advantages.

�Lagoon biogas systems have an enormous potential and are relatively cheap

�By biogas upgrading to natural gas quality the gas utilization can be enlarged

�Biogas production is also important as part of the chain in biofuel production, particularly for second generation biofuels:

� Conversion of the wet by-product from fermentation;

� Supply of heat and electricity for the ethanol distillation;

� Conversion of glycerin, by product of biodiesel production

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Please contact us for more information

Ecofys Germany GmbH

Stralauer Platz 34

10243 Berlin

Germany

Frank Hofmann

T: +49 (0) 30 2977 3579 41

E: f.hofmann@ecofys.de

W: www.ecofys.de