FactSheet Anaerobic Digestion

7/31/2019 FactSheet Anaerobic Digestion

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AnAerobic digestion


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1. descriPtion oF tecHnoLogY

2. cUrrent distribUtion And ProsPectiVe oF tecHnoLogY

3. LegAL FrAMeWorK

4. AnAerobic digestion And bioPLAstics: stAndArds, certiFicAtion And LAbeLLing

5. interActions betWeen bioPLAstics And tecHnoLogY

6. beneFits And cHALLenges

6.1 Beets

6.2 Chaeges

7. sUccessFUL cAses

8. Annex - reFerences; LinKs etc.

index


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1. descriPtion oF tecHnoLogY

Withi bioogica soid waste treatmet, a distictio ca be made betwee

two major categories: one being aerobic composting and the other one being

aaerobic digestio or biogasicatio.

I compostig, orgaic matter is degraded b a microbia popatio co-

sistig o bacteria ad gi cosmig oxge ad prodcig CO2, water,

compost or humus and a lot o heat (exothermic). Because o the heat

prodctio, the temperatre i a compostig pie icreases sigicat. I

aaerobic digestio, orgaic matter is degraded b a microbia popatio

cosistig o bacteria i the absece o oxge ad prodcig methae

and carbon dioxide (= biogas) and compost without practically any exother-

mic heat. The biogas ca be treated i a Combied Heat ad Power Pat

(CHP), prodcig eectricit ad heat, or ca be pgraded to bio-methae.

Tpica ot o 1 to o biowaste, 120 m3 o biogas ca be prodced with a

tota eectricit ied o 250 kWh ad a et eectricit ied o 200 kWh.

Rather dieret techoogies ca be distigished i aaerobic digestio.

Oe distictio betwee dieret techoogies is the temperatre at which

the aaerobic digestio is operated. Temperatre is extera cotroed,

and digesters are run either at mesophilic temperature (35-40C), or atthermophiic temperatre (50-55C). These are two distict temperatre

zoes at which dieret tpes o aaerobic bacteria show maximm actii-

t (respectie mesophiic ad thermophiic bacteria). The rate o actiit is

higher at thermophiic temperatre. Frther, aaerobic digestio processes

ca be 1-phase or 2-phase. I 1-phase, the compete digestio is takig

pace i oe it or digester. I 2-phase ermetatio, the rst hdrosis

ad acidicatio phase ad the sbseqet methaogeic phase are r

i separate taks. I dr aaerobic digestio, the process is r at a mois-

tre cotet 85%.

Practically all commercial anaerobic digestion systems consist o a frst

step o aaerobic ermetatio, oowed b a aerobic compostig, sta-

biisatio secod step. Sice ermetatio is a kid o mixed process, the

otpt is ot stabiised or ermeted. I order to redce the resida

biological activity and to obtain complete maturity o the compost end

product, the residue rom the anaerobic digestion phase is thereore

aerobica composted.

Anaerobic digestion is particularly suited or organic waste with a high

moistre cotet sch as kitche waste ad ood waste, athogh it ca

be used or various dierent types o waste streams. Anaerobic digesti-

o pats hae bee bit ad hae bee operatioa or ma ears or

the treatmet o mixed, micipa soid waste, or biowaste (obtaied ater

sorce separated waste coectio), or resida waste ad or ma tpes

o idstria waste.

Anaerobic digestion is oten the preerred biological waste treatment option

in densely populated areas such as big cities or countries like Japan or

Korea. This is de to good odor prodctio cotro ad a redced eed

or srace area.

Recet, aaerobic digestio has aso become a importat paer i the

area o renewable energy production out o energy crops (e.g. corn). The net

energy yield per hectare is higher compared to the production o bio-diesel or

bio-ethanol. Also in bio-refneries, anaerobic digestion could play an important

role with high-value plant parts being used or green chemistry and residual

egeta matter (ater processig or ow-ae pat parts) beig treated i

aaerobic digestio or the prodctio o eerg ad compost.


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2. cUrrent distribUtion And ProsPectiVe oF tecHnoLogY

Figre 1 beow gies a oeriew o the deeopmet o digestio capacit

i Erope i the ast two decades. From three pats i Erope with a tota

capacit o 87,000 tos per ear i 1990, aaerobic digestio capacit i

Erope has grow to a tota o 171 pats ad a digestio capacit o more

than 5 million tons per year in 2010. Figure 2 gives an overview o the

digestio capacit i dieret Eropea cotries. Both the tota capacit

as we as the aerage capacit per pat i a gie cotr is dispaed.

As ca be see, some cotries ted to hae smaer pats (e.g. Germa-

, Switzerad, Astria), whie others hae arger istaatios (e.g. Spai,

Frace). Figre 3 gies a oeriew o the eotio ad ratio o respec-

tie mesophiic ad thermophiic digestio capacit i Erope. Abot oe

third o the capacity is thermophilic, whereas two thirds are mesophilic.

Figre 4 gies a oeriew o the eotio ad ratio o respectie wet

ad dr digestio capacit i Erope. The ratio is abot 50/50 with a sight

dominance or dry systems. Figure 5 gives an overview o the evolution and

ratio o respectie 1-phase ad 2-phase digestio capacit i Erope. As

ca be see, the ast majorit is 1-phase.

Digestion capacity in Europe is increasing rapidly. Many digesters are being

built in Mediterranean countries such as Spain and France. Most plants are

dr ad 1-phase, ad r at mesophiic temperatre. The eotio or the

next years can be deducted rom the various graphs below, the data o which

are based o the bids or proposas pbished i the Eropea Jora.

FIGuRE 1. EvOluTIOn OF DIGESTIOn CAPACITy In EuROPE (Eu + EFTA COunTRIES) (WITH TPA = TOnES

PER AnnuM)

1.600

Germa

ny

1.400

1.200

1.000

800

600

400

200

0

80.000

70.000

60.000

50.000

40.000

30.000

20.000

10.000

0

Spain

France Ital

y NL UK

Switze

rland

Belgiu

mPor

tugal

Austria

Swede

nMa

lta

Luxem

burg

Norwa

y

Denma

rkPol

andFin

land

InstalledCapacity(kTon/y)

Total Capac ity Average Capac ity

FIGuRE 2. DIGESTIOn CAPACITy In vARIOuS EuROPEAn COunTRIES (2010) In TOnS PER yEAR


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4.000

till199

0

3.500

3.000

2.500

2.000

1.500

1.000

500

0

100%

90%

80%

70%

60%

50%

40%

30%

0

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

>2009

Cumulative(kTon/y)

20%

10%

2006

2007

2008

2009

2010

2011

% Meso % ThermoMeso Thermo

FIGuRE 3. EvOluTIOn AnD RATIO OF MESOPHIlIC AnD THERMOPHIlIC DIGESTIOn CAPACITy

FIGuRE 4. EvOluTIOn AnD RATIO OF WET AnD DRy DIGESTIOn CAPACITy

till199

0

3.500

3.000

2.500

2.000

1.500

1.000

500

0

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

Cumulative(kTon/y)

2006

2007

2008

2009

2010

70%

60%

50%

40%

30%

20%

10%

0%

% Wet % DryWet Dry


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4.000

till1

990

3.500

3.000

2.500

2.000

1.500

1.000

500

0

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

Cumulativ

e(kTon/y)

2006

2007

2008

2009

2010

4.500

5.000

80%

70%

60%

50%

40%

30%

20%

10%

0%

90%

100%

% One % TwoOne Cumulat ive Two Cumulat ive

FIGuRE 5. EvOluTIOn AnD RATIO OF 1-PHASE AnD 2-PHASE DIGESTIOn CAPACITy

3. LegAL And PoLiticAL FrAMeWorK

Iormatio o aaiabiit o techoog i geera ad i dieret co-

tries ca be od i chapter 2. With regard to aorabe egisatio, the

sitatio is idetica to that or aerobic compostig ad the acceptace o

compostabe packagig i biowaste. I most cotries athorities are ot

aowig the additio o compostabe packagig or prodcts to biowaste

which is sigicat hiderig the breakthrogh o biopastics. O i The

netherads the additio is aowed.


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4. AnAerobic digestion And bioPLAstics:

stAndArds, certiFicAtion And LAbeLLing

The ormatie bechmark or the orgaic recoer o packagig ad bio-

pastics i Erope is represeted b the Eropea harmoized stadard

En 13432 "Packagig - Reqiremets or packagig recoerabe throgh

compostig ad biodegradatio - Test scheme ad eaatio criteria or

the a acceptace o packagig". This stadard aims "to determie the

compostabiit ad aaerobic treatabiit o packagig ad packagig ma-

terias".1 Accordig to the En 13432, "compost is ot o the a prod-ct o the aerobic compostig process bt aso the aerobica stabiized

prodct o the aaerobic biogasicatio process".2 I practice, the ocs

is o the prodctio o a a compost, ree o cotamiats. This ca be

obtaied thaks to two steps: a rst aaerobic phase oowed b a aero-

bic phase, eeded to stabiise the aaerobic sdge. The En 13432 does

ot ocs o the recoer ied o the packagig as biogas. Howeer, the

aaerobic biodegradatio ca be estimated with specic stadards (e.g.

ISO 11734, ISO 14853, ISO 15985, Ecetoc #28, ASTM D.5210-92, ASTM

D.5511-02, ASTM D.5526-94). I the En 13432, a ote ca be od:

aaerobic biodegradatio ad disitegratio ca be eried as a optio

(ot madator). For biodegradatio, 50% is reqired ater 2 moths as

aaerobic ermetatio is oowed b aerobic compostig, drig which

biodegradatio ca rther cotie. With regard to disitegratio, the

stadard reqires that ater 5 weeks o combied aaerobic ad aerobic

treatmet at most 10% o the origia sampe ma remai ater sieig

oer 2mm mesh size. no rther detais are specied. I a ote it is rther

metioed that these reqiremets might chage i the tre, wherther iormatio ad experiece become aaiabe.

The discssio ad stadardisatio o reqiremets or aaerobic biode-

gradatio or preerab aaerobic treatabiit is sti i a ear, iitia phase.

Oe idea, which is aso circatig, is to reqire o disitegratio ater

aaerobic testig, argig that biodegradatio ca be achieed i sbse-

qet aerobic compostig ad/or soi appicatio.

no specic certicates or abes o aaerobic treatabiit exist crret

(2010), or are oresee or the ear tre.

5. interActions betWeen bioPLAstics And tecHnoLogY

I order to be compatibe biopastics shod, rst o a, be biodegraded d-

rig the treatmet process, jst as with aerobic compostig, sice aaerobic

digestio is a bioogica waste treatmet process. Whether the biodegrada-

tio occrs drig the rst aaerobic phase or drig the secod aerobic

phase has o impact o the qait o a compost, whie it cear has o

the biogas prodctio. Correct recoer is assred as og as biopastic is

eeta biodegraded ad o resides are et.

I this cotext, whether or ot biopastics are prodced rom reewabe

resorces is ot reeat. The ke eemet is or them to be biodegradabe

ad compatibe with the aaerobic digestio process.

Cocerig techica precoditios o treatig biopastics i aaerobic

digestio pats, a distictio mst be made betwee wet ad dr techo-

ogies. I most dr sstems, biopastics ca be added i some bodar

coditios are ed: the shod be redced i partice size beore ete-

rig the digestio (jst ike biowaste itse), ad sieig shod be ocated

at the ed o the process i order to eabe as mch biodegradatio ad

disitegratio as possibe i both the aaerobic digestio ad the aerobic

compostig step.

I the case o wet techoogies, pretreatmet o biopastics is reqired

to make them processabe. Otherwise, the are ote remoed either b

fotatio or b sedimetatio i the rst ppig ad hdrosis phase ad

thereore are ot rea eterig the digestio (except whe biopastics

are qick sobe or dispersibe). Aother sotio cod be to add the

biopastics direct to the 2d aerobic compostig step (cosiderig the

retetio time i this 2d step is mch shorter tha the residece time i

a tpica compostig process).

The major derig reaso wh seera biopastics show a dieret bio-

degradatio behaior i aerobic compostig ad i aaerobic digestio

coditios is de to the ifece o gi. Fgi are abdat aaiabe

ad er actie i aerobic compostig, whie i aaerobic ermetatio, o

1EN 13432: Packaging. Requirements or packaging recoverable through composting and biodegradation. Test scheme and evaluation criteria or the fnal acceptance o packaging, Scope, Clause 1.2EN 13432: Packaging. Requirements or packaging recoverable through composting and biodegradation. Test scheme and evaluation criteria or the fnal acceptance o packaging, Scope, Clause 5.


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gi are actie. Some pomers are mai (or ee o) degraded b -

gi ad ot b bacteria, ad wi thereore biodegrade o i aerobic

compostig ad ot, or o mch sower, i aaerobic digestio. As a

matter o act, this is aso the case or the atra pomer igi, which ca

be od i wood, straw, shes, etc.

O the other had, whe biopastics do biodegrade aso i aaerobic er-

metatio, there is a dobe beet. First o a, eerg is prodced rom

the biopastics der the orm o biogas to be coerted to eectricit. Se-

cod, as most biopastics are er rich i carbo ad do ot cotai

itroge (or er itte), the additio o biopastics to biowaste wi improethe carbo to itroge (C/n) ratio o the mixtre. Biowaste teds to be ow

i C/n, which is sometimes a probem i aaerobic digestio, b addig a

carbo-rich sbstrate, the C/n ratio is icreased.

So ar, itte iormatio o aaerobic biodegradatio o biopastics is

kow, ad rther research wod be wecome to assess the potetia

biogas (eerg) prodctio de to the biopastics. Idea, biopastics wod

biodegrade ad aso disitegrate drig the aaerobic phase i a aaero-

bic digestio pat, jst as the major part o atra biowaste does. How-

eer, i the biopastic disitegrates drig the aaerobic phase ad the

aterwards biodegrades compete drig the aerobic stabiisatio phase

or drig the se o digestate or compost i soi, it ca aso be cosideredto be compatibe with aaerobic digestio.

6. beneFits And cHALLenges

6.1 Benets

Eerg prodctio. This ca ead to a tripe beet or wi-wi-wisitatio: (1) biopastics cotai reewabe resorces, (2) drig biode-

gradatio, (reewabe) eerg is prodced i the orm o biogas ad, (3)

the resida matter ad biomass prodced remais as compost.

Improemet o C/n ratio. As biowaste, especia whe mai

kitche waste, is ote rich i proteis, the C/n ratio ca be reatie

ow (


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8. Annex - reFerences; LinKs etc

1. De Baere . ad Matthews B. (2008). State-o-the-art 2008. Waste Maagemet Word, J-Agst 2008

February 2011

European Bioplastics e.V.

Marienstrae 19/20

10117 Berlin

Phone: +49 (0) 30 284 82 350

Fax: +49 (0) 30 284 84 359

[email protected]

www.european-bioplastics.org

not a certied compostabe biopastics wi degrade to the same

extet i the aaerobic digestio step, ad the ma perorm dieret

i the dieret techoogies. For this reaso, more iormatio is

eeded o the behaior o dieret biopastics i dieret aaerobic

digestio sstems.

Pretreatmet ca be a critica actor ad determie the processabiit

o a compostabe biopastic i a aaerobic digestio pat.

6.2 Challenges

I some AD pats, o-reccabe paper ad biopastics are added

to biowaste withot hiderig the good operatio ad ctioig o

these pats or ma ears aread, e.g. the AD pats i Brecht ad

Teeie, Begim (both dr 1- stage sstems).

Compostabe bags are accepted i arios pats, e.g. Skeetea

Swede (wet oe-stage aaerobic digestio pat); SIS, Passa,

Germa (dr horizota pg fow pat); ZAW-SR, Eiterhoe, Germa,

(dr batch aciit); ETRA, Bassao de Grappa, Ita (dr ertica pg

fow pat),; ACEA Tri, Ita (wet aaerobic 1-stage digestio pat).

7. Successful Cases

Documents

FactSheet Anaerobic Digestion