joan mata alvarez

Technologies and approaches for anaerobic

digestion

Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008

Joan Mata-AlvarezUniversitat de Barcelona

Dpt. Chemical Engineering

GRUP DE RECERCA EN BIOTECNOLOGIA AMBIENTAL

XARXA DE CENTRES DE SUPORT A LA INNOVACIÓTECNOLÒGICA

DEPARTAMENT D’ENGINYERIA QUÍMICA

Outline

• Aims• Introduction• Technologies and approaches

(Substrates)


(Substrates)• Environmental advantages• Heavy metals considerations• Some final remarks

Outline

• Aims

To offer a global vision of what can AD do and which


what can AD do and which are their strengths and weakness of this technology

ANAEROBIC DIGESTION

Multistep process

ORGANIC MATTER


BIOGAS + CEL MAT.

Reduced amount

65% CH435% CO2

No external electron acceptor

Process Organicpolymers

Organicmonomers

Reducedorganics

NO3-

SO4=

NH4+

H2SAceticacid

Carbondioxide

H2 CH4 Microorganisms

Hydrolysis oforganic polymersFermentation oforganicmonomers

Fermentativebacteria

Oxidation ofreduced organics

Obligate hydrogenproducing bacteria(OHPA)

Acetogenicrespiration ofbicarbonate

Homoacetogenbacteria

Oxidation ofreduced organicsby SRB and NRB

Sulfate-reducing(SRB),nitrate-reducing

TWO-STEP REPRESENTATION

ORGANIC MATTER

VOLATILE

Hydrolysis /Fermentation


by SRB and NRB nitrate-reducing(NRB) bacteria

Oxidation ofacetate by SRBand NRB

SRB and NRB

Oxidation ofHydrogen by SRBand NRB

SRB and NRB

Aceticlasticmethanogenesis

Aceticlasticmethanogenicbacteria

Hydrogenotrophicmethanogenesis

Hydrogenotrophicmethanogenicbacteria

Organic polymers : Carbohydrates, Lipides, ProteinsOrganic monomers : Sugars, organic acids, aminoacidsReduced organics : Volatile fatty acids (propionic, butiric, valeric)

Pohland, 1992

VOLATILE FATTY ACIDS

BIOGAS

Methanisation

• First full scale applications in a widespread basis were in Germany and Austria (80’s)

• Since then, this technology has attracted the attention to different countries. For


instance, in 95-96, in began to be considered in Spain.

• The overall installed capacity of AD plants treating OFMSW is now around 4 MM t/y

EVOLUCIÓN DE LA CAPACIDAD

2500000

3000000

3500000

4000000

4500000

TO

N/A

ÑO

First applications in Germany and Austira (2nd half 80’s)

In 95-96 began to be considered in Spain,

Europe Spain

Evolution of the installed capacity in Europe and Spain


0

500000

1000000

1500000

2000000

<1990 91 92 93 94 95 96 97 98 99 2000 2001 2002 2003 2004 2005 2006

TO

N/A

ÑO

EuropeTotal Tot. Acum .

SpainTotal Tot. Acum .

EVOLUCIÓN DE LA CAPACIDAD

2500000

3000000

3500000

4000000

4500000

TO

N/A

ÑO

First applications in Germany and Austira (2nd half 80’s)

In 95-96 began to be considered in Spain,

Evolution of the installed capacity in Europe and Spain

Europe Spain

• The overall installed capacity of OFMSW – AD in Europe is around 4 million ton/year, half of which are treating biowaste.


0

500000

1000000

1500000

2000000

<1990 91 92 93 94 95 96 97 98 99 2000 2001 2002 2003 2004 2005 2006

TO

N/A

ÑO

EuropeTotal Tot. Acum .

SpainTotal Tot. Acum .

treating biowaste.• However it is still a small share

compared with the total MSW produced in Europe or with the installed incineration capacity (more than 10 times higher).

DIGESTER

GREEN ENERGY:•CHP Application•Injection NG grid•Vehicle fuel

Biowaste

1 m1 m 33 Biogas: Biogas: ((60 % CH4)

6 kWh600 kg CO 2 emm. savings


CLO1.3 TWh energy100 Tg CO2/y

• Technologies and approaches


approaches

TECHNOLOGIES

Basically divided into two:• Dry: Over 15% TS


• Wet: Under 12% TS

Scheme of a wet AD plantWASTE STREAM

TROMMEL COARSE FRACTION

(NON-ORGANIC)

RECOVERED MATERIAL

RECOVERY OF RECYCLABLES

RESIDUAL WASTE

FINEFRACTION(ORGANIC)

PULPER/ SHREDDER


DILUTION AND THERMAL CONDITIONING

REMOVAL OF SAND AND GRITREMOVAL OF PLASTICS AND

LIGHT MATERIALSLIQUID

EFFLUENT

WASTEWATER

DIGESTATEDEWATERING

SYSTEMDIGESTER

Scheme of an AD plantWASTE STREAM


(NON-ORGANIC)

RECOVERED MATERIAL


RESIDUAL WASTE


PULPER/ SHREDDER

• “Dry” technology is simpler (less pre-





EFFLUENT

WASTEWATER

DIGESTATEDEWATERING

SYSTEMDIGESTER

• “Dry” technology is simpler (less pre-treatment and less water involved)

• Recirculation is needed to assure adequate inoculation of the feed.

Scheme of an AD plantWASTE STREAM


(NON-ORGANIC)

RECOVERED MATERIAL


RESIDUAL WASTE


PULPER/ SHREDDER





EFFLUENT

WASTEWATER

DIGESTATEDEWATERING

SYSTEMDIGESTER

Industrial technologies in Europe

AN DSD-CTAD.U.T. OrgaworldPaques RoedigerT.B.W. WABIO

MAT-BTAHAASE

< 3 plants 7-10 plants > 15 plants

KOMPOGASLINDE (KCA/BRV)VALORGAOWS-DRANCOROS-ROCA


WABIOIMK Werhle Werk Cecchini Komptech Babcock Alteno ISKAFarmatic SchwaBeconHeraBioEnergy (Horstmann)Heese

Number of plants% Capacity in Europa

Different types of physical and biological unit operations commonly found in AD plants

MECHANICAL SEPARATION

BIOLOGICALOPERATION:

Trommel

Screen (static or vibrating)

Magnet


ANAEROBICDIGESTION

COMPOSTING

Magnet

Foucault

Optical classification

Air classification

Hand separation

SUBSTRATE FED

TEMPER. USE OF BIOGAS

MODE OFOPERATION

Biowaste Mesophjilic CHP Batch

MS-OFMSW Thermophilic Grid Injection

Continuous

Cosubstrates Vehicle Fuel


FLOWPATTERN

NUMBER OF STEPS

SOLID CONTENTS

DIGESTATETREATM.

Mixed Single Dry No treat.

Plug flow Two-steps Wet Composting

Rat

e of

the

AD

pro

cess

Psichrophilic MesophilicThermophilic

Rat

e of

the

AD

pro

cess

Psichrophilic MesophilicThermophilic

Temperature ranges of operation

Beacon Conference on BiologicalTreatment Perugia 22-23 May 20083rd BFCNet WORKSHOP

BIOMASS FERMENTATION and FUEL CELLS as KEY to… 19-21 Jan 05

0 10 20 30 40 50 60 70 80

Temperature

Rat

e of

the

AD

pro

cess

35 550 10 20 30 40 50 60 70 80

Temperature

Rat

e of

the

AD

pro

cess

35 55

Thermofilic vs. Mesophilic AD


At low HRT, TAD gives better

yieldsAt high HRT,

yields are similar

Specific values depend on thespecific substrate

Supernatant withmore VFA content

C.B.A.

Inoculum recycle

DRANCO KOGAS VALORGA

PLUG-FLOW DIGESTERS


Digestedpaste

Biogasrecirculation

Feed

Feed Digestedpaste

Feed Digestedpaste

(Vandevivere et al., 2003)

Pre-treated OFMSW

FIRST STEP

RecirculatedLiq. Fraction

.

Fed. Screw .


)

SECOND STEPLiq. FractionDEWATER.

• AD plants in Barcelona

Ecoparc-2 de Montcada, Valorga

80,000 t/a


Ecoparc-1 de Barcelona, Linde

140,000 t/a 90,000 t/a


LINDE BRV in Valladolid (16,000 t/y)


DRANCO PLANT

Terrassa (Spain, 25000 t/y)

BEKON PLANT

Munich (Germany, 16000 t/y)

Good mass transfer (transport phenomena, contact

microorganisms-substrate)Good heat transfer

(specially in thermophilic systems)

REQUIREMENTS


(specially in thermophilic systems)Absence of mechanical problems(experience with different types of substrates)

Some operational dataSome operational dataSome operational dataSome operational data• Biogas production: 90-150 m3 biogas / ton of OFMSW (depending on substrate quality)

• This represents 100 - 150 KWh/t electricity surplus

• Biogas production: 90-150 m3 biogas / ton of OFMSW (depending on substrate quality)

• This represents 100 - 150 KWh/t electricity surplus


electricity surplus

•Thermophilic dry digesters may be operated at OLR’s of 10 - 12 kg VS/m3.d.

• At this load volumetric production is high: 5 - 7 m3/m3 reactor * d

electricity surplus

•Thermophilic dry digesters may be operated at OLR’s of 10 - 12 kg VS/m3.d.

• At this load volumetric production is high: 5 - 7 m3/m3 reactor * d

Substrates


• At full scale it can be applied to the OFMSW of different origins, combined or not with composting

• Basically it is applied to:

Biowaste MS-OFMSW

Mixed


OFMSWGrey bag

Biowaste AD approaches:

- Co-digestion:- Sewage Sludge- Agricultural wastes- Farm wastes- Agroindustrial Wastes.


- Agroindustrial Wastes.- Food markets- etc

Codigestion Possibilities

BIOWASTE in WWTPBiowaste AD plant+ SS

Common in some


• Interesting (uses already existing infrastructures)• Loading rate Digesters low

Common in some plants

EFECTOS DE LA ADICION DE FORSU EN LOS FANGOS DE DEP URADORA SORE EL LA PRODUCCION DE GAS Y EL TIEMPO DE RESIDENCIA

120,0

140,0

160,0

180,0

200,0

PO

RC

EN

TA

JE D

E IN

CR

EM

EN

TO

EN

LA

P

RO

DU

CC

IÓN

DE

BIO

GA

S O

DE

ELE

CT

RIC

IDA

D

19,5

20,0

20,5

21,0Incremento biogas/electricidad

Nuevo Tiempo de Residencia


0,0

20,0

40,0

60,0

80,0

100,0

0,0 2,0 4,0 6,0 8,0 10,0 12,0 14,0 16,0 18,0

PERCENTAJE DE INCREMENTO EN EL CAUDAL DE ENTRADA A L DIGESTOR

PO

RC

EN

TA

JE D

E IN

CR

EM

EN

TO

EN

LA

P

RO

DU

CC

IÓN

DE

BIO

GA

S O

DE

ELE

CT

RIC

IDA

D

17,5

18,0

18,5

19,0

19,5

• Environmental advantages


Advantages of AD for treating biowaste

• Use of biogas as a renewable resource implies savings on fossil fuels and GHG emissions. It can also reduce NO2emissions compared with other fuels.


emissions compared with other fuels. • Regarding the use of compost: • Savings on mineral fertilizers and on

organic matter (peat and straw), which also represents savings of GHG emissions.

Other advantages of compost or digestate soil application

SHORT TERM:• Less possibilities of soil erosion• Less irrigation requirements (better


• Less irrigation requirements (better water and nutrient hoding capacity)

• Better soil structure (porosity)

Other advantages of compost or digestate soil application

SHORT TERM:Less requirements for pesticides (phytosanitary effects)WHICH INDIRECTLY FAVOURS ENERGY GLOBAL


WHICH INDIRECTLY FAVOURS ENERGY GLOBAL REQUIREMENTS FOR AGRICULTURE.

LONG TERM:Additionally use of compost on agriculture

may sequestrate carbon in the soil

An example(Erhart 2008)


•The humus content of the solid decreased in the unfert. Control (3.4 to 3.15%) which is 6250 kgC/ha•With compost increased to 3.5-5.7% which is 1900 to 6500 kgC/ha depending on the compost app. Rate, which represented 10-19% of the Org.Carbon applied

• Regarding heavy metals (HM)…


(HM)…

Mass balance with codigestion

Biowaste Biowaste Rim 60% COMPOST D.Lgs 217/06Q, ton/y 60.000 Q, ton/y 65.300 TS, % 31 Sludge Rim 10% TS, % 51 TVS, % 84 TVS, %Cd 0,14 Green Rim 30% Cd 1,0 1,5Cr 7,80 Cr 33Hg 0,036 Hg 0,9 1,5Ni 4,00 Ni 28 100Pb 5,30 Pb 47 140Cu 25,10 Cu 143 150Zn 48,50 Zn 437 500

DIGESTER

Biowaste Rem: 60&

Sludge Rem: 10%

Green w. Rem: 20%

(Bolzonella and Cecchi, 2008)


Sludge GreenQ, ton/y 40.000 Q, ton/y 51.000 TS, % 20 TS, % 50TVS, % 70 TVS, % 80Cd 1,9 Cd 0,3Cr 35,0 Cr 12Hg 2,9 Hg 0,1Ni 26,3 Ni 14Pb 91,3 Pb 14Cu 272,0 Cu 33Zn 970,0 Zn 104

Cu and Zn close to the standards

More stringent HM limits should be avoided

Heavy metals content in crops(Erhart et al., 2008b)


• After 10 years of biowaste compost appl. no significant increases in HM mobility were observed. • Several crops have lower Cd conc. than wihtout fertilizer while Cd in minerally fertilized were significant higher

Another example Veeken et al. (2004).

Sequential chemical extraction of the fractions of biowaste showed that Cu, Pb, and Zn are very strongly bound to


Pb, and Zn are very strongly bound to the organic fractions and less than 1% is water soluble at different pH’s.

� Carefully selecting the limits to promote C recovery

Pre-dessertification stage


• Some final remarks


• Plants have quite different capacities, ranging from 16,000 t/y to more than 140,000 t/y and treating all kinds of OFMSW.

• Many plants have been started up without

Some final remarks


• Many plants have been started up without having in mind the implementation of separate collection of the organic fraction (just to boost recyclying objectives and to divert organic matter from landfill) and others without having yet implemented it.

Some final remarks

• The succes of biowaste AD is similar to other technologies, with plants showing economical and or operational problems


• Energy aspects are the most important when compared with other technologies

• Derived compost is a very valuable product. Macronutrient alone would need ca.90 kWh/t to be produced as mineral fertilizer

• Anaerobic co-digestion of biowaste and sludge can be a good solution to be implemented on specific places with very interesting costs

Some final remarks


very interesting costs

• Progress of AD technology is linked to the cooperation of technology providers, operators and clients

• Attention to the stringent limits of HM on compost

Grazie per la sua cortese attenzione!

Thank you for your kindattention!


Grazie per la sua cortese attenzione!

[email protected]

joan mata alvarez

Documents