joan mata alvarez
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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)
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
(Substrates)• Environmental advantages• Heavy metals considerations• Some final remarks
Outline
• Aims
To offer a global vision of what can AD do and which
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
what can AD do and which are their strengths and weakness of this technology
ANAEROBIC DIGESTION
Multistep process
ORGANIC MATTER
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
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
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
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
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
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
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
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.
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
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
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
CLO1.3 TWh energy100 Tg CO2/y
• Technologies and approaches
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approaches
TECHNOLOGIES
Basically divided into two:• Dry: Over 15% TS
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
• 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
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
DILUTION AND THERMAL CONDITIONING
REMOVAL OF SAND AND GRITREMOVAL OF PLASTICS AND
LIGHT MATERIALSLIQUID
EFFLUENT
WASTEWATER
DIGESTATEDEWATERING
SYSTEMDIGESTER
Scheme of an AD plantWASTE STREAM
TROMMEL COARSE FRACTION
(NON-ORGANIC)
RECOVERED MATERIAL
RECOVERY OF RECYCLABLES
RESIDUAL WASTE
FINEFRACTION(ORGANIC)
PULPER/ SHREDDER
• “Dry” technology is simpler (less pre-
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
DILUTION AND THERMAL CONDITIONING
REMOVAL OF SAND AND GRITREMOVAL OF PLASTICS AND
LIGHT MATERIALSLIQUID
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
TROMMEL COARSE FRACTION
(NON-ORGANIC)
RECOVERED MATERIAL
RECOVERY OF RECYCLABLES
RESIDUAL WASTE
FINEFRACTION(ORGANIC)
PULPER/ SHREDDER
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
DILUTION AND THERMAL CONDITIONING
REMOVAL OF SAND AND GRITREMOVAL OF PLASTICS AND
LIGHT MATERIALSLIQUID
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
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
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
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
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
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
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
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
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
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
Digestedpaste
Biogasrecirculation
Feed
Feed Digestedpaste
Feed Digestedpaste
(Vandevivere et al., 2003)
Pre-treated OFMSW
FIRST STEP
RecirculatedLiq. Fraction
.
Fed. Screw .
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)
SECOND STEPLiq. FractionDEWATER.
• AD plants in Barcelona
Ecoparc-2 de Montcada, Valorga
80,000 t/a
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
Ecoparc-1 de Barcelona, Linde
140,000 t/a 90,000 t/a
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
LINDE BRV in Valladolid (16,000 t/y)
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
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
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
(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
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
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
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
• 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
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
OFMSWGrey bag
Biowaste AD approaches:
- Co-digestion:- Sewage Sludge- Agricultural wastes- Farm wastes- Agroindustrial Wastes.
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
- Agroindustrial Wastes.- Food markets- etc
Codigestion Possibilities
BIOWASTE in WWTPBiowaste AD plant+ SS
Common in some
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
• 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
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
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
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
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.
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
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
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
• 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
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
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)
Beacon Conference on BiologicalTreatment Perugia 22-23 May 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)…
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
(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)
Beacon Conference on BiologicalTreatment Perugia 22-23 May 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)
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
• 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
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
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
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
• Some final remarks
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
• 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
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
• 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
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
• 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
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
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!
Beacon Conference on BiologicalTreatment Perugia 22-23 May 2008
Grazie per la sua cortese attenzione!
jmata@ub.edu
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