Biogas from Energy Crops and Biowastes Other/Oth_42...Plug flow systems – Result from a high...
Transcript of Biogas from Energy Crops and Biowastes Other/Oth_42...Plug flow systems – Result from a high...
Biogas from Energy Crops Biogas from Energy Crops and and BiowastesBiowastes
Charles Banks Charles Banks
University of SouthamptonUniversity of Southampton
Acknowledgements - Current project
Acronym: CROPGEN
Title: Renewable energy from crops and agrowastes
Contract: SES6-CT-2004-502824
Duration: 1 March 2004 – 28 February 2007
Total cost: 2.5 M€EC funding: 2.1 M€
website: www.cropgen.soton.ac.uk
Old technology - new application
• The technology of biochemical methane generation is well established
• Traditionally it has been used for waste stabilization
• Current focus is on energy production
• To be cost-effective in this role may require
– engineering and technical improvements to increase conversion efficiencies
– Selection and production of biomass feedstocks from a variety of sources
• including novel and multi-use crops and agro-wastes from integrated farming systems, commercial and industrial wastes and by-products.
BIODEGRADABLE ORGANIC MATERIAL
(CARBOHYDRATES, FATS, PROTEINS)
HYDROLYSIS SIMPLE SOLUBLE ORGANICS
ACID FERMENTATIONPROPIONIC ACID
BUTYRIC ACID
LONG CHAIN VFA
ACETIC ACID
ACETOGENESIS H2 + CO2ACETIC ACID
ACETOCLASTIC
METHANOGENIC
BACTERIA
HYDROGEN-USING
METHANOGENIC
BACTERIA
CH4 + CO2
METHANOGENESIS
Anaerobic digestion in its simplest form
• Closed reactor
• System of gas collection
• Production of biogas
• Production of digestate
Anaerobic
reactor
Gas storage
Energy
Heat
Energy use
excess
Product
Product use
Fibre compost
Product and Energy use
Storage and pretreatment
DIGESTER
Digestate
separator
Liquor
Fibre (straight to land)
Vehicle engine
Transport
CHP
Electricity
Process heat Space heat
Hot water
Gas engine turbine
Gas burner
or boiler
Biogas storage
Biogas cleaning
BIOMASS and AGRO-WASTE
Hydrogen reformation for fuel cell applications
Process types
Wet
Thermophilic
One stage Multi-stage
Dry
Mesophilic
Process differences
Wet Process Dry Process
• less than 15 % feedstock solids concentration
• one or several stages
• usually operate at 35oC
• requires water addition or recycle
• larger reactor
• proven technology for sewage sludge digestion
• more applicable to co-digestion with other waste
• more than 15% feedstock
solids concentration
• usually one stage
• can operate at 35oC or
55oC
• minimal water addition
• smaller reactor
• becoming most popular
choice for MSW
• more data and reference
plants needed
Wet digesterDry digester
mesophilic
thermophilic
Instantly recognisable!
Dry digester
Biogas as a renewable energy source
Local and
national
analysis
boundary
energy crops and crop residues
digestate
gas
FYM & slurry
residues
Anaerobic
digester
Crop and
animal
production
Processing plantproduct
Heat and power
Transport fuel
Local
housing,
industry, commercetransport
transport
Fuel, fertilizers, equipment CO2
CO2
CO2
waste
CO2
transport
analysis
boundary
analysis
boundary
Results: storage and pretreatment
• Some potential to increase methane production by alkaline and water-based pre-treatments, and certain spoilage organisms.
• More important, poor treatment or storage conditions reduce
biogas yields.
Digestion trials
• Single phase digestion trials on a wide range of substrates at laboratory and large scale providing valuable design data
Pilot plant trials for crops and agro-wastes
Results: single phase digestion trials• Single phase digestion trials on a wide range of substrates at
laboratory and large scale providing valuable design data
Volumetric and specific gas yields per kgVS. Trend lines based on 50-day average.
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05
Inp
ut
oT
S [
t/d
]
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Gas
au
sb
eu
te [
Nm
3/k
g o
TS
]
oTs Input [t oTS/d]
Biogasausbeute [Nm3/kg oTS]
Methanausbeute [Nm3/kg oTS]
Inp
ut
VS
[t/
d]
Ga
s y
ield
[N
m³/
kg
VS
]
Phase separation innovations
Single stage
Two stage
Permeating
bed
UASB
or AF
Plug flow
Uncoupling of solids and liquid retention time
Hydrolysis
and
acidification
reactor
Methanogenic
reactor
Two phase systems(coupled and uncoupled)
Permeating beds
Plug flow reactors
Permeating bed reactors
– Single bed systems using grass
and maize have given poor results even with pH control
– Permeating bed with second stage
high rate methanogenic reactors
gives greater potential for stable operation and biogas production
– May be some potential for certain
crop types but preliminary results
indicate that overall process
efficiency is likely to be poorer
than for single phase mixed reactors
– Potentially an interesting mix of fermentation products
Plug flow systems
– Result from a high initial loading in the reactor
– Plug flow may limit the overall loading that can be achieved
– Give an interesting gas and acid production profile (H2)
– May have potential for certain
waste types and the concept
could be further exploited for
refined fuel production and biorefinery intermediates
– Still to explore very high solids
systems with high recycle rates
R2 VFA profile and gas production
Day 1
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l-1
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Ethanol Methanol C-2 C-3 i-C4 C-4 i-C5 C-5 C-6 C-7 Biogas
R2 VFA profile and gas production
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Ethanol Methanol C-2 C-3 i-C4 C-4 i-C5 C-5 C-6 C-7 Biogas
Two phase systems
– Overall performance for the treatment of market wastes at thermophilic temperatures and the loading used shows no advantage in process stability or performance compared to single phase controls
– Uncoupling of solids and liquids retention time in a first phase mixed reactor using maize as a substrate failed to improve rates of hydrolysis and solids destruction
Digester VFA
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mg
CO
D/l
SSCSSC
SSC
SSC
start-up I II III
Digester alkalinity
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mg
CaC
O3/l
Alkalinity pH 4
Alkalinity ph 6
SSC
SSC SSC
SSC
start-up I II III
Process modelling• The anaerobic digestion model 1 (ADM1) has been adopted as a
basis for the establishment of:
– Virtual Laboratory
– DSS
European-wide
database on crop
species
Add of a Save option
Simulated results for
anaerobic digestion in
form of Figures and
Data matrices (Print
option)
ADM1
based model
Choice of Substrate
and Mixture of
Substrates
Choice of reactor and
plant type
Input of measured
crop and input data
Choice of reactor
specific data
Input of measured
reactor data
Possibility to change
Parameter
Change of model
Parameter for the
model from project
partners and own
research
European-wide
database on crop
species
Add of a Save option
Simulated results for
anaerobic digestion in
form of Figures and
Data matrices (Print
option)
ADM1
based model
Choice of Substrate
and Mixture of
Substrates
Choice of reactor and
plant type
Input of measured
crop and input data
Choice of reactor
specific data
Input of measured
reactor data
Possibility to change
Parameter
Change of model
Parameter for the
model from project
partners and own
research
Results: process modelling
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Time [days]
Bio
gas p
rod
ucti
on
[m
3d
-1]
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10
20
30
40
50
60
70
80
90
Meth
an
e c
on
ten
t [V
ol%
]
Biogas production (measured)
Biogas production (model)
Methane content (measured)
Methane content (model)
Preliminary results with original
ADM1. The model follows the
course of the experiment, but
the correlation is too low for
practical application
Adjusted model after first
manual calibration (khyd = 1 d-1)
Energy models
• Data base of energy inputs into the cultivation of different crop types established
• Factors affecting the energy use in the process have been identified
• Equations developed to account for energy usage in the digestion process
• Energy usage model developed based on typical anaerobic digestion plant configurations and substrates
Energy balance
• Inputs / outputs
• Direct energy
• Indirect energy
• Energy balance
• Energy ratio
Energy inputs
biofuel production
crop
production
biomass feedstock
direct energy
inputs
indirect
energy
inputs
fuel by-products
indirect energy inputs
other agricultural
inputs
Fossil fuels or substitute fuels from
the production process
machinery
labour
Direct and indirect energy
• Direct energy
– consumption of energy directly in the production process -includes:
• fossil fuels
• labour
• Indirect energy
– energy which has been used in producing something then used in the production process - includes:
• fertiliser
• pesticides / herbicides
• machinery
Direct & indirect energy inputs
constructionheat, powerprocessing
transport equipmentfuelproduct distribution
energy input type
production,
application equipmentapplication fuelfertiliser
production and transportfuel
equipmentfuelharvest
indirectdirectoperation/input
equipmentfuelcultivation
Energy inputs in maize crop production
operation
No of
operations equipment time (h/ha)
energy of
equipment
MJ/ha tractor (kW)
fuel used
(l/ha)
CO2 indirect
(kg/ha)
subsoil 1 subsoiler 1.333 120 90 14.6 5.4
plough 1 plough+press 1.333 120 90 17.5 5.4
drill/harrow 1 combined drill and harrow 0.62 158 90 3.9 7.1
fertiliser 1 fertiliser spreader 0.36 45 55 1.2 2.0
spray 2 sprayer 0.54 68 55 2.4 3.1
harvest 1 forage harvester 2 420 17.5 33.6
cart 1 trailer 2 120 55 7.8 5.4
ensile 1 tractor and bucket 1.48 8 55 5.8 0.4
tractor 90 kW 3.286 564 45.1
tractor 55 kW 4.38 297 23.8
fuel used (litres) 2785 MJ/ha 70.7 213.6
total indirect 1920 MJ/ha 131.2
hours
labour 9.7 18.8 MJ/ha
seed kg/ha 16 215 MJ/ha 2.4
chemicals (kg/ha)
N 150 6045 MJ/ha 285.6
P2O5 200 680 MJ/ha 140
K2O 175 1277.5 MJ/ha 79.3
packaging & transport 1362 MJ/ha
sprays 12.8 2432 MJ/ha 63.0
total energy input to crop production and storage 16.7 GJ/ha 915.2 kg/ha
Crop production inputs
0 1 2 3 4 5 6 7 8 9
fuel
machinery
fer tiliser
pesticides
labour
Energy requirement GJ ha-1
sugar beet
maize
wheat
soya
lucerne
Digester energy flows
digester 500m³ digestate
tank
gas collector
heat exchanger
p4
p3
p2
mix1 reception tank mixer 3.0 kJ s-1 0.64 hrs d
-1
mac1 feedstock macerator 2.2 kJ s-1 1.75 hrs d
-1
p1 digester feed pump 3.0 kJ s-1 1.75 hrs d
-1
p2 digester discharge pump 3.0 kJ s-1 1.75 hrs d
-1
p3 digester mixing pump 2.2 kJ s-1 7.25 hrs d
-1
p4 digestate heating pump 0.5 kJ s-1 8.0 hrs d
-1
reception tank
mac1 p1
mix1
air 2°C
dry ground 5°C
cladding steel 0.75mm
structural steel 6mm
insulation 100mm
concrete 300mm
digester contents 35°C
Main energy inputs are heat and electricity
An energy balance
GJ/year49,932energy value
GJ/ha157
m32,331,092biogas produced
m31,398,655methane
GJ/ha30
GJ/year9566total energy requirement
GJ/year259.5digestate disposal energy
GJ/year1350digester embodied energy
GJ/year420parasitic electricity requirement
GJ/year2133parasitic heat requirement
GJ/year93crop transport
GJ/year5310.6crop energy requirement
ha318crop area
t/day34.8daily load
m32000digester capacity
unitvalue
36%
20%1%
22%
4%
14%
3%
crop energy requirement nitrogen fretiliser
crop transport parasitic heat requirement
parasitic electricity requirement digester embodied energy
digestate disposal energy
Digestate
• the digestate is what remains after the biogas has been removed
• it contains most of the nutrients of the original feedstock
• the nutrients are in a form which are more available for crop uptake
• it has a consistency similar to slurry (approx 10% solids)
• it can be separated into solid and liquid fractions
Effect of digestate use on the energy balance
GJ/ha126.9mineral
GJ/ha22.7total energy requirement
GJ/ha30.1total energy requirement
GJ/ha6.04energy for nitrogen
net energy yield
GJ/ha134.3digestate
GJ/ha157methane energy value
GJ/ha9.3crop energy requirement
digestate fertiliser
GJ/ha16.7crop energy requirement
mineral fertiliser
unitvalue
Example energy comparisons
61.111740.4
energy of fuel produced
(GJ/ha)
13.241.49.2
energy for processing
(GJ/ha)
12.811.912.7
energy for crop production
(GJ/ha)
6.911.53crop yield (t DM/ha)
8563crop yield (fresh yield t/ha)
150147195fertiliser (N kg/ha)
wheat
grain
sugar
beet
OSR
seedcrop
bioethanolbiodieselfuel
Elsayed, M. A., Matthews, R. and Mortimer, N. D. (2003) Carbon and Energy
Balances for a Range of Biofuels Options, School of Environment and
development, Sheffield Hallam University, B/B6/00784/REP
8.346.836.363.795.502.352.201.84energy ratio (output/input)
166157.189124.8
8.38810.8
1616.715.511.9
1512.66.911.5
3840856
160150150147
whole
crop
triticalemaize
wheat
grain
sugar
beet
methane
146.1141.7132.465.5102.135.163.718.5net energy produced (GJ/ha)
166
8.3
11.6
15
38
80
whole crop
triticale
methane
Potential vehicle fuel produced per ha
0 1000 2000 3000 4000 5000
whole crop wheat CH4
silage maize CH4
whole crop OSR CH4
tops
wheat grain bioethanol
OSR biodiesel
wheat grain CH4
sugar beet bioethanol
sugar beet CH4
litres diesel equivalent per hectare (after processing energy deducted)
beet
Potential CHP per hectare
0 2 4 6 8 10 12 14 16 18
wheat grain
wheat whole crop
sugar beet
sugar beet tops
maize whole crop
OSR whole crop
potential output MWh per ha
heat
electricity
Feedstocks for biofuel production
• for biodiesel
– oilseed rape
– sunflower
– linseed
– soya
– peanut
• for bioethanol
– wheat
– sugar beet
– maize
– sugar cane
– lignocellulosicmaterial
• for biogas– barley
– cabbage
– carrot
– cauliflower
– clover
– elephant grass
– flax
– fodder beet
– giant knotweed
– hemp
– horse bean
– jerusalem artichoke
– kale
– lucerne
– lupin
– maize
– marrow kale
– meadow foxtail
– miscanthus
– mustard
– nettle
– oats
– pea
– potato
– rape
– reed canary grass
– rhubarb
– ryegrass
– sorghum
– sugar beet
– triticale
– turnip
– verge cuttings
– fetch
– wheat
Which
crops?
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7Barley
Cabbage
Carrot
Cauliflower
Clover
Comfrey
Cocksfoot
Elephantgrass
Flax
Fodder beet
Giant knotweed
Hemp
Horse bean
Jerusalem artichoke
Kale
Lucerne
Lupine
Maize
Marrow kale
Meadow foxtail
Miscanthus
Mustard
Nettle
Oats
Pea
Potato
Rape
Reed canary grass
Rhubarb
Rye
Ryegrass
Sorghum
Sudangrass
Sugar beet
Sunflower
Sweet sorghum
Triticale
Turnip
Vetch
Wheat
White cabbage
methane potential m³/kg VS added
CO2 and energy cycles
gas scrubbing
transport &
spreading
digestion
vehicle fuel
Sun
biomass
Biogas
digestate
CHP
CO2
vehicle fuel
heat &
electricity
cutting, collection &
transport
energy
material
electricity
biomass