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Manure, the sustainable fuel
for the farm
Workshop name
Venue, dd month yyyy
Speaker‟s name
Workshop content
• Introduction
• Project planning
• Project implementation
• Biogas plant operation
• Economy
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Introduction
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Small scale Biogas Plants in …
(Remark: Please insert data or graph related
to the biogas market in your country)
Incentives for the implementation of
small scale biogas plants:
4
• Governmental Goals
• Emmission trading certificates
• Renewable Energy Law
• Subsidies
• Personal incentives: energy
independancy, additional income
Biogas Technology
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Process conditions:
- Under exclusion of air (anaerobic)
- Moisture (max. 20 % DM in wet digestion)
- Heat: 35°C – 45°C (often), 50°C – 55 °C (rare)
- Neutral to slightly alcaline pH-value
Microbial(Biological)Process
(wet) Biomass
Solid, liquid manure, org. residues, energycrops
Digested substrate
Nutrients
Biogas (CH4, CO2)
The Digestion Process
• Well-known feedstock;
• Potentially available in significant quantities;
• Good for co-digestion with other feedstock
such as food waste;
• Economically feasible only if biogas digester
is located at the place of manure production:
• transportation of manure is costly
• manure has relatively low-biogas yields.
Manure
Characteristics of Liquid Manure Collection
Daily fresh supply is important!
Manure store for longer periods of time (due to slatted/
perforated floors and manure cellar) decreases
specific gas yield
Preferable:
Stables with external manure storage
A manure system based on scrapers
Usage of daily fresh manure
Additional benefit: hygienic advantages on the stable
atmosphere due to a reduction of harmful gases from
the manure
Characteristics for Solid Manure Collection
10/30
Quantity and quality of material removed from outdoor
feedlots is influenced by uncontrollable climatic
conditions
Significant soil is removed during cleaning which leads
to high ash content in the manure
Dry matter content of harvested manure averaged
75% as compared to the original excreted manure that
is approximately 10%.
Ash content of harvested manure is approximately
66% as compared to a 20% ash content in excreted
manure
Organic matter content: 25-30% (50-80% excreted
manure)
CosubstratesOld breadApple pomaceSpent grains / daffBiowaste (households)Grease trapFlotation fatFrying fatVegetable residuesGrain sweepingsCerial mashGlycerineCoffee draffCacao shellsPotatoe leafsPotatoe peelsPotatoe mashLeafsMolassesWheyFruit pomaceRape meal extractColza cakeLawn cuttingsCanteen / Catering WasteOnion peels……
Organic Residues
Corn Cob MixEnsiled fodder peasEnsiled fodder beetsCereal mashCereal strawGrass silageRye total plant silageOat silagePotatoesPotatoe mashClover grass silageAlfalfa silageCorn seedsCorn silageRape seedsRye grainsRed clover silageEnsiled beets (in general)Sun flower total plant silageTriticale total plant silageTriticale grainWheat total plant silageWheat grainsEnsiled sugar beets…..
Energy Crops
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Source: Handreichung Biogasgewinnung und –nutzung, Fachagentur Nachwachsende Rohstoffe e. V.
Landfill gas5%
Sewage sludge11%
org. Residues7%
Slurry and Manure / Dung
27%
Agricultural by-product
25%
Material from land
conservation activities
3%
Energy crops22%
Share of different digestible organic mass
flow related to the total potential
The Gas
CvHwOxNySz
Organic Substance
Bacteria
Heat
Biogas: (composition)
CH4: 45 – 70 Vol-%
CO2: 25 – 50 Vol-%
O2: 0 – 3 Vol-%
N2: 0 – 5 Vol-%
H2O: 0 – 10 Vol-%
H2, NH3, H2S in ppm-level
1 m³Biogas
= 0,6 Liter Fuel Oil(with 60 Vol-% CH4)
Digestor Types
Completely mixed reactor (standing): Slurry storage made of concrete or steel, mixedand heated, can come in differnt hights andwidths
Plug flow reactor (horizontal): Steel
or concrete tank with paddle stirrer, heated
Biogas plants are operated in different ways:
Overflow system
communicating vessels
• Through hydrostatic pressure, liquid level is
at the same height in the connecting pipe
• Liquid levels balance themselves
• Overflow works
Functional principle
The Conversion process
Process heat
to digester
Biogas
Electric energy Thermal energy
Energy for use
Energy conversion
(CHP, Fuel cell)
Vorgrube
Kondensat-abscheider
Feststoffeintrag
Basic Components of a small scale
Biogas Plant
Rührkessel-reaktor Endlager
Überschusswärme
HeizöltanksBHKW
Further plant components which could be necessary for
the digestion of organic residues and energy crops:
• Reception bunker or –pit
• Crushing technology
• Separation of impurities
• Hygienisation unit
• Hydrolysis tank
• Dosing unit
Advantages & Aims of Biogas
Technology
1. Energy– Production of gas, heat and
power
2. Ferilizer value– Avoidance of nutrient losses
– Reduction of plant corrosion
– Improvment of fluidity
– Improvment of plant
compatibility
– Improvment of plant health
– Reduction of germination
capacity of weed seeds
3. Environmental Compati-
bility– Reduction of odour
– Reduction of methane and
ammonia emissions
– Reduction of nitrate leaching
– Hygiensiation
– Recycling of organic residues
– Avoidance of sewer connection
in remote areas
Feedstock & Microbiology
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Biogas formation
• Biogas is formed by microorgani-
sms that degrade organic material
under anaerobic conditions
• Naturally occurs e.g. in
landfills, bogs & mires, manure
storage tanks
• Complex & interdependent process
that happens in several stages
Feedstock for Biogas plants
www.de.wikipedia.org www.duden.de
www.de.wikipedia.org www.fraunhofer-umsicht.de
IBBK Fachgruppe Biogas GmbH
Organic matter – feedstock for
microorganisms
• Feedstock (fresh
matter) consits of:
water + dry matter
Volatile solids [from % FM or % DM ]
Mineral solids (ash)
Water content
Dry
matt
er
(DM
)
Fre
sh
matt
er
(FM
)
• Microbes “eat”
volatile solids
(= VS),
The 4 Steps of Biogas Formation1. Step
Hydrolysis2. Step
Acidogenesis3. Step
Acetogenesis4. Step
Methanogenesis
hydrolyticBacteria
acidogeneticBacteria
acetogenicBacteria
methanogeneticBacteria
Fatty acids(Propionic acid)
Alkohols
BiomassPolysacharids
ProteinsFats
SugarsAminoacidsFatty acids
BiogasCH4/CO2
H2/CO2
Acetic acidH2
one-stage
process
biogas digestate
The different degradation processes ...
• … occur at the same time simultaneously
In agricultural biogas plants the separation of the
degradation stages plays a minor role
• … strongly depend on each other
Intermediate products are needed for following processes
• … can cause mutual inhibition
▪ Intermediate products may not accumulate
▪ Product inhibition
• … develop slowly in advanced stages
Hydrolysis is the fastest, methane formation
the slowest
Odour reduction of animal slurry
through digestionR
ela
tive c
oncentr
ation [%
] x
Retention time [days]
An import basic substrate for biogas
production: manureMean values of few raw manure and digestate samples
of “Biogas plant Oberlungwitz”
Raw manure Digestate
DM [%] Nitrogen Ammonium Phospho-
rous
Potash Magnesium Calcium pH-value
Temperature ranges
• Psychrophil (< 25 °C)
low growth rate long retention times
inefficient for biogas production no longer in use
• Mesophil (32 - 45 °C)
stable biocoenosis satisfying gas yield with acceptable retention time
common, particularly in wet fermentation processes
• Thermophil (50 - 60 °C)
high gas yield after short retention time
sensitive biocoenosis caution with rapid degradable substrates,
(hydrolysis develops too fast)
Project planning 1 – Process
parameters
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Dry matter contents
Dry matter (DM):
DM [%FM] = Measure unit for the sum of total solids in the substrat related to fresh mass
Volatile Solids (VS):
VS [%FM] = Measure unit for the sum of volatile solids in the substrat related to fresh mass
VS [%DM] = Share of the volatile solids in dry matter
• Biogas production only possible from VS!
• Important: determination of degradable part of VS
(Hydraulic) Retention time t, HRT
[days]x
d
m³Input SubstrateDaily
[m³] VolumeWorking[d]HRT
Working Volume = Usefull reactor volume
• central planning parameter with manure plants
• less important parameter with energy crops or waste
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Retention time of solid feedstock
m³
tContent DigesterDensity
[t]feestock solid of Tonnage[m³]Input
Density Digester Content ≈ 1 t/m³
• Solid feedstock is added by tonnage
converstion to volume needed:
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Example:
daily manure input: 5 t/Tag
Digestor – Working Volume: 300 m³
Gas space: 30 m³
d 54
³1
5
m³ 30 - 300 VZ
m
td
t
Recommended retention times with mesophilic temperatur in
digester: (depending on process and reactor)
min max
Liquid hen manure: 20 - 40 Days
Liquid pig manure: 22 - 50 Days
Liquid cow manure: 25 - 60 Days
Solid cow manure with straw: 40 - 90 Days
³][
)(
³BR
mumeworkingvol
dVSkgDayDrymatter
dm
oDMkg
• Dry Matter (DM, VS, CSB, TOC) - Load per m³ working volume
• Tendency for higher loading rate (Energy crops, Waste)
• Alternative: Digester load
- related to VS in Reactor (bacterial density)
- at the moment no relevance
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Organic Loading Rate BR
Project planning 2 –
Feedstock
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Feedstock related biogas yields
Source: LFL
20
20
56
176
185
208
292
590
598
875
48
57
0 100 200 300 400 500 600 700 800 900 1000
Dairy slurry (8,5 % TS)
Pig slurry (6 % TS)
Poultry manure (15 % TS)
Total plant silage (38 % TS)
Corn silage ( 33 % TS)
Gras silage (40 % TS)
Weizenstroh (86 % TS)
Corn, dry (87 % TS)
Wheat grains (87 % TS)
Used oil & fat (95 % TS)
Kitchen waste (14 % TS)
Vegetable waste (15 % TS)
spez. Biogas yield [m³Bioas/tSubstrat]
Biogas yields from feedstock
Is determined by:• Ingredients of the
substrate
– Organic content (volatile solids / VS)
– Proportion of fat, protein and carbohydrates
• Retention time in digester
• Form of preparation
• Process temperature
Source: C. Tidjen, FAL
Methane production Maize
silage
Process time [d]
Organic constituentsGas yield [m3/kg]
Methane content [%]
Raw protein 0,7 71
Raw fat 1,25 66
Raw fiber 0,79 50
Free N extract materials 0,79 50
Source: Roediger
Detailed feedstock data
Remark: values are general, for exact valuesan individual substrate analysis has to be undertaken!
Manure
Energy crops and agricultural subproducts
Agroindustrial and slaughter house wastes
FeedstockDM
[% FS]oDM
[% FS]oDM
[% TS]Methane[Vol%]
m³CH4/t oTS
m³ Biogas/ t FM
Cow manure 8,5% 7% 85% 55% 280 20
Pig manure 6% 5% 85% 60% 400 20
Hen manure 15% 11% 75% 65% 500 56
Maize corn dry 87% 86% 98% 53% 690 590
Grass silage 40% 36% 89% 54% 584 208
Wheat corn 87% 85% 98% 53% 701 598
Maize silage 33% 32% 96% 52% 586 185
Wheat straw 86% 79% 92% 51% 369 291
Green grain silage 38% 35% 93% 53% 496 175
Vegetable waste 15% 11% 76% 56% 500 57
Kitchen waste 14% 11% 82% 60% 420 48
Old fat 95% 87% 92 % 68% 1000 45
Source: LFL
Operators‟ do‟s & dont‟s
• Do start slowly → give micro-organisms time to adapt
• Do provide stable conditions for your little co-workers:
– Regular feeding of same ration
– Maintain a constant temperature
• Do regular plant checks
– Keep a data log
• Don‟t be erratic & unreliable!
Project planning 3 – Biogas
plant components
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Planning and designing of
Components
Mixing pit:Storage time
Digester:Organic loading rate,Retention time,Substrate mixing
Substrate storage:Storage time
SolidsFeeder:Bunker size
CHP:Gas potential
Silo:
Required area,
Volume,
Storage time
• Storage capacity max. ca. 5 days
• Leachate of silo and percipitation (if possible)
• Possibilities of mixing-in co-substrates
• Not too big: Mixing energy
Solids feeder
• Storage capacity of min. 1 day
• Density of energy crops loose ca. 0,5 t/m³
• Avoid too long storage time: composting!
• Control of mass flow instead of time
Sizing of feeding systems
Mixing pit
Digester sizing
• Design according to hydraulic retention time (manure based plants)
– 50–60 days
• Design according to organic loading rate (energy crop and waste
plants)
• Loading rate will be higher with more energy crops
– Less manure BR = ca. 4 kg oTS/m³ d
– More manure BR = max. 2 kg oTS/m³ d
• Future plant extention should be included in planning
– First step lower organic load => bigger digester than needed
– Easier operation from the beginning
– After a successful learing time organic load can be increased
• Digestate storage requirement
• Consider mass loss through biogas process
– Very low with liquid manure (ca. 5 %)
– Relatively high with energy crops and wastes (ca. 25 %)
– Very high with corn of grain (ca. 75 %)
• Formula for design (6 months storage):
• Consider already available storage!
• Post digester = Storage volume
Necessary storage Vol.[m³] = (Substrate input[t] – Mass loss[t]) / 2
Sizing digestate storage tank
• Expected gas yield and expected methane contentBiogas [m³/a] * CH4-Cont. [%] = Methane yield [m³ CH4/a]
• Energy content methane: 10 kWh/m³Methane yield [m³ CH4/a] * 10 kWh/m³ = Brutto energy [kWh/a]
• Elektrical efficiency hel (30 – 40 %)Brutto energy [kWh/a] * hel = Elektrical Energy [kWh/a]
• Desired full load hours hfull = ca. 8.000 h/aElektr. Energy [kWh/a] / hfull [h/a] = theor. continous load [kW]
Sizing of CHP unit
Environmental & Social
benefits
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Environmental Benefits
Triple benefits for GHG-emission reduction:
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1. Methane emission reduction through bettermanure management agricult. GHG ↓
2. Energy production from biogas (power, heat,
vehicle fuel) GHG from fossil fuels ↓
3. Better fertiliser value less need for mineral
fertiliser GHG from fertilser production ↓
Environmental Benefits
plus
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4. Weed and pathogen control through AD
5. Phosphate recycling saves scarce P-
sources
6. Reduced odour emissions from animal
husbandry
Manure vs. Digestate
Advantages of digestate
• low in odour → appreciated by
population
• improved plant compatibility
• better flowability → easier soil penetration
• high share of NH4 → more effective, better
control of fertilising effect, reduced leaching
into ground water
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Social Benefits
AD gives farms & rural areas new perspectives:
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+ Additional income for farms (or reduced energy
costs, e.g. through self-supply in Belgium)
+ Local companies are involved in construction
of AD plants, maintenance and repair
Support of SME in rural areas
Strengthening of a regional financial circuit
• Decentral (renewable) energy production
diversification of energy supply
→ 50% of renewable energy plants are owned
by citizens (partly aiming at supplying
regional energy)
→ 754 energy cooperatives
→ 70 new public service companies since 2005
Social Benefits from renewables –
facts from Germany (status quo 2012)
52
Source: IÖW: Wertschöpfung durch Erneuerbare Energien, SR 210/15, Dez. 2015
• Direct national added value from renewables:
18.9 billion €
→ 12.5 billion € (= 66 %) remain on commu-
nal/ municipal level
→ 177.150 full-time jobs, 75 % in planning,
production & installation
Social Benefits from renewables –
facts from Germany (status quo 2012)
53
Source: IÖW: Wertschöpfung durch Erneuerbare Energien, SR 210/15, Dec. 2015
Main messages
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• Manure is available free of costs→ Additional income for farms
• AD is good for the environment→ 3-fold reduction of agriculture„s CO2-
footprint
• AD makes rural live more attractive→ Creates or keeps jobs in rural areas
→ Less smell from animal husbandry
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