Potential for Potential for Anaerobic Digestion of Anaerobic Digestion of Crop ResiduesCrop Residues
Ron Fleming & Malcolm MacAlpine (Ridgetown Campus of University of
Guelph), Jim Todd (OMAFRA)
CSBE09-706
FundingFundingOMAFRA – Alternative Renewable
Fuels Plus programU of Guelph/OMAFRA Agreement
ObjectivesObjectivesSuitability of various agricultural by-
products, mainly related to vegetable production and processing, as feedstocks for AD
Feedstock handling, processing and storage requirements
Optimum conditions to maximize methane production
Economic potential of using vegetable wastes as energy feedstocks
Nutrient quality of digestate
OverviewOverview3 year project – 2008 to 2010Use a pilot scale anaerobic digester Potential in Ontario to use organic
“waste” materials common in agriculture to produce energy through the use of an anaerobic digester◦Consider livestock manure as an input◦Look at crop residuals from various
field crops
Top 10 Vegetable Crops for Top 10 Vegetable Crops for Marketed Production in Marketed Production in OntarioOntario
Example: Tomato WasteExample: Tomato WasteAvailable for 8 weeks –
August/SeptemberWaste represents 3 to 13% of
total harvested3 types of processing wastes:
◦Pomace (mostly skins) – 800 t in 2008
◦Lye sludge (+/- 94% water) and Screenings (stems, seeds, etc) – 16,000 to 19,000 t
Potential Biogas YieldsPotential Biogas Yields
100 200 300 400 600
25 36
Liquid cattle manure
Liquid swine manure
93 103
155 171
195 202
Fodder beetsGrass
Green maize, dough stageCorn silage, dough stage, high-grain
Grass silage, first cutCorn silage, waxy stage, high-grain
35 39
68 90
291
220 400
469 486
552 600
657
Food waste
Potato mash, freshWhey
Potato peelingsSilage from sugar beet leafs
Brewer`s grain silage
Skimmed greaseMolasses
Waste breadCanola cake, 15 % fat
Waste greaseBaking wastes
(m3 biogas/tonne)
Description of AD SystemDescription of AD System152 cm diameter, 130 cm depth,
flexible domed top, total volume = 2.7 m3; liquid volume = approx. 1.8 m3
Complete-mixed mesophilic system
Mobile Anaerobic DigesterMobile Anaerobic Digester
Feeding Hopper and Feeding Hopper and AugerAuger
Auger Tube OutletAuger Tube Outlet
Mixing Paddle and Heating Mixing Paddle and Heating CoilsCoils
Electric and Heating Electric and Heating SystemsSystems
Gas Analyzer and Flow Gas Analyzer and Flow MeterMeter
Flare and Pressure Relief Flare and Pressure Relief TubeTube
Test MethodTest MethodVarious materials/mixtures
testedApprox. 4 weeks for each recipeDaily Monday to Friday:
◦Gas samples analyzed◦Gas volume recorded◦Gas flared◦Mixer started◦Material added
Loading rateLoading rateRanged from 0.5 to 1.2 kg VS/m3
digester capacityAverage hydraulic retention time
ranged from 21 to 40 days
Input #1 Input #1 Sugar beets + swine manureSugar beets + swine manure
www.extension.umn.edu/.../DC7715.html
Adding mixture of sugar beets and manure to feed hopper
Input #2Input #2Liquid swine manureLiquid swine manureHad been stored for several
monthsRepresents an input that is
plentiful
Input #3Input #3Sweet potatoesSweet potatoesChopped fineAdded to
digestate, mixed and added to digester as a slurry
No new liquids added
Input #4Input #4Sweet potatoes + (fresh) Sweet potatoes + (fresh) swine manureswine manure
Digestate removedSweet potatoes mixed with fresh
swine manure
Input #5Input #5Swine manureSwine manureFreshly produced manure
Input #6Input #6Dried tobacco Dried tobacco Nicotine-free tobacco leaves
(dry)Mixed with digestate before
adding to digester as a slurry
Sample AnalysisSample AnalysisBiogas:
◦Methane (CH4), Carbon Dioxide (CO2)
Inputs and outputs: ◦N, P, K, pH, NH4-N, C, ash
◦Calculated C:N ratio◦Calculated Volatile Solids
Results for 2008Results for 2008
Example of Daily Inputs and Methane Example of Daily Inputs and Methane Production – Sweet Potatoes & Swine Production – Sweet Potatoes & Swine manuremanure
Example of Cumulative Gas Production Example of Cumulative Gas Production and VS Inputs – Sweet Potatoes & Swine and VS Inputs – Sweet Potatoes & Swine manure manure
Sugar beets & swine manure – poor gas production – but – first test for the unit & problems with temperature control
Fresh swine manure yielded twice as much methane as older swine manure
Dried tobacco was the most difficult to mix
Digestion led to a decrease in DM and an increase in NH4-N
Input Biogas Methane content
Swine manure + sugar beets
57%
“Older” swine manure 64%
Sweet Potatoes 48%
Sweet Potatoes + manure
56%
“Fresh” swine manure 63%
Nicotine-free tobacco leaves
49%
Input Methane Produced (L/kg VS)
Swine manure + sugar beets
233
“Older” swine manure 336
Sweet Potatoes 547
Sweet Potatoes + manure
585
“Fresh” swine manure 670
Nicotine-free tobacco leaves
358
Advantages of this test Advantages of this test setupsetupCan change recipe fairly easily Don’t need huge quantities of
inputsIs a good demonstration unit –
technology transfer
LimitationsLimitationsCurrently only able to add inputs 5
days per weekA few design problems – e.g. input
auger not sufficient for many materials – some re-design needed
Initial difficulty keeping temperature constant – has been resolved
Assumes gas production stabilized within 4 weeks
This yearThis yearContinue testing – vegetable
wastes + other farm organic materials
Document logistical considerations for various materials
Document economic considerations
Questions?Questions?
