Transcript Potential for Anaerobic Digestion of Crop Residues

Potential for Anaerobic
Digestion of Crop Residues
Ron Fleming & Malcolm MacAlpine (Ridgetown
Campus of University of Guelph),
Jim Todd (OMAFRA)
CSBE09-706
Funding
OMAFRA – Alternative Renewable Fuels
Plus program
 U of Guelph/OMAFRA Agreement
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Objectives
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Suitability 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
Overview
3 year project – 2008 to 2010
 Use 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
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◦ Consider livestock manure as an input
◦ Look at crop residuals from various field
crops
Top 10 Vegetable Crops for
Marketed Production in Ontario
Example: Tomato Waste
Available for 8 weeks – August/September
 Waste represents 3 to 13% of total
harvested
 3 types of processing wastes:
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◦ Pomace (mostly skins) – 800 t in 2008
◦ Lye sludge (+/- 94% water) and Screenings
(stems, seeds, etc) – 16,000 to 19,000 t
Potential Biogas Yields
657
Baking wastes
Waste grease
Canola cake, 15 % fat
Waste bread
600
552
486
469
Molasses
Skimmed grease
400
220
202
195
171
155
291
103
93
90
68
Food waste
Corn silage, waxy stage, high-grain
Grass silage, first cut
Corn silage, dough stage, high-grain
Green maize, dough stage
Brewer`s grain silage
Grass
Fodder beets
Silage from sugar beet leafs
Potato peelings
Whey
Potato mash, fresh
Liquid swine manure
Liquid cattle manure
39
35
36
25
100
200
300
400
(m3 biogas/tonne)
600
Description of AD System
152 cm diameter, 130 cm depth, flexible
domed top, total volume = 2.7 m3; liquid
volume = approx. 1.8 m3
 Complete-mixed mesophilic system
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Mobile Anaerobic Digester
Feeding Hopper and Auger
Auger Tube Outlet
Mixing Paddle and Heating Coils
Electric and Heating Systems
Gas Analyzer and Flow Meter
Flare and Pressure Relief Tube
Test Method
Various materials/mixtures tested
 Approx. 4 weeks for each recipe
 Daily Monday to Friday:
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Gas samples analyzed
Gas volume recorded
Gas flared
Mixer started
Material added
Loading rate
Ranged from 0.5 to 1.2 kg VS/m3 digester
capacity
 Average hydraulic retention time ranged
from 21 to 40 days
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Input #1
Sugar beets + swine manure
www.extension.umn.edu/.../DC7715.html
Adding
mixture of
sugar beets
and manure
to feed
hopper
Input #2
Liquid swine manure
Had been stored for several months
 Represents an input that is plentiful
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Input #3
Sweet potatoes
Chopped fine
 Added to digestate,
mixed and added to
digester as a slurry
 No new liquids added
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Input #4
Sweet potatoes + (fresh) swine
manure
Digestate removed
 Sweet potatoes mixed with fresh swine
manure
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Input #5
Swine manure
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Freshly produced manure
Input #6
Dried tobacco
Nicotine-free tobacco leaves (dry)
 Mixed with digestate before adding to
digester as a slurry
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Sample Analysis
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Biogas:
◦ Methane (CH4), Carbon Dioxide (CO2)
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Inputs and outputs:
◦ N, P, K, pH, NH4-N, C, ash
◦ Calculated C:N ratio
◦ Calculated Volatile Solids
Results for 2008
Example of Daily Inputs and Methane Production
– Sweet Potatoes & Swine manure
Example of Cumulative Gas Production and VS
Inputs – Sweet Potatoes & Swine 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
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Input
Swine manure + sugar beets
Biogas Methane
content
57%
“Older” swine manure
64%
Sweet Potatoes
48%
Sweet Potatoes + manure
56%
“Fresh” swine manure
63%
Nicotine-free tobacco leaves
49%
Input
Swine manure + sugar beets
Methane
Produced
(L/kg VS)
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 setup
Can change recipe fairly easily
 Don’t need huge quantities of inputs
 Is a good demonstration unit –
technology transfer
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Limitations
Currently only able to add inputs 5 days
per week
 A 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
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This year
Continue testing – vegetable wastes +
other farm organic materials
 Document logistical considerations for
various materials
 Document economic considerations
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Questions?