Putting waste to work
Efficient digestion process could offer economic and environmental
benefits
By Brita Ball
Utilizing farm animal manure to produce biogas could enhance the sustainability
of farming, protect the environment and create new economic opportunities
in rural areas, says a University of Guelph research engineer.
Ron Fleming of the University's Ridgetown campus is studying an anaerobic
digestion process for manure. During this process, methane is produced
and can be used to generate electricity and heat. The anaerobic digestion
process also produces a nutrient-rich material that can be safely spread
on fields.
"Biogas is a win-win situation for the farmer and society,"
says Fleming. "It provides a sustainable way to produce energy and
creates a more environmentally friendly form of livestock manure."
In this system, manure from livestock farms is put into an air-tight
tank. By providing a certain level of heat and an environment without
oxygen, specific anaerobic bacteria are encouraged to break down the organic
matter. After about three weeks, these bacteria leave a slurry solution
containing all the original nutrients after converting various manure
compounds into carbon dioxide and methane gas.
Methane can be used as a fuel. In most cases, it's burned to power a
generator, which produces electricity and heat. The heat created by the
generator can be captured and used to warm the digester, helping the digestion
process. Some heat can be used for other useful purposes, such as heating
buildings. The liquid digestate can be used as an environmentally friendly
fertilizer: the digestion process kills most harmful bacteria and greatly
reduces odours from the liquid, making it more acceptable to neighbours
than untreated manure.
Fleming is working to optimize pig manure digestion, using an 8,000-litre,
pilot-scale digester. He's testing "recipes" of manure and other
materials to determine the cost effectiveness of digestion with various
mixtures. He also has a 2,000-litre demonstration unit that will be used
to examine the feasibility of digesting organic by-products of the fresh
vegetable industry, such as waste sweet potatoes.
As well, he's conducting side-by-side trials between anaerobic digestion
and traditional composting, to compare the energy inputs and outputs,
volumes and nutrient content of various materials. Recent projects have
looked at the feasibility of using either spent mushroom substrate or
hatchery waste as inputs for both an anaerobic digester and a composter.
Fleming says adding off-farm materials that are high in carbon, such
as food processing wastes, can boost methane yield, compared to manure
alone. In the past, regulations have made it very difficult to move some
of these materials to on-farm systems, but government agencies in Ontario
have been working to streamline this process for certain materials. Mixing
these waste products with livestock manure in an anaerobic digester has
the potential to make the best use of their energy and nutrient potential.
There are only a handful of anaerobic digesters on Ontario farms, and
a fairly small number in all of Canada. In comparison, Fleming says there
are more than 3,500 units on farms in Germany, where electricity prices
are higher. The system represents a significant investment for Ontario
farmers, but interest is at a high level, and recent "green energy"
incentives in Ontario should help to encourage the growth of this industry
in Ontario.
This research is funded by the Ontario Ministry of Agriculture, Food
and Rural Affairs, Ontario Pork, the Ontario Hatchery Association and
the Canadian Mushroom Growers' Association. Funding was also provided
in part through contributions by Canada and the Province of Ontario under
the Canada-Ontario Research and Development Program (CORD) administered
in Ontario by the Agricultural Adaptation Council, and the Alternative
Renewable Fuels program.
-30-
Ron Fleming, 519-674-1612,
Brita Ball was a writer with SPARK (Students
Promoting Awareness of Research Knowledge), a student research writing
program at the University of Guelph.
Learn more
