Capturing methane gas from manure is taking the world by storm — in warm countries.
In energy-poor countries of Southeast Asia, for example, biodigester facilities are popping up like mushrooms, including on large-scale livestock operations seeking less expensive and more reliable power, as well as ways to reduce odour and create a new revenue stream from selling compost. Some companies not only offer nearly turnkey technology, but contracts for selling the processed manure to local market gardeners.
But in colder climes such as Manitoba, the fact that anaerobic methane generators are dependent on thermophilic — warmth-loving — microbes, means that what works in the summer often fails when the mercury plunges in the winter.
“You need to keep this in a big tank at 40 C — it’s like heating a swimming pool all winter,” said Jeremy Langner, a renewable energy systems engineer with Manitoba Hydro.
“We’re trying to prove that you can make that work in Manitoba with smart design.”
Making it work
Langner gave an overview of the latest anaerobic digester demonstration project on a local dairy farm (one of five currently underway in the province) in a presentation at Hog Days.
Key to the project is Combined Heat and Power, known as CHP in green energy circles. A typical electrical generator converts mechanical energy into electricity via pistons or turbines. However, up to 80 per cent of the fuel used is lost as waste heat. CHP strategies aim to capture that heat and reroute it for use as a process-supporting energy source.
Given the high capital cost of bioenergy projects, multiple benefit streams are required to make them viable.
The $850,000 project designed by the Ontario division of German company PlanET and overseen by Langner is being built at Sweetridge Farms, a 230-head dairy in Winkler. It is scheduled for completion this spring.
The biogas digester is targeting not just electricity from methane via a 72-kW generator, but also bedding from dewatered, leftover solids and reusing of waste heat from the generator to keep the digester and its occupants warm in the winter months.
The digester is 50-foot-diameter, insulated concrete silo with a rubberized membrane cap over top. It is partially below ground, and embedded into its walls are PVC tubes that will circulate hot water captured from the generator in order to maintain an optimal temperature of about 40 C for the bacteria year round.
“It’s similar to how you do an in-floor heating system,” said Langner.
A spider-web-like wooden frame on the roof of the silo will remove corrosive, engine-destroying hydrogen sulphide gas present in the biogas by creating a habitat for organisms that eat H2S and convert it into “icicles” of elemental sulphur.
The liquids, which will be thoroughly deodourized after processing and unattractive to flies, will be spread as liquid manure on cropland. Also, much of the phosphorus in the manure will be retained in the solids.
Langner showed photos of the project, which includes a tiny “man-door” at floor level that will allow access for maintenance.
“You wouldn’t want to open that when it’s full,” he joked.
Tours of the facility will be organized next summer once it is complete and livestock producers interested in renewable energy systems are welcome to consult with Manitoba Hydro, which offers “pre-feasibility” studies. If the project still looks doable, Manitoba Hydro will pay up to half of the first $10,000 for a feasibility study, and 25 per cent of construction costs, up to a maximum of $15,000.
Hydro also offers upfront incentives based on the amount of electricity that will be generated at a rate of 15 cents per kilowatt hour, or as high as 50 per cent of project costs up to $1 million. The maximum electrical incentive is $1 million.
For projects displacing natural gas, the incentive rate is 30 cents per cubic metre per year, said Langner, up to a maximum of $250,000. Both incentive programs can be combined.