Project spins brown into gold

Turning manure into energy isn’t cheap, but it could be economically feasible for a large western Canadian feedlot, according to the Prairie Agricultural Machinery Institute.

The feasibility study conducted by the research facility is part of its ongoing study into manure and biogas production.

Many farms in Europe and parts of Canada are already making money from biogas, but those systems traditionally rely on a liquid manure system.

The PAMI project has been examining a novel system that uses solid manure, which is more practical within the western Canadian beef industry.

While smaller and cheaper than other anaerobic digesters, a full-scale, solid-state system could still cost $5 to $15 million, said Joy Agnew, PAMI project manager.

“It really is only an option for large feedlot facilities because of the high capital cost associated with it,” said Agnew.

“You need to have a large facility with a large amount of waste to deal with and currently a large cost to deal with.… The payback period, however, remains a fraction of a liquid system, the costs of which can exceed $30 million.

“Going to a solid-state system might actually make it more economically viable than a liquid system if someone has looked into digestion in the past and said, ‘oh, it’s not economically viable, maybe it is if you look at a solid state system instead.’ ”

PAMI conducted an economic analysis of the solid-state technology, comparing it with traditional manure management systems such as stockpiling and composting and assigning a dollar value on all aspects of production, including odour emissions, social perception and greenhouse gases.

The biogas system was found to be feasible despite the high cost of entry, but development work needs to be done.

The analysis included determining a monetary value for the leftover materials, called digestate, from biogas production as fertilizer and capitalizing on carbon tax credits. It puts the total value of digested manure at $2 to $19 per tonne.

“Based on our numbers and including the capital costs of digestion, it shows that overall, like over a 20 year lifespan of the digester, the digester has the highest net positive return per tonne of manure that’s handled,” said Agnew.

Saskatchewan doesn’t have a carbon offset program, so the analysis uses Alberta’s model.

The cost of the system would increase depending on what the user wants to do with the gas.

“If you want to upgrade it to be put back into the natural gas grid, then you’re on the upper end of that,” said Agnew.

“But if you’re able to use the power and heat on site, you’re on the lower end. Most of the cost comes in the gas handling and gas conversion equipment.”

Agnew has been conducting trials at a pilot facility at the Termeunde Research Ranch near Lanigan, Sask., since 2012, using manure from the neighbouring Pound-Maker Agventures feedlot.

The system can use 10 tonnes of material at a time.

Agnew has tested mixtures of manure and other organic materials. For example, the addition of potatoes didn’t produce any more gas but did kill pathogens such as late blight.

“So we didn’t get a lot of gas, but it proved that it is a great disposal method for that kind of waste,” said Agnew.

In an interview this fall, Agnew said she was testing dead stock from a feedlot in the digester.

“I can’t tell you how much gas we’re going to get out of it, but at the bench scale (test), the manure and carcass gave us the most,” she said.

Agnew said there’s also interest from municipalities in using the solid-state technology to produce energy from food waste and yard trimmings, which could hold greater potential.

“The scaling up of it is all dependent on industry uptake,” said Agnew.

“Manure, it’s a great feedstock for digestion, but it’s a very low biogas producing feedstock. So that’s why we are now working with cities and municipalities to get a richer feedstock like food waste because it’s possible that you could make it economical at a fairly small scale.

“The actual reactor sizes that we have at our pilot facility might the sufficient to make a solid state digester for food waste and yard trimmings work.”


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