Anaerobic digesters have popped up on farms across Ontario in recent years, but there are none quite like the digester Rob McKinlay has installed at Harcolm Farms at Beachville, Ontario.
What makes it unique is its size – at 20 kilowatts, it’s 10- to 20-times smaller than the other 42 digesters currently operating on Ontario farms. In this episode of RealAgriculture’s Dairy School, McKinlay explains that the “mini” digester provides an opportunity to make the farm carbon neutral and also produce enough electricity to power the 72-cow milking operation, with the option to sell surplus electricity back to the Ontario grid.
In this video, McKinlay is joined by consultant John Hawkes from Martin Energy Group, who notes that the Bioelectric digester was designed in Belguim for dairy farms in that country, which are comparable in size to Ontario dairy operations. About 200 of the digesters have been sold in Europe.
“What we’re trying to do here is capture whatever energy or benefit we can with the material we have,” says Hawkes. Like bigger digesters, the mini uses heat and mixing to create gas from organic material. In this case, that’s dairy slurry produced from the Harcolm herd. No off-farm waste is processed, which is usually the case with larger digesters, Hawkes notes.
McKinlay says integrating the digester into his farm operation was surprisingly simple. The biggest challenge was the fact that Harcolm Farms was a sand-bedded barn, certainly not ideal for digesters. However, the infrastructure of the sand system – alley scrapers, cross cutters and reception pit – made it easy to integrate the digester. “There’s nothing more complicated than blocking off the pipe that goes to the manure pit and… dropping a pump in,” says McKinlay.
From a return on investment perspective, McKinlay notes it was important to maximize potential for electricity sales as well as cost off-sets. Here the primary goal is to meet the energy demands to power the farm. By connecting to the grid, Harcolm Farms has the ability to sell surplus electricity and also meet electricity needs at peak activity for farm operations. The farm will use separated solids from the digester to bed the cows.
When it comes to cost, Hawkes says the 20-kilowatt system will cost in the $350,000 to $450,000 range. In the video, he breaks down the math, which includes an annual $35,000 cost off-set for electricity and propane replacement. He expects farmers could see full payback in less than ten years. “It’s pretty similar to what you would see with a combine or other large farm investment,” says Hawkes who feels further system refinements could, over time, reduce the payback period to eight years.
Overall, McKinlay gives the digester high marks. He says most of the questions he gets from farmers focus on operations and management requirements.
“Day-to-day, I feed the digester while I’m going through my routine making feed for the cows. Otherwise it runs on its own,” says McKinlay. “There’s also a well-developed app to interface with the machine. We get text messages if there is any issue.”
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