By Lisa Boonstoppel-Pot

     When he was on the panel for on-farm diversification at the Stratford Dairy XPo (see Dairy Diversification story), Dave Green of Greenholm Farms near Embro alluded to the profitability of two biodigesters on the Embro dairy farm he runs with his father Gord. So when I got to the farm to see the digesters in action, I asked for some numbers. How much money do they actually make? Is the paperwork stress and sourcing issues worth it? Definitely, said Dave. When running at peak capacity, on a diet of manure and other organic waste, the anaerobic biodigesters create methane which is transformed into 12,000 kilowatts of electricity per day. Installed under a Feed-In Tariff (FIT) government contract in 2012 and 2018, the two digesters pay out at 18.5 cents per kilowatt for a sum of $2,200 per day. “If we had taken the same money and invested it in cows and quota, it would not touch the income we make from the digesters,” says Dave, who admits technology is something he is particularly interested in which is why he dived into the paperwork required to earn a FIT contract to make the digesters profitable. Unfortunately the program stopped accepting applications in 2016 and hasn’t been replaced with a program as lucrative to encourage more farmers to install biodigesters. Nevertheless, Dave is in the process of researching a third biodigester to use as a power source for the dairy operation since power generated by the first two is fed back into the grid. Plus, he loves the circular concept of making the most of the farm’s resources. Not only does the farm manure and organic waste create energy, it also creates a rich fertilizer for spreading on crop yields. “It’s value added ... you get more out of what you produce,” says Dave. So while farmers wait for future funding to encourage and promote the greater use of renewable energy sources, learning from the process at Greenholm Farms can prepare them if/when that funding appears. Gord and Dave Green milk 250 Holstein cattle at the sixth generation dairy farm and it’s a busy place. Off-shore workers are cleaning in the dairy barn while Dave hauls tankers of liquid manure and Gord walks in with his barn clothes, clearly busy as well. Trucks roll in, bringing in a variety of materials including soluble corn distillers (discarded because of high levels of DOM), off-spec milk, grease trap waste, surplus whey, apple waste (cores, peels and pulp) and potatoes to feed the biodigesters. It’s a bit of a muddy mess with this wet spring weather and there is finishing work to be done after the second digester was installed in 2018. Before installing both digesters, the Greens researched how much the the hydro component would cost. Digesters sized 200 kw and above need to hook into a three-phase circuit and they aren’t available everywhere. The closest one to the Green farm was on the next concession which, luckily, the farm could reach through its own fields. They installed the lines themselves. That saved a LOT of money as connecting the digesters to a three-phase circuit can cost up to $200,000 per kilometre. “There’s always lots of interest in biodigesters but a lot of people get stopped because they don’t have access to a three-phase circuit,” said Dave. Once the Greens built the first digester, they began feeding in their own manure and declared their “doors open for business” to anyone needing to dispose of organic waste. “No one showed up,” remembers Dave. Relationships had to be forged and now the Greens are part of a new venture called Cornerstone Renewables, a hands-on group, that is owned by two beef farmers, six dairy farmers, a greenhouse operator, an Ag entrepreneur and a research site at the University of Guelph. Their website states: “In addition to the manure from the more than 10,000 cattle we manage on our farms, Cornerstone currently processes approximately 200,000 tonnes per year of organic waste. At the present capacity to process 220,000 tonnes per year, which makes us capable of producing 173 Megawatts of electricity, 200 Megawatts of heat every day, and 100,000 tonnes of feed per year from the fertilizer we produce. At capacity our combined efforts will reduce CO2 emissions in the atmosphere by 400,000 tonnes per year, which is equal to 78,500 cars per year.” Intense! Through the group, accessing organic waste is no longer a problem. In fact, the farmers charge a tipping fee of $20 per tonne of which a percentage goes back to Cornerstone Renewables to fund the company. Gord says the digesters “love rotten material” and greasy products like the grease trap waste. Ultimately, the bacteria that transforms the manure and organic waste into methane need to have heat and action (stirring). “Stir it and heat it and you get gas. It’s the same principle as a cow’s rumen,” explains Dave. Balancing it can sometimes be tricky. Digesters can get sick which happens when the bacteria are overfed. They will quit performing and go dormant. In really bad situations, they can die. “We’ve never killed our digester,” says Dave. “But we’ve been too close for comfort,” interjects Gord. Overfeeding the digester affects the pH levels. The methanogens in the digester prefer a pH range of 7.5 to 8.5. Outside of that, they get sick. The digester methanogens are fed throughout the day, little bits at a time. The manure pumps are set to run 12 to 20 times a day. Input of organic waste is now managed by Cornerstone Renewables, which has hired a buyer to source materials. When the Greens were independent of the group, they sourced materials from other smaller businesses. The company, however, has the capability to accept larger amounts so now they can accept waste from companies like Maple Lodge Farms. Another thing to watch with anaerobic biodigesters are the engines that run them. They are constantly running and generate a lot of heat. “The engines can blow up sometimes and then you can be down for a while. It hasnt happened here and good thing because we don’t have a $700,000 engine sitting around to plunk in.” Each digester cost about $2 million to install at Greenholm farms. Installing the biodigesters was not without financial risk, certainly. Break-downs do happen and Dave says you kind of feel like you are on-call, like with robot milkers. Infrastructure issues with Hydro One can be frustrating. The grid trips regularly and has some instability concerns. Every time the power flicks off, Dave has to restart the biodigester engines. Also, it’s not a white-shirt business. “If you have digesters, get ready to be dirty,” says Dave. “This is a whole new level of getting covered in manure.” However, when everything works right, the farm manure rolls in to feed the digester and income flows out to pay back those loans. Plus, the digestate left over “grows crops like nobody’s business,” says Dave. Gord says the digestate is more like hog manure, providing an accessible form of nitrogen that corn really thrives on. Also, the Greens use the dry portion of the separated solubles to bed the freestalls and pack pens in the dairy barns. “I was sure scared at the start, fearing mastitis but our somatic cell counts have not changed at all,” says Dave. He believes because they use mats, layer the digestate on top, then scrape it off during stall cleaning, that helps. “I think if we had deep packs, the bacteria could grow.” Both Dave and Gord hope the government will see the continued benefits of renewable energy on the farm and offer new funding so more farmers can consider installing anaerobic biodigesters on their farms.◊