The Win/Win/Win of Biogas
By Cam Mather
People often ask me what William “Bill” Kemp is up to these days when he’s not updating one of his previous books such as The Renewable Energy Handbook or working on a new one.
Bill’s day job involves engineering green power systems and he has designed and installed hydroelectric power stations all over the world. Right now he is finishing work on a biogas system. This system takes the methane gas from cow manure and uses it to power a generator, which produces electricity. Under the Green Energy Act in Ontario the farmer is paid a premium for this power because it’s green. The electricity generated this way is particularly desirable because it’s “dispatchable”. Unlike solar and wind, which can be intermittent, this unit can produce electricity for the grid at all times and it can be guaranteed to be there during peak hours when it’s most needed.
Ten years ago in a town called Walkerton, Ontario, rainwater washed cow manure into a well that contaminated the municipal water system. The e-coli in the manure made at least 2,500 people ill and seven people died. The beauty of Bill’s biogas systems is that because the manure is heated in the digester, pathogens like e-coli are killed, making it safe to spread on farmland. Farmers who install one of these biogas systems may end up making more money from selling electricity to the grid than from selling milk. Electricity is a major expense for a dairy farm, and with a biogas system, the farm can produce its own power. The system also creates hot water, which dairy farms also use a lot of. Methane gas is 20 times more harmful a greenhouse gas than carbon dioxide is, and in these units that methane gas is being burned to produce electricity, with CO2 as the by-product. So the grid wins with green power, the farmer wins with an income source and the environment wins with less dangerous manure and methane no longer ending up in the atmosphere.
It’s not often that you can take a number of problems such as manure contamination, farmers struggling to earn a decent income, a grid needing new generation and a potent greenhouse gas like methane escaping into the atmosphere, and find one solution that solves them all. It’s pretty rare to find someone who isn’t just raging against the machine, pointing out the problems, but is actually fixing the mess. In this case, in a very elegant way.
Here’s a description of what you’re looking at in this photo.
- The small red building on the right is the manure reception building, which holds the pumping equipment to fill the digester (the big tank on the left.)
- The blue container unit in front of the digester contains the manure mixers, heating, gas cleaning and compression system. Underground pipes feed biogas to the power generation units.
- The power generation units are the two containerized units just to the left of the pump building with the silver exhaust scoops. Each unit generates 250 kW of electrical energy and 1 million BTU of thermal energy using a hot water pumping system. Electricity is fed to the last blue container, which contains the electrical metering and switchgear and feeds power to the grid.
- Hot water flows up to 1 kilometer away across the farm, heating 2 homes, 2 worker apartments, dairy wash water, swimming pool, grain dryers, etc. In all, the heat system displaces approximately $60,000 per year of propane, heating oil and electricity.
- The area in the far left that is fenced contains a biogas flare that burns off any extra gas that might be produced. This is used primarily when an engine is down for service, etc.
- Lastly, the digested manure is fed into the new building behind the pump house. Here, the digestate is fed into a solid/liquid separation unit. The liquids are stored as fertilizer and the dried solids are used for cattle bedding, which is a soft, peat moss-like material. This saves the farm the cost and work of planting some 500 acres of straw and allows the land to be used to grow more corn or other crops.
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