By Asha Kreiling
Where there are cows, there is poop — and lots of it! On average, a dairy cow produces an astonishing 30 gallons of manure each day. That hefty load of dung weighs in at around 120 pounds! These are scary statistics on their own, but aside from its sheer mass, cow manure is a serious environmental and public health issue. When not managed properly, as is often the case on industrial scale feedlots, cow waste can pollute streams and drinking water sources, as well as crop farms. Additionally, decomposing waste is a big emitter of greenhouse gases like sulfur dioxide and methane.
Traditionally, farmers scoop manure into big heaps, compost it and spread it over fields as fertilizer. But some farms are now doing more by using manure to generate electricity. Dairy farms, such as some in the state of Vermont and in the city of Tillamook, Oregon, have implemented methane digesters, which literally convert cow poop into power. Cow dung is collected and fed into giant, steaming hot, anaerobic digesters in which bacteria converts it into biogas. The biogas is burned, fueling a natural gas engine, causing an electric generator to spin, and voilà! Poop-power electricity is born. All the generated electricity is then fed into a utility system, and can be distributed to homes and businesses for use.
In Vermont, residents can buy a fraction of or all of their energy from the statewide “Cow Power” program for a premium. It costs four cents per kilowatt hour more than the typical rate and, on average, adds up to an extra $6 a month per home. The premium goes directly to local farms and supports cleaner, renewable energy. Twelve dairy farms in Vermont are currently participating, so they are enjoying the extra income from electricity sales while also helping the environment. The dry solids left over are separated and recycled into fertilizer or bedding for farm animals — another way farmers save money and resources.
In Oregon, a company called Farm Power Northwest pays Tillamook farmers for their cow manure. The manure is piped into a digester and converted into biogas the same way it is done in Vermont. Leftover liquid containing valuable soil nutrients, phosphorus and nitrogen, is piped back to farmers to be used as a cleaner, more easily manageable fertilizer.
Biogas derived from cow manure is a promising alternative energy source that is good for farmers, local economies, and the environment. As long as there are cows, biogas will be a widely available, renewable resource. Manure management mustn’t be limited to scooping and spreading poop. It has potential to mitigate greenhouse gas emissions, reduce water contamination, and protect public health.
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