Harvesting the Power of Poop
Posted by moviegoer from the General category at 15 Sep 2009 12:24:47 pm.
A dairy cow typically produces 150 pounds (54 kilograms) of manure per day. Multiply those 150 pounds by the scores of cattle, and that equals one large -- and odoriferous -- waste situation. With concerns about groundwater contamination and fecal-borne diseases passed through contact with animal waste, farmers are continually on the lookout for ways to stay safe and make the clean-up job easier.
Methane digesters are based on old technology and do a remarkably good job at handling manure cleanup. In addition to getting rid of the waste, the methane digesters offer an added bonus. The methane can be used to produce electric energy, which in turn can help save farmers money. According to Sustainable Conservation, a methane digester is a wastewater and solids treatment technology. When used on a farm, it processes animal waste under anaerobic conditions, yielding methane gas and reducing the volume of solids and treated liquids. The methane can be sold or used to generate electricity on the farm; the solid matter left behind is a valuable soil amendment; and the liquids become an easily applied fertilizer, with plant available nutrients and low pathogen levels.
Typically, large farms will store liquid and solid manure produced by livestock in large waste ponds. The manure is later pumped back onto fields as a source of fertilizer. But this type of storage scenario poses a host of problems, including strong odors, pathogens in the manure, and the fact that heavy rains or storms can flood the ponds and land where manure has been spread, allowing manure to reach local water sources. Using a methane digester is a workaround and a viable solution. Plus, methane is a greenhouse gas much more powerful than carbon dioxide. So harnessing the methane -- rather than have it simply rise up into the atmosphere -- is another benefit for the farmer and environment.
The U.S. government has started to hand out subsidies to farmers to install methane digesters to offset costs. Something to consider about the digesters is that they do not simply make manure and other waste vanish. The digested manure will still need to be applied as fertilizer to mitigate the amount of waste. Digesters may not be the best solution for a small farm and are better left for a larger operation. Also it's important to note that some communities fight the installation of largescale methane digesters because of their industrial appearance and because they attract added traffic by waste haulers. Still, many environmentalists say the positives far outweigh the negatives in this situation.