Magazine / April, 2013 9
ANIMAL WASTE
Biogas energy.
Biogas energy converts animal waste into clean burning gas allowing for farmers to reduce pollution and produce own heat and electricity. The energy comes from animal manure becoming an ultimate win-win energy source. It allows farmers to produce their own electricity and also reduces water contamination, odor pollution and carbon emissions caused by animal wastes. Biogas is produced when bacteria decomposes manure anaerobically, without the presence of oxygen, into a gas mixture, gas mixture is used to generate heat, hot water, electricity, leftover manure can be used as fertilizer, bedding and mulch. Biogas produces enough electricity to power over 45,000 homes and provides 1,600 megawatts of energy and reduces emissions of global warming pollution, equivalent of taking 6.5 million cars off the road.
How it works.
Biogas recovery systems have main components of a manure collection system, an anaerobic digester, and a biogas handling system. The collection system and anaerobic digester is a covered tank which stabilizes the manure and optimizes methane production. The handling system pipes the resulting gas to the device it fuels, the generator and a storage tank for the remaining discharge. Lagoons are pond like basins that retain biogas but are limited to warm climates because during the cold months methane production is suppressed. Plug-flow digesters are long, narrow, heated tanks that are installed partially underground to retain heat. They work only with dairy manure and complete-mix digesters are heated tanks made of reinforced concrete. They require diluted manure mix such as manure with water.
Advantages.
o Biodigesters reduce manure odour and turns the Volatile Organic Compounds into odorless methane and carbon dioxide
o Air quality improve and hydrogen sulfide is captured in biogas and destroyed during combustion
o Cleaner water, reduce bacteria levels in animal waste, less runoff to surface waters
o Reduce biochemical oxygen demand, greenhouse gas reduction
o Reduce reliance on fossil fuels and reduce methane emissions
Where it is used.
Commonly used on the farms where production occurred, for electricity and water hearing, excess electricity can be sold back to the grid. Dairy and swine operation can produce cost effective biogas and recovery systems can handle liquid, slurry, semi-solid manure. Risks can occur because it may generate as much waste as a small city and can affect the water supply and air quality. By capturing the manure, biogas recovery systems can drastically reduce or eliminate untreated waste runoff
Cost of biogas.
o Biogas digester depends on the size of the operation and method of management
o Manure is collected once a week and electricity that is not used can be sold back locally
o Bio-digesters produced enough electricity to power over 45,000 homes
o Methane is the most potent greenhouse gas and is 21 times more powerful than carbon dioxide
o Biogas can be profitable through operations with 500 cows or 2,000 swine