Anaerobic Digestion Found to Hold Many Advantages to Agriculture

As the US nation looks to agriculture for renewable fuels from crops and other sources, many researchers are realizing that there are developing countries such as China and India which have already have developed a manure management system that produces energy, saves valuable nutrients for fertilizer, and provides great benefits in improved sanitation health and bio-security for those using it.

It has even been in use on some farms in the US, although until energy prices began to rise recently it was not even close to being economically viable.

That system is anaerobic digestion, and furthermore it can cut greenhouse gas emissions and stops offensive odours

Without proper management, animal manure can get into groundwater supplies, and odour problems can produce a nuisance for nearby residents, and this is happening more frequently as dairy and pig farm sizes grow and urban sprawl moves into farmland.

University of Florida researchers say that,

The key to our waste management system is a natural biological process called anaerobic digestion that relies on microorganisms to transform animal manure into methane gas.

Anaerobic digesters, which process waste under oxygen-free conditions, are different than conventional aerobic systems that use oxygen to treat the waste. Anaerobic digesters can, the same researchers suggest, process five to 10 times more waste than aerobic systems. Because the waste is enclosed to keep oxygen out, anaerobic digestion keeps odors in.

With anaerobic digestion, the methane produced can be used to heat water or generate electricity, eliminating greenhouse gas emissions that contribute to global warming. To demonstrate the technology at a working dairy farm, a large-scale anaerobic digester at University of Florida's 500-cow Dairy Research Unit in Hague, Florida is now generating biogas from manure flushed from animal barns and milking parlors.

The patented waste treatment technology is being made available for licensing by University of Florida's Office of Technology Licensing.

About 40 cubic feet of methane per day can be produced from the waste of each dairy cow, these researchers estimate.

The anaerobic digester processes manure from the large volumes of water used to flush waste from animal holding areas at the dairy. Because manure flushed from these areas is so diluted by water, only two types of anaerobic digesters are practical for dairies – covered lagoons and fixed-film digesters, researchers.

In covered lagoons, which are less efficient than fixed-film anaerobic digesters, the digestive bacteria float around, making only random contact with the manure particle

, this problem is not seen in fixed-film reactors it is claimed.

Generally, the fixed-film design is suitable for any livestock manure that is diluted with water for transport or processing, such as dairy and swine waste.

First, by capturing biogas, anaerobic digestion can reduce natural emissions of methane, a potent greenhouse gas. Second, when anaerobic digestion produces renewable fuel to replace fossil fuels such as coal, oil and natural gas, production of carbon dioxide from burning
those fossil fuels is avoided.

The anaerobic digester also lowers the levels of pathogens; starvation and competition with other microorganisms help kill pathogens that might be in the manure.

Just like many researchers across many countries, the potential for anaerobic digestion to solve several major problems, is remarkable.

Could we really have the possibility of developing a sustainable option for dairies and other livestock operations that produces renewable energy and protects the environment? Many think so, and governments and investors will do well to look seriously at encouraging the further development of anaerobic digestion technology.

Based upon an article by University of Florida, published February 2006.