in Recycling News

Recycling News (8-3-2014)

Every day thousands of tons of food go to landfill in the USA. There’s a lot we can do to reduce this, including better labeling, education about food safety and more sensible shopping, but inevitably there will always be a degree of waste. Unfortunately food is a bad thing to dispose of in landfill; as it decomposes it releases methane, a greenhouse gas that’s far more powerful and destructive than carbon dioxide. Now a US Air Force cadet has helped to develop a solution that’s designed to solve this problem for deployed military units, but has the potential to be scaled up for large-scale general use.

The problems of waste disposal on military operations can be extreme. There’s usually no proper infrastructure available and transport constraints mean shipping waste back to the USA for disposal is usually impossible. Often troops are forced to use undesirable options like open-air burning to dispose of not only food but human waste. The results can be widespread pollution and even a disease risk. Now Cadet Marcus Penner and the Air Force Civil Engineer Center have come up with a potential answer.
The AFCEC system is based around a digester, a large bag made from heavy duty vinyl. It’s partly buried to assist with temperature regulation, and fed with waste (either food, sewage or a mixture of both) mixed into a slurry. Two complementary bacteria strains are introduced into the digester and break the waste down into a variety of organic compounds. One of the major byproducts is methane, but because this is produced inside the digester it can be collected and used as a fuel. Gas pressure inside the digester expels the remaining processed waste into a collection vat. The resulting sludge can be dried and used as a safe fertilizer. As well as reducing the requirement for disposal facilities this can be used to benefit local populations, which can benefit the mission.
AFCEC is looking at developing portable digester kits, including packs of premixed bacteria colonies, which can be rapidly shipped to deployed units. However the same technology can be used in a larger, permanent facility as an alternative to simply dumping food waste in landfill, or as a supplement to a conventional sewage plant. Penner is currently planning larger-scale trials to ensure the process scales effectively, but there’s no reason why it shouldn’t.
The current project is aimed purely at military applications – AFCEC’s mission is to provide infrastructure and engineering support to deployed USAF units. However the same principles could be easily adopted by other federal agencies or local waste disposal facilities to cover a whole range of applications. Large institutions such as colleges or prisons, or small communities, could use the technology to both reduce energy bills by exploiting the methane production and cut down their waste volume; even if the fertilizer option isn’t taken up the waste that remains is less polluting and much less bulky. It’s an ingenious solution to a long-standing disposal problem, and while the basic technology isn’t new this is a much more refined application of it.