Food waste is an untapped energy source that mostly ends up rotting in landfills, thereby releasing greenhouse gases into the atmosphere. Food waste is difficult to treat or recycle since it contains high levels of sodium salt and moisture, and is mixed with other waste during collection. Major generators of food wastes include hotels, restaurants, supermarkets, residential blocks, cafeterias, airline caterers, food processing industries, etc.
In the U.S., food waste is the third largest waste stream after paper and yard waste. Around 12.7 percent of the total municipal solid waste (MSW) generated in the year 2008 was food scraps that amounted to about 32 million tons. According to EPA, about 31 million tons of food waste was thrown away into landfills or incinerators in 2008. As far as the United Kingdom is concerned, households throw away 8.3 million tons of food each year. These statistics are an indication of the tremendous amount of food waste generated all over the world.
The proportion of food waste in the municipal waste stream is gradually increasing and hence a proper food waste management strategy needs to be devised to ensure its eco-friendly and sustainable disposal. Food waste can be recycled via:
- In-vessel composting (IVC): A treatment that breaks down biodegradable waste by naturally occurring micro-organisms with oxygen, in an enclosed vessel or tunnel;
- Anaerobic digestion (AD): A treatment that breaks down biodegradable waste in the absence of oxygen, producing a renewable energy (biogas) that can be used to generate electricity and heat.
Currently, only about 3 percent of food waste is recycled throughout the U.S., mainly through composting. Composting provides an alternative to landfill disposal of food waste, however, it requires large areas of land, produces volatile organic compounds and consumes energy. Consequently, there is an urgent need to explore better recycling alternatives. Anaerobic digestion has been successfully used in several European and Asian countries to stabilize food wastes, and to provide beneficial endproducts. Sweden, Austria, Denmark, Germany and England have led the way in developing new advanced biogas technologies and setting up new projects for conversion of food waste into energy.