[The Vector] Biogas that Doesn’t Compete with Food Crops

Growing crops to create biogas has become a controversial renewable energy source because it creates competition for land for food crops. But there is another major source of biogas that doesn’t compete with food crops. In fact, exploiting it would considerably reduce greenhouse gas emissions.

The UK government has plans to generate hundreds of thousands of megawatt hours of electricity from food waste. Food waste is just as much a problem for the United States. According to a 2004 study by the University of Arizona reducing US food waste by half could reduce adverse environmental impacts by 25 per cent through reduced landfill use, soil depletion and applications of fertilisers, pesticides and herbicides.

Timothy Jones, an anthropologist at UA spent 10 years measuring food loss, and here is what he found:

almost half the food in the United States goes to waste. He started with practices in farms and orchards, before going onto food production, retail, consumption and waste disposal. Nationwide, he calculated household food waste alone added up to $43 billion. The cost of shipping food waste from homes and businesses to disposal sites costs about $1 billion per year.

On average, US households waste 14 per cent of their food purchases. Jones estimated an average family of four currently tossed out $590 per year in meat, fruits, vegetables and grain products.

According to the EU Commission, kitchen and food waste along with garden waste accounts for 88 million tonnes of municipal waste across Europe each year.

The UK government has calculated that treating 5.5 million tonnes of food waste in anaerobic digestors to create methane gas could generate between 477 and 761 GWh of electricity each year – enough to meet the needs of up to 164,000 households.　The UK creates more than 6.5 million tonnes of food waste per year. The UK is already processing much of its sewage in AD systems, cutting CO2 emissions by 16 per cent and generating 650MW of power for the national grid. The Swedes are running cars, trucks and even a train on biogas.

In England, a number of local authorities are already collecting food waste separately in specially designed caddies for electricity generation. One of the advantages of anaerobic digestion is that, unlike many composting systems, it can take cooked food waste.

One of the drivers for the development of food waste AD plants in the UK is steep increases in landfill taxes. That has encouraged the UK food retail sector to get on board. Sainsbury’s, one of the country’s leading supermarket groups is building five “food-to-energy” sites around the UK over the next two years. That will cut £2 million off the group’s £9 million annual food disposal bill.

The UK’s largest supermarket group TESCO is building a new 528,000 sq. ft. distribution centre that will be completely powered by renewable energy generated from food waste. A combined heat and power (CHP) plant will turn 230,000 tonnes of food waste into heat and electricity. Generating the electricity onsite eliminates the costs of connection to the grid.

It is still early days for the UK plan. Most of the plants being built at the moment will generate small quantities of electricity. A typical development is the 2 MW CHP plant being built by Denmark-based supplier of anaerobic digestion technology Xergi for the Scottish and Southern Energy utility. It will handle around 80,000 tonnes of waste each year.

In the United States there has been considerable investment and development of anaerobic digester systems. According to an AgSTAR estimate in April 2010 there are 151 anaerobic digester systems across the country – 130 of them are generating about 340,000 MWh of electricity as well as thermal energy from biogas. An additional 52,000 MWh per year are in the pipeline. But virtually all of them are on commercial livestock farms.

The potential of urban food waste in the US has yet to be tapped.