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Garden Food Waste Digesters help to reduce carbon footprint - COMMENT UPDATE

Centralised treatment of food waste using methods such as in-vessel composting or anaerobic digestion can cause more greenhouse gases than household treatments using Food Waste Digesters (FWDs), says an environmental study. The study titled Comparison of Greenhouse Gas Emissions from the Centralised and Household Treatments of Food Waste found that centralised treatment of food waste produces between 10 and 40 times more CO2 emissions than garden food waste digesters. Speaking to MRW environmental consultant Dr Alan Knipe who wrote the study said: The Government is favouring anaerobic digestion as a method to treat food waste because they can also get electricity out of it. But when dustcarts collect this food waste from households they are producing harmful greenhouse emissions that we can avoid. It is an expensive method, dirty and dangerous (collecting food waste by dustcarts). If each household had a food waste digester it will bring massive savings in reducing carbon footprint. However, Knipe did acknowledge that not everybody could have access to food waste digesters particularly those who live in flats. The study showed that the major contribution to the anthropogenic (man-made) greenhouse gas emissions for the centralised approach arises from the day-to-day operations of the dustcarts and the treatment plant. He found that the total anthropogenic greenhouse gas emissions for the centralised approach range from about 50 to 214kg of CO2 equivalent per tonne of food waste. By contrast, household treatment generates around 5kg CO2 equivalent per tonne of food waste. In light of this latest study, garden food waste digester company Green Cone will lobby Government over these new findings. Green Cone managing director John Cockram said: If Government is serious about working towards a carbon-neutral society, then these findings are particularly disturbing and must be urgently addressed. A realistic optimal household food waste management strategy for a local authority, in terms of delivering targets, minimising costs and achieving acceptable health, safety, environmental and operational risk management, should be a combination of both centralised treatment and household treatment. Knipe realises that the food waste digester has taken off in many islands such as the Falklands, Guernsey and Jersey where there is lack of space for landfill. However, he states that it depends on the Government on whether the food waste digester will take off in the UK. Comment: Dr Knipe's comments would suggest that in an ideal world we would all have room to compost food waste at home, and we woudn't need centralised collection. Some of us are lucky enough to be able to do that. But the reality is that we will continue to rely on centralised collection, not only for domestic refuse but also for the much larger volumes of trade waste for which County Councils are not the WDA, the disposal of which is left to commercial contractors who rely heavily on landfill. Anaerobic digestion can be shown to make a significant contribution to reducing reliance on landfill, as in Sweden for instance, where domestic waste is collected without reliance on the waste carts which rightly concern Dr Knipe, and the biogas is even used to displace mineral fuels in transport. Unfortunately, at a time when Government is wavering about giving the necessary degree of support to technologies like AD which would make a very significant contribution to reducing GHGs as well as minimising landfill, it only takes a few reports like this to give a further excuse for delay. Has Dr Knipe actually measured the GHG emissions from composting, whether centralised or home-based, and compared them to the emissions when these are captured for use in generating electricity, or even used for district heating? Posted by Peter Fane, Eunico, 28/11/07

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