Tesco carbon footprint study confirms organic farming�s energy efficiency but excludes key climate benefit of organic farming � soil carbon
Wednesday, April 30, 2008
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A study looking at the carbon-footprint of a range of key consumer staples sold through Tesco has reported that the two organic products studied generated no more and in some cases less greenhouse gases than the same amount grown non-organically.
Peter Melchett, Soil Association Policy Director said:
“We congratulate Tesco for making an important start in helping people to reduce the impact of their food on the climate - something the Government has so far failed to do. By encouraging people to choose to put the most climate-friendly food in their shopping baskets, the everyday necessity of eating could be transformed into one of the most effective environmental acts everyone can take.
“We also welcome the fact that Tesco have been clear that their researchers were not able to include what we believe is one of the main advantages of organic compared to non-organic farming. Overall, organic farming has a reduced carbon footprint as it stores carbon in the soil, as well as using less fossil fuel energy. Given this omission, the Tesco findings for the carbon footprint for organic potatoes and tomatoes are particularly positive.”
The Soil Association welcomes work to develop carbon labelling for food. However, at the moment most studies in the UK, including the work done for the Tesco, do not reflect the actual carbon footprint of organic food production. Tesco’s researchers acknowledged that they were not able to take into account the amount of carbon that can be stored or released from agricultural soils by different farming practices. Yet controlled long-term trials show that organic farming adds between 100-400kg an extra carbon per hectare to the soil each year, compared to non-organic farming. When this stored carbon is included in the carbon footprint of organic food, it reduces the total greenhouse gas emissions by between 25-75%. 
Organic farming avoids the release of large amounts carbon from farmland soil, compared to non-organic farming by building the level of organic matter in the soil. The reasons for this include the fact that organic farmers always have grass in their crop rotations, and use manure or compost.
As well as the soil carbon benefit, a study for the Government by Cranfield University has shown that on average organic farming is about 26% more energy efficient than non-organic farming for producing the same amount of food. This is because organic farmers do not use artificial nitrogen fertilisers, which are produced from fossil-fuels and give off large amounts of greenhouse gases in their manufacture and use - making just one tonne of nitrogen fertiliser emits nearly 7 tonnes of carbon dioxide equivalent greenhouse gases. Nitrogen fertiliser is the single main use of energy in farming, accounting for 37% of agriculture’s total energy use, and the largest global source of the greenhouse gas nitrous oxide, which is over 300 times more damaging than carbon dioxide.
 International Trade Centre UNCTAD/WTO and Research Institute of Organic Agriculture (FiBL); Organic Farming and Climate Change; Geneva: ITC, 2007. The report gives three examples of calculations of the overall global warming impact of organic crops where soil Carbon has been included. In the case of a crop trial, the inclusion of soil carbon reduces the overall comparative organic carbon footprint from 53% more per kg than non-organic to 80% less/kg than non-organic, and from 2% more per kg than non-organic to 26% less per kg in a survey of 18 Bavarian farms. A nine year trial in Michigan of organic arable crops found that organic crops had a carbon footprint of 36% less per kg compared to non-organic.
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