Compost Can Turn Agricultural Soils into a Carbon Sink, Thus Protecting Against Climate Change

Applying organic fertilizers, such as those resulting from composting, to agricultural land could increase the amount of carbon stored in these soils and contribute significantly to the reduction of greenhouse gas emissions. Carbon sequestration in soil has been recognized by the Intergovernmental Panel on Climate Change and the European Commission as one of the possible measures through which greenhouse gas emissions can be mitigated.

"Furthermore, increasing organic matter in soils may cause other greenhouse gas-saving effects, such as improved workability of soils, better water retention, less production and use of mineral fertilizers and pesticides, and reduced release of nitrous oxide."

Composting can contribute in a positive way to the twin objectives of restoring soil quality and sequestering carbon in soils. Applications of organic matter (in the form of organic fertilizers) can lead either to a build-up of soil organic carbon over time, or a reduction in the rate at which organic matter is depleted from soils. In either case, the overall quantity of organic matter in soils will be higher than using no organic fertilizer. Results of the studies carried out suggests that soils where manure was added have soil organic carbon levels 1.34% higher than un-amended soils, and 1.13% higher than soils amended with chemical fertilizers, over a 50-year period.

Organic fertilizers can control the decline of soil organic matter that has occurred in relatively recent decades, by contributing to the build-up in the stable organic fraction in soils, and having the effect, in any given year, of ensuring that more carbon is held within the soil.

Science Daily (Feb. 27, 2008)