Composting farm manure could slash gas emissions

Minor changes to the way farmers traditionally deal with animal manure could make a significant impact in efforts to reduce pollution and emissions of potent greenhouse gases.

According to research carried out by Gurpreet Singh at Canada’s University of Alberta, composting manure rather than simply stockpiling it could dramatically reduce the emissions of methane and other gases.

In Canada the gases released by agricultural waste – methane, nitrous oxide and carbon dioxide – are the fourth largest contributor to the country’s greenhouse gas emissions.

Mr Singh took two 50-tonne piles of manure from beef cattle and left one to rot down of its own accord while taking a more active approach to the management of the other, treating it as compost and regularly turning, mixing and folding the pile.

Taking into account the energy used to operate machinery to turn the compost and then spread the final product from each of the piles onto land for use as fertiliser, he found that as well as producing a better quality fertiliser, the emissions from the composted pile were a third lower than those of the conventional pile.

The pile left to decompose generated 133 kilograms of C02 emissions per tonne, while the compost emitted just 92 kilograms per tonne.

In the static mound the anaerobic digestion of the waste lead to far higher methane emissions.

There was very little difference in the emission of nitrous oxide or carbon dioxide in the two piles.

If implemented by farmers across Canada the technique could reduce the country’s annual emissions of greenhouse gases by the equivalent of 16 million tonnes of carbon.

The slight hurdle to persuading farmers to adopt Mr Singh’s composting techniques is the cost – as much as 50,000 Canadian Dollars to fit a tractor with the compost-turning equipment and pay the annual bill for the extra labour needed.

Mr Singh acknowledged the cost might be prohibitive but suggested that if Canada wanted to meet its commitments under the Kyoto Protocol the management of livestock waste would be a new avenue to explore.

by Sam Bond

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