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BY FEEDING cows and sheep a daily dose of methane-munching bacteria,
researchers in Scotland hope to limit the animals鈥� contributions to global
warming. Methane is one of the most potent greenhouse gases, trapping the Sun鈥檚
heat 21 times more effectively than carbon dioxide, the most abundant greenhouse
gas.

Ruminants are responsible for almost a third of all methane pollution in
Europe that passes into the atmosphere. Jamie Newbold and his colleagues at the
Rowett Research Institute in Aberdeen believe they can staunch the flow by
feeding the animals with bacteria that convert methane into less harmful
CO₂. 鈥淐arbon dioxide is by far the lesser of the two evils,鈥� says
Newbold.

Ruminants have a four-chambered stomach: in the forestomach, called the
rumen, bacteria make methane as they break down food. The Rowett team screened a
dozen species of bacteria which might produce less gas, by mixing each in turn
with digestive fluid from the rumen. He then exposed the mixture to methane. The
best strain, Brevibacillus parabrevis, converted half the methane into
CO₂. 鈥淲e added methane containing the isotope, carbon-13, and measured
how much of the isotope was switched into carbon dioxide,鈥� says Newbold.

When Newbold added 10 grams of the bacteria to the regular daily diets of
three sheep, methane production went down by around 17 per cent. Newbold
calculates that this could reduce Europe鈥檚 methane output by 4 or 5 per cent,
more than half the 8 per cent target set for the EU by the Kyoto protocol to
tackle global warming. 鈥淚t鈥檚 roughly half what we need to do,鈥� he says.