When organic matter decomposes, rots, in anaerobic conditions the types of micro-organisms that do the work emit methane as a waste product. That's why swamps, rice paddies, lake bottoms and land fills emit so much methane. When there is air present, oxygen to be more precise, aerobic microbes that emit carbon dioxide wastes do more of the work.

Ruminants such as cattle, sheep and goats harbor anaerobic organisms in their guts, something like human intestinal flora, that decompose the tougher bits of grasses and forbs, the cellulose, and emit methane in the process. Though this is completely natural and has happened for eons as giant herds of ruminants roamed the continents before humans ever domesticated some of them (think bison), it has become a target of climate change nutters.

Scientists at Gramina, a joint biotech venture by Australia’s Molecular Plant Breeding Cooperative Research Centre and New Zealand rural services group PGG Wrightson Genomics, are developing a grass that will not only cut the amount of methane cows burp up when chewing the cud but will also grow in hotter climes, according to the latest issue of Chemistry & Industry.

This means that farmers should be able to maintain dairy herds’ productivity and profitability in the face of a changing climate, while cutting down their gaseous burps and reducing their contribution to global warming. . .

Gramina will use sense suppression technology to prevent the expression of the enzyme O-methyl transferase. Suppressing this enzyme leads to an increase in the digestibility of the grass without compromising its structural properties and therefore less burps and less methane. . .

However, some scientists suggest that a cow’s absolute methane emissions might go up.

Alistair Macrae, a lecturer in farm animal health and production at the University of Edinburgh, UK, says a diet too rich in highly digestible carbs can actually increase the amount of methane a cow belches out. This is because gut microflora convert more of these sugars into propionic acid, which creates a more acidic environment resulting in more methane.

Ian Givens, a professor of animal science, at the University of Reading, UK, says that more digestible forage could push up a cow’s absolute methane emissions but productivity gains would mean less methane per unit of milk.

Beever agrees and says, ‘It could increase methane emissions but it could also increase milk yields, effectively cutting the amount of methane produce per litre of milk.’

The weasel words that take back the talk about methane reduction and slide over to an emissions intensity argument mask the real story here: "an increase in the digestibility of the grass". This means more production, or less forage for the same production. If the grasses have other useful traits such as good nutrition and growth habits then this will be a great benefit for the continuing struggle to feed the world.