Environmentally friendly flatulence

Roger Hegarty isn't a big fan of fart jokes. But over the course of a decade studying livestock methane emissions for the New South Wales state government in Australia, he's found that few people have been able to resist sharing their favorite wind-breaking witticism. "There isn't a fart joke in the world I haven't heard," he says with good-natured weariness. He'd be thrilled not to hear any of them again, particularly considering that 95% of the gas actually issues from front end of the animal, not the rear.

In any case, the production of methane and nitrous oxide from farming of cows, sheep, and other farmed animals is no laughing matter. In Australia alone, There are now roughly 25 million cattle in pastures and feedlots, and 100 million sheep. In 2004, together they produced some 65 million tons of "carbon dioxide equivalent," a measure that allows the warming effects of all sources of greenhouse gas to be compared. That's about 13% of the country's total greenhouse gas emissions. Suffice to say, that's a lot of gas.

Despite the scale of the problem, Hegarty and his colleagues have encountered people in the agricultural business who believe they have more urgent matters to attend to. Cattle and sheep farmers are already sinking beneath a mountain of other concerns, he explains, and in many cases, the last thing they want to know about is greenhouse gas. But in the past couple of years, scientists like Hegarty who are interested in ways to cut greenhouse gas emissions from agriculture have witnessed the emergence of a technology that could make them and the farmers happy.

It started with a drive to improve the feed efficiency of cattle, by reducing the amount of grain or grass they need to build muscle. Over the past 15 years, Australian scientists and cattle breeders have developed a method for identifying breeding bulls that can eat less yet produce the same amount of meat as others.

Researchers at Australia's Beef Cooperative Research Center found that blood levels of insulin-like growth factor 1 (IGF-1) in early life were a good indirect marker for feed efficiency. The concept has the potential to save farmers plenty of money and has already begun to catch on. The cattle-breeding industry in Australia now lists the results of feed-efficiency tests as a selling point for some bulls at market.

Hegarty, however, also realized that a side effect of lower food consumption would be lower methane production. "We saw that this could be one of those rare win-win situations," he says, so he asked his colleague Andrew Alford to run some numbers and see what kind of impact the push to greater feed efficiency might have on methane production in the longer term.

As Alford points out, putting solid figures on something like this isn't exactly straightforward. The sheer numbers of variables, combined with the shifting sands of greenhouse gas modeling, mean that any calculations should be considered as only indicators. Nevertheless, he marshaled the best data currently available and estimated that herds bred from feed-efficient bulls could reduce their methane production by as much as 16% over 25 years.

Extrapolating those figures nationally by using a gene flow model to simulate the spread of genes for improved feed efficiency, Alford and colleagues estimated that carbon dioxide-equivalent emissions from Australian beef cattle could be three percent lower in 25 years. The results were presented at the Australian Society of Animal Production Conference in Perth, Australia, in mid-July.

As Alford told conference attendees, an even greater financial benefit might benefit farmers if any future carbon-trading program were to encompass the cattle industry. He estimated that a producer with a 100-cow herd in southern Australia could save an average $216 a year from improved feed efficiency over the 25 years. In the later years the benefit is far greater. For farms with thousands of animals, this translates into significant money.

For now, the impact of feed efficiency on greenhouse emissions is not likely to be the first priority of any farmer, Hegarty admits. "We don't believe that any person buying a bull has methane production at the top of their agenda." But given the trajectory of climate change, methane production might be a concern someday. At that point, putting up with all those fart jokes may start to seem worthwhile.