Cow Burps Bump Up Methane

By Dr. Karl

Published 05 October 2010

In Methane myth gives cattle a bum steer, I talked about how livestock produced about 20 per cent of the world's methane and how most people wrongly believed that this methane came from the back-end of the livestock.

Largish animals, such as cattle, pump out around 280 litres of methane per day, while sheep (which are far smaller) produce only 25 litres.

In terms of volume, methane is the number two greenhouse gas, after number one, which is carbon dioxide.

We humans — and the livestock and agriculture that we manage — dump a lot less methane than carbon dioxide into the atmosphere. But methane is about 22-or-so-times more potent as a global-warming gas than carbon dioxide.

So, one tonne of methane has the same carbon dioxide equivalent as 22 tonnes of carbon dioxide.

If you take account of this extra potency of methane, in the USA, methane is responsible for two per cent of their greenhouse gas damage.

Different countries have different proportions of heavy industry and primary industry, or of smoking chimneys and bucolic pastures. In the USA, there are fewer cattle than people: about two head of cattle for every five people.

There are only four million New Zealanders living on their two islands. But they share their home with 45 million sheep, 10 million cattle and over one million farmed deer.

Because New Zealand has so little heavy industry, over 50 per cent of its greenhouse-gas emissions arise from methane from enteric fermentation (the guts of livestock), according to Katherine Hayhoe, an atmospheric scientist at the University of Illinois.

So about 50 per cent of the greenhouse gases that New Zealand emits is methane. And this methane is about 22-times more potent than carbon dioxide.

In Australia, sheep and cattle produce 14 per cent of our greenhouse-gas damage.

This figure is measured in carbon dioxide equivalents. In other words, the actual volume of methane is a bit less than one per cent. But because methane is about 22-times more potent than carbon dioxide, it comes out equivalent to 14 per cent of greenhouse-gas damage.

Most of Australia's methane emissions come from the agriculture sector. Our tens of millions of cattle and sheep produce 90 per cent of this methane; about three million tonnes per year.

Methane from cattle is a significant worry, so various bodies around the world have researched this.

The first thing is to work out from which end of the cattle the methane comes. (At last, we get to the answer.)

The NSW Department of Agriculture in Armidale has been using a reverse aqualung combined with a small vacuum pump. Instead of delivering gas into the lungs, it samples what comes out.

It turns out that the vast majority of the methane — around 95 per cent — comes out from the mouth.

In plain-and-polite words, most livestock-related methane comes from burping (or eructation if you want to be polite), not from farting (or the other end if you want to be polite).

In the USA, Representative Henry Bonilla wrote an editorial in the Pecos Enterprise, a newspaper in Reeves County in Texas. He claimed that by funding research on cow belching, the Environmental Protection Agency was taking things too far.

In effect, he was saying that we should not know, and should not find out, what the situation really is.

On the other hand, in Australia, the CSIRO has taken the opposite approach. It has produced a colour-coded map of methane emissions, covering all of Australia.

Already, research has shown that we can reduce methane emissions from livestock.

First, by adding urea to the diet of livestock, this reduces the amount of methane emitted.

Second, New Zealand scientists found that if the livestock ate plants rich in condensed tannins, they would produce up to 16 per cent less methane.

Unfortunately, these plants are more expensive than the livestock's regular feed.

Third, we can breed cattle to have improved feed efficiency. According to Andrew Alford, a livestock research with the NSW Department of Primary Industries, in the next quarter century this would reduce methane emissions from livestock by three per cent and, at the same time, give bulkier cattle.

Fourth, antibiotics given to cattle can attack the bacteria that produce the methane and so reduce the methane output.

However, we need to consider the issue of bacteria becoming resistant to these antibiotics, and passing on this resistance to bacteria that attack humans.

A fifth approach is being taken by CSIRO Livestock Industries. They've come up with a vaccine to slow down these methane-producing bacteria. The vaccine drops methane production by 20 per cent.

Because there's a greater efficiency of processing food in the animal's gut, there's also a mild increase in weight, and possibly wool production, for sheep.

Sixth, what about cutting back on how much meat we eat?

And so on.

But the point of all of this is that methane comes out of the mouth of the cattle, not the back end. I guess a lot of us can't tell one end of a cow from another.

Source: ABC Science News