Excuse me! The problem with methane gas

Box 3 | Moderating methane

Because around 60 per cent of methane is produced by human-related activities, changing the way we do some of these activities could help to reduce the amount of methane in the atmosphere.

Couth cows and kangaroo burgers

We could all become vegetarians or reduce our meat and dairy intakes. That way, there’d be fewer cattle and sheep needed. But it might be hard to convince Australians to give up their family roast or barbecued steaks. Australia has over 90 million sheep and 29 million cattle.

However, Australian scientists are tackling livestock emissions. In early 2009, the Australian Government committed nearly $27 million to research ways of reducing methane and other greenhouse gases arising from agriculture. The research involves 18 projects, including selectively breeding livestock to produce less methane; reducing methane emissions by eliminating certain livestock gut microbes; and reducing methane emissions by changing the diet of livestock.

Another suggested way of achieving lower methane emissions would be to eat meat from farmed kangaroos. Because kangaroos are not ruminants, they don’t belch out nearly as much methane. So perhaps kangaroo burgers and sausages might help save the planet – but only if you could convince lots of people to change their diet!

Drying out

Draining naturally occurring wetlands is a simple way to decrease methane levels, but this can increase carbon dioxide emissions as well as having unwanted environmental effects when animal and plant habitats are changed.

Finding different ways to grow rice – such as dry rice farming – or developing more productive rice varieties could help reduce methane levels.

One way to prevent methane being made at landfill sites is to cover the site to stop rain penetrating into the ground. Australian scientists are now looking at reducing methane levels at rubbish tips by growing plants and trees on their surface. The idea is for the plants to take up the water that would otherwise seep down and promote the anaerobic decomposition of rubbish, which produces methane. This method – known as phytocapping – has been tested successfully by researchers at the Central Queensland University.

Making use of methane

Because methane can be used as a fuel, there are several possibilities for recycling the gas and using it as a source of energy. Even though this might produce some carbon dioxide, the overall contribution to climate change would be less than if the methane wasn’t used. For years, methane produced by decomposing matter at some rubbish tips or landfill sites has been tapped as a source of the gas.

Yet another way to reduce methane levels is to lower emissions from fossil fuel industries. For instance, methane is collected from some Australian coal mines for energy production. And the CSIRO and the Australian Government Department of Climate Change have been involved in a pilot project to use methane from a Chinese coal mine to help power a gas turbine – in effect, turning a waste gas into a fuel.

Importantly, governments are now recognising the role of methane as a greenhouse gas. Methane has been included in Australia’s draft emissions trading scheme, the Carbon Pollution Reduction Scheme and the European Union is also looking at including methane (and other greenhouse gases) in its Emissions Trading Scheme which up to now has only included carbon dioxide.

Boxes
Box 1. Methane levels
Box 2. The oceans’ massive methane reserves

Related sites
How kangaroo burgers could save the planet (New Scientist, 25 December 2008)
Cooperation on capturing Chinas mine methane emissions (Ecos, April-May 2006)
Putting a green cap on garbage dumps (Science Daily, 3 December 2008)
Methane (Greenhouse gas online, United Kingdom)
Australia's policy response (Nova: Science in the news, Australian Academy of Science)

External sites are not endorsed by the Australian Academy of Science.
Posted November 2009.