Tony Abbott's compost idea is not so corny

IT wasn't fear of global warming that prompted farmer Cam McKellar to start producing a humified compost that captures and stores carbon in his soil.

IT wasn't fear of global warming that prompted farmer Cam McKellar to start producing a humified compost that captures and stores carbon in his soil.

Rather, it was a simple business decision.

"It's about increasing the fertility of the soil, improving yields and producing better-quality food," says Mr McKellar, who runs a 1200ha corn and mixed-crop farm at Spring Ridge, 100km southwest of Tamworth in northeast NSW.

"About 10 years ago we just hit a brick wall. Our production was going down, we were getting disease, so we had to take a big look at ourselves and overhaul the whole operation."

But if the 51-year-old veteran crop farmer is not motivated by cutting carbon emissions per se, he believes Tony Abbott is on the right track in announcing a $1 billion fund to subsidise carbon-cutting practices such as soil carbon storage and tree planting.

While Mr McKellar now undertakes biological farming - using a humified compost to capture and store carbon in the soil, and shunning acid fertilisers and pesticides - others are looking to alternative techniques such as biochar to lift soil carbon levels.

Biochar is a type of charcoal produced by heating natural organic materials such as crop waste and wood chip, which is returned to the soil.

Depending on its feedstock, biochar is between 30 and 80 per cent carbon, in a form that can remain stable for perhaps a thousand years.

The practice has the backing of a growing roster of green heavy-hitters, including Nobel Peace Prize winner Al Gore. James Lovelock, the influential British environmentalist, supports its use if limited to plant matter that would otherwise be left to decay.

Several firms in the US and Europe are currently testing prototypes, and the technology is also being widely researched and tested in Australia.

Lukas Van Zwieten, a principal research scientist with Industry and Investment NSW, says the advantage with biochar is that the exact amount of carbon in it can be quantified. More than 200 field trials in Australia are being run with different types of biochars, on different crops and on different soils. "In some cases we are seeing some very, very positive results," Dr Van Zwieten said.

"We have had a doubling in biomass production in corn yield, but that is in one specific soil with one specific type of biochar, and that cannot be automatically translated to all biochars in all situations."

Most Australian soils are very low in carbon. Carbon can be increased by a range of changed farm practices, including switching from ploughing to no-till cropping, and retaining crop stubble.

When Australia ratified the Kyoto Protocol, it did not sign up to soil carbon because that category included both man-made and natural changes.

Bushfire and drought can severely reduce soil carbon, and the Australian government was worried a dry year or a big bushfire year could result in a carbon liability.

Greg Butler, from the South Australian No-Till Farmers' Association, said increased carbon brings on-farm benefits, including increased productivity and better capture of rainfall.

But he also cautioned that selling soil carbon left farmers with a "custodial risk".

If the carbon paid for decreased, the farmer became financially liable.

"Soil carbon is living, fairly volatile carbon," Mr Butler said.

"It is a food source. But biochar is inert.

"That doesn't come with any of the custodial problems,"

Peter Cosier, from the Wentworth Group of Concerned Scientists, yesterday welcomed the Coalition's commitment to increasing carbon stored in Australian soil and vegetation.

"The whole issue of using landscapes to help us with climate change and get multiple benefits is now a mainstream public debate," he said.

"Six months ago, we were struggling to get people to take notice of this issue at all." Back then, the group released a report stating that Australia could store an additional 1000 million tonnes of CO2 equivalent in soils and vegetation each year.

Mr Cosier said it is possible for Australia to cut carbon emissions by 5 per cent by 2020 from storing carbon in vegetation and soils.

He would also like to see a targeted program of planting trees on degraded land, and the inclusion of biochar.

Mr Cosier said that while biochar "is not part of the international rules", Australia should consider adopting the technology as one of many measures capable of reducing carbon dioxide emissions."

Johannes Lehmann, professor of soil fertility management at Cornell University, New York, said it had the potential to remove "a few billion tonnes" of carbon from the atmosphere a year.

"This could be one of the top 10 solutions to climate change," he said.

"It would be irresponsible to not probe its possibilities."

Additional reporting: The Sunday Times