Environment

WHATEVER you may think of our addiction to fossil fuels, there is no shortage of ideas on how to extract every last tonne. Field trials are now showing that all it takes is common fertiliser.

Natural gas is often present in coalfields, clinging to the coal. It is extracted through wells drilled into the coal seam, but once production tails off the industry usually moves on.

That's when biogenic methane companies propose to move in. By pumping water and nutrients back down the wells to feed microbes living in the coal they expect to be able to kick-start the microbes' methane-producing metabolism. More gas can then be harvested.

The US Geological Survey and CSIRO, the Australian national science agency, have been exploring the idea for a number of years. "We have shown that this process works on coal in the lab, and I think that it will be possible to make it work on an industrial scale," says Phil Hendry at CSIRO in North Ryde, New South Wales. The Canadian company Profero Energy intends to test biogenic methane technology in Canadian tar sands (New Scientist, 18 April, p 8).

Although biogenic methane produced this way has been on the agenda for several years, it's unclear which methods will work best, says Elizabeth Jones, a microbiologist at the US Geological Survey.

Mark Finkelstein, vice president of biosciences at Luca Technologies, a firm based in Golden, Colorado, begs to differ. In field experiments in 2007, his company generated enough gas from 100 leased wells in Wyoming to heat 16,000 homes for a year. Finkelstein will not give details of the nutrients his company uses to fertilise the subterranean organisms, but says you could buy most of them "off the shelf".

The results of the 2007 experiment were compelling: "We made 1 billion cubic feet [30 million cubic metres] of methane," Finkelstein says. That's above and beyond what would have been made without the nutrients.

Money from the sale of the extra gas was split between Luca and the wells' owner, who Finkelstein says does not wish to be named. "Most of Luca's expenses in 2008 and part of 2009 were covered by gas sales," he says.

The company now owns and "farms" some 630 wells in the US that the traditional industry classifies as marginal. By the end of this year that number will have risen to 1000, Finkelstein says.

He points out that utility companies are considering converting from coal to methane to cut down on their carbon footprint. "Luca's technology can help make this transformation more reliable and economic," he says. He is also keen to point out that Luca makes use of existing infrastructure. "The wells have been drilled and the roads, pipes and compressors to capture gas are already there."

"Given the demand for fossil fuels, it seems to me inevitable that such 'exotic' forms of fossil carbon will be developed and exploited," says Myles Allen, head of the Climate Dynamics group at the University of Oxford. "This all points to the need to neutralise their impact on climate by developing and implementing technologies for carbon capture and sequestration."

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