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鈥檚 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鈥� methane-producing metabolism. More gas can then be harvested.
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鈥淲ater and nutrients pumped into the wells kick-starts microbes鈥� methane-producing metabolism鈥�
The US Geological Survey and CSIRO, the Australian national science agency, have been exploring the idea for a number of years. 鈥淲e 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,鈥� 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 (麻豆传媒, 18 April, p 8).
Although biogenic methane produced this way has been on the agenda for several years, it鈥檚 unclear which methods will work best, says , 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 鈥渙ff the shelf鈥�.
The results of the 2007 experiment were compelling: 鈥淲e made 1 billion cubic feet [30 million cubic metres] of methane,鈥� Finkelstein says. That鈥檚 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鈥� owner, who Finkelstein says does not wish to be named. 鈥淢ost of Luca鈥檚 expenses in 2008 and part of 2009 were covered by gas sales,鈥� he says.
The company now owns and 鈥渇arms鈥� 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. 鈥淟uca鈥檚 technology can help make this transformation more reliable and economic,鈥� he says. He is also keen to point out that Luca makes use of existing infrastructure. 鈥淭he wells have been drilled and the roads, pipes and compressors to capture gas are already there.鈥�
鈥淕iven the demand for fossil fuels, it seems to me inevitable that such 鈥榚xotic鈥� forms of fossil carbon will be developed and exploited,鈥� says , head of the Climate Dynamics group at the University of Oxford. 鈥淭his all points to the need to neutralise their impact on climate by developing and implementing technologies for carbon capture and sequestration.鈥�
