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.