Keeping cellulosic crops green

Flow has long talked about the necessity of using cellulosic materials instead of food crops to produce our ethanol. Notwithstanding the potential impact of invasive species like switchgrass, it just makes sense to use fuel sources that aren’t going to raise food prices throughout the world and, in many cases, are more efficient sources of energy anyway. Moreover, there’s been evidence that secondary crops like switchgrass can actually improve soil quality, and there’s an understandable desire to make sure that we make the most out of the fuel sources we have.

But a recent study by the American Society of Agronomy found that one of the ways of maximizing a field’s energy output, crop residue removal, can actually have extremely negative effects on the soil itself. In fact, according to one of the study’s authors, if more than 50 per cent of crop residue is removed, the soil can actually become a carbon source, rather than a carbon sink.

On a very basic level, this adds another argument against attempting to use edible grains as fuel sources. It means that in addition to food crops needing to be preserved because of their use in human beings, rather than gas tanks, they also have the potential to increase our greenhouse gas emissions, rather than decrease them — counteracting one of the central purposes behind alternative fuel sources. Instead, the study suggests, would-be biofuel producers should concentrate on growing warm season grasses and short-rotation woody crops.

Just another reason to keep the food on our tables, separate from the fuel in our tanks.