As discussed last week, recent growth of concern over both energy security and climate change has seen the star of the fledgling biofuels industry – which has been offered up as at least partial panacea to both issues – rise rapidly.

Assuming this is true, another obvious question arises: if biofuel production is to be ramped up, where will the necessary biological inputs come from?

One option might be to divert some current agricultural land or crop yield into biofuel production. But adding additional demand for existing supply is likely to drive up food prices, in the process threatening food security among poorer countries.

Mexico is to some degree bearing witness to this at present (see here). Increased diversion of corn into US ethanol production has driven up commodity prices and thus the price of Mexico’s traditional staple – corn tortillas.

This might be countered by clearing more land for cultivation, which must inevitably further reduce the extent of the world’s remaining ecosystems, and with it their attendant biodiversity and carbon stock. Illustrating the point, demand for palm oil, pushed higher by the crop’s value as a high energy feedstock for biodiesel production, is driving rapid clearance of tropical forests in Borneo (see here).

Additionally, environmental input of pesticide and fertiliser would be likely to increase, as would demand on water and degradation of soil. Weighing all of this up against climate change is a complex reckoning, but if the point of protecting climate is to maintain the integrity of ecological systems and the human ones they underpin, then investing in technologies that prove ecologically disastrous is simply running on the spot.

All of which might be at least partially alleviated by mating crops and production processes that maximise energy return on investment (EROI), thus reducing resource requirements – and therefore environmental impact – per unit energy produced.

The production of cellulosic ethanol – which utilises the energy contained in the complex carbohydrates bound up in plant fibres, rather than the starches in the fruits or seeds alone (as is currently the case with ethanol production) – is seen as promising. Published studies estimate a potential EROI of +4-6, though these numbers have their critics (perhaps most vociferously in David Pimentel of Cornell University).

That said, the technology still has some hurdles to clear before becoming viable. And it seems unlikely that, even at it’s best, biofuel production could displace anything close to today’s rates of fuel consumption, much less tomorrow’s, without profound environmental and social implications.

In the meantime, we need a very clear accounting of the potential energy and climatic benefits of biofuels, measured against potential environmental costs. If public money is to be made available for development of biofuels with the ostensible aim of improving environmental outcomes – a very public good – then those outcomes need to be comprehensively demonstrated.