Australian researchers are studying the possibility of turning crops like agave, hemp, or the native saltbush and wild-growing sorghum into biofuels of the future. Studies show that it’s possible to extract non-traditional plant oils and turn them into biodiesel for vehicles, machinery and even aviation fuel.
Currently oils extracted from palm and soy cost roughly twice the price of crude oil in Australia. “It really is fundamentally an economic problem rather than a technological problem,” says Dr Allan Green, innovation leader for biobased products at CSIRO Agriculture and Food. His solution is to modify plants to make them produce more oil per section of land, which means harvesting and production costs would predictably fall. Green and his colleagues patented a way of modifying the genetic levers that control oil output in plants, so a plant produces oil not just in its fruit or seeds but in its leaves as well.
Presently the technology shows one can increase oil production in tobacco to a third or more of the leaf’s weight, producing more oil than occurs naturally in any plant. If this technique is demonstrated in a crop that already produces oil in its seeds or fruit, the hope is that oil output could be multiplied, though that theory has yet to be proven.
Technology in processing is also influencing the direction of the biofuel industry. Traditional approaches use fermentation to turn plant sugars into bioethanol, or oils that can be chemically transesterified for biodiesel production. Much research has gone into finding the perfect crops for these applications: plants dense in sugar-laden cellulose, but without the extraction-complicating lignins; or plants that pump out high oil volumes. Another consideration is a more flexible methodology, with regard to the kinds of plants that can be utilized.
One process, hydrothermal liquefaction uses heat and pressure to break up the long-chain molecules in whole plants into bio-crude oil, essentially reducing eons of geological time into a matter of hours. The resulting bio-crude oil can then be refined as a petroleum-based crude oil would be, producing an array of fuels as well as plastics and other products.
Similarly, torrefaction, which has been adapted from roasting coffee, can turn essentially any plant matter into bio-coal pellets. While both of these processes are energy intensive, “combining them with renewables like solar panels or wind turbines – or locating them near power stations that could harvest excess heat, would make the operations more environmentally sustainable,” says Rachel Burton, leader of the ARC Centre of Excellence for Plant Cell Walls at University of Adelaide.
The advantage of a non-traditional approach is that producers wouldn’t be limited to crops designed to be biofuel-only commodities but instead could choose varieties that deliver value-added benefits. Agave could be used to produce a high-value tipple, for instance, or hemp farmers could harvest seed for food and fiber for carpeting or fabric along with biofuels.
The biofuel industry could prove to be a very diverse one according to Green. “The amount of fuel we need to move away from petroleum is massive, so there’s plenty of space for all technologies,” he says.