An interesting headline of No-Kill Farming: The rise of low-cost low-carbon biofuels through continuous harvest, took the lead in Biofuels Digest earlier this month. In an essay, Jim Lane reviewed the companies that are taking the first step in creating fuel production systems that do not need arable land, including algae, cyanobacteria and plant cell cultures.
Back on dry land, continuous harvesting and minimizing inputs are also key to the sustainability of lignocellulose feedstocks. For example, grasses can be mown and re-grown, with less nutrient requirement than harvesting whole plants, and C4 grasses also have the advantage (in theory) of a more efficient carbon fixing pathway.
In work just published in Biotechnology for Biofuels, Jaclyn DeMartini and Charles Wyman look at the biofuel potential of a low-input crop of mixed prairie species. A natural prairie crop was harvested and the sugar yield and recalcitrance to digestion were measured in anatomical fractions of the three most abundant species: a C3 grass (Poa pratensis), a C4 grass (Schizachyrium scoparium), and a legume (Lupinus perennis). The overall glucose and xylose yields from the mixed plot were good and improvements are proposed by increasing the leaf:stem ratio and subsequent sugar yield of the crop, or by modifying stems to make them less recalcitrant.