Redefining Agricultural Residues as Bioenergy Feedstocks

Abstract

The use of plant biomass is a sustainable alternative to the reduction of CO₂ emissions. Agricultural residues are interesting bioenergy feedstocks because they do not compete with food and add extra value to the crop, which might help to manage these residues in many regions. Breeding crops for dual production of food and bioenergy has been reported previously, but the ideal plant features are different when lignocellulosic residues are burnt for heat or electricity, or fermented for biofuel production. Stover moisture is one of the most important traits in the management of agricultural waste for bioenergy production which can be modified by genetic improvement. A delayed leaf senescence or the stay-green characteristic contributes to higher grain and biomass yield in standard, low nutrient, and drought-prone environments. In addition, the stay-green trait could be favorable for the development of dual purpose varieties because this trait could be associated with a reduction in biomass losses and lodging. On the other hand, the stay-green trait could be detrimental for the management of agricultural waste if it is associated with higher stover moisture at harvest, although this hypothesis has been insufficiently tested. In this paper, a review of traits relevant to the development of dual purpose varieties is presented with particular emphasis on stover moisture and stay-green, because less attention has been paid to these important traits in the literature. The possibility of developing new varieties for combined production is discussed from a breeding perspective.

Keywords: chlorophyll content; climate change; photosynthesis; senescence.

Figure 1

World CO₂eq emissions by crop type from agricultural waste in four conventional crops since 1990–2012.

Figure 2

Main CO₂eq emitters from agricultural waste reported by the Food and Agriculture Organization of the United Nations (FAO). Average 1990–2012 and 2012.

Figure 3

World burning of crop residues (dry matter) for 2012 and projections for 2030 and 2050.