Feedstock Variability: Causes, Consequences and Mitigation of Biological Degradation

Feedstock variability is a general term for a broad range of biomass properties that can impact the efficient and continuous operation of a biorefinery. Corn stover, for example, can be considered waste or a coproduct feedstock of the corn grain industry. It usually costs less than dedicated energy crops. However, even if corn stover is relatively cheap at the farm, collecting, transporting, and storing it creates logistical challenges that increase its cost as a feedstock. Importantly, how it is grown, harvested, and stored can impact quality. Take storage systems, for example. They are fundamental to feedstock supply logistics, as biomass harvest is seasonal, and biorefineries require a continuous, yearlong supply. But as is common when organic material is stored outdoors, feedstocks like stover bales break down over time due to biological degradation, also known as self-heating. The U.S. Department of Energy Bioenergy Technologies Office convened the Feedstock-Conversion Interface Consortium in part to investigate such feedstock variability - both the challenges it presents and how companies might address it. In a series of planned articles, we will highlight our current understanding of the sources and impacts of feedstock variability on biomass conversion. In this initial article, we begin with the consequences of biological degradation on the quality of biofuel feedstocks. Degradation during storage can disrupt downstream processing and conversion yields. In some cases, it can mean procuring and processing additional feedstock to compensate for losses.