12.3.1 Resource Constraints

In this chapter, reference is made to production of the biomass (growing the plants) only in the context of (1) when during the year the biomass can be harvested, and (2) the properties at harvest, principally the moisture content. Any biomass crop that provides an extended harvest season has an advantage — remember, any business (not only bioenergy) wants to operate as many hours per year as possible. Herbaceous crops cannot be harvested during the growing season, thus storage is always a component in the logistics system design.

Two examples from opposite ends of the harvest-season spectrum are offered. In the Southeast, wood is harvested year-round. It is said to be “stored on the stump”. Weather conditions in the Southeast are such that few harvest days are lost in the winter due to ice and snow. At the other end of the spectrum, consider the harvest of corn stover in the Upper Midwest. The grain harvest is completed in the fall and then the stover is collected. In some years, there are less than 15 days between the completion of the grain harvest and the time when the fields are covered with snow and no stover can be collected. All feedstock required for year-round operation of a bioenergy plant using only corn stover must be harvested in a two — to five-week period — a significant challenge for the logistics system.