Virgin Biomass Production


The manufacture of synfuels or energy products from virgin biomass requires that suitable quantities of biomass chosen for use as energy crops be grown, harvested, and transported to the end user or conversion plant. For continuous, integrated biomass production and conversion, provision must be made to supply sufficient feedstock to sustain conversion plant operations. Since at least 250,000 botanical species, of which only about 300 are cash crops, are known in the world, it would seem that biomass selection for energy could be achieved rather easily. This does not necessarily follow simply from the multiplicity of biomass species that can be considered for energy usage. Com­pared to the total known botanical species, a relatively small number are suitable for the manufacture of synfuels and energy products. The selection is not easily accomplished in some cases because of the discontinuous nature of the growing season and the compositional changes that sometimes occur on biomass storage. Many parameters must be studied in great detail to choose the proper biomass species or combination of species for operation of the system. They concern such matters as growth area availability; soil type, quality, and topography; propagation and planting procedures; growth cycles; fertilizer, herbicide, pesticide, and other chemical needs; disease resistance of monocul­tures; insolation, temperature, precipitation and irrigation needs; preharvest management, crop management, and harvesting methods; storage stability of the harvest; solar drying in the field versus in-plant drying in connection with conversion requirements; growth area competition for food, feed, fiber, and other end uses; the possibilities and potential benefits of simultaneous or sequential growth of two or more biomass species for synfuels and foodstuffs; multiple end uses; and transport to the conversion plant gate or end-use site.

As mentioned in earlier chapters, biomass chosen for energy applications, in the ideal case, should be high-yield, low-cash-value species that have short growth cycles and that grow well in the area in which the biomass energy system is located. Fertilization requirements should be low and possibly nil if the species selected fix ambient nitrogen, thereby minimizing the amount of external chemical nutrients that have to be supplied to the growth areas. In areas having low annual rainfall, the species grown should have low con­sumptive water usage and be able to utilize available precipitation at high efficiencies. For terrestrial energy crops, the requirements should be such that they can grow well on low-grade soils so that the best classes of agricultural or forestry land are not needed. After harvesting, growth should commence again without the need for replanting by vegetative or coppice growth. Surpris­ingly, several biomass species meet many of these idealized characteristics and appear to be quite suitable for energy applications. This chapter addresses the important factors that affect biomass production for energy applications.