The use of plant biomass for energy has existed since humans mastered the use of fire, although utilization beyond the open fire has evolved. The concept of using recent biomass as a major energy feedstock is being revisited, driven by high consumer demand (growing population), declining domestic oil supplies, increasing cost of fossil fuels, and a desire to curb the emission of greenhouse gases (Johnson et al., 2007b). In general terms, agriculture and forestry are the economic sectors commercially producing a wide array of bioenergy feedstocks (e.g., grains, herbaceous annuals, herbaceous perennials, and woody perennials). For this review, biomass feedstock is any nongrain, plant-derived feedstock. These commodities can serve as feedstock for cellulosic ethanol or other thermochemical platforms such as gasification or pyrolysis.
The type of bioenergy feedstock produced and the desired energy product can alter the management implications, which likely will vary by region. It is also likely that a given farm operation may produce multiple feedstocks, including corn and soybean grain, perennial grasses, and crop residues. The potential risks and benefits of growing and using feedstocks vary considerably (Johnson et al., 2007b). The challenge of establishing a perennial biomass system depends on prior management. Conversion of highly diverse grassland systems to low-diversity or monoculture perennial systems could reduce the environmental benefits of these lands. Conversely, converting from high-input, annual crop species to perennial species could reduce input requirements (fertilizer, fuel, pesticides) and reduce erosion risks, and thus have positive environmental impacts (Mann and Tolbert, 2000). Agronomic, environmental, and economic issues need to be addressed for the wide range of feedstocks and feedstock combinations to assure sustainability.