Herbaceous Perennials: Placement, benefits and incorporation challenges in diversified landscapes

Authors: Mitchell, Robert - Rob; OWENS, VANCE - South Dakota State University; GUTTERSON, NEAL - Mendel Biotechnology; Richard Jr, Edward; BARNEY, JACOB - Virginia Polytechnic Institution & State University

Submitted to: Sustainable Feedstocks for Advanced Biofuels
Publication Type: Book / Chapter
Publication Acceptance Date: 3/10/2011
Publication Date: 9/27/2011
Citation: Mitchell, R., Owens, V., Gutterson, N., Richard Jr, E.P., Barney, J. 2011. Herbaceous Perennials: Placement, benefits and incorporation challenges in diversified landscapes. Sustainable Feedstocks for Advanced Biofuels. 6:84-98.

Interpretive Summary: Although there is no one-size-fits-all bioenergy feedstock, herbaceous perennial feedstocks will fill numerous and critical roles in the bioenergy landscape. First, perennials do not have the annual establishment requirements and associated economic and net energy inputs. Second, they require fewer chemical inputs (herbicide and fertilizer) than annual row crops. Third, perennials produce large quantities of biomass. Finally, perennials provide a number of important ecosystem services such as soil stabilization, soil carbon sequestration, and wildlife habitat beyond what annual crops are capable. Although these characteristics are important, herbaceous perennial crops must be economically viable to be acceptable to producers and biorefineries, and environmentally sustainable to be acceptable to society. Our objective is to present the benefits and challenges of growing herbaceous perennials and provide regionally-specific scenarios for their use at the landscape scale. In the near term, biofuel feedstocks in an agro-ecoregion must have a limited impact on the production of traditional agricultural crops: i.e. not displace currently utilized agricultural land for biomass-specific crops, and not utilize edible (food or feed) crops for biomass. Consequently, optimizing sustainable yield will drive not only the economic feasibility of selected herbaceous perennial feedstocks, but also the capacity of the landscape to meet all other necessary agricultural and social demands. Within agro-ecoregions, feedstock selection will be site-specific based on yield potential, climate, landscape position, potential ecosystem services, and producer-driven acceptance such as economics, familiarity, and willingness to commit land to long-term feedstock production.

Technical Abstract: Herbaceous perennial feedstocks will fill numerous and critical roles in the bioenergy landscape. Our objective is to present the benefits and challenges of growing herbaceous perennials and provide regionally-specific scenarios for their use at the landscape scale. The primary herbaceous perennial feedstocks will vary by agro-ecoregion and will include switchgrass, Miscanthus, alfalfa, native polycultures, sugar cane, and energy cane. In the near term, optimizing sustainable yield will drive the economic feasibility of herbaceous perennials. However, within agro-ecoregions, feedstock selection will be site-specific based on landscape position, potential ecosystem services, and producer-driven acceptance such as economics, familiarity, and committing land to long-term feedstock production. For example, in the central and northern Great Plains, managed switchgrass monocultures produce three times more dry matter and provide fewer establishment and management challenges than extensively managed native polycultures. Since yield is of paramount importance, native polycultures may be suited only to situations where ecosystem restoration and increased plant species diversity are primary objectives. In the Midwest, Miscanthus x giganteus produces more biomass with fewer inputs than other herbaceous perennials, though the cost of establishment and time required to keep stands in production to offset the cost of establishment may limit producer acceptance on a large scale until non-invasive, seeded varieties can be developed. In the Gulf Coast states, sugar cane has been in production for more than 200 years, so expanding production for bioenergy provides fewer barriers. The Southeast has the most diverse selection of herbaceous biomass crops which will be determined by local growing conditions, available harvest technology, and environmental considerations. Challenges in the Southeast include reluctance to adopt novel crops and the predominance of degraded soils on sites available for cultivation. Balancing biomass production, ecosystem services and producer acceptance will be major challenges for a diversified landscape in the new bioeconomy.