Perennial herbaceous crops with potential for biofuel production in the temperate regions of the USA

As the US government in the Energy Independence and Security Act of 2007 has mandated that 60.5 billion litres of advanced biofuels are to come from cellulosic sources in the near future, there is increasing need to produce high-yielding, well-adapted and renewable bioenergy crops. Moreover, the US Department of Energy's 'Billion-Ton Update: Bioenergy Supply for a Bioenergy and Bioproducts Industry' predicts that the temperate regions of the USA will contribute much cellulosic feedstock. In this review, the authors focus on herbaceous crops in the temperate regions of the USA and the potential these crops have to contribute to the production of advanced biofuels in the future. Featured are examinations of perennial grasses including Andropogon gerardii, Arundo donax, Miscanthus×giganteus, Panicum virgatum, Phalaris arundinacea, Sorghastrum nutans and Spartina pectinata; polystands represented by the Conservation Reserve Program (CRP) and tallgrass prairie; and the broadleaved herbaceous crops (forbs) Helianthus grosseserratus, Sida hermaphrodita, Silphium perfoliatum, Solidago gigantea and Vernonia gigantea. Growth characteristics, and when available, yield information is presented for each individual crop or mixed planting system. When the agronomics have been determined, individual species, rather than polystands, have been most commonly employed in the existing biomass production. P. virgatum (switchgrass) is an example of an herbaceous crop that has been grown in monostands in temperate regions of the USA. Conversely, CRP lands and tallgrass prairie have provided the benefits of multifunctional polystands that can improve water quality, air quality, soil erosion, greenhouse-gas emission, wildlife habitat, aesthetics, employment and rural communities along with net biomass productivity. Biomass yield information for many herbaceous crops is limited.