Perennial grasses as sustainable bioenergy crops for marginal lands

摘要

To minimize energy dependence on foreign petroleum imports and reduce fossil fuel consumption, the US Government has mandated the annual use of 136 billion liters of biofuels by 2022. Of the 136 billion liters, 61 billion liters should be produced from cellulosic biofuels. This will likely lead to increased production of dedicated energy crops for renewable biofuels. Since an ideal biomass crop should not compete with food crops for land use, biomass crop production on marginal lands can reduce land-use competition between energy and food crops. Chapter 1 of this dissertation provides an introduction and rationale of the research with a general discussion of the marginal lands and comparative potential of the various feedstock crops used in the experiments.;As a biomass crop in the US, switchgrass has been studied extensively and has been identified as a model biomass crop by the US Department of Energy (DOE). Cultivars of this species are generally considered as drought tolerant and are able to grow in a wide range of environments including some marginal lands. Miscanthus x giganteus has a high biomass yield potential and has been extensively evaluated for biomass in EU and recently in US. They also have moderate tolerance to heat, cold, drought, salinity, and flooding. Prairie cordgrass is native to North America and can be grown on lands that are too wet for corn, switchgrass, and big bluestem. They are highly tolerant to flooding and salinity. Big bluestem was primarily evaluated for forage purpose, but recently it has also been evaluated for bioenergy feedstock potential.;In Chapter 2, the biomass yield and performance of four perennial grass species: Miscanthus x giganteus, big bluestem (Andropogan gerardii Vitman), 'Kanlow' switchgrass (Panicum virgatum L.) and four natural populations of prairie cordgrass ( Spartina pectinata Link.) were investigated in wet marginal land. A three-year study from 2011 to 2013 investigated the biomass yield and tissue lignocellulosic composition among the compared species in 45 cm and 90 cm row spacing treatments. Biomass yield at 45 cm spacing was significantly higher than that at 90 cm spacing for all the populations compared during the first three years in this experiment. Switchgrass had the greatest biomass yield during all three years in 45 cm spacing, but it was not significantly different from two of the prairie cordgrass populations and Miscanthus x giganteus by the end of the experiment in 2013. There was no significant difference found among the grasses for cellulose and hemicellulose concentration in tissue.;Waterlogging in poorly drained soils can cause flooding that can delay early-season planting and also, cause difficulties in field operation in late season. High salinity is also a problem causing potentially arable land to be classified as marginal in the US. In Chapter 3, I investigated the potential of two natural populations of prairie cordgrass and a switchgrass in Illinois locations including poorly drained soils in Urbana and Pana, and a highly saline soil in Salem. A three-year study showed a reliable amount of biomass yield for all three grass populations by the end of the third year. All three locations produced acceptable amounts of lignocellulosic contents even when considering that these crops were produced in marginal settings. This research concludes that the evaluated grass populations have a good potential to be grown in a poorly drained, as well as salt-affected marginal land.;In Chapter 4, I evaluated and screened 17 populations of prairie cordgrass (Spartina pectinata) along with Kanlow switchgrass ( Panicum virgatum 'Kanlow') in poorly drained soil in Urbana, IL, and plots irrigated with saline water in Pecos, TX. A two-year study from 2012 to 2014 showed a great variation among the prairie cordgrass populations for biomass productivity. However, a Kansas-originating population produced the greatest biomass yields averaged over two years in both locations. Averaged over two years, Kanlow switchgrass was the top producer in both locations. We also found much variation in tissue mineral concentration among the populations in the two locations. Our study demonstrates that genetics and environment can have a great influence on grass performance.