Abstract
Switchgrass (Panicum virgatum L.) and giant miscanthus (Miscanthus x giganteus Greef & Deuter ex Hodkinson & Renvoize) are productive on marginal lands in the eastern USA, but their productivity and composition have not been compared on mine lands. Our objectives were to compare biomass production, composition, and theoretical ethanol yield (TEY) and production (TEP) of these grasses on a reclaimed mined site. Following 25 years of herbaceous cover, vegetation was killed and plots of switchgrass cultivars Kanlow and BoMaster and miscanthus lines Illinois and MBX-002 were planted in five replications. Annual switchgrass and miscanthus yields averaged 5.8 and 8.9 Mg dry matter ha−1, respectively, during 2011 to 2015. Cell wall carbohydrate composition was analyzed via near-infrared reflectance spectroscopy with models based on switchgrass or mixed herbaceous samples including switchgrass and miscanthus. Concentrations were higher for glucan and lower for xylan in miscanthus than in switchgrass but TEY did not differ (453 and 450 L Mg−1, respectively). In response to biomass production, total ethanol production was greater for miscanthus than for switchgrass (5594 vs 3699 L ha−1), did not differ between Kanlow and BoMaster switchgrass (3880 and 3517 L ha−1, respectively), and was higher for MBX-002 than for Illinois miscanthus (6496 vs 4692 L ha−1). Relative to the mixed feedstocks model, the switchgrass model slightly underpredicted glucan and slightly overpredicted xylan concentrations. Estimated TEY was slightly lower from the switchgrass model but both models distinguished genotype, year, and interaction effects similarly. Biomass productivity and TEP were similar to those from agricultural sites with marginal soils.
Highlights
Climate change awareness has prompted research into alternative energy sources to replace fossil fuels
As with cell wall polysaccharide and theoretical ethanol yield (TEY) determinations, these results suggest the possible validity of the NIRSC switchgrass bioenergy model for prediction of TEP of both species under the conditions of this study
Between species and among miscanthus lines, concentrations of all cell wall polysaccharides differed according to the five-polysaccharide NIRSC switchgrass bioenergy prediction model, resulting in higher TEY for switchgrass but no differences among cultivars
Summary
Climate change awareness has prompted research into alternative energy sources to replace fossil fuels. (2018) 11:562–573 other energy sources, reduce dependence on fossil fuel use [1], and offer economic returns to growers in rural areas. Increasing world food demands may constrain availability of agricultural land for bioenergy production from corn grain [3,4,5,6]. The use of corn stover for production of cellulosic ethanol increases ethanol production per land area, but growing corn for fuel still requires agricultural lands that could be used for food crops and can reduce contributions of valuable organic material to soil health [9, 12, 13]
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