Where's the nitrogen? The timing and impacts of internal nitrogen cycling on switchgrass (Panicum virgatum L.) yield and biofuel quality

Wilson, Danielle
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Research focused on dedicated bioenergy crops that can be used to meet our advanced biofuels goal, i.e., made from non-food sources like agricultural residues and lignocellulosic feedstocks, has found switchgrass (Panicum virgatum L.) to be a leading candidate species. Switchgrass requires nitrogen (N) in greater quantities, compared to other nutrients, for plant biomass production, but high N concentration ([N]) is undesirable in the harvested biomass feedstock for two reasons: 1) it is economically and environmentally expensive to replace N removed from cropping system and 2) N reduces the conversion efficiency of biomass to biofuels via thermochemical conversion. Immediate reductions in the [N] of the harvested portions of perennial feedstocks, including switchgrass, can be achieved by exploiting seasonal internal N cycling. The biology of switchgrass provides some opportunity to naturally manipulate the [N] of this biomass feedstock, but there is a trade-off between the quantity and quality of the feedstock depending on the time of harvest. The research objectives of this project were to: 1) elucidate the spatial and temporal distribution of N in above- and below-ground tissues of field-grown switchgrass to determine its impacts on yield and N removal and 2) determine how switchgrass harvest date influences biofuel quality from fast pyrolysis. We recommend harvesting post-frost switchgrass biomass for improved long-term yields and reduced [N] in the harvested portions of biomass that can result in reduced N removal. This will benefit both biomass producers and also thermochemical facilities who will receive low-N biomass to reduce conversion costs.

bioenergy, biomass crop, bio-oil, thermochemical conversion