Switchgrass harvest timing & harvest/storage method influence quantity, quality & sustainability aspects of a lignocellulosic ethanol production system in the northern corn belt/great lakes region

A three year field study was conducted to help develop agronomic suggestions on how to create an economically viable and sustainable switchgrass crop production phase of a lignocellulosic ethanol production system, in the Northern Corn Belt/Great Lakes region, that facilitates the procurement, storage, and delivery of a high quantity of high quality lignocellulosic feedstock. An early fall chop/ensile harvest scenario may maximize harvest yield, facilitate a more timely harvest, not affect winter hardiness, and potentially be most profitable for growers. Successive early fall harvests may significantly reduce both feedstock cellulose and lignin contents, however theoretical ethanol yields indicated that an early fall harvest did not significantly impact potential ethanol yield. An early fall harvest resulted in a significantly higher glucose hydrolysis yield, which suggests that an early fall harvest timing may be most conducive to increasing enzymatic hydrolysis efficiency. Life cycle assessment suggested that an early fall chop/ensile harvest scenario throughout the ten year lifetime of a dedicated switchgrass bioenergy stand in this region may minimize environmental impacts while also potentially being the most economically sustainable option for a grower. Insignificant reductions in feedstock ash content during the fall or between harvest/storage methods suggested increased grower flexibility to choose an appropriate region-specific harvest management strategy without compromising the potential for cofiring in energy production.