Economic and Environmental Analysis for Corn Stover and Switchgrass Supply Logistics

Abstract

Supply logistics systems for corn (Zea mays L.) stover and switchgrass (Panicum virgatum L.) with two collection methods, round bales and rectangular bales, are developed. A location in the US Midwest is assumed with corn grown on highly productive crop land and switchgrass grown on less productive land. Bales (15 % moisture wet basis) are stored at local storage sites within 3.2 km (2 mi) of the field at harvest time. Biomass is transported to an end user within a 48 km (30 mi) throughout the year. Round bales are converted to bulk product [bulk density of 240 kg m⁻³ (15 lb ft⁻³)] by tub grinding followed by roll-press compacting before truck transport. Rectangular bales are delivered by truck without processing. Total delivered cost is $97.70 Mg⁻¹ ($88.63 ton⁻¹) for corn stover and $137.87 Mg⁻¹ ($125.07 ton⁻¹) for switchgrass when delivered as a bulk compacted product. Total delivered cost is $90.25 Mg⁻¹ ($81.87 ton⁻¹) for corn stover and $128.67 Mg⁻¹ ($116.73 ton⁻¹) for switchgrass when delivered as rectangular bales. Life-cycle fossil energy consumption is higher for delivering switchgrass (9.9 to 13.8 % of energy in dry matter) than for corn stover (5.8 to 9.5 % of energy in dry matter). Excluding any potential change in soil organic carbon (SOC), life-cycle greenhouse gas (GHG) emissions are 59.2 to 99.8 kg CO₂e Mg⁻¹ for delivering corn stover and 231.8 to 279.6 kg CO₂e Mg⁻¹ for delivering switchgrass. The effect of change in SOC on the life-cycle GHG emissions for corn stover and switchgrass is discussed.