Large‐scale production, harvest and logistics of switchgrass (Panicum virgatum L.) – current technology and envisioning a mature technology

Abstract

Switchgrass (Panicum virgatum L.) is a promising cellulosic biomass feedstock for biorefineries and biofuel production. This paper reviews current and future potential technologies for production, harvest, storage, and transportation of switchgrass. Our analysis indicates that for a yield of 10 Mg ha⁻¹, the current cost of producing switchgrass (after establishment) is about $41.50 Mg⁻¹. The costs may be reduced to about half this if the yield is increased to 30 Mg ha⁻¹ through genetic improvement, intensive crop management, and/or optimized inputs. At a yield of 10 Mg ha⁻¹, we estimate that harvesting costs range from $23.72 Mg⁻¹ for current baling technology to less than $16 Mg⁻¹ when using a loafing collection system. At yields of 20 and 30 Mg ha⁻¹ with an improved loafing system, harvesting costs are even lower at $12.75 Mg⁻¹ and $9.59 Mg⁻¹, respectively. Transport costs vary depending upon yield and fraction of land under switchgrass, bulk density of biomass, and total annual demand of a biorefinery. For a 2000 Mg d⁻¹ plant and an annual yield of 10 Mg ha⁻¹, the transport cost is an estimated $15.42 Mg⁻¹, assuming 25% of the land is under switchgrass production. Total delivered cost of switchgrass using current baling technology is $80.64 Mg⁻¹, requiring an energy input of 8.5% of the feedstock higher heating value (HHV). With mature technology, for example, a large, loaf‐collection system, the total delivered cost is reduced to about $71.16 Mg⁻¹ with 7.8% of the feedstock HHV required as input. Further cost reduction can be achieved by combining mature technology with increased crop productivity. Delivered cost and energy input do not vary significantly as biorefinery capacity increases from 2000 Mg d⁻¹ to 5000 Mg d⁻¹ because the cost of increased distance to access a larger volume feedstock offsets the gains in increased biorefinery capacity. This paper outlines possible scenarios for the expansion of switchgrass handling to 30 Tg (million Mg) in 2015 and 100 Tg in 2030 based on predicted growth of the biorefinery industry in the USA. The value of switchgrass collection operations is estimated at more than $0.6 billion in 2015 and more than $2.1 billion in 2030. The estimated value of post‐harvest operations is $0.6–$2.0 billion in 2015, and $2.0–$6.5 billion in 2030, depending on the degree of preprocessing. The need for power equipment (tractors) will increase from 100 MW in 2015 to 666 MW in 2030, with corresponding annual values of $150 and $520 million, respectively. © 2009 Society of Chemical Industry and John Wiley & Sons, Ltd