Harvest and Storage of Two Perennial Grasses as Biomass Feedstocks

Abstract

Some perennial grasses, such as reed canarygrass (RCG) and switchgrass (SWG), have prolific yield and low inputs, making them attractive as biomass feedstocks. When harvested as biomass, these grasses are more mature and have much greater yield than when harvested as animal forage. Much is unknown about how harvest equipment performance and storage characteristics are affected by these crop conditions. The objective of this research was to determine the crop yield and drying rate, baling rate, bale density, and bale storage characteristics of these grasses harvested as biomass feedstocks. After the establishment year, the three-year average yield of RCG was 21% less than SWG (7.70 vs. 9.69 Mg DM ha-1) using a single-cutting system that occurred in August. When the crops were left standing over winter and harvested in the spring, DM yields were reduced by 17% and 26% for SWG and RCG, respectively. When crop yield was similar, switchgrass tended to dry faster than reed canarygrass. Drying rates of these grasses were faster than typically experienced with forage crops like alfalfa. Bale density averaged 163 kg DM m-3 with no significant differences between crops or type of wrap (twine or net). Dry bales stored outdoors for 9 to 11 months averaged 3.8%, 4.8%, 7.5%, 8.7%, and 14.9% DM loss for bales wrapped with plastic film, breathable film, net wrap, plastic twine, and sisal twine, respectively. Bales stored under cover averaged 3.0% DM loss. The chemical and physical properties of bales stored outdoors were spatially variable. Preservation by ensiling in a tube produced average DM losses of 1.1% at average moisture of 39.9% (w.b.).