Evaluation of harvest time effects on the combustion quality of warm- and cool-season perennial grasses in two contrasting semi-arid environments

Abstract

In order to achieve economically viable and sustainable solid biofuel production from perennial grasses, high biomass productivity must be complemented by good combustion quality. The aim of this research was to compare the combustion quality of 7 cool-season perennial grasses, comprising bulbous canary grass, reed canary grass, smooth brome grass, orchard grass, tall wheatgrass, tall fescue, and perennial ryegrass, and 3 warm-season perennial grasses, comprising switchgrass, miscanthus, and giant reed, over 2 harvest times (autumn, winter/early spring) in 2 contrasting semi-arid environments (Adana, and Cankiri, Turkey). Delaying the harvest from the autumn to the winter or the spring significantly increased the lignin contents of each of the 3 warm-season grasses and generally decreased the contents of all of the minerals, except for Al and Fe, in miscanthus and switchgrass, and K and Na in giant reed, at both locations. Similar trends were also generally observed for all of the cool-season grasses, except for the orchard grass that was grown in Cankiri. Additionally, delayed harvest resulted in lower slagging tendency and sintering risk in all of the perennial grass species, except for giant reed in Cankiri. However, the autumn harvest caused significantly higher lignin, but generally lower N, P, K, Ca, S, Si, Al, and Fe contents, slagging tendency, and sintering risk in most of the cool-season grasses that were grown in Adana. On the other hand, despite the autumn harvest in Adana, and the spring harvest in Cankiri provided a substantial improvement in combustion quality of the cool-season grasses, mainly due to the reduced mineral and increased lignin contents, they still exhibited relatively lower combustion quality than miscanthus and switchgrass, especially in Adana. These results showed that further effort is needed to improve the combustion quality of cool-season grasses in order for them to be primary biomass feedstock alternatives for dry marginal lands of semi-arid environments.