|Richard Jr, Edward|
|Doran-Peterson, Joy -|
|Baldwin, Brian -|
Submitted to: Biomass and Bioenergy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 26, 2013
Publication Date: April 26, 2013
Citation: Knoll, J.E., Anderson, W.F., Richard Jr, E.P., Doran-Peterson, J., Baldwin, B., Hale, A.L., Viator, R.P. 2013. Harvest date effects on biomass quality and ethanol yield of new energycane (Saccharum hyb.) genotypes in the Southeast USA. Biomass and Bioenergy. 56:147-156. Interpretive Summary: Energycane (Saccharum hyb.) is a biomass feedstock related to sugarcane with lower sucrose content, but with greater biomass yields and better cold tolerance. Two commercial sugarcanes, two high-sugar (Type I) energycanes, and five high-fiber (Type II) energycanes were planted at Tifton, GA, USA to evaluate biomass yields and effects of delayed harvest. Beginning in early October, 2008 five monthly samples were taken to determine the effects of delaying harvest through the winter on the composition and conversion to ethanol. Samples were harvested monthly again in fall/winter of 2010–2011. Mass fractions (proportion of the total mass) of moisture and nitrogen in the plant tissue changed little with the later winter harvests; however, potassium mass fraction decreased with later harvests in both years. Total ash mass fraction tended to decrease into mid-winter, but then increased. Free sugar mass fraction decreased significantly in the colder winter of 2010–2011, causing an increase in the overall proportion of fiber in the biomass. This also appears to explain the apparent increase in ash late in the winter. The composition of biomass fiber (cellulose, hemicellulose, and lignin) was generally quite stable over time. A laboratory procedure that converted the biomass to ethanol was employed to estimate differences in ethanol yields from the sequentially harvested energycane biomass. Ethanol yield from Type II energycanes was more stable over time, because they contain fewer free sugars. Degradation of sugars over the winter in the high-sugar types resulted in decreased ethanol production. Type II energycanes produced the greatest biomass yields, while sugarcanes produced the least.
Technical Abstract: Energycane (Saccharum hyb.) is a perennial bioenergy crop derived from sugarcane, but with higher fiber, greater biomass yields, and better cold tolerance than typical sugarcane. Two commercial sugarcanes, two high-sugar (Type I) energycanes, and five high-fiber (Type II) energycanes were planted at Tifton, GA, USA in a randomized complete block design with four replications. Beginning in October, 2008 (plant-cane crop year) five monthly samples of three stalks each were taken to assess the effects of delaying harvest on biomass composition and quality for ethanol production. The monthly harvests were repeated in the winter of 2010–2011 (second-ratoon crop year). Delaying harvest into the winter months resulted in minimal reductions in biomass moisture and N mass fractions, while K mass fraction decreased significantly. Free sugar mass fraction also decreased, thus causing the biomass to have an apparent increase in relative mass fractions of ash and neutral detergent fiber (NDF). The reduction in free sugars was more pronounced in the colder harvest season (2010–2011). The composition of biomass fiber (cellulose, hemicellulose, and lignin) was generally stable over time. A bench-top partial saccharification and co-fermentation (PSCF) protocol employing xylose-fermenting E. coli was used to assess ethanol yields from the sequentially harvested biomass. Ethanol yield from sugarcanes and Type I energycanes was more variable over time, due to degradation of free sugars. Thus, early harvest is recommended to avoid loss of fermentable sugars for these types. Type II energycanes can be harvested later during the winter months with little change in conversion properties.