Posted on Dec 01, 2009
The United States Federal government mandates production of 21 billion gallons of renewable fuel from non-corn sources to be blended with gasoline by 2022. This project will further the development of technologies allowing sorghum production to adapt to future lignocellulosic feedstock demands while promoting sorghum as a competitive biofuel feedstock. Two major limitations to ethanol production from lignocellulosic feedstocks are development of enzymes to break bonds between fibers and the storage of feedstocks. The environment, cultivar, type of material ensiled, and the use of fibrolytic enzyme additives all affect the ease of ethanol extraction from lignocellulosic material. Fibrolytic enzyme additives hydrolyze cell wall bonds which improves storage of silage, while simultaneously serving as a pretreatment for further processing to ethanol.
The overall goal of this project is to identify the effect of management practices, including environment, cultivar, whole plant versus dual crop, and post-harvest fibrolytic enzyme application, on the use of sorghum silage as a pretreated biomass feedstock for lignocellulosic conversion technologies. Objectives are to determine 1) whether an applied fibrolytic enzyme cocktail improves the aerobic stability, silage quality, and degradation of fiber; and 2) to evaluate sorghums dual crop potential when comparing the characteristics of silage made from the whole plant (including grain) versus the stover.
This experiment will consist of 3 replicated plots of 4 cultivars planted at 3 locations (Beeville, Kingsville, and College Station, TX). The sub-plot is the type of harvested material to be ensiled, either whole plant or residue after grain removal. At harvest, material will be chopped and ensiled as either no applied enzyme (control) or after enzyme is applied. Chemical composition of plant material will be measured pre- and post-ensiling; whereas, silage quality and aerobic stability will be measured post-ensiling. Results of this research will translate into information which improves the extraction of ethanol from sorghum lignocellulosic feedstock, thus enhancing the sorghum industry as a whole.
Cost of enzyme for treating 1 acre (or one ton) of silage is expected to be $15.00, an increase of digestibility of 5% should recover this cost. Ethanol must sell for $1.07 per gallon in order for it to be profitable and pretreatment to begin fiber hydrolysis is necessary to meet this economic threshold. Several target audiences will be impacted by the results of this research. Target audiences include: sorghum producers, lignocellulosic biofuel processors, dairy producers, and feedlot operators. Producers of sorghum for biofuels and processors of feedstock will benefit from information which may improve the storage longevity of sorghum silage and simultaneously decentralize pretreatment of sorghum silage for ethanol production. Throughout Texas, and much of the Southwestern United States, sorghum is stored as silage for feeder cattle and dairy cattle feed. Increasing digestibility of sorghum silage will decrease the amount of feed necessary to produce a pound of milk or meat, thereby reducing nutrient excretion.This information will be disseminated through resources already available to Texas AgriLife and the Texas A&M System, including websites, field days, and interaction between extension and research personnel and producers.