Grease trap waste (GTW) is a low-quality waste material with variable lipid content that is an untapped resource for producing biodiesel. Compared to conventional biodiesel feedstocks, GTW requires different and additional processing steps for biodiesel production due to its heterogeneous composition, high acidity, and high sulfur content. Life-cycle assessment (LCA) is used to quantify greenhouse gas emissions, fossil energy demand, and criteria air pollutant emissions for the GTW-biodiesel process, in which the sensitivity to lipid concentration in GTW is analyzed using Monte Carlo simulation. The life-cycle environmental performance of GTW-biodiesel is compared to that of current GTW disposal, the soybean-biodiesel process, and low-sulfur diesel (LSD). The disposal of the water and solid wastes produced from separating lipids from GTW has a high contribution to the environmental impacts; however, the impacts of these processed wastes are part of the current disposal practice for GTW and could be excluded with consequential LCA system boundaries. At lipid concentrations greater than 10%, most of the environmental metrics studied are lower than those of LSD and comparable to soybean biodiesel.
Sorghum has potential as a domestic source of wax for applications in the food and nonfood industries. The waxes extracted from sorghum have similar physical properties to those of Carnauba wax, a common imported commercial wax. This work focused on the extraction, fractionation, and characterization of waxes from sorghum kernels. Extraction was performed by varying the extraction conditions including temperature and solvents (hexane, ethanol, and methanol). A fractionation technique was developed to separate and quantify waxes from nonwaxes. The fractions were then characterized using a reverse‐phase high‐performance liquid chromatography method developed in our laboratory that utilizes an evaporative light‐scattering detector for quantification. The results showed that the average amount of wax extracted from the surface of intact sorghum kernels was about 0.3 wt% using hexane at temperatures between 25 and 120°C and 1000 psi. The yield of wax via hexane extraction increased with temperature and ranged from about 0.06 to 0.39 wt%. Extraction with alcohols resulted in higher yields of extracts, but after fractionation to remove nonwax components, the yield of waxes was reduced by 31% for ethanol and 47% for methanol compared to hexane.
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