Development of a cheap system for reuse of glycerol by-product discharged from the biodiesel fuel (BDF) production process is needed in parallel with development of a low-cost BDF production system. In this article, optimization of compost fermentation of glycerol by-product was studied. The type and amount of additive nitrogen source was studied, and good utilization of glycerol was observed when 0.5 g of urea was added to a mixture of 625 g dry sawdust, 25 g of microbial seed, and 50 g of glycerol by-product. To achieve effi cient compost fermentation, repeated batch fermentation was applied and fi ve batch cultures were repeated. Although the pH level and nitrogen and water contents were maintained at suitable levels for microbial growth, the glycerol consumption rate gradually decreased with accumulation of oily compounds in the compost. Finally, a material cost evaluation of the compost fermentation proposed in this study was performed. The total material cost decreased to ¥0.57 /l of BDF when employing an existing compost system for the fermentation process, although sawdust used for mushroom cultivation was used in this study at the very high cost of ¥123 /kg dry sawdust. However, the cost of disposal of the glycerol byproduct as an industrial waste was ¥5.2 /l of BDF produced; therefore, there might be an economical advantage to compost fermentation of glycerol by-product from BDF production.
This paper aims to form a chromium carbide containing layer on metal mold steel by EDM finishing in chromium powder mixed working fluid in order to improve the surface characteristics for long life of metal mold, such as surface hardness, corrosion resistance and releasability of molded resin. The surface characteristics of carbon tool steel with low chromium content finished by EDM in chromium powder mixed working fluid were compared to those of alloy tool steel SKD11 with high chromium content. Experimental results shows that surface hardness, corrosion resistance and releasability of molded resin could be significantly improved to the same high level for both kinds of steel by EDM finishing in chromium powder mixed fluid.
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