The economic costs of three biodiesel plants with capacities of 8000, 30 000, and 100 000 tons year -1 were analyzed and assessed. The plants employ continuous processes using an alkali catalyst and the raw material of soybean oil. Six major economic cost factors were computed and examined. These include the fixed capital cost (FCC), total capital investment cost (TCC), total manufacturing cost (TMC), net annual profit after taxes (NNP), after-tax rate of return (ARR), and biodiesel break-even price (BBP). The NNP and ARR of plants with capacities of 8000, 30 000, and 100 000 tons year -1 are -24 × 10 3 , 1975 × 10 3 , and 8879 × 10 3 U.S. dollars (USD), and -10.44, 40.23, and 67.38%, respectively. The values of BBP of the three plants are 862, 724, and 678 USD ton -1 (price in July 2007). The plant with a capacity of 100 000 tons year -1 is economically feasible, providing a higher NNP and more attractive ARR with a lower BBP. Among the system variables of the plants examined, plant capacity, price of feedstock oil and diesel, and yields of glycerine and biodiesel were found to be the most significant variables affecting the economic viability of biodiesel manufacture. In summary, this study aims at the need to obtain useful information for economic cost analysis and assessment of the production process of biodiesel using soybean oil. It provides an appropriate indication for the promotion of biodiesel in the future, targeting the reduction of the cost of feedstock oil with the increase of the yields of valuable products with a reasonable plant capacity.

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Abstract:The mechanical heat treatment (MHT) is one of the pre-treatment alternatives for conditioning the municipal solid waste (MSW) before its further separation, recovery and reuse. The MHT would result in the change of properties of constituents of MSW, making it suitable for separation. For example, the plastics may be softened and shrunken. Therefore, the MSW via the pre-MHT can be more easily separated into various fractions of resources such as metals, plastics, compost-like and primary refuse derived fuel (RDF) or bio-char for further re-utilization.The objective of this study was to examine the efficiency and effective of energy recovery and volume downsize of plastics via MHT process. The commonly used plastic, high-density polyethylene (HDPE) was tested. The changes of weight, triple components, true density and calorific value of target plastic before and after the MHT with saturated steam at 100, 150 and 180 o C were examined. The effects of temperature on the performance of MHT were assessed. The results indicated that an increase of MHT temperature induces more significant shrinkage and higher volume density, enhancing its feasibility for the separation from non-plastic materials. The information obtained in this study is useful for the rational design and proper operation of MHT system for treating the used plastics in the MSW and separating it for the re-utilization as energy resource.