the used oils were not the entirely same for laboratory and pilot scale experiments.
3.5. Economic analysis of biodiesel production
It is known that feedstock cost is the major problem to the market feasibility of biodiesel. In this study, low cost feedstocks such as chicken fat and fleshing oil were used for biodiesel production and compared to vegetable oil based biodiesel. Therefore, the economic analysis of biodiesel cost was conducted for a large scale biodiesel plant (10 tons) to be more suitable to biodiesel industry. The operating costs of biodiesel plant were computed. The capital, plant construction, and labor costs were not included. In the economic analysis, glycerin recovery was not also included. However, the excess methanol used in the pretreatment and transesterification reactions was considered as economic gain. It was assumed that 90% of the methanol used in the pretreatment and 80% of the excess methanol used in transesterification reactions were recovered. The prices of the feedstocks, chemicals and utility costs were given in Table 6a. The prices of the chemicals and oils were obtained from the local companies. The calculation was done based on those prices. However, the prices may differ in any other country due to the currency difference. Therefore, it should be noted that the final costs of the biodiesels are valid only for Turkey.
The ingredient amounts for the pilot scale biodiesel production were described in Tables 3a and 4a. Based on the amounts, electricity and water consumption in the pilot scale biodiesel production, biodiesel costs were conducted for a large scale biodiesel plant (10 tons/day) which should be more suitable for biodiesel industry. The obtained costs were shown in the Tables 6a and 6b.
Due to higher FFA content of chicken fat, it was necessary to use higher amount of catalysts compared to fleshing oil for pretreatment reactions as seen in Table 6b. Using higher amount of catalysts increases the price of CFME. This means that the FFA level of the feedstock directly influences the biodiesel cost. The operation cost of CFME is the lowest. However, it was still more expensive than the other methyl esters due to high cost feedstock. The COME price was 15.7% and 43.1% higher when compared to CFME and FOME, respectively.
4. Conclusion
The objective of this study was to produce biodiesel from vegetable oil and low-cost animal fats with high free fatty acid in a biodiesel pilot plant. For this aim, corn oil was used as vegetable oil, while chicken fat and fleshing oil were selected as animal fats. These feedstocks were used for producing biodiesel in a pilot scale and it was investigated that if any unique processes were required to scale up from laboratory scale to pilot plant scale. According to the results, there were no significant differences in the fuel properties of methyl esters between laboratory and pilot plant experiments. Methyl esters produced in the laboratory and pilot plant experiments showed similar properties. One or two step acid catalyzed pretreatment reaction process was effective in decreasing the FFA level of the animal fats to less than 1%. After decreasing the FFA level of the animal fats, alkaline catalyzed transesterification reactions resulted in good ester yields. Ester yield value of the COME was slightly higher than those of animal fat methyl esters. The fuel properties of produced methyl esters were close to each other. The most apparent differences in the fuel properties were the sulfur content and cold flow properties of the COME, which were lower compared to animal fat methyl esters. Especially, the cold property of the FOME was unacceptable to use in winter climate. The cold flow properties of the FOME should be improved with cold flow enhancers or it may be mixed with petroleum diesel fuel which has better cold flow properties. Experimental results showed that the sulfur content of the biodiesel feedstock is very important to get low sulfur content biodiesel after transesterification. The sulfur content of COME was much lower than those of animal fat methyl esters. On the other hand, the first sulfuric acid catalyzed pretreatment