An Economic Analysis of the Supercritical Methanol Transesterification of Rapeseed Oil to Biodiesel.

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1. Introduction
As worldwide energy consumption has been increased, so has concern over the depletion of natural resources like petroleum. This concern has sparked growing interest in biodiesel fuel (BDF).1-6 BDF is a group of fatty acid methyl esters (FAMEs), a diesel-equivalent fuel derived from biological sources; it is biodegradable and nontoxic and produces less carbon dioxide than petroleum diesel. Conventional BDF is commonly produced from vegetable oil via transesterification reaction with an alkali/acid catalyst as shown in Figure 1. In recent years, alternative BDF production process using supercritical methanol has been suggested. Meanwhile, the conventional BDF production process requires neutralization units, catalyst separation units, and washing and drying units to remove water as shown in Figure 2.7,8 However, the noble supercritical process does not require catalysts, and therefore, the neutralization, washing, and drying steps can be also omitted from the process. Furthermore, the supercritical process can increase the yield and allow the waste oil to be used as a raw material, negating the need to pretreat free fatty acids (FFAs)or water. However, due to the high temperature and pressure requirements for the supercritical reaction, high capital and manufacturing costs are expected...

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...6. Conclusions
Process design and an economic analysis were performed to assess the profitability of the supercritical process for BDF fuel production. It was found that the total capital cost for supercritical processes for BDF was 1.5-1.6 times higher than that of the conventional alkali-catalyzed process. The total manufacturing cost of the supercritical processes including indirect cost and general expense, however, was lower than that of the alkali-catalyzed process due to the higher glycerol credit and zero cost of both catalysts and solvents. The payout time of case 1 (supercritical, our experiments) and case 2 (supercritical10,11) were longer than that of the alkali-catalyzed process because the lower total manufacturing cost could not compensate for the higher total capital cost. However, case 3 (supercritical25) had a shorter payout time owing to the lowest total manufacturing cost. The higher yield of case 3 made the cost of the raw material and the waste disposal lower and the total manufacturing cost lowest by using a lesser amount of oil for raw material. Consequently, the supercritical process can be more profitable than the alkali-catalyzed process, even when using virgin oil as a raw material.

A supercritical fluid is a substance that is at a temperature and pressure that is so high that the distinction between a liquid and a gas disappears. This state is characterized by the absence of a heat of vaporization.

In the above paper, experiments were conducted at between 250C and 400C, at pressures of 350 bar. The source of heat was electricity, which comes from a wall socket by magic.

Other than that, no comment. Here is a link to an abstract of the paper, from which one can obtain access in a good scientific library or by subscription to the American Chemical Society Journal.

The paper is titled: "Design and Economic Analysis of the Process for Biodiesel Fuel Production from
Transesterificated Rapeseed Oil Using Supercritical Methanol."

It is the work of Korean chemists.

http://pubs.acs.org/doi/abs/10.1021/ie8005287?prevSearch=%255Btitle%253A%2Brapeseed%2Bsupercritical%2Bmethanol%255D&searchHistoryKey=">Ind. Eng. Chem. Res., 2009, 48 (11), pp 5370–5378