Final Report: Technology for Enhanced Biodiesel EconomicsEPA Contract Number: EPD07052
Title: Technology for Enhanced Biodiesel Economics
Investigators: Kittrell, J. R.
Small Business: KSE Inc.
EPA Contact: Manager, SBIR Program
Project Period: March 1, 2007 through August 31, 2007
Project Amount: $70,000
RFA: Small Business Innovation Research (SBIR) - Phase I (2007) RFA Text | Recipients Lists
Research Category: SBIR - Agriculture and Rural Community Improvement , Small Business Innovation Research (SBIR)
In the present Phase I program, new catalyst developments are being exploited that permit the direct liquid phase conversion of glycerol into propane at mild operating conditions and without an external hydrogen source. The Phase I feasibility study entailed the development of new catalyst compositions for the glycerol conversion reactions; laboratory studies demonstrating the performance of the technology, including catalyst activity and selectivity; and economic analyses to demonstrate economic feasibility. The Phase I feasibility study fully demonstrated the technical and economic feasibility of economically producing propane in high yields from glycerol.
The overall goal of this Small Business Innovation Research Phase I project was to establish the technical and economic feasibility of an innovative process technology to enhance the economics of biodiesel production through upgrading the byproduct glycerol to a propane fuel (LPG), which: (a) is widely used today; (b) has an existing distribution system; (c) can accommodate the large volumes of byproduct glycerol; and (d) has attractive economics to support the biodiesel production. The Phase I upgrading technology does not require extensive supporting services, such as a hydrogen plant.
The United States currently consumes about 60 billion gallons of diesel fuel annually. The production of one gallon of biodiesel produces about 1 pound of byproduct glycerol. If biodiesel is produced to meet only 3 percent of the U.S. diesel fuel demand, more than 1.8 billion pounds of glycerol, also known as glycerin, will be coproduced. The current annual worldwide demand for glycerol is only 0.5 billion pounds. As a result, the oversupply of glycerol already has depressed glycerol prices in the United States and in Europe. Since 1995, the price of refined glycerol has dropped from 90 cents per pound to 35 cents per pound today. In 2006, the price of the raw, or crude, glycerol byproduct of biodiesel production was 2 cents per pound.1
One key to a successful Phase I technology is the development of a novel liquid phase reactor system that simultaneously: (1) reforms glycerol to produce hydrogen, and (2) hydrogenates glycerol to propane in the same reactor at similar reactor conditions. Such a catalyst system has been demonstrated in the present Phase I program. As a liquid, the raw glycerol is readily mixed with recycle water, pumped to a pressure of about 400 psi, and fed into a tank reactor at about 200°C. The reactor contents are in the liquid phase, with a solid catalyst. The reaction products leave in the vapor phase, consisting of propane, excess water vapor, and carbon dioxide. When the reactor product is cooled at about 400 psi to ambient temperatures, the propane and water condense, but the carbon dioxide remains a vapor. After cooling, a three-phase separator separates the products, producing the liquid propane product without further compression. Carbon dioxide exits the process as a gas, and water is produced as a separate liquid phase.
A second key to a successful technology is the development of active and selective catalysts, to completely convert glycerol to propane at mild conditions. In the Phase I program, 61 catalysts were synthesized and evaluated. To achieve excellent process economics, it is essential that high selectivity be maintained for the reacting system. That is, the hydrogen should be used only to produce propane from glycerol, without other side reactions. The high selectivity of the catalysts developed in the present Phase I program is shown by the green bars in Figure 1.
In the Phase I program results, shown by the green bars, propane is produced directly from glycerol at 95 percent selectivity. A small amount of methane is formed, probably by methanation of carbon dioxide (hydrogen + carbon dioxide can form methane). Phase II catalyst improvements will reduce the small amount of methane byproduct from the Phase I catalyst, shown by the green bars of Figure 1. For comparison purposes, the data shown by the yellow bars of Figure 1 are taken from patents for which alkanes are being produced from sorbitol, a six carbon compound. Clearly, the selectivity of the literature catalysts are inferior to the Phase I catalyst, apparently as a result of cracking the hexane product of sorbitol hydrogenation.
Figure 1. Excellent Selectivity of the KSE Phase I Catalyst
Based on the Phase I program results, the manufacturing cost for producing propane from glycerol has been calculated. Summary Phase I results are presented in Figure 2, which provides the manufacturing costs for two different glycerol valuations. Additional cases are presented in the report.
Glycerin (or glycerol) has experienced a declining price scenario for decades. With the advent of biodiesel plants, byproduct glycerin production has increased substantially, causing further downward pressure on glycerol pricing. The crude glycerol from biodiesel plants was priced at 2 cents per pound in 2006. The market for crude glycerol has recovered somewhat in 2007, to about 6 cents per pound. Hence, in Figure 2, raw glycerol prices of 5 cents/lb and 0 cents per pound were used.
Figure 2. Elements of Phase I Manufacturing Cost of Propane from Glycerol
Based on current raw glycerol prices, the Phase I technology can produce propane at about 30 to 90 cents per gallon, as shown in Figure 2. This manufacturing cost for the Phase I KSE technology already includes a rate of return on capital employed. Current spot prices for bulk propane at the salt domes of Mont Belvieu, Texas, are quoted at $1.26 per gallon2, according to the Energy Information Agency of the U.S. Department of Energy. Of course, prices of bulk propane in other regions of the country are markedly higher than those at Mont Belvieu, Texas; prices are approximately double those of Mont Belvieu in the Northeast United States. In most parts of the United States, payout time on investment in the KSE Phase I technology will be less than 1 year.
New catalysts, operating conditions, and plant configurations were established in the Phase I program to convert glycerol to propane economically. No feed to the plant other than glycerol is required. Part of the reactor feed glycerol is converted to hydrogen and used in the same reactor to convert the rest of the glycerol to propane. The plant is inexpensive, simple, safe, and operates at mild conditions. Liquid propane (or LPG) can be produced directly from the plant, and such plants can be economically distributed in locations throughout the United States where biodiesel plants are built. When propane is sold at local prices, the manufacturing cost for producing propane will pay out the plant investment in less than a year.
Kotrba R. The glycerin spread. Biodiesel Magazine. September 2007. Web Site: http://www.biodieselmagazine.com/article-print.jsp?article_id=1797.
U.S. Energy Information Administration. Web Site: http://tonto.eia.doe.gov/dnav/pet/hist/rprousgd.htm.