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Research / Discovery

Biodiesel and natural gas - fuels for the future?

June 4, 2009

Anthony Marchese and Dan Olsen, two of the Department of Mechanical Engineering newer faculty members, help lead the department's research in energy conversion.

Combustion chemistry of fuels

Marchese (photo at right) works in the Engines and Energy Conversion Laboratory, or EECL, on the combustion chemistry of fuels, in particular biodiesel fuel made from algae. His focus is on understanding and predicting the emissions that are likely to occur through the use of algae-based biodiesel in engines.

Natural gas engines

Olsen (photo below) also works in the EECL on large stationary and industrial natural gas engines. He works on improving the efficiency and reducing the emissions from the burning of natural gas in these engines. He also works on the applications of digester gas sewage, coal gas, and straight vegetable oil (a.k.a. SVO) as engine fuels.

Algae-based biodiesel emissions

Marchese has become heavily involved in the algae-based biodiesel research that has been ongoing in the EECL for some time. He is focusing on the emissions aspects of using such fuels. The future potential of this technology is great because algae-based fuels do not compete with food as do corn- or soybean-based fuels; and algae can produce thousands of gallons of fuel per acre-year as compared to tens of gallons per acre-year for food crops, such as corn and soy.

Vegetable oil fuel requires engine modifications

It's possible to use vegetable oil straight in a diesel engine and it is also possible to convert the vegetable oil to biodiesel. To use vegetable oil directly, engine modifications must be made. For example, vegetable oil is more viscous than diesel fuel so a fuel heater must be installed in order to reduce the fuel viscosity so it will flow through the injectors properly. One of the ways to use SVO is to have a double-tank system in which one tank has ordinary petro-diesel while the other has the SVO.

Straight vegetable oil is different from biodiesel even though both are biologically based. The process to convert vegetable oil or animal fat into biodiesel uses ethanol or methanol in a process called alcoholysis (often referred to as transesterification) to separate the fatty acids from the glycerol and make the resulting fuel directly usable in an engine designed to run on number 2 petroleum diesel fuel.

Biodiesel vs. petro-diesel

Is biodiesel cleaner than petro-diesel as is commonly claimed? Biodiesel produces significantly lower amounts of particulates in exhaust emissions. However, there is no improvement in oxides of nitrogen (NOx), a primary contributor to photochemical smog. In fact, there may be an increase of up to around 10 percent in NOx. Most current diesel engines will run without modification on what is called B20, a mixture of 20 percent biodiesel with 80 percent petro-diesel, but it turns out that higher concentrations of biodiesel in the fuel is likely to produce problems of poor compatibility with some materials currently used in diesel engines.

Natural gas as engine fuel

Can natural gas be used as an engine fuel? In fact, it has been used for many years for the engines that pump natural gas through long distance gas pipelines used around the world. Large stationary natural gas engines run on the gas in the pipelines to pressurize and pump the gas at around 1,000 psi through these pipelines.

Researchers at the EECL have been conducting research for nearly 15 years on these large engines to improve the efficiency of the engines and to reduce their emissions. Actually, natural gas has no particular advantage in terms of NOx and CO emissions, but it produces lower concentrations of particulates than do diesel engines and emits lower amounts of Volatile Organic Compounds (called VOCs) compared to diesel engines.

Improving efficiency, emissions

Olsen continues his stationary and industrial natural gas engine research aimed at improving efficiency and lower emissions. Some of his recent work is considering small natural gas engines for distributed electrical power needs and he is starting
some new projects on SVO.


Original story published in the Department of Mechanical Engineering newsletter, Vol. 11, No. 2, Spring 2009.