Renewable Diesel Fuels

Background

Reducing our country's dependence on foreign oil and the rising costs of crude oil are primary reasons for a renewed interest in alternative fuels for the transportation sector. Stringent emissions regulations and public concern about mobile sources of air pollution provide additional incentives to develop fuels that generate fewer emissions, potentially reducing the need for sophisticated, expensive exhaust after-treatment devices.

Diesel engines offer improved fuel conversion efficiency, greater torque over a wider engine operating speed (improved acceleration), and potentially lower emissions compared to gasoline engines, making them an attractive power source for future passenger car vehicles. Current fuel injection and controls technology now prevent the black smoke and noise previously associated with diesel engines. By using a renewable fuel, the diesel engine could help reduce both foreign oil dependence and greenhouse gas.

Renewable diesel fuels are commonly grouped into three categories:

• Biodiesel, a fatty acid methyl ester, is commonly produced from soybean, yellow grease, or other sources of triglyceride through the transesterification process.
• Synthetic diesel fuel, typically produced from cellulosic sources (wood, plant, biomass material) is usually produced using the Fischer-Tropsch process.
• Renewable diesel fuel is produced using a proprietary thermal depolymerization production technology, where plant and/or animal fats are processed with hydrocarbon feedstocks. Renewable diesel fuels differ from alternative diesel fuels due to their renewable feedstock source.

Previous research has shown that different renewable fuel feedstocks can have a significant effect on combustion quality, engine-out emissions, and performance. For example, certain renewable diesel fuels measurably increase nitrogen oxides (NOx) emissions in the engine’s exhaust while others have been NOx neutral. The explanation for this trend is not well understood and requires additional research to fully investigate the phenomenon.

Increasing the use and acceptability of renewable diesel fuels has the potential to benefit industry and society. Fuel derived from a renewable resource directly addresses the issue of a finite oil sources and reduces the U.S. dependence on foreign oil. Renewable diesel also allows the fuel's constituents to be tailored to improve combustion and reduce emissions while maintaining conventional diesel fuel-like performance.

Argonne's Research

Argonne researchers are focusing on the acquisition and dissemination of emissions, efficiency, and performance data, from both engines and vehicles operating on various renewable diesel fuels. Argonne's extensive engine and vehicle testing facilities are being used, along with the latest acquisition equipment for in-cylinder combustion and exhaust system analysis. In addition, mechanistic models with an emphasis on practical applications are being developed, using Argonne's world-class chemistry kinetics, dynamics, and quantum chemistry. Argonne's vertically integrated research team bridges basic combustion research and applied engine systems to improve the understanding and use of various renewable diesel fuels.

Argonne's research team is working to maximize the benefits of renewable diesel fuels while minimizing the barriers to implementing their use, thereby easing the economic impact to manufacturers and consumers. Identifying hurdles and generating solutions are keys to the successful implementation of renewable diesel fuels.

Several projects are aimed at this objective, including:

• Experimental investigation of biodiesel injection characteristics using a light-duty diesel injector
• Emissions, performance, and in-cylinder combustion analysis in a light-duty diesel engine operating on a Fischer-Tropsch, biomass-to-liquid fuel
• Comparing the performance of SunDiesel and conventional diesel in a light-duty vehicle and heavy-duty engine

September 24, 2007