Co-Optima Helps Steer Nation Toward a Net-Zero-Carbon Transportation Future

The U.S. Department of Energy (DOE) Co-Optimization of Fuels & Engines (Co-Optima) initiative recently wrapped up six years of fuel and engine research designed to more rapidly reduce dependence on international petroleum and cut emissions, while slowing global warming. DOE’s Sandia National Laboratories played a major role in the collaborative undertaking. Findings are now available in a recently released report.

Experts from Sandia National Laboratories and eight other national labs worked together to give American industry and policymakers the scientific knowledge, data, and tools needed to decide which new fuel-engine combinations could most realistically benefit drivers, businesses, and the environment.

Researchers partnered with peers from more than 40 universities and companies to examine how simultaneous improvements to fuels and engines could maximize energy efficiency and the use of renewable fuels, while decreasing emissions for the entire on-road fleet.

The Co-Optima team identified approximately 25 domestically sourced, bio-based fuels that produce 60% fewer greenhouse gas (GHG) emissions than those generated by petroleum-based fuels when used in light-duty (LD), medium-duty (MD), and heavy-duty (HD) vehicles. The scientists also found ways to eliminate more than 99% of some of the most harmful freight truck criteria pollutants.

In addition, Co-Optima research revealed ways to improve fuel economy by 10% for today’s turbocharged car engines and an extra 14% using advanced engines. Co-optimization strategies showed potential to increase HD engine efficiency by up to 4%.

Much of the Co-Optima research focused on components known as blendstocks, which can be produced from sustainable resources such as forestry and agricultural waste and combined with petroleum-based fuels. The team screened more than 1,000 options to pinpoint high-performing blendstocks that can potentially be produced at commercial scale from the estimated billion-ton annual supply of U.S. biomass resources.

Sandia’s Co-Optima research included the study of high-performance fuels and advanced engine development:

High-Performance Fuels

• Developed a suite of software tools to accelerate research and development for biofuels production. The tools can be used to predict biofuel properties, determine the physical properties of fuel blends, and provide retrosynthetic analysis of biofuel production targets.
• Discovered a new combustion phenomenon where certain biofuels (prenol and six others) “hyperboost” octane in gasoline to improve engine efficiency.
• Identified blends of fusel alcohols (waste components from the ethanol production process) that can maximize improvements to net fuel economy by blending into E10, a gasoline blended with 10% ethanol that is available to drivers in most states in the U.S. 
• Demonstrated the initial production and scale-up of several promising heavy-duty transportation fuels that provide improved performance and lower particulate and carbon emissions beyond bio- and renewable diesel.

Advanced Engine Development

• Developed a new computer modeling framework that considers combustion inside the cylinders of a vehicle’s engine at all points in that vehicle’s drive cycle. The framework enables engine developers to predictively model the impact of new fuels on vehicles’ fuel economy.
• Determined that the higher fuel octane ratings of typical premium-grade gasoline are optimal for use by conventional turbocharged engines and advanced multimode engines that use spark-assisted compression ignition (SACI). A multimode engine that uses a premium-grade gasoline enables a 17% fuel-economy gain relative to a conventional spark ignition (SI) combustion engine that uses a regular-grade gasoline.
• Demonstrated that renewable and oxygenated fuels can be paired with ducted fuel injection (DFI) to enable vast reductions in both soot and nitrogen oxide emissions—or NO_x—relative to conventional diesel combustion. The demonstration effectively breaks the traditional soot-NO_x  trade-off, a term used to describe the challenge to lower both soot and NO_x beyond the reductions provided by current technologies.
• Established a new and effective fuel-blending strategy that provides strong fuel economy benefits at part-power conditions using advanced compression ignition (ACI) operating strategies, while maintaining the ability to reach high-power conditions using a turbocharger and conventional SI operation.

Many challenges remain in the U.S. effort to reach net-zero emissions by 2050. Research by manufacturers is still needed to determine what more significant changes in engine operation and component materials will be required to approve use of these sustainable Co-Optima fuels in commercial engines.

That said, these fuels could eventually meet 100% of future demand for air, marine, and rail fuel, while still leaving enough to meet the fuel needs of long-haul freight trucks that are harder to electrify. Ultimately, the new fuels and engines identified through Co-Optima research will burn cleaner, produce fewer life cycle GHG emissions, and make important contributions to the nation’s transition to a net-zero-carbon-emissions energy future.

Sponsored by DOE’s Vehicle Technologies Office and Bioenergy Technologies Office, Co-Optima partners include Sandia National Laboratoriesand Argonne, Idaho, Lawrence Berkeley, Lawrence Livermore, Los Alamos, Oak Ridge, and Pacific Northwest national laboratories; the National Renewable Energy Laboratory; and numerous industry and university partners.  

Read the full report or summary, learn more about the Co-Optima initiative, and get more details on consortium partners and projects.