US labs research biofuel solutions for different types of engines


Biofuel is poised to become an economical and climate-friendly solution to reducing carbon emissions from cars and trucks, according to two new studies. The U.S. Department of Energy’s (DOE) Argonne National Laboratory collaborated with the DOE’s National Renewable Energy Laboratory (NREL), the Pacific Northwest National Laboratory (PNNL), and the Idaho (INL) on research. The results showed that biofuel combined with an advanced engine design can reduce greenhouse gas (GHG) emissions by around 60% while improving fuel efficiency or reducing tailpipe emissions.

Pahola Thathiana Benavides, Argonne Energy System Analyst, Andrew W. Bartling, NREL Process Engineer, and Steven Phillips, PNNL Engineer, were the lead analysts for the two studies published in ACS Sustainable Chemistry & Engineering.

“The idea is to develop new biofuels mixed with conventional fuels to improve engine performance. This means that a gasoline-powered car or truck could go further on the same amount of fuel, or a diesel vehicle could meet more stringent emissions standards,” says Troy Hawkins, Argonne Group Director for the Fuels and Products group, and author on ACS Sustainable Chemistry & Engineering Studies.

Biofuel has significant advantages over petroleum gasoline. But the motors themselves are also essential for energy efficiency. Designing low-carbon fuels and engines to work together can maximize energy consumption and vehicle performance.

“We are at the intersection of new innovations in engines and biofuels,” says Hawkins. “Our goal was to develop new biofuels blended with conventional fuels to improve engine performance. This means that a gasoline car or truck could go further on the same amount of fuel. Or a diesel vehicle could meet stricter emission standards.

In both studies, Argonne scientists worked with other national laboratories to identify promising fuels for different types of engines. Researchers considered cost, environmental impact and potential for expansion into commercial markets.

The research is supported by the Co-Optimization of Fuels & Engines (Co-Optima) initiative jointly led by the DOE’s Office of Energy Efficiency and Renewable Energy, Office of Bioenergy Technologies, and Office of Vehicle Technologies.

Argonne is part of the Co-Optima consortium of nine national laboratories and more than 20 academic and industrial partners. The consortium is studying how simultaneous innovations in fuels and engines can boost fuel economy and vehicle performance while reducing emissions.

Scientists and experts from each DOE lab played an important role in every phase of the research, Hawkins said.

“This research is a great example of how the labs can work together to help the DOE accomplish its mission,” says Hawkins.

Co-Optima’s research is driven by the goal of identifying and understanding bioblends, or biofuels. Biofuel is produced from biomass – organic materials including plants, agricultural waste and wet waste. Biofuel can be blended with conventional fuel to reduce emissions and improve fuel and engine performance.

Working with fuel experts from Co-Optima, the researchers used a screening process to develop a list of biofuels for their research, Benavides said.

Argonne scientists developed the list of biofuels in conjunction with experts, including Daniel Gaspar, PNNL technical team leader and member of the Co-Optima management team, Gina Fioroni, senior scientist at NREL, Robert McCormick, senior researcher at NREL, and Anthe George, senior manager at DOE’s Sandia National Laboratories (SNL).

“We worked with other experts to use specific criteria to narrow down many biofuel candidates to a shortlist for our research. This list was compiled based on the required properties and the combustion mode of the engine,” comments Benavides.

Converting biomass to biofuel is a complex process involving variables in feedstocks, conversion technologies, and fuel types. It is particularly difficult to find biofuel pathways that also meet economic, technological and energy objectives.

A study was co-authored by Benavides. The team evaluated 12 biofuel production pathways to optimize multi-mode internal combustion engines. Multi-mode engines can provide greater efficiency and cost savings by using different methods of ignition, combustion and/or fuel preparation, depending on driving requirements.

The researchers used renewable biomass feedstocks found in forest by-products such as wood waste and agricultural by-products such as corn stalks. They used conversion technologies including either fermentation, high temperature and pressure catalysis, or a combination of the two.

“We found that not only are seven biofuels competitively produced, but these seven are diverse in terms of feedstocks used and conversion technology,” Bartling says. “This means biorefineries can be more flexible in choosing where and how to build their facilities.”

Researchers from NREL and PNNL carried out a technical and economic assessment of biofuel production chains, by analyzing costs and technological performance.

“Our results have shown that many biofuels are competitive with today’s cost of petroleum fuel,” Phillips says.

The researchers also analyzed the environmental impact. A pathway life cycle analysis using Argonne’s GREET model (greenhouse gases, regulated emissions and energy used in technologies) showed impressive results. Ten biofuels have the potential to reduce GHG emissions by 60% compared to petroleum gasoline. The list includes alcohols, mixtures of furans and olefins.

The second study was co-authored by Bartling. Researchers analyzed 25 ways to produce biofuel optimized for a type of engine known as mixture-controlled compression ignition. This diesel engine is mainly used in the transport of goods.

To develop biofuel production pathways, researchers have used feedstocks ranging from plant materials such as wood chips or corn stalks, to soybean and cuphea oils, wet waste and recycled grease. They used conversion technologies such as fermentation, gasification and hydrothermal liquefaction.

“The diverse set of biomass resources available in the United States has great potential to replace some of the fuels and chemicals that now come from petroleum,” said Damon Hartley, operations research and analytics group leader at the INL. “However, one of the biggest hurdles is the high variability in raw material quality. This can have a big impact on material performance during conversion.”

As with the first study, most technologies performed well. Most biofuels were competitive with current gas prices.

In terms of environmental impact, GHG emissions have been reduced by more than 60% in 12 of the 25 sectors, according to the GREET life cycle analysis.

“We assessed the life cycle GHG emissions for each path of controlled mixture compression ignition engine. This included not only tailpipe emissions, but also upstream emissions from growing biomass, transporting feedstocks, producing and distributing biofuels,” explains Hawkins.

The researchers did not intend to produce a definitive list of biofuels, Benavides says. Instead, the studies offer a guide to stakeholders on selecting the biofuel pathways that best meet their needs.

“We provide guidance to researchers and industry on evaluating biofuels based on a number of complex variables,” adds Benavides. “Life cycle and techno-economic analysis is important to orient stakeholders early on. We cannot tell stakeholders what choices to make, but these tools can point them in the right direction from the start.

While many of these biofuel pathways could potentially be cost competitive, it is too early to lock in prices in an ever-fluctuating gas market. “The challenge is to provide competitive prices over the long term,” continues Hawkins.

While these biofuel production pathways target diesel cars and trucks, Argonne researchers are also investigating the potential for using these pathways in hard-to-electrify sectors like aviation and marine industries. The goal is to bring biofuel to market in a range of industries as quickly as possible.

“The DOE is constantly working on sustainable solutions to decarbonize the transportation sector. Biofuel is a big part of that,” says Hawkins. “We will continue to build on the important work of Co-Optima.” In addition to Argonne, ORNL, NREL, PNNL, INL, and SNL, other US DOE National Laboratories participating in the Co-Optima initiative are Los Alamos, Lawrence Berkeley, and Lawrence Livermore National Laboratories.

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