In order to seriously address climate change, major changes will be needed in the transportation sector in the United States, as it accounts for 29% of our total greenhouse gas emissions in the United States. Electric cars and SUVs are widely touted as a solution; however, this change is only climate friendly if the grid used to charge them is radically shifted to renewable energy sources such as wind or solar.
However, electrification is not a particularly viable alternative to diesel engines which play many important roles in modern society. They power trucks, trains, boats and barges, many public and school buses, heavy agricultural and construction equipment, military vehicles and generators to produce emergency electricity. The functional advantage of diesel engines is that their high torque makes them powerful enough to move heavy loads while their high efficiency is good for long trips or extended tasks. A disadvantage is that diesel engines have air pollution problems (particle and NOx emissions).
This diesel sector is a key part of the challenge of climate change. According to the U.S. Energy Information Agency (EIA), annual diesel consumption in the U.S. in the transportation sector in 2020 was 44.6 billion gallons, or 16% of total petroleum consumption. in the United States and generating 26% of fossil CO.2 transport sector emissions. The easiest way to “decarbonise” the sector would be to expand the use of biodiesel made from vegetable and animal fats. An exciting new option could be to use bioethanol made from plant-based carbohydrates. There are pros and cons for each biofuel option, but in reality there are logical roles for both.
Biodiesel is already an established industry with a global market value of US$23.2 billion, which is expected to reach US$25.9 billion by 2026. It is most often blended at 20% with regular diesel and sold as the B20. US production capacity in 2022 was 2.25 billion gallons/year, which is about 5% of current diesel use. Biodiesel is made from oilseed crops like soybeans, but also from used restaurant frying oil, animal fat from rendering plants.
The most common biodiesel blend on the market today is B20 with 20% biodiesel and 80% petroleum-based diesel. It can be used for almost all new or old diesel engines. Many existing diesel engines can also use an 80% biodiesel blend, but above that level fuel efficiency begins to decline and there are low temperature storage issues. Biodiesel production would need to be increased significantly in order to achieve a significant reduction in the carbon footprint of the diesel engine sector, but this would disrupt the mechanical and distribution aspects of the segment as little as possible.
The new option mentioned earlier would be to modify existing diesel engines so that they can use carbohydrate-derived bioethanol. This strategy is being pursued by a company called “ClearFlame Engine Technologies”. The state of the technology will be discussed below, but first some information about this particular fuel.
Bioethanol is also an established industry supplying the automotive sector with 10-15% blends. The global market in 2020 was worth US$33.7 billion and is expected to grow to US$64.8 billion by 2025. Production is mainly based on corn or sugar cane but could come from other sources. The American production capacity for this fuel is 17.4 billion gallons/year. While this is nearly eight times the annual biodiesel production capacity, it would still take a substantial increase in bioethanol production for ClearFlame technology to be used to completely eliminate the climate change profile of the US diesel engine industry. even if the volumes of bioethanol are already sufficient to decarbonize 23% of road use.
Comparison of energy profiles
The CO2 released by the combustion of biofuels is classified as “biogenic” insofar as it has recently been captured during photosynthesis by plants, as opposed to the “fossil carbon” released by the combustion of petroleum-based fuel. Even so, the production of a biofuel still has a fossil carbon “footprint” based on the fossil energy involved in its manufacture (e.g. fertilizer and other inputs to grow the crop, tractor fuel, electricity, transportation to the refiner and fermentation). process itself). The “energy ratio” is the amount of energy in the final biofuel product divided by these production energy requirements. The carbon efficiency of biodiesel and bioethanol has improved as production systems have matured. Biodiesel efficiency increased from 3.2 in 1998 to 5.52 in 2011. Bioethanol efficiency tends to be lower for typical corn-based installations (an average of 2.1 in one study), but it can be as high as 4.0 in some production facilities according to another USDA study. The overall bioethanol profile could also be improved by adding carbon capture capability during production, and the agricultural share of the footprint could be reduced by using “electrified nitrogen fertilizers”. Ultimately, either of these biofuels could make a significant difference to the carbon footprint of today’s fossil diesel sector.
Ethanol cannot currently be used in diesel engines; however, it is the ambitious vision of a start-up called ClearFlame to overcome this limitation. Their goal is not to replace them, but to modify existing engines so that they become “fuel agnostic”.
The ClearFlame story begins with two graduate mechanical engineering students who met at Stanford in 2009. One of their professors, Dr. Chris Edwards, inspired these students to look to technology as a way to pursue values. societal ones such as the decoupling of energy needs from fossil fuels. . Switching to electric vehicles was, he said, an important solution for some markets, but billions of people around the world would need a different sustainable solution. The students, BJ Johnson and Julie Blumreiter went on to earn their PhDs at Stanford. In 2017, they started a venture focused on the goal of retrofitting existing diesel vehicles and equipment with “fuel-agnostic engines” that could use any low-carbon fuel, especially ethanol.
As ambitious as that sounds, they have been taken seriously by the venture capital community and by key elements of the industries they hope to serve. Their development work was conducted at Argonne National Laboratory and they initially raised $3 million with an impressive list of grantee partners (US Department of Energy, NSF, USDA, TomKat Center for Sustainable Energy, John Deere and Stanford University), followed by securing $17 million. in a Series A funding in 2021, led by Breakthrough Energy Ventures, founded by Bill Gates, with participation from Mercuria, John Deere and Clean Energy Ventures.
ClearFlame’s engine modification involves a higher temperature combustion process – which combines small plumbing changes with a different fuel injection system to allow “diesel style” combustion of any low carbon fuel, including 100% ethanol. This modification should be practical for almost all engines manufactured since 2010. A recently published study by Gladstein, Neandross & Associates analyzed the total cost of ownership of a truck equipped with ClearFlame and found that it should cost less per kilometer than diesel. , natural gas, electric and hydrogen, of which potentially 40% less than electric and 30% less than hydrogen, thanks in particular to the low cost of fuel ethanol. ClearFlame aims for the technology to essentially pay for itself in the first 18-24 months. In addition to the carbon footprint reduction based on the fuel change (~40%), these engines would generate much less smog and 100 times less soot. With individual states like California setting fuel and emissions standards, this cleaner profile would be helpful for interstate shippers. The benefit of biofuels would also be attractive in countries like Sweden or the UK that have carbon taxes. For companies that have their own distribution fleets, this change could help meet sustainability or carbon footprint goals or commitments while reducing costs.
The critical next step for this technology is now underway as industry players have to “kick the tires” to see if the modified engines have the performance and endurance needed for these demanding uses. The first ClearFlame modified trucks began road testing in 2022. Prototype farm equipment is being evaluated by John Deere, which is pilot testing the ClearFlame technology. Pilot generator sets are also being tested.
If the results meet expectations, the next challenge is to look at fuel delivery issues. Complete bioethanol would be readily available to power agricultural machinery typically based near the fermentation facilities where it is made. It is then delivered to fuel terminals at a full 98% concentration to be mixed with something like automotive fuel. Regional trucking fleets could tap into these supplies if bigger pumps were in place to fill their tanks quickly. Future use for long-haul trucking would require some infrastructure adjustments at truck stops, but would still utilize existing liquid dispensing terminals
This technology is being followed with interest by many players in the vehicle and equipment sector. It is also an important element for the farming community. For example, a member of the Iowa Corn Association sits on the board of ClearFlame. The idea of orienting the diesel engine sector more towards biofuels is also interesting from the point of view of energy independence. The hope is that “down the road” it will turn out to be another solution that fits the ecomodernist vision.