You may have been reading about alternative fuels on this blog—or elsewhere. We know it can be confusing. So here is a handy glossary to help you remember the difference between diesel, renewable diesel, biodiesel, and other fuels.
Ammonia in your decarbonization journey
Ammonia is a chemical used industrially on a large scale as a precursor to a variety of nitrogen-containing substances, such as fertilizers and explosives. It also has many other applications, ranging from being used as a glass cleaner, to a reagent used in flue gas scrubbing systems, to being used as a rocket fuel (the X-15, an experimental rocket-power aircraft, which still holds the speed record for a manned aircraft, ran on ammonia).
Ammonia has also seen some historical use as a motor fuel. During World War II, for example, the Belgian regional bus company converted some of its buses to run on ammonia due to the shortage of diesel fuel.
Green ammonia in your decarbonization journey
Almost all ammonia being manufactured today is obtained via a chemical reaction between hydrogen and nitrogen. Since most hydrogen used for this purpose is made from natural gas using a process that releases significant amounts of CO2, manufacturing of ammonia is CO2-intensive. If green hydrogen is used, however, ammonia can be made with no or minimal CO2 emissions. In other words, green ammonia can be made.
This is of interest for industries that are heavy users of ammonia. Fertilizer companies such as Spain’s Fertiberia, for example, are actively pursuing this strategy.
In the transportation sector, green ammonia is seen as an energy carrier that is easier to handle and store than green hydrogen. The shipping industry, in particular, has shown substantial interest in powering large ship engines with ammonia. A recent survey by Lloyd’s register indicates industry participants expect ammonia use in the shipping industry will significantly increase in the next 10 years.
In Japan, where utilities are looking for ways to keep their coal-power plants open, green ammonia is used as a partial substitute for coal in pilot projects. In the long term, supporters see green ammonia as a way to turn existing power plants into zero-emissions facilities by 2050.
Biodiesel in your decarbonization journey
Biodiesel is a renewable low-carbon intensity or carbon-neutral fuel made from fats such as vegetable oil, animal fats or used cooking oil through a chemical process known as transesterification. The oils can also be blended with diesel to reduce well-to-wheels CO2 and other polluting emissions. Blends with varying proportions of biodiesel are available. B20, containing 20% biodiesel, is a common blend which advantageously balances cost and emissions. It can be used in most engines with no modifications. Many Cummins Inc. diesel engines can run on B20, and the company plans to make its new engines compatible with an increasing range of biodiesel blends. Besides motor vehicles, biodiesels are used across a range of industries, from data centers to ships.
Diesel in your decarbonization journey
Diesel is a fossil fuel obtained from oil. It is relatively cheap, widely available and performs well. Diesel engines are durable, reliable, and can provide all the torque needed for heavy-duty applications. The infrastructure needed to produce, transport and distribute diesel is universally available. Diesel, however, is not without drawbacks. Besides causing greenhouse gas emissions, diesel vehicles release nitrogen oxides, carbon monoxide, soot, and other pollutants. All of these cause air pollution and can be harmful to human health. Regulations on the use of diesel are therefore tightening in countries around the world. Diesel may lose some ground to alternative fuels, but it is not about to go away. Diesel engines have come a long way towards cleaning up their emissions. And while no aftertreatment system can truly scrub CO2 emissions from diesel engines, there are applications where it will make more sense to offset CO2 emissions somewhere else than to seek to directly decarbonize the application. The emission reductions capability of alternative fuels should be evaluated when making a selection.
Renewable diesel in your decarbonization journey
Hydrotreated vegetable oil (HVO) or renewable diesel is made from vegetable fats and oils. It can be used in most diesel engines without modification, across all Cummins standby generator sets and many Cummins engines used for on-highway applications. Used as a drop-in replacement for diesel, it performs equally well. After factoring in the emissions associated with the processing, transportation and distribution, HVO well-to-wheels emissions are about 70% lower than those of diesel.
The use of HVO is limited by the amount that can be made using existing production plants—about 550 million gallons per year in the United States. Multiple new plants are under construction, which should significantly expand the amount of HVO available and may lead to an increase in adoption.
There are a range of examples of companies that are successfully using alternative fuels. Companies such as Microsoft, for example, have switched to HVO fuel for their Cummins-supplied generators that provide backup power to its data centers in Des Moines, Iowa (U.S.) and Phoenix, Arizona (U.S.).
Green hydrogen in your decarbonization journey
Green hydrogen, or hydrogen made using renewable energy, may very well be the green energy carrier of the future. Green hydrogen can fuel both fuel cell electric vehicles and vehicles equipped with an internal combustion engine specially modified for hydrogen. Hydrogen will make a lot of sense for heavy-duty commercial applications, which is why Cummins is currently developing a 15-liter and a 6.7-liter hydrogen engine. Cummins’ hydrogen fuel cells are already powering vehicles around the world—from buses and trucks to trains. Besides being manufactured using renewable energy, part of hydrogen’s appeal is that the main waste product of hydrogen combustion or fuel-cells is water, and although hydrogen fueled internal combustion engines will have NOx emissions, they can be reduced to very low levels.
Natural gas in your decarbonization journey
Natural gas has been used as a fuel in vehicles for decades and is the most widely used alternative fuel. It performs as well as diesel in vehicles, and in some cases lowers emissions of greenhouse gases and other pollutants such as NOx and particulate matter. Natural gas is therefore a popular choice for heavy vehicles that operate in urban environments, such as garbage trucks, buses and delivery trucks.
Natural gas is also widely used in stationary applications. Natural gas, for example, can be used in highly efficient cogeneration systems providing electricity, heat, and, in some cases, cooling. Cummins has supplied equipment for numerous cogeneration systems, such as the system at Clark University, in Massachusetts (U.S.), where Cummins supplied a 2 MW QSV91G gas generator.
Renewable natural gas in your decarbonization journey
Renewable natural gas is obtained from biogas, a methane-rich gas resulting from the fermentation of organic waste such as cow manure, sewage sludge or landfill organics. Adequately processed, renewable natural gas is nearly indistinguishable from natural gas. It can be used in any natural gas engine and in many industrial applications, such as power generation, giving up to a 97% reduction in CO₂, compared with diesel. Renewable natural gas is already emerging as a fuel for prime power generation in niche applications near to sources of renewable natural gas. Cummins carried out one such project in Delaware (U.S.) where landfill gas is used to power a combined heat and power (CHP) system to provide industrial customers with clean energy.
Natural gas and hydrogen blends in your decarbonization journey
Green hydrogen can be blended with natural gas and injected into existing natural gas distribution systems. This automatically reduces the carbon intensity of all natural gas uses served by the pipeline. Using pipeline systems to distribute fuel blends that include hydrogen is not new and, for example, has been practiced for years on the island of Oahu in Hawaii (U.S.). Various pilot schemes plan to replace up to 20% of natural gas by volume content in distribution systems and blending will be widespread in Europe over the next 10 years, with the U.S. not far behind.
Methanol in your decarbonization journey
Methanol, also known as wood alcohol, is a promising energy carrier derived from hydrogen or from biomass. Unlike hydrogen, methanol is a liquid at ambient temperature, making it easier to store and handle. It can be readily synthetized from hydrogen using well-known industrial processes. Methanol is a versatile fuel that is being used in a variety of applications today including Indy cars and monster trucks.
Several pilot projects designed to produce methanol from captured CO₂ and green hydrogen are up and running with more to come on-line in the next five years. The development of the process will be linked to the expansion of green hydrogen and CO₂ capture technologies.
When choosing an alternative fuel, it is important to consider the advantages and disadvantages of the alternative fuel and its state of adoption.