What are they and how do they work?

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Fossil fuels won’t last forever. While many experts argue about the exact year we might see the final nail in the coffin, the reality is that factors like increased consumption and the discovery of new reserves could make it unpredictable. Regardless, it’s still widely believed that they will run out at some point, so switching to renewable energy sources that can take their place is a race against time. Some are betting that the answer may actually lie in our waste.

According to the U.S. Energy Information Administration (EIA), more than a quarter of all U.S. energy use was attributed to transportation in 2022. Given this, it’s not surprising that finding alternative fuel sources and designing engines that can use them efficiently may be just what we need to get things moving. And one possible solution experts have suggested to solve this problem is switching to biofuels like biomethane.

In 2023, Fortune Business Insights reported that not only was the alternative fuels industry already worth over $460 billion, but it was also expected to be valued ten times that in just nine years. In addition, there’s just over a decade left until the European Union officially bans the sale of new fossil-fuel cars in 2035. Knowing this, investors have increasing incentives to support the development of alternative fuels. What role does biomethane play in this, and what sets it apart from other alternative fuels?

What is biomethane?

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Before we get into what biomethane is, we first need to understand its most important component: biogas. Simply put, biogas is one of the products that naturally forms after the anaerobic fermentation of organic materials. Under normal circumstances, this process occurs without human intervention in places like landfills, farms, and waste treatment plants.

Historically, biogas has been used to power everything from street lights to Apple data centers. But for it to work as a viable alternative in gas engines, the biogas had to be further processed to improve its quality and efficiency. Part of this is to reduce the risk of damage to engines designed to use natural gas, especially since some biogas can contain harmful chemicals like siloxanes. Fortunately, scientists have been able to optimize this process to create an alternative fuel, renewable natural gas (RNG). According to the Environmental Protection Agency (EPA), RNG can be added directly to existing fossil natural gas distribution infrastructure and used in existing gas engines (with some additional refinement compared to its use in other applications).

Currently, most of the world’s biomethane is a product of biogas that has been refined or “upgraded.” To take biogas to the next level, the EPA states that this process removes contaminants such as nitrogen, carbon dioxide, and other volatile organic compounds. However, the IEA also states that there are alternative ways to produce biomethane, such as exposing certain biomass to specific conditions, such as extreme pressure and heat.

How biomethane engines work

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Because it works essentially like natural gas, biomethane can use a similar infrastructure in its distribution practices and can be used in internal combustion engines (ICEs) that are designed for it. In fact, many European countries, such as Sweden, France and Germany, have been adding biomethane to their natural gas networks for years. In 2010, Volkswagen began testing the Bio-Bug in the UK, the first biogas-powered car (that could also run on petrol), which it claims did not lose any efficiency. In partnership with sustainable energy company GENeco, the six-month trial used human excrement collected from residential homes in Bristol to produce the alternative fuel. However, biomethane has recently come into the spotlight.

In December 2023, Scania released a heavy-duty version of its OC13 engines for commercial trucks that it claimed could boost fuel economy by up to 5% for commercial fleets. A year later, leading Japanese carmakers Toyota, Suzuki, and Nissan also shared their plans to develop vehicles that reflect the growing need to reduce emissions, including investing in biomethane engines. In fact, one of the long-awaited biomethane-powered vehicles that will soon hit the streets is the Suzuki WagonR.

In this regard, many Japanese companies have made significant progress over the years in developing and experimenting with supporting technologies, such as plants processing agricultural waste into biogas and testing ships powered by liquefied biomethane.

Problem with biomethane engine systems

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Today, even electric vehicles have a hidden carbon footprint throughout their supply chain and end-of-life experiences. So what exactly is the problem with biomethane engines? For starters, a decade-long study by Elsevier (PDF) on the risks of large-scale biogas production found that damage to processing plants, particularly fermenters and gas buffers, can lead to both poisoning and combustion.

Unfortunately, some scientists still worry that biomethane plants are failing to consider the public health and safety implications of processing, even in recent times. In 2022, another study in the journal Environmental Justice found that the anaerobic digestion process necessary to produce methane also emits other toxic emissions, such as NOx, which can cause a range of health problems, from respiratory problems to mood disorders.

On the business side, the Journal of Cleaner Production published a study that highlighted several existing logistical challenges related to delivering biomethane to large-scale fleet operations in 2023. Additionally, the MDPI case study also revealed that biomethane may be less efficient than its natural gas counterpart, mainly due to reduced methane concentration, in the same year. However, these may just be issues that new technology can solve, especially now that automakers are actively developing engines specifically designed for biomethane. That said, it is important to note that despite all the challenges listed above, there is still much to be gained by exploring the potential of biomethane engines.

Why biomethane engines may still be the future

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On the issue of moving away from fossil fuels, our team recently spoke with Dr. Laine Mears, chair of the Automotive Manufacturing Department of Automotive Engineering at Clemson University. In an interview, he said, “I wouldn’t say there are engineering obstacles, I would say it’s more of a market inertia and economic factors that keep gasoline (and diesel) vehicles on the road.” In other words, there are many renewable energy alternatives, but people need to be incentivized to make the switch.

In a way, biomethane engines can do this, especially since they have many features that can make them easier to use and produce. Unlike other forms of renewable energy that have many location constraints, there is a lot of organic waste everywhere. And of course, increased use of biomethane engines and demand for fuel can help close the loop on many wastes from important industries like manufacturing and agriculture.

Not to mention that there were many promises that it would be a much cheaper alternative to natural gas. For example, according to the European Biogas Association, the cost of producing biomethane in Europe in 2022 was about a third of the cost of natural gas. Finally, because it can be used in existing natural gas vehicles, it may be less painful for ordinary consumers to switch.