Not bad for a number two driver? Inside the car powered by sewage

Motorsport's sustainability drive continues at a pace. Derided by many as a greenwashing exercise that doesn't go far enough, and considered by others as an unnecessary pursuit that is in danger of stripping the very essence of racing away, it has a much wider scope than the perceived over-electrification of championships. This goes beyond just propulsion; building an entire car sustainably with limited impact on the environment is not only an industry that'll become more profitable with time, but it's also a noble pursuit.

Taking waste products and finding methods of reusing them or their constituent elements to create something new is one of the key cornerstones of sustainability practices. There's the common, garden forms of doing so - quite literally, when using old vegetation as compost and pulping old paper to form brand new sheets for the A4 print-out next to you.

In further advances, materials that have been viewed as difficult to dispose of, such as carbon fibre, can now be recycled and pressed back into service through developments pioneered in the aeronautical industry; here, partial pyrolysis of the resin can allow engineers to reclaim the fibres and weave them into a new ream of CFRP.

But when we talk about waste, what about...well, your waste?

Tons of sewage is pumped into pipelines underground, most of which is parted from its water content and treated before returning to the ecosystem (or, as apparently decreed by recent controversies, expelled directly into the sea). The solids remaining can be used as fertiliser, or turned into methane by bacteria for a renewable source of gas. Burning methane isn't exactly a perfect solution as an energy source, as it counts carbon dioxide as one of its byproducts.

Methane's global warming potential (GWP) is, over a 100-year timescale, 28 times higher than CO2 according to the European Commission, but lingers in the atmosphere for a shorter period - around 10 years - for one that can stick around for over 300 years. It's all a trade-off, and it's up to world leaders to pick their poison: rapid overheating, or the slow-burn.

If you're wondering that "there must be something else we can do with all this sewage", then you're right - there is. And, as you're reading a motorsport publication, then there's a solution that should immediately pique your interest.

A desire to increase the sustainable content of fuels is noble, but more can be done - as University of Warwick researchers have proven

Photo by: Gold and Goose / Motorsport Images

The University of Warwick has, for 15 years, pioneered its CleanTech programme - a series of developments based on sustainability employed in the arena of motorsport. This began with a "chocolate-powered" Formula 3 car - with an engine converted to run on biodiesel produced from chocolate waste products, with a steering wheel produced from derivatives of vegetable waste, and composite bodywork produced from flax fibres. You can't quite grow a car, but you can certainly grow most of the constituent parts needed...

The subsequent step, Waste2Race, takes the notion of transforming waste materials into a sustainable solution for motorsport even further - using hydrogen fuel sourced from sewage. A first-generation Ginetta LMP3 car using the previous examples of recycled carbon fibre and natural fibre reinforced polymers has been selected as the basis for this, underpinned by a hydrogen internal combustion engine.

Elaborating on the decision to encapsulate the sustainable developments into a racing car, Dr James Meredith of the University of Warwick explains that using motorsport can demonstrate the use cases for each one - rather than simply presenting the developments with limited context.

"The highlight has always been around trying to demonstrate that you can do motorsport and you can be environmentally responsible at the same time"
Dr James Meredith

 "This is the third racing car we've built around sustainability, and it started off probably 20-odd years ago," says Dr Meredith. "If you make a piece of sustainable material, it usually looks like a square plate or a bit of small bits of it, and it doesn't look very exciting.

"If you can apply it to a racing car, suddenly it looks like, 'Oh wow, that might do something useful'. So that was where our logic started. We converted a Formula Student car that we did some green things to, natural-fibre bodywork and such, and that precipitated the next one we did, which was a Formula 3 car.

 "We put a lot more effort into that, good ideas: a lot of recycled carbon, some natural-fibre composites. We ran it on biodiesel and the biodiesel was made from waste chocolate - you can essentially use waste cocoa butter to make the fuel.

"What we wanted to try and do [with Waste2Race] was essentially build on the success of the previous cars and the highlight has always been around trying to demonstrate that you can do motorsport and you can be environmentally responsible at the same time."

First-generation Ginetta LMP3 car has been selected as the basis for the Waste2Race programme

Photo by: University of Warwick

Meredith says that the decision behind opting for a hydrogen ICE rather than a fuel cell-powered vehicle was largely a romantic one, with the aim of demonstrating a technology that goes against the current aversion - and often, fear from some areas of the motorsport fanbase - to the greater scope of hybridisation and electrical power.

He states that "actually sound, smell and everything else is a key ingredient - if you go down a route of sort of a pure electrical fuel cell, you miss out on some of that". But how do you turn sewage into a hydrogen fuel source?

The method is not too dissimilar to the earlier one outlined with the conversion of sewage to methane, in that it uses microbes to digest the sewage and produce gas - but crucially, there's another link to recycling carbon fibre for a very different purpose.

"We had a parallel piece of research: could we use recycled carbon fibre for high performance applications? If you put it into a flat panel is reasonably easy, but can you use it for an energy absorption structure?" Meredith explains. "Actually, the work we did around that did demonstrate that we could use it for energy absorption, which was great, but a bit later on a project came along where essentially we were looking at microbial electrolysis cells and the carbon substrate that goes into those devices.

"Essentially it's a carbon tube or substrate in a tank of fluids, and microbes grow on that carbon substrate. Those microbes are fed with something and then produce gas at the end of the day. The project was to look at whether or not this expensive carbon substrate that the microbes grow on, could that be replaced with recycled carbon fibre?

"And actually, the answer was, yes, it can. So you can make a much cheaper substrate for the device, but actually it showed a slightly enhanced performance of the microbes ability to turn sewage into hydrogen.

"You've got substrates on which you grow a particular type of microbe, they munch their way through the sewage. In theory, clean water comes out of the end of this and actually they give off a high sugars byproduct. There's a load of synthetic biology involved in selecting the type of microbe and how well it grows and what temperature it works at and all that sort of stuff. Fundamentally, it's something eating the sewage and producing gas."

These microbes are known as "electrogenic bacteria" and are able to produce electrons and hydrogen ions under certain conditions. The carbon substrate, which on a microscopic level has a series of fibres, houses these bacteria.

Opting for a hydrogen ICE adds further complexity to the Waste2Race project

Photo by: University of Warwick

This emittance mechanism of the bacteria is triggered by its metabolism. They eat and digest the sewage, producing an oxidation reaction; electrons then pass through the anode to the cathode to generate electricity and water as the ions react with oxygen.

This describes how a microbial fuel cell (MFC) would work but, for the generation of hydrogen gas, a microbial electrolysis cell (MEC) is needed. Only two differences are required here; firstly, the cathode area must be covered to inhibit reactions with oxygen, and secondly a further source of electricity is needed to convert the ions into hydrogen gas. Theoretically, this could be stored energy from an MFC to create a self-fulfilling cycle.

Waste2Race uses products from Wastewater Fuels to make this happen and, although only currently available on a small scale, Meredith says that the company is currently scaling up its technology to allow for a more widespread use of hydrogen. In theory, should the technology's reach grow, then the use of more available hydrogen gas can be employed as a fuel source for further consumer applications: transportation, shipping, heating, and anything else that could benefit from an energy source currently fulfilled by fossil fuels.

"I don't think you could take one of these units to a race circuit and then take the sewage from the people attending and turn it into fuel for the race series or something. But it might be possible"
Dr James Meredith

" At the moment, the scale of the operation is not appropriate for producing a huge amount of hydrogen," says Meredith. "However, we are currently in the process of bidding for money - and I think the company involved, Wastewater Fuels, are actually producing a larger-scale system at the moment. Over the next year or two, the scale of it will be a lot more significant. Previously, actually, the hydrogen hasn't really been kept; it's quite a small amount and you can't do a great deal with it.

"But actually now it's going to be producing hydrogen in a scale that we can then consider compressing it and having it available for, let's say, some of the other vehicles around the site where the hydrogen is being produced. So it's moderately significant.

"I don't think you could take one of these units to a race circuit and then take the sewage from the people attending and turn it into fuel for the race series or something. But it might be possible."

With hydrogen combustion engines becoming viewed more favourably as an alternative to electrical power, particularly as Le Mans has a hydrogen-fuelled category in the pipeline for the near future, finding sources that could supply a handful of cars will rely on ingenuity within the engineering and biochemical industries.

Hydrogen has a pathway to race at Le Mans in the near future, but could waste be utilised too at the world's most famous endurance race?

It's important to note that hydrogen combustion processes are not zero-emission, as it forms some nitrous oxide byproducts. Meredith says that this can be mitigated with the calibration of the engines, adding water vapour into the combustion chamber, or running the engine lean - but ultimately, Nox products are the penance for an otherwise for the otherwise clean development of the hydrogen fuel.

Nonetheless, the space of generating electricity and hydrogen fuel from the microbial digestion of sewage has its credentials and, if the technology is indeed scalable, it can become a transformative technology across global industry - not just motorsport. Both first and second-generation biofuels are either in development for, or already in use for racing applications; perhaps sewage-derived gases can be termed as the turd-generation fuel...

The Waste2Race car appeared at the University of Warwick’s Festival of Innovation, part of the University's 60th Anniversary celebrations in 2025.

Could the technology have a transformational impact on the future of motorsport?

Photo by: University of Warwick