Lowering emissions with leftovers

A high-quality fuel that offers a 90% reduction in greenhouse gases and can be used in a diesel engine without modification – John Kendall considers whether HVO is too good to be true

One of the strengths of the diesel engine is that it can run on a range of fuels, because the heat needed to start the combustion process is generated by compressing air in the cylinders until it becomes hot enough to ignite the fuel. Rudolf Diesel’s earliest experimental engines were designed to be fuelled by coal dust, for instance. One of the drawbacks with fossil fuels like conventional diesel is that they consist of a range of chemicals that are present in the fuel, which means that when burnt, substances present in the fuel that we don’t particularly want to also ignite as they can cause toxic air pollution.

Biodiesel showed that we could produce diesel fuel from a range of substances including animal fats and crops like rapeseed, which contain fewer of the polluting elements. On the other hand, the obvious problem with crop-derived fuels is that they compete for land use with food crops.

If we take a step further along the chain, instead of using fuels produced from crops, we could use oils produced from crops that have already been used in food production. Instead of pouring the waste oil away, it can be treated and turned into a high-quality diesel fuel.

That is the principle behind hydrotreated vegetable oil (HVO) – a renewable biodiesel fuel without the main drawbacks of conventional biodiesel. Although burning the fuel produces carbon dioxide emissions, the theory is that this is offset by the CO2 absorbed while the crop was growing. That ignores the energy needed to turn the waste oil into diesel fuel, but it is arguably better than extracting oil from the ground and processing it solely for the purpose of burning it.

The attractions of HVO include the fact that it produces high-quality fuel which burns well and with fewer emissions than conventional diesel. It is also a ‘drop-in’ fuel that can be used as a direct substitute for conventional diesel fuel without any need to modify engines.

There are some potential clouds on the horizon, though. The EU is considering a proposal that would promote the use of HVO for aviation and maritime fuels, to the exclusion of road. There is some logic to this. These sectors are likely to prove the most difficult to de-carbonise and restricting use of HVO to these, while road transport transitions to electric, would help to clean up these heavily polluting sectors.

“You’ve got to think about all the properties of HVO,” says Magnus Hammick, chief operating officer of HVO supplier Green Biofuels. “You’re going to get 90% reduction in greenhouse gases. That’s brilliant. We know we need to do that. The other aspect of burning paraffinic fuels like HVO & GTL [gas to liquid fuels] is that they offer cleaner burning, so you get a local air quality benefit. Now personally I would rather see that local air quality benefit in inner-city areas and rural locations with fragile habitats, rather than being put in a plane that’s flying over the Atlantic Ocean.

“Then you’ve got to think about the feedstocks. Are there enough feedstocks to feed the trillions of litres of aviation fuel that are required versus a more achievable target, which is road and non-road mobile diesel replacement?”

Now that the UK is outside the EU, there is no reason to think that this EU proposal would automatically be taken up by the UK government, although Andrew Scott, head of electric mobility and product development at Renault Trucks UK and Ireland, does not see the possibility as much of an issue: “The EU’s recent policy announcement reflects its long-standing commitment to reduce and in time eliminate the use of crop-based materials in the production of fuels. Renault Trucks does not consider this to be a change in policy, rather the expected confirmation of previous plans.”

All major truck manufacturers’ recent models can operate on HVO and some customers have been keen to adopt the fuel. Builders’ merchant Travis Perkins has a large nationwide vehicle fleet, which accounts for over 70% of the company’s Scope 1 and 2 carbon emissions. “Having explored the decarbonisation opportunities of HVO, we decided to use it as a stepping stone in the implementation of our net-zero

RESTRICTED USAGE: The EU is considering limiting HVO to the aviation and maritime sectors, with road transport encouraged to transition to electric

STEPPING STONE: Builders’ merchant Travis Perkins is using HVO to lower its emissions while electric and hydrogen technologies develop carbon delivery,” says head of environment James Vance. “It is a great low-carbon alternative component that will play an important role in reducing the greenhouse gas emissions from our vehicles until the infrastructure for electric vehicles improves and the development of more long-term solutions, such as hydrogen, becomes a reality.”

Hackney Council has a long track record of being an early adopter of low-carbon transport fuels. The local authority first ran electric vans on its fleet in 1998 and began trials with B30 biodiesel in 2008, opting to run vehicles on 100% biodiesel in 2010. Corporate fleet manager Norman Harding has been involved in using low-carbon fuels since before he joined the local authority in 2007.

He first heard about HVO when on a biofuels working group with the Greater London Authority. He then persuaded TfL and the GLA to pay for testing of the fuel at the Millbrook Proving Ground in Bedfordshire, using fuel supplied by Green Biofuels, then a much smaller company.

“We set a baseline using pump diesel, then we cleaned the fuel systems out and changed the filters, so there was no contamination from normal diesel,” Harding explains. “The first test results we got were just unbelievable. We got a 12% CO2 reduction at the tailpipe, and because it’s made from a recycled waste product – cooking oil, animal fats and organic matter – it’s 80% efficient before it goes through the combustion process, but we also got a 69% NOx reduction at the tailpipe.”

The working group was so surprised by the results that it repeated the exercise to make sure it hadn’t made a mistake – and got exactly the same results. Harding then got involved in a working group for refuse collection vehicles including Veolia, Biffa, Dennis Eagle and others: “We created a test cycle that replicated a refuse collection round. Everyone agreed it was representative of a bin collection; we even had granulated rubber in the compaction compartment to simulate the compaction of waste. We did a number of bin-lift movements and we allowed for transit time from the end of the round to the tipping site and back again, so it was generic,” says Harding.

The results showed a 12% reduction in CO2 emissions at the tailpipe and a 28% reduction in NOx. As Harding observes, the CO2 reduction seemed consistent, but the drive cycle inevitably makes a difference to any reduction in NOx. Today, Hackney Council uses HVO for all its heavy trucks and wheelchair-accessible buses, most of its agricultural and civil engineering plant and around 40% of its LCV fleet. Access restrictions to the fuelling site limit further take-up for LCVs at the moment, but most of the council’s 520-strong vehicle fleet operates on the fuel.

“We saved just over 2,500 tonnes of CO2 by using HVO last year and I’ve got a potential further 1,000 tonnes of CO2 if I can get the rest of my light commercial fleet into my depot where we’ve got the bulk fuel tanks, or if I can find an alternative depot,” says Harding. The only downside of using HVO is the price, which works out more expensive than forecourt diesel.

This echoes Travis Perkins’ experience. The company highlights challenges around procurement costs for HVO, lack of fiscal stimulus, market availability, an

EARLY ADOPTER: Hackney Council has been using biodiesel since 2008 and, according to corporate fleet manager Norman Harding, it saved 2,500 tonnes of CO2 in 2022 by running most of its vehicles on HVO

OVERCOMING OBSTACLES: Travis Perkins powers 215 vehicles across 34 sites with HVO, but highlights several challenges along the way immature regulatory framework and standards that are not yet well formulated.

Travis Perkins uses HVO across 34 sites to power 215 vehicles. The fuel used is supplied under the Zemo Partnership Renewable Fuels Assurance Scheme (RFAS). As James Vance at Travis Perkins explains: “This means we can use the UK government’s carbon conversion factors to report on CO2 emission benefits with confidence. As a result, we have full visibility of the true ‘well to wheel’ benefit per litre of HVO versus fossil fuel.”

Travis Perkins has reduced consumption of conventional diesel by around 1.3 million litres per year. Using the RFAS calculations, this translates into a 92% CO2 saving compared with conventional diesel.

Magnus Hammick at Green Biofuels attaches some importance to the RFAS: “It’s a bit ironic, isn’t it? You buy a litre of diesel which has 7% FAME [fatty acid methyl ester biodiesel], as all forecourt diesel must. You don’t ask where the FAME has come from or what the feedstocks are that went into the FAME. You buy a litre of HVO and you want to know who used the cooking oil, which frying pan it went in, and everything about it.

“It’s really important, though. No one wants to say that you’re doing something good and to inadvertently add to the deforestation or land use change and things like that, so that whole chain and the pathways to customers are vital.”