For some years, the government has been supporting efforts to develop low-carbon transport fuels. The good news is that there are now several credible alternatives; the bad news is that none of them is perfect. Peter Shakespeare reports

Low carbon fuel made up 3% of UK transport fuel in 2015/16, generating emissions savings equating to taking over a million cars off the road. According to the Department for Transport (DfT), a UK market for biofuels estimated to contribute £30 million per year to the economy has been successfully created by the Renewable Transport Fuel Obligation (RTFO). This is one of the main policies for reducing carbon emissions from road transport and meeting UK climate change targets. The RTFO requires fuel suppliers to provide an amount (currently 4.5% by volume) of sustainable renewable fuels.

Earlier this year the government consulted on changes to the RTFO to increase the trajectory of low carbon fuels to 2030 and extend eligibility to cover aviation fuels and hydrogen. The consultation proposed raising biofuel volumes to 9.75% in 2020 to achieve 5-6% renewable energy in transport, and maintain at least that level of obligation to 2030 and beyond. DfT says this would support the achievement of UK carbon budgets and meet the terms of EU environmental directives that it remains committed to meet. A Royal Academy of Engineering July report (see below) was also positive.

That consultation also sets out proposals to limit the contribution from crop-derived biofuels to promote more sustainable biofuels such as those made from waste. The most recent government numbers, for the 12 months to April 2016, indicate that crop-sourced biofuel – bioethanol – amounted to 789m litres, and biodiesel totalled 733m litres. Together they made up 3% of fuel in total, compared to mineral diesel’s 55%.

The biggest biodiesel feedstock, making up more than a third of supply, is used cooking oil; for bioethanol, feedstocks include wheat, sugar beet and corn. In fact, both crop-based oils and used cooking oil can make the two types of biodiesel in the UK: FAME (fatty acid methyl ester) and HVO (hydrogenated vegetable oil), though at 8m litres, the latter was tiny in comparison with the former. Suppliers include Crown Oils and WP Group.

The main difference between HVO and FAME is in the production process. FAME uses methanol as a catalyst in an esterification process; HVO uses hydrogen as the catalyst. The hydrogenation process removes the oxygen from the fuel, while esterification does not. FAME is prone to oxidisation which leads to contamination. FAME must be closely monitored to make sure it is still usable; HVO can be stored for much longer. Biodiesel producer Olleco says that FAME, when blended in a mix with 93% mineral diesel, can be stored for considerable periods, and needs only the same precautions as normal diesel, such as annual tank monitoring, using antioxidants and regular fuel turnover. Most of the large independent fuel distributors supply biofuels and can provide advice on use and storage.

Truck manufacturers have adapted diesel engine technology to allow greater use of biofuels. Scania says all its Euro VI engines currently in production can, regardless of the generation, be run on HVO. The introduction of the new nine-litre range also sees the arrival of the first engines for its ‘Next Generation’ trucks that can be specified for use with alternative fuels – the DC09 320 and 360 (above). Both can be specified to run on either diesel, 100% FAME biodiesel, or any blend of those. One condition for this is that the biodiesel versions must be serviced in shorter intervals, and to a greater extent, as FAME has corrosive properties.


The biggest feedstock for bioenergy globally is palm oil. In Finland, Neste Oil has developed a process to produce HVO, resulting in increasing amounts of palm oil being imported and used in its production. Refiners Esi, Repsol and Total have all ramped up HVO production from palm oil, whose green credentials have been questioned.

Within the EU, rapeseed oil has been the principle feedstock, and in 2016 13.7 million tonnes of biofuel was produced there, driven by EU Renewable Energy Directive targets and subsidies.

Almuth Ernsting is director of environmental group Biofuelwatch. He says: “At present, most UK biodiesel comes from wastes and residues, not virgin plant oils. The single biggest feedstock is used cooking oil. What is problematic is that much of this feedstock is imported long distances, often from countries which themselves burn large amounts of palm and soybean oil to meet their own biofuel targets.”

HVO is one of three so-called ‘paraffinic fuels’ synthetically manufactured from coal, natural gas or biomass. They are said to be cleaner-burning than mineral diesel, and have been officially recognised since April 2016 under the EN15940 standard.

Biomethanol is another one of these; it makes up about 2% (31m litres) of UK renewable fuels, and is produced in a gas-to-liquid process from wood waste in the Fischer-Tropsch process.

The third such fuel is GTL (gas to liquid), made from natural gas. Britain’s largest independent fuel distributor, Certas Energy, is the sole supplier of Shell GTL fuel in the UK, and it recently made it available at its HGV refuelling station at the Port of Liverpool. Shell’s Helix Rimula engine lubricant is a GTL motor oil. Other global GTL suppliers are Petro SA, Petronas, SASOL and Chevron.

Certas says GTL fuel has improved combustion properties and so helps reduce emissions. Shell says that GTL fuel can be used in all existing engines without the need for any engine modification, new infrastructure or vehicle investment. Tests have shown that for on-road heavy duty vehicles such as buses, utility vehicles and trucks, the fuel can reduce NOx emissions by up to 37% and particulates by up to 38%.

Despite the confusion and doubts around fossil fuel alternatives, the world must, and is, moving to lower emission mobility. Biodiesel and paraffinic fuels may be part of the mix that will be needed to power the future.


A hybrid bus that runs on both diesel and liquid nitrogen has completed a series of trials to bring it one step closer to the road. The bus – CE Power – has been built by engineers at Horiba Mira, part of the Innovate UK consortium. It features a zero-emission Dearman engine, alongside a conventional diesel power plant. At below 20mph, the system warms liquid nitrogen until it boils, creating enough pressure to drive the multi-cylinder Dearman engine. At higher speeds, the diesel engine takes over.


The makers of the Opti-Diesel fuel additive claim it increases the combustion efficiency of diesel fuel. When tested in South Africa by mining firm Glencore in 2016, it is said to have reduced NO2 emissions by 55%, CO emissions by 75% and particulate matterby 47%. In the UK, special transport company Collett & Sons has trialled the additive, and Opti-Diesel reports that supermarket Asda is currently conducting a 90-truck, six-month trial at one of its distribution centres.


Sustainability of Liquid Biofuels, by the Royal Academy of Engineering –

RTFO consultation (now closed) –

2015-6 RTFO report –

2015-6 RTFO statistics –

Paraffinic Fuels for Europe –


See Certas Energy and Shell at the IRTE Conference, 28 September, Chesford Grange, Kenilworth:

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