Diesel alternatives19 January 2022

Plant operators are moving away from conventional diesel-powered equipment and into alternatives; but the reasons for this change are varied. Some want to reduce their carbon footprint for reasons of corporate social responsibility (CSR), while others are driven by clients and local regulators who demand improvements in air quality. By Toby Clark

Whatever the reason, there is now an unprecedented range of alternative fuels and drive systems; some promise to reduce CO2 and other greenhouse gas (GHG) emissions, while others offer improved air quality from reductions in nitrogen oxide (NOx) and particulate (PM) emissions – or reduced noise in sensitive areas.

While low-emission zones seem to be concentrating on enforcing current diesel emissions standards, some contractors and clients are going further. Property group Lendlease is phasing out fossil fuels such as diesel and petrol and fuel gases such as LPG on all its UK construction projects. The firm currently uses 400,000 litres of diesel per year in the UK, and says it could cut over 1,000 tonnes of carbon emissions. Permitted alternatives include hydrotreated vegetable oil (HVO) – if derived from waste matter – hydrogen fuel cells, renewables and electrified plant. The policy came into effect for new projects in late 2020, and for existing projects from November 2021.

Alternative liquid fuels are perhaps the easiest way to improve local air quality – but they may not reduce your carbon footprint. ‘First-generation’ biofuels are made directly from a food or animal feed crop, such as bioethanol (usually made from sugar cane or maize) and biodiesel, typically made from vegetable oils. But beware ILUC (indirect land use change), where the cultivation of material for feedstock has a negative effect on CO2 emissions elsewhere.

Second- and third-generation biofuels are produced from feedstock that does not compete directly with food crops; this might include municipal waste – for example, used cooking oil (UCO) or fats, oils and grease (FOG) – as well as agricultural residues (wheat straw), non-food crops and algae.

Biodiesel has been a component of conventional diesel fuel for a while, and it is possible to use a blend such as B20 (20% biodiesel) without modification in most engines. Pure biodiesel (B100) is not compatible with all machinery, but offers more GHG reduction: about 60%-90% less CO2 emissions than mineral fuel, depending on the feedstock.

HVO is made by reacting vegetable oils (such as rapeseed or palm oil) or waste matter (used cooking oil or animal tallow) with hydrogen at high temperature and pressure, producing a ‘paraffinic’ fuel which meets the EN15940 standard. As supplier Nationwide Fuels puts it, “It can be used as a direct drop-in alternative for diesel” and “offers better combustion, filtreability and cold temperature performance.” HVO can be blended with conventional fuels, though pure HVO can be found sold as HVO100.

HVO does not contain fatty acid methyl esters (FAME) – a typical component of biodiesel – which is hygroscopic and prone to bacterial growth, leading to tank corrosion and filter blockages. Indeed, some suppliers claim their HVO has a 10-year shelf life.

Pure HVO has other benefits: its high cetane number of 70+ should indicate superior ignition qualities, and indeed its tailpipe emissions are excellent. Suppliers claim “an 86% reduction in particulate matter” and “30% reduction in NOx,” although the latter depends on engine specification. HVO also has a low cloud point, the temperature below which liquid fuel starts to ‘gel’, causing problems with filter blockage. HVO’s figure of around -32ºC suggests excellent low-temperature performance.

HVO is undeniably ‘greener’ than mineral diesel, although the hydrogen used in its manufacture may come from natural gas. The typical figure given is around 90% reduction in carbon emissions. Suppliers reckon that HVO costs up to 20p/litre more than mineral diesel, but the main drawback is supply: although production facilities are set to triple in capacity by 2025, they remain a small fraction of demand, and there is a global shortage of feedstock.


Another drop-in replacement for mineral diesel is GTL (gas-to-liquid) fuel, offered by Shell, among others. But this is synthesised from natural gas, so there is no intrinsic reduction in GHG emissions.

Nevertheless, GTL has few impurities, a low hazard rating and excellent combustion qualities, so it should be better for local air quality. Shell reckons on a 6%-25% reduction in NOx emissions for off-road machinery compared to conventional diesel, and a 10%-90% reduction in particulates. GTL costs around 5% more than mineral diesel.

The UK government states that the upcoming move from rebated ‘red’ diesel to more highly-taxed ‘white’ diesel for most off-road applications “is expected to incentivise rebated fuel users to seek to use greener alternatives,” yet bizarrely the measure still applies to fuels such as biodiesel, HVO and GTL.

BOX: Battery-electric

Full-electric plant is becoming much more common, thanks to the absence of local emissions and noise. Forklift trucks are moving from lead-acid to Li-ion batteries, and even large units are going electric: Hyster’s 16-tonne capacity J16XD12 runs on a 350V battery system. JCB introduced the 19C-1E battery-electric excavator last year, and is widening its battery-powered range to dumper trucks, access platforms and the 525-60E telehandler (pictured).

Hybrid generators combine an internal-combustion electrical generator with a ‘smart’ battery pack, switching the generator off automatically – which is useful in sensitive environments such as residential areas at night. Off Grid Energy offers portable units such as its PowerCube (pictured below), which can supply 400V three-phase electricity at up to 30kVA – ideal for events or site welfare setups. At one London building site where noise was an issue, generator runtime was reduced by 87 hours per week, using 609 litres less fuel and reducing maintenance costs.

Fuel cells are an alternative to batteries, using hydrogen and air directly to generate electricity and emitting only water. The US Postal Service found that fuel cell materials handling equipment could be run more cheaply than traditional battery-electrics. Equipment costs are high, but developments such as mass-produced fuel cell modules from Toyota could reduce that dramatically.

JCB has made a massive investment in ‘green’ hydrogen, undertaking to buy 10% of the renewably-sourced hydrogen made by Fortescue Future Industries. But having experimented with fuel cells – and demonstrated a reliable 20-tonne excavator – JCB is moving towards internal-combustion engines fuelled directly by hydrogen. JCB’s engine is based on its 4.8-litre Dieselmax turbodiesel, but with spark ignition, and produces similar power and torque to the diesel. Production is scheduled to start next year, and the firm reckons that it will cost around the same as a diesel unit. Hydrogen is currently around twice the price of diesel, and the fuelling infrastructure is limited, but mobile refuelling stations are on the way.

Other firms are persevering with biomethane (LNG or CNG) as a green(er) fuel for IC engines – New Holland offers tractors powered by CNG.

Toby Clark

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