With the looming introduction of Euro VII engines we ask: Can diesel be cleaner in HGVs?

The forthcoming Euro VII emissions standards, set to be implemented by the European Union, will introduce stricter limits on pollutants from heavy goods vehicles (HGVs) to reduce environmental impact, particularly in urban areas. Expected to come into effect in 2027, Euro VII aims to significantly lower nitrogen oxides (NOx) and particulate matter emissions compared to Euro VI standards. For HGV operators, Euro VII will likely mean upgrades in vehicle technology, such as enhanced exhaust after-treatment systems and real-time emissions monitoring.

This standard could lead to increased vehicle costs and operational changes, as manufacturers develop compliant engines and fleets adapt to stricter limits. Additionally, Euro VII aligns with the EU's broader goals for decarbonisation, pushing the industry towards lower-emission and, eventually, zero-emission transport solutions. Though the UK has yet to confirm direct adoption of Euro VII, similar emissions regulations could be considered given environmental targets and alignment with EU standards for cross-border operations.

Can diesel be 'cleaned up' for heavy goods vehicles (HGVs) in the UK and Europe?

The improvements listed below have their limits, compared to zero-emission solutions like electric and hydrogen, but many still have a place in today's haulage industry. Cleaner fuel and fuel systems can reduce harmful emissions while leveraging diesel's unmatched power and efficiency for long-haul trucking. Here's a breakdown of how diesel fuel and HGV engines can be improved for cleaner operations in the HGV market:

Advanced Emissions Control Technologies

Reducing harmful emissions from diesel engines has been a top priority, especially given that HGVs contribute significantly to NOx and particulate pollution.

Various control systems have been developed to tackle pollutants without compromising performance: Selective Catalytic Reduction (SCR): This technology has been a game-changer for diesel engines, especially in Euro VI-compliant HGVs. SCR systems work by injecting a urea-based solution, commonly known as AdBlue, into the exhaust stream.

The urea reacts with NOx emissions, converting them into nitrogen and water vapour, which are harmless. SCR systems have achieved significant reductions in NOx emissions, a critical pollutant associated with respiratory illnesses and smog, and are especially effective in keeping HGVs within stringent emissions limits in the UK and Europe. Diesel Particulate Filters (DPF): DPFs address another harmful emission: particulate matter (PM).

These filters capture soot particles, preventing them from being released into the atmosphere. Over time, DPFs go through a process called regeneration, where the captured soot is burned off at high temperatures. This system is essential in urban areas with high traffic density, as particulate emissions contribute to air quality issues.

However, DPFs require regular maintenance, as a clogged DPF can reduce engine performance and fuel efficiency. Exhaust Gas Recirculation (EGR): EGR is another method for cutting NOx emissions. By recirculating a portion of the exhaust gases back into the engine's combustion chamber, EGR systems reduce combustion temperatures, which is a key factor in NOx formation.

Although not as effective as SCR in heavy-duty applications, EGR complements other emissions control systems and is particularly useful in reducing emissions during low-speed, city-based driving, where HGVs often encounter higher emission rates.

Cleaner Diesel Blends and Additives

Improving diesel's environmental impact can also be achieved by modifying the fuel itself. Blending diesel with biofuels or using additives offers tangible benefits without requiring significant changes to HGV engines: Biodiesel Blends: Biodiesel is produced from renewable sources such as vegetable oils and animal fats.

When blended with conventional diesel, it helps reduce CO2 emissions, as biodiesel emits less CO2 throughout its lifecycle. In the UK and Europe, B7 (a blend containing 7% biodiesel) is widely used, with higher blends like B20 (20% biodiesel) gaining traction. Biodiesel can also help reduce particulate emissions, though it's not a cure-all.

Higher biodiesel blends may require engine adjustments and can impact fuel economy slightly, so operators often weigh the benefits of lower emissions against operational changes. Hydrotreated Vegetable Oil (HVO): HVO is a chemically modified biofuel that can be used as a direct replacement for traditional diesel. Produced from renewable raw materials, HVO offers a substantial CO2 reduction--up to 90% lower emissions.

HVO also produces fewer NOx and particulate emissions, making it one of the cleanest biofuels available for HGVs. Since HVO is compatible with existing diesel engines, it's an attractive option for operators who want to reduce emissions without investing in new vehicles. However, cost and supply availability of HVO are considerations, as it's generally more expensive than regular diesel.

Diesel Additives: Some fuel companies now offer diesel blends enhanced with additives aimed at improving combustion efficiency and reducing emissions. These additives help optimise the fuel burn, lowering the formation of soot and NOx. In addition to environmental benefits, additives can improve engine performance and fuel economy, though the gains are typically moderate.

Additives won't replace the benefits of using biofuels or synthetic diesel, but they can be a practical measure to achieve incremental improvements in emissions and efficiency.

Synthetic Diesel (eDiesel)

Synthetic diesel, also known as eDiesel or Fischer-Tropsch Diesel, is a promising alternative to conventional diesel, offering a carbon-neutral fuel option. Produced from renewable electricity, water, and CO2 captured from the atmosphere, eDiesel could play a role in reducing the carbon footprint of HGV fleets: Renewable Production Process: The process involves using renewable energy to electrolyse water, creating hydrogen.

This hydrogen is then combined with captured CO2 to produce a synthetic fuel chemically similar to diesel. The fuel's carbon-neutrality lies in its use of atmospheric CO2, essentially recycling emissions instead of adding to them. Cleaner Combustion: eDiesel combusts with fewer NOx and particulate emissions than conventional diesel, which could make it particularly useful for HGVs operating in regions with strict emissions regulations.

However, the technology is still in the development stage, with high production costs and limited availability. If renewable energy costs continue to drop, eDiesel might become a more viable option for HGV operators in the future.

Hybrid Diesel-Electric Systems

For HGVs, full electrification is challenging due to battery weight and charging requirements. Hybrid systems, combining diesel engines with electric motors, offer a transitional solution:

Dual Power Sources for Efficiency: In hybrid HGVs, the electric motor can take over in low-speed, low-load situations, such as urban traffic, where diesel engines are less efficient and produce higher emissions. The diesel engine is then engaged for long-haul journeys on motorways or when carrying heavy loads, where diesel's efficiency is maximised. Reduced Emissions in Urban Areas: Hybrid HGVs can reduce emissions in cities where stop-start driving is common, cutting fuel consumption and lowering particulate and NOx emissions.

Although hybridisation doesn't eliminate diesel use, it's a useful stepping stone towards zero-emission fleets, especially for urban logistics. Hybrid systems require a more complex drivetrain and an initial cost investment, but they can deliver fuel savings and emissions reductions that benefit operators and cities alike. Many operators see hybrids as a practical way to reduce their carbon footprint without waiting for fully electric HGVs to become widely feasible.

Low-Carbon Diesel Production

Beyond tailpipe emissions, the carbon footprint of diesel can also be addressed through cleaner production processes.

Traditional diesel refining is energy-intensive, generating significant CO2 emissions. However, newer refining methods aim to lower the lifecycle impact of diesel: Renewable Energy in Refining: By using renewable energy sources to power refineries, fuel producers can reduce the carbon emissions associated with diesel production.

This approach is still in its early stages but holds potential as more refiners look to decarbonise their operations. Carbon Capture in Refineries: Some refineries are adopting carbon capture technologies to trap CO2 emissions during production. Captured CO2 can be stored or repurposed for other industrial uses, reducing the environmental impact of the refining process.

While these measures don't directly impact emissions during HGV use, they contribute to lowering the overall lifecycle emissions of diesel, supporting operators in meeting sustainability targets.

Limitations of Cleaner Diesel

Despite these advancements, there are inherent limitations to "clean" diesel for HGVs: Emissions Reduction Ceiling: Even with all these technologies, diesel combustion still generates CO2, NOx, and particulate matter. These emissions can be reduced, but not entirely eliminated, making diesel a short-term solution at best under zero-emission goals.

Regulatory Pressure: The UK and EU have set ambitious targets to phase out diesel and other internal combustion engines in HGVs by the 2040s. Cleaner diesel options may help operators meet current standards but are unlikely to comply with long-term regulations that demand zero emissions. Zero-Emission Alternatives: Electric and hydrogen HGVs eliminate tailpipe emissions entirely and are being prioritised by policymakers as the future of trucking.

Diesel, despite being made cleaner, is still seen as a stopgap rather than a permanent solution.

Conclusion

Cleaner diesel offers a range of tools, from emissions control systems and biofuel blends to synthetic alternatives and hybrids. While these measures can reduce emissions, they can't eliminate them, and diesel will likely play a diminishing role as the industry transitions to zero-emission vehicles. Cleaner diesel can be a valuable bridge for operators, helping them reduce their environmental impact while preparing for an electric or hydrogen future.

For now, cleaner diesel provides a way to manage emissions and keep HGVs compliant with regulations in the UK and Europe, but its long-term role is likely limited.

As technology advances and zero-emission infrastructure expands, the shift away from diesel in the HGV sector is expected to accelerate.