The ground investigation (GI) sector is under mounting pressure to decarbonise. Clients, regulators, and the public expect visible progress, and the industry is responding with a mix of innovation and pragmatism. Two alternative fuels, palm oil free Hydrotreated Vegetable Oil (HVO) and synthetic fuels (such as Gas-to-Liquid (GTL)) are now widely discussed as practical options for reducing emissions from plant and transport. But how do they really compare in terms of sustainability, performance, risk, and procurement for GI projects?

This article aims to provide a clear, evidence-based comparison, drawing on the latest industry guidance, certification schemes and feedback from across the sector. The goal is to help GI professionals make informed decisions that balance environmental responsibility, operational reliability and commercial reality.

What is Palm Oil Free HVO?

Palm oil free HVO is a second-generation biofuel made from 100% renewable and waste-derived feedstocks, such as used cooking oils and animal fats. All UK HVO is imported from Europe, Asia and the USA. Unlike first-generation biodiesels (Fatty Acid Methyl Ester (FAME)), HVO is chemically stable, resistant to water ingress, and free from sulphur and aromatics.

Once processed into HVO, it’s impossible to distinguish sustainable palm oil waste from virgin palm oil, the latter which may carry links to unethical practices including potential modern slavery. This lack of transparency is a key reason why some clients have chosen to ban HVO on their sites.  Therefore, to ensure sustainable HVO is being used, it requires certification before use of each batch.

To ensure traceability and sustainability, HVO can be certified under schemes such as the International Sustainability and Carbon Certification (ISCC) and the UK’s Renewable Fuels Assurance Scheme (RFAS), and are now widely available from suppliers such as Certas and Speedy.

HVO has many benefits, including:

• Drop-in fuel: HVO is a direct replacement for diesel, requiring no engine modifications and it meets the EN15940 standard for paraffinic fuels.
• Green House Gas (GHG) savings: When made from genuine waste feedstocks, HVO can deliver up to 90% lifecycle greenhouse gas (GHG) reduction compared to fossil diesel.
• Air quality: HVO produces lower nitric oxide, nitrogen dioxide, particulates, and CO₂ emissions than standard diesel, but real-world benefits depend on engine type, after-treatment, and maintenance.
• Storage: HVO has a long shelf life (up to 10 years), is less prone to microbial growth (“diesel bug”) than FAME biodiesel, and is more stable in storage than standard diesel.
• Original Equipment Manufacture (OEM) approvals: HVO is approved by a wide range of plant and vehicle manufacturers including JCB, Caterpillar, Volvo and Komatsu.

Surprisingly  prices in mid-2025 for HVO are slightly lower (~£1.37 – £1.40 per litre) than fossil diesel (~£1.44 – £1.47 per litre).  Beyond cost, the environmental benefits, improved reputation, and long-term savings make HVO a strong choice for use on your sites.

HVO is already in use across several RSK businesses, including Structural Soils and RSK Habitat Management, with successful trials at sites like Avonmouth and Lichfield. However, as discussed above, not all HVO is created equal. Sustainability depends heavily on feedstock sourcing, and some suppliers still rely on virgin crops or palm oil derivatives. Furthermore, demand for used cooking oil (UCO) is rising and there is a risk of supply interruptions.  Therefore, controls and supplier audits are essential to ensure genuine environmental benefit.

What are Synthetic Fuels?

Synthetic fuels in the context of the GI industry usually refers to Gas-to-Liquid (GTL) diesel, produced from natural gas via chemical conversion (Fischer-Tropsch process). GTL is also paraffinic, FAME-free, and meets EN15940, but is fossil-derived.

There are some benefits of Synthetics, including:

• Drop-in fuel: GTL is a direct replacement for diesel, requiring no modifications.
• Air quality: GTL offers reductions in particulates and NOx, but does not deliver significant lifecycle GHG savings compared to fossil diesel.
• Sustainability: GTL is not renewable; its main benefit is improved local air quality, not carbon reduction.

However, there are challenges, including:

• Energy-intensive production
• Limited commercial availability
• Slightly cheaper than HVO; however, 10% more expensive than diesel.

Therefore, synthetic fuels are promising but not yet practical for widespread use in GI applications. Their deployment is constrained by cost and scale, and production volumes remain low.

Certas Energy and Speedy have confirmed that their HVO is derived from waste-based feedstocks and meets stringent sustainability criteria. They have also highlighted the importance of transparency in sourcing and carbon accounting.

Looking Ahead

For the GI industry, HVO represents a viable interim solution and is now widely available in the UK.  However, supply is still limited by the availability of genuine waste feedstocks and the UK is reliant on imports from Europe, Asia and the USA.  Reflecting the cost of both certification and the limited supply of waste feedstocks, HVO carries a cost premium over standard diesel and GTL. As demand for UCO is rising, there is a risk of supply interruptions; therefore, long-term agreements with reputable, RFAS approved suppliers are recommended for critical operations.

Increasingly, Tier 1 contractor clients are mandating HVO or equivalent for site operations and some require evidence of RFAS certification and batch-specific Renewal Fuel Declaration (RFD’s).

Synthetic fuels may play a role in the future, but for now, their deployment is constrained by availability and scale.

As we move towards net zero, it is essential to balance ambition with pragmatism and HVO, when responsibly sourced, offers a meaningful step forward. Therefore, continued investment in hydrogen and synthetic fuel technologies will be key to achieving long-term sustainability.

Structural Soils, part of the RSK Group, with our clients approval, have been using HVO fuel on the majority of our larger sites in our plant.

Further information on Responsible Sourcing of HVO can be found on Supply Chain Sustainability School follow the link below. https://learn.supplychainschool.co.uk/local/resourcelib/catalogitem.php?id=8460

Article provided by Eric Downey, Associate Director, Structural Soils Ltd www.soils.co.uk