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Let’s Talk About HVO for Boaters

If you care about the marine environment, you will be considering how to minimise your carbon footprint when out on the water.

Like most cruising sailors, you probably power your current boat with a diesel engine and you may not be ready yet to transition to electric drive.

However, by switching to HVO, you can reduce your CO2 emissions and environmental impact without modifying your current diesel engine.

What is HVO

Hydrotreated Vegetable Oil (HVO) is a ‘renewable diesel’. It is also known as a second generation biofuel. It should not be confused with hydrogenated vegetable oils which are saturated fats used in food production and bad for cholesterol.

HVO is produced from vegetable oil feedstocks, but the finished fuel contains no vegetable oils, esters or oxygen.

A paraffinic mineral diesel fuel of high purity which is clear and odourless, HVO has a high cetane number which benefits cold starting and noise. The absence of aromatic compounds reduces particulate emissions.

HVO is less susceptible to water uptake and, as it contains no vegetable matter or oxygen, it is far less likely to suffer from diesel bug. Because it is highly paraffinic, it is therefore very stable and can be stored for long periods without deterioration.

HVO is a ‘drop-in’ marine fuel, which is approved for use in any concentration up to 100% in diesel engines with no modifications by most manufacturers.

The production process occurs in stages and at high temperatures and pressures over a catalyst with hydrogen, leading to a paraffinic mineral diesel fuel of high purity which is clear and odourless.

  • For more detailed technical information, see Cruising Association technical volunteer and charter engineer Malcolm’s Denham article, which appeared in its magazine Cruising.

 

 

 

The Sustainability of HVO

Over the last five years, all UK-supplied HVO has been produced from waste materials, according to the Government’s RTFO (Renewable Transport Fuel Obligation) data.

An accepted list of feedstock materials used for making renewable fuels are provided as guidance for the RTFO and Sustainable Aviation Fuel Mandate. Wastes and processing residues, such as used cooking oil, tallow, brown grease, palm oil mill effluent, spent bleaching agent or tall oil, can receive twice the number of Renewal Transport Fuel Certificates per litre compared with biofuel. This ensures there is little incentive to use crop-based materials.

Under the RTFO, renewable fuel supply chains are required to meet criteria for greenhouse gas emissions savings, feedstock sustainability and supply chain traceability. Suppliers must ensure that HVO sold in the UK is manufactured from sustainable sources and does not result in environmental damage due to land use change, such as deforestation for palm oil.

Greenhouse gas emissions savings figures for HVO are:

2019: 91%
2020: 85%
2021: 89%
2022: 89%
2023: 83%
2024: Provisional 83%

Variations in the figure from year to year are due to different sources and volumes of the waste feedstock, hence manufacturers’ claims of up to 90% CO₂ savings.

  • For more detailed information about the sustainability of HVO, see the Cruising Association’s Research and Technical Service article [link to follow] in June 2025 Cruising.

 

 

 

Benefits of HVO for Boaters

As one of the most viable solutions for existing boats with diesel engines for a clear and safe route to greener boating in the UK, HVO is:

  • Certified by the UK Government as sustainable
  • Safer for the environment, providing a significant reduction in CO₂ emissions from the fuel’s use and production
  • An ideal drop-in replacement for existing marine diesel engines
  • Suitable for use in any concentration from 1% to 100%, without engine modifications.
  • Approved by virtually all marine engine manufacturers, with no compromise in performance
  • Stable and clean-burning
  • Less likely to suffer from issues like ‘diesel bug’
  • See the Cruising Association’s Frequently Asked Questions on HVO for more information.

 

HVO is a Second-Generation Biofuel

HVO’s benefits and compatibility are undeniable, yet there remains a degree of scepticism within the boating community about the reliability and safety of this second generation renewable fuel.

Some of this misinformation is due to issues experienced by boaters with the first-generation biofuel FAME (Fatty Acid Methyl Ester).

First-Generation Biofuels and FAME

In the 1980s, diesel was all from fossil sources, but many oil companies experimented with vegetable oils as ‘extenders’. All vegetable oils are fatty acids, so esterifying produces Fatty Acid Methyl Ester (FAME), which, as a first generation biofuel, contains oxygen.

The introduction of biofuels in the 2000s was driven by targeted reductions in greenhouse gas emissions. In 2004, EN590, the road diesel specification, had a maximum of 5% FAME, increasing to 7% maximum in 2009. Whilst some vehicles have run on 100% FAME, it is nearly always used as a blending component in fossil derived diesel.

As FAME is hygroscopic, it absorbs water. Being vegetable based, it can contain bacteria, fungi and yeasts and microbes different to those in fossil-based diesel. An increase in water absorption, the presence of oxygen and a greater variety of microbes make FAME diesel more susceptible to ‘diesel bug’, which forms at the fuel water interface. Poor ‘washing’ of the FAME before blending into diesel can lead to residual soaps, found as brown deposits blocking fuel filters, as shown in the photo, right [by Jonathan Mosse].

HVO does not suffer from the drawbacks of first-generation biodiesel.

HVO Test and Trials

HVO is tried and tested with proven performance in a wide range of commercial and recreational boats and engines.

IWA’s Sustainable Boating Group has undertaken trials in various types of boat engines of different vintages, as well as in other common marine diesel fired equipment such as heating systems and cookers. All have performed well using HVO in place of their usual supply.

A Cruising Association RATS (Regulatory and Technical Services) also carried out a survey of CA volunteers to gather information of how typical cruising vessels use their engines. The findings supported the fact that any decarbonised propulsion method must support the range and power needed for safe cruising, and have the appropriate refuelling and recharging infrastructure.

In November 2023 ICOMIA (International Council of Marine Industry Associations) published an analysis of the effectiveness of different types of new propulsion technology in terms of decarbonisation of recreational craft. The UK representative to ICOMIA is British Marine.

One conclusion of the report, Pathways to Propulsion Decarbonisation for the Recreational Marine Industry, was that, for most existing yachts which make limited use of their engines, the most sustainable option was to retain existing serviceable diesel engines and to switch to a sustainable biofuel rather than to replace serviceable engines with a pure electric or hybrid electric drive.

[The photo, left, shows historic narrow boat Spey taking part in IWA’s trials]

Campaigning for Change

Despite the performance and safety evidence of HVO and the proven environmental benefits for boaters, HVO at the ‘pump’ is complex to market to the marine sector.

It is inherently more expensive than mineral diesel and the price is volatile.

HVO is subject to the same duty and VAT rules as red diesel (the ‘60/40’ split).

The Renewable Transport Fuel Obligation (RTFO), the Government scheme which supports renewable fuels, also contributes to the regulatory and supply complexity as inland waterways vessels are eligible to use HVO which is supported by Renewable Transport Fuel Certificates, whereas seagoing vessels are excluded.

The overall result is the creation of two key barriers which are preventing the widespread adoption of HVO in the recreational boat sector – Limited Availability and Unstable Price.

The HVO Joint Working Group exists to make HVO available and affordable to all recreational craft, both seagoing and inland, by raising awareness and working with Government to change policies.

FIND OUT MORE

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