HVO as a substitute for diesel on leisure boats

Hydrotreated Vegetable Oil (HVO) is a type of biofuel that can be used as an environmentally friendly substitute for diesel. In addition to being a significant step towards greener boating, it may also improve safety by reducing incidence of engine failure due to microbial growth, known as ‘diesel bug’.

What is HVO?

HVO is a very stable biofuel that does not easily degrade over time and that is water resistant helping prevent diesel bug and fuel contamination.

It is produced from non-food biomass such as agricultural residues, waste oils, and other non-edible plant materials in a process where it is cleaned, oxygen is removed, and paraffinic hydrocarbons are created.

The first commercial HVO plant was built in 2010. Currently HVO is mainly used in road vehicles and industrial machinery.

It is known as a ‘drop-in’ fuel as most engines and equipment need no modifications to use it.

HVO is different to FAME biofuel

Fatty Acid Methyl Ester (FAME) biofuel is produced from the transesterification of fats and oils such as soya-bean oil, rapeseed oil, or palm oil.

While both methyl esters and paraffinic hydrocarbons can be used as fuels, their chemical structures and properties are different. FAME biofuel is hygroscopic, attracting water, whereas HVO resists water absorption due to its lack of oxygen. The presence of water in fuel creates an environment conducive to microbial growth (diesel bug).

FAME biofuel is added to conventional fossil diesel to reduce carbon emissions and meet the Renewable Transport Fuel Obligation (RTFO) introduced in the UK in 2008. B7 diesel is 7% FAME and 93% fossil diesel.

B7 diesel in leisure boating

Various sources give the shelf life of B7 diesel as 6 to 12 months. Ideal conditions would be in an airtight container at a steady low temperature. These is not the normal conditions in a diesel tank on a boat which has a breather to the atmosphere and experiences a range of temperatures throughout the year.

Diesel from a filling station may already be a couple of months old. For a car or van this is not usually an issue but on a sailing boat, where the aim is to use the engine as little as possible, the rate of consumption of diesel is low so it has longer to degrade and for diesel bug to develop.

Diesel bug

Diesel bug is a collective term for a range of fungi, bacteria and yeasts that can infect diesel and that feed on the organic materials it contains, and particularly the added FAME biofuel. FAME biofuel also attracts water which the diesel bug needs to thrive. Diesel bug creates a black sludge at the bottom of the tank. If the tank contents are not agitated this might go unnoticed as fuel is usually drawn from higher up in the tank. However, if the sludge gets to and blocks the fuel filters the engine will stop working which could be a serious safety issue. Diesel bug treatments are available to slow the development of diesel bug and to help break down the sludge.

HVO for leisure boating

HVO is a good choice for leisure boating for several reasons:

  1. Environmental Benefits: HVO reduces greenhouse gas emissions by up to 90% over the lifecycle compared to traditional diesel and, as it is made from waste products it contributes to the circular economy.
  2. Safety: HVO is less hygroscopic than B7 diesel so it absorbs less water, reducing the risk of diesel bug and sludge formation which can clog fuel filters and cause engine failure. HVO also has a higher flash point (typically above 70°C) than B7 diesel (around 57°C) meaning it is safer to handle and store.
  3. Cleaner Burning: HVO burns more cleanly, producing fewer particulates and pollutants, which helps in maintaining air quality and reducing engine wear.
  4. Compatibility: HVO can be used as a direct replacement for diesel in existing engines without any modifications. Major marine engine manufacturers have assessed their engines and confirm compatibility with HVO on their websites.
  5. Longer Shelf Life: HVO has a shelf life of up to 10 years compared to traditional diesel 6-12 months, reducing the need to replace degraded fuel.
  6. Reduced Maintenance: With fewer deposits and cleaner combustion, HVO can lead to reduced engine maintenance and longer engine life.
  7. Cold Weather Performance: HVO performs well in cold weather, ensuring reliable operation even in lower temperatures.

Availability around the Forth

Many of the larger fuel suppliers only sell in volumes larger than the capacity of leisure boat fuel tanks. However, LubiQ Fuels in Grangemouth sell HVO in 10 litre or 20 litre jerrycans. They also deliver.

HVO is more expensive than B7 diesel, however, this should be considered against the benefits in safety and maintenance and the small amount typically used in a season.

Further information

Further information can be found on the engine manufacturers and fuel suppliers websites.

Yanmar https://www.yanmar.com/marine/technology     

Volvo Penta https://www.volvopenta.com/en-gb/about-us/how-hvo-can-benefit-you

Beta Marine https://betamarine.co.uk/inland-accessories

LubiQ Fuels https://lubiq.uk

Anne Shedden – FYCA Executive