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Biofuels for greener boating

With about 80,000 diesel-powered boats on the inland waterways, the best way to make boating greener now is to replace fossil diesel fuel with a biofuel.

Biofuels for boats

The first generation of biodiesel suffered from problems such as diesel bug and blocked fuel systems. However, second generation biofuel has none of these problems and is more than 90% carbon neutral.  When ‘green’ hydrogen becomes available, this will rise to virtually 100%.  As such, it looks like it will be the drop-in replacement fuel for those keen to run their existing diesel engines into a zero carbon future.

Hydrotreated Vegetable Oil (HVO) is a second generation biofuel that is gradually becoming readily available for regular commercial marine use.  Whilst it is currently still a more expensive fuel option, IWA is campaigning for tax cuts to reduce the cost of HVO for boaters.

What is HVO (Hydrotreated Vegetable Oil)?

Hydrotreated Vegetable Oil (HVO) is a second generation biofuel.  It is made by converting waste vegetable oils and animal fats into diesel fuel using hydrogen.


  • is made from waste oils (and not directly produced on land otherwise that would otherwise be used for growing food)
  • mixes with all other diesel fuels and has full approval from current engine manufacturers
  • does not attract water or promote the development and growth of diesel bug
  • is completely stable when stored (up to 10 years)
  • remains free-flowing down to at least -25℃
  • produces less air pollution than mineral diesel
  • can give up to a 10% reduction in fuel consumption

Read our biofuels FAQs

Read the latest news (May 2024) here.

Biofuels FAQs

Can you mix HVO and mineral diesel in the boat tank?

Yes. HVO is 100% miscible so can be added and mixed in any proportion. It can similarly be mixed in retailers’ tanks.

How can a boat be heated in a more sustainable way?

In an existing boat the best option, at least in theory, is to burn wood from renewable sources, though that gives rise to problems of particulate emissions which could result in its being illegal while potentially compromising the health of the boater when stoking the fire!

After that comes burning oil or gas in purpose-designed appliances with a likely 70% efficiency. Direct electric heating from a generator will only be 25-30% efficient, as that is all the generator is likely to achieve, though using it to provide domestic hot water and some space heating can potentially raise the overall efficiency by up to 10%.

Waste heat recovered from propulsion systems including diesel engines, generators or, potentially, fuel cells can also be used, especially in new builds.

In a new build there is also the option of installing a water-source heat pump. The efficiency of this is likely to exceed 300%, meaning that, even using power from a diesel generator, the heat produced will be at least comparable with the calorific value of the original fuel. However, questions have been raised about the performance of such pumps in very cold conditions and this requires further work.

In all cases, HVO can be used in place of mineral diesel. HVO offers a net CO2 reduction of up to 90% compared to mineral diesel.

For further information, see our briefing note on environmental guidance for boaters.

Are there any targets for banning diesel powered boats?

As far as we are aware, the same rules will apply as to the road sector.  Existing diesel boats will not be banned but building new ones will.  The date is currently 2035 with a probable later date for hybrids. In any event, when diesel engines cease to be produced for high volume applications such as road and plant use, basic units to marinize for inland waterways applications will probably cease to be available.

What is the extra cost of all this technology? Will it cause boating to be unaffordable for many and see a reduction in numbers of boats on the system?

At the moment, cost is a significant issue. An electric-drive package from a single supplier is likely to cost at least double that of a diesel drive. This may improve with time.

This can currently be reduced significantly by mixing and matching products from different manufacturers and particularly by using components not marketed as ‘marine’. For example, an 8 kVA marine generator costs about £15k, while an equivalent industrial one can be bought for about half that. It will need extra soundproofing but that will cost a few hundreds of pounds against a saving of thousands. However, all this requires appropriate technical knowledge.

To set against the capital cost, a well-designed, generator-based, electric drive system will use only 30 to 40% as much diesel as a diesel propulsion engine, an ongoing annual saving of around £150 a year for a boat using 250 litres of diesel per annum.

Electric-drive boats also qualify for a reduced licence fee from most navigation authorities, saving at least as much again.

Looking further ahead there seem to be three, potentially cheaper, scenarios:

  • If and when battery technology improves to the point where charging only from a shore-line becomes viable, the generator can be eliminated completely. A network of towpath power/charging points needs to be available for this option to work.
  • Significant cost savings seem likely if or when fuel cells which will run on hydrocarbon gases become available and affordable.  It has been suggested that the cells themselves could cost less than generators, though the only one we currently know about is much more expensive. Because the batteries will only need to do a buffering job, they can be considerably smaller when supported by a fuel cell.  Unfortunately, attempts to acquire a suitable fuel cell for evaluation have so far drawn a blank.
  • Hydrogen fuel cells are already technically viable, but they are currently expensive. Hydrogen is also expensive and a hydrogen refuelling infrastructure is not in place.

Heat from a fuel cell can, in theory, provide all the heating a cruising narrowboat needs for 8 or 9 months of the year, representing a further saving.

Regardless of the above, the existing fleet, hopefully fuelled with HVO, will be with us for a significant time.

How much will HVO cost following the Department for Transport announcement, and where can I buy it?
  • The approximate cost of HVO vs mineral diesel, as at the end of 2023, assuming a 60/40 split for tax and duty purposes and a retailer’s markup of 15p/litre is estimated to be:
    Mineral Diesel    147 pence per litreHVO                      200 pence per litreAs with mineral diesel, in the current market conditions, the cost of HVO is, and will continue to be, very volatile. This volatility is exacerbated by the variable value of Renewable Transport Fuel Certificates, the subsidy currently applied to HVO.

    Unfortunately, the value of this subsidy has decreased dramatically in the last two years, resulting in HVO becoming less competitive with  mineral diesel.  The objective of the IWA/RYA/Cruising Association Joint HVO Working Group remains :

    “To persuade the various government departments involved to adopt policies that will make HVO affordable and available to leisure boaters.”

    The current stockists we are aware of (as at the end of 2023) are listed below and their prices may vary from those given above. We hope, and expect that, following the recent Department for Transport clarification, more stockists will become available to boaters.

    • Crown Oils will sell direct to the public in quantities as small as 205 litre drums and 1000 litre IBC. Crown Oils provide a country-wide link up with a range of small, private fuel distributors, as with all bulk fuel deliveries the minimum quantity is 500 litres. In London and the Home Counties they also operate as Speedy Fuels and in the Midlands as Beesley Fuels.
    • New Era(who operate as GBF Ltd). Quantities from 1000 IBCs to bulk.
    • Scottish Canals – Broxburn – Union Canal – Contact Mark Smith (07796 938318; [email protected])
    • Scottish Canals – Auchinstarry – Forth & Clyde Canal– Contact Mark Smith (07796 938318; [email protected])
    • Scottish Canals – Speirs Wharf – Forth & Clyde Canal, Glasgow Branch– Contact Mark Smith (07796 938318; [email protected])
    • Aqueduct Marina, The Outlanes, Church Minshull, Nantwich CW5 6DX (01270 525041;
    • Stonebridge Lock Boatyard, Marsh Lane, Tottenham N17 0XD (07909 520920;

    Information for boatyards:
    Crown Oils are offering to install a separate tank, free of charge, for a trial period where a marina or boatyard, etc, wishes to trial HVO.  They have self-contained, ready-to-go, units that can be just dropped into place.  Anyone wishing to follow up on this should contact Ryan Abreu at Crown Oils on 07585 792918.

Where does the Raw Material to make HVO come from? Is it sustainable?

HVO imported to the UK is manufactured from 100% renewable & sustainable waste derived raw materials, accepted by the Renewable Transport Fuel Obligation and certified by the International Sustainability and Carbon Certification System.

The accreditation process is overseen by the UK Department for Transport, assisted by the Zemo partnership:

There is currently no HVO manufactured in the UK, which is unfortunate. It comes from a variety of international sources.

As with all biofuels, there is a limited supply of vegetable oils and animal fats that can be used to make HVO without affecting world food supplies. Hence the current policy of the UK government is only to encourage the use of HVO where there is no practical alternative to decarbonise. We argue that there is no practical alternative to decarbonise the existing inland waterways fleet and, in any case, it is transition fuel on the way to full electrification.

In what engines and other appliances can I use HVO?

‘Modern’ canal engine suppliers all approve the use of HVO, and IWA has trialled HVO in most types of ‘traditional’ canal boat engines, including a Bolinder!

IWA has also carried out extensive trials with 100% HVO in other diesel burning appliances that are commonly found on canal boats, such as boilers, heaters and cookers, and these have included Eberspacher, Mikuni and Webasto central heating units. The trials have shown that HVO burns cleaner than gas oil (red diesel), leaving noticeably fewer residues.

No problems have been found when using HVO in either case and it appears to be a superior fuel to mineral diesel, not least because it has less noxious tail pipe emissions, especially NOx and particulates.  See also the question about diesel bug below.

How much diesel is used on the Inland Waterways and would a further subsidy on HVO for leisure boaters have a material effect on government revenue?

It is very difficult to obtain reliable figures for the volume of diesel used on the inland waterways and the consequent revenue that the government derives from it. A Freedom of Information request to the HMRC failed to give a definitive answer, and we must assume that they don’t know!

Our best estimate is that it is 0.05% or less of retail mineral diesel fuel sales in the UK, and hence we believe that a further subsidy would be marginal in terms of its effect on government revenue.

What effect does using B7 diesel or HVO have on the already known problems with diesel bug?

‘Diesel Bug’, the deterioration of mineral diesel in storage under damp conditions and the subsequent growth of microorganisms which lead to fuel system blockages, is well known to boaters.  See this photo of the impacts.  The ‘condition’ is often likened to beef dripping – though one probably has to be of a certain age to appreciate this analogy. Those of us that do remember the layer of white fat on the top of the bowl, with the glutinous, brown, jelly-like substance underneath, will immediately warm to the description (or not as the case may be)!

The current addition of 7% ‘FAME’ biodiesel to mineral diesel (B7) has made matters worse by increasing the propensity of the fuel to absorb moisture and thus promoting the growth of diesel bug, and the formation of sticky solids.  These are thought to be the result of residual glycerol and the presence of soaps in the biodiesel.

Fortunately, HVO exhibits none of these problems and can be used in any proportion with mineral diesel up to and including 100% HVO.  Put simply, HVO does not encourage the growth of diesel bug.

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