End emissions, save the combustion engine

Hans Buitelaar
Monday, 22 May 2023

Electric propulsion is the silent emission reducer but long range power from internal combustion engines remains necessary. Clean fuels provide a future for roaring exhaust pipes.

A farewell for fossil fueled combustion engines is coming. The once beloved source of mobile power is waved with a suitable growl as automobile enthusiasts in growing numbers tune their vehicles with noisy exhaust pipes. Horsepower-packed versions of family cars with shiny rims and exotic wrapping leave their 20th century footprint with rubber marks on urban tarmac in a last attempt not to appear obsolete. Meanwhile, modest and down-styled electric cars out-accelerate the noisy gasoline gobblers at traffic lights, in silence and driven by environmentally conscious commuters.

Electric mobility is heralded as the new era in transport. But is this really the end of internal combustion engines? Petrolheads may find hope in the German  ‘nein’ against the European Commission proposal to ban sales of new vehicles with internal combustion engines in the EU from 2035 onwards. March this year, Berlin and Brussels politicians reached an agreement on the German amendment to the EU Directive on CO² emissions from cars and vans, to allow also combustion engines that run on synthetic fuels produced from renewable sources. A much as Germany is on course with the other EU member states to bring greenhouse gas emissions down to almost zero by that time, German industry and government officials argued that not only electric mobility should be embraced as the greener solution. Combustion engines can run on sustainable fuels. Changing fuel, rather than changing the whole vehicle, has a sustainable aspect in itself.

Trial and error

Introduction of new fuels has been going on for over a decade now. Some of the fuels that claimed to offer a contribution to reducing harmful emissions have been failures. Some fuels did more harm than good and some caused engine problems. Biodiesel and bioethanol require large amounts of plant oil. Growing enough crop to fuel a large container vessel could jeopardise agriculture for food production. Some bio fuels have been produced from palm oil, requiring large tropical plantations that have been established in rainforests, destroying the habitat of orangutans. The bio components, obliged by law in most European countries, attract water into the fuel and cause large algae growth in tanks where the fuel is not refreshed regularly.  Especially boats and yachts suffer from this, as they may sit in their berths for a month or more before their next use. Other alternative fuels like LNG and GTL are produced from natural gas instead of crude oil, which is still a fossil fuel. GTL should be able to replace diesel without engine adaptations, but often causes stalling engines and abrupt throttle responses that make it very hard to control the speed.


The industry is on a learning curve and newly developed fuels can be used safely in most types of engines while they appear to really offer substantial reduction of harmful emissions along the chain of fuel production to the exhaust pipe.  Road transport, cargo ships, inland vessels and industrial machines are starting to change fuels. The large scale of these professional fuel consumers increases production start-up, distribution and worldwide availability and ensures reliability of energetic properties. What are these new fuels and will they be widely available in marinas or along the waterside? Could they replace gasoline or diesel without engine adaptation? Will my engine run just as good with them? Will it make sense for environmental reasons to change to other fuels, or do they just represent a last spasm of the internal combustion engine? Big industry conglomerates invest large amounts of money in the creation of production capacity and infrastructure for new fuels like methanol, HVO and hydrogen. Their industry knowledge and money hints to a future for combustion engines.

Fueling electricity

Clean water is the emission caused by propulsion systems running on hydrogen. The best known application of this energy carrier is to run it through a stack of membranes where it reacts to oxygen, resulting in electricity and water. The electricity then drives an electric engine. The use of hydrogen fuel cells reduces dependency on batteries and provides an extension of range. The technology is rady available for boats and yachts. In Norway, TECO 2030 has started production of hydrogen fuel cell stacks. Their fuel cell generators can be installed modular and stacked. Each unit provides 400 kW of power. A pack of four delivers 1600 kW and so on. The fuel cells can operate with fuel conditioning systems, that can prepare methanol or ammonia And other H² based carriers for use in the fuel cell. Whereas hydrogen itself is only kept in high pressure tanks, methanol and ammonia are liquid at normal temperatures. The fuel conditioning system solves the problem of high pressure hydrogen storage. The TECO stackable fuel cell is specifically designed for marine use. The REXH2 fuel cell was developed by Toyota in collaboration with French hydrogen pioneers EO Dev. In its one cubic metre box, it provides 70 KW of power for hours. The REXH2 is the power source fitted in multple boats, like the Hynova tender.

Burning water

While using hydrogen as a fuel to provide acceptable range over electric yachts that rely on batteries only, the applications mentioned use electric end propulsion. There is no internal combustion of hydrogen. Use of hydrogen in combustion engines is very well possible. Dutch research centre TNO won the EARTO Innovation Award last October for their development of the H²ICE; a retrofit hydrogen combustion kit can convert existing engines into hydrogen engines overnight. Together with truck manufacturer DAF, the researchers aim to develop conversion sets for larger diesel engines to enable these to run on hydrogen. Existing diesel engines are still at use but run on hydrogen after conversion, causing zero carbon dioxide emission. TNO specifically aims at the maritime industry with their engine conversion kit. As they demonstrate the conversion with road truck engines, comparable to the size of a yacht diesel engine, this application may well be available for yachts, soon. 


Combatting harmful exhaust gas emissions delivers best results when the whole chain from fuel production to propeller is considered. Hydrogen is not a fuel by itself, it can be used as a carrier of energy. It can be produced by the process of electrolysis. Water and electricity are applied and hydrogen is the result of a relatively simple process. If this process is performed efficiently, some 75 percent of the electric energy applied can be harvested from the hydrogen. So there are efficiency losses. Hydrogen can only be considered a clean fuel when it is produced using electricity that was produced from renewable sources like wind or solar energy. Governments and energy companies over the world are preparing large scale hydrogen production from the excess electricity production of offshore wind parks on windy days. If these plans are realised, this will induce large availability of green hydrogen.


Pioneers are paving the way for hydrogen, everyday users still have their combustion engines in their boats. If it runs on diesel, consider using HVO. Hydrotreated Vegetable Oil can be safely used in diesel engines without any adaptation to the engine, it will run just as good, but it will cause 90 percent less carbon dioxide emissions. The fuel is produced from waste materials in a process in which it reacts with hydrogen. No fossil fuels are used. This fuel does not attract water and causes no algae to flourish in tanks. There is almost no emission of particles, soot and nitrogen. HVO is widely available already, but is more expensive than fossil diesel.


Gasoline engines may run on biobutanol,  yet no gasoline engines are on the market yet that run on this fuel without adding fossil gasoline. This is also the case with the EcoGen 90 gasoline mixture that was used by Suzuki Marine to demonstrate the quick adaptation of the boating industry to new fuels. The outboard manufacturer navigated a center console boat along the Atlantic coastline of the United States from Florida to Washington DC where the America boating congress was held, to show reliability and possibilities of alternative fuels.


Methanol is a fuel that can be produced in an environmentally sound manner quite easily. Large shipping companies and ship builders like Damen Shipyards Group consider methanol the most viable power source to become the maritime fuel of the future. It can be used in gasoline engines and in diesel engines as well with some conversions to the fuel system.  British yacht builder Archipelago Yachts has developed the first yacht to run on methanol. It is an expedition catamaran. Two Enmar direct injection methanol combustion engines provide propulsion. Electricity for all household luxury on board is provided by a methanol-to-hydrogen fuel cell. With tanks filled, the power cat should cover a range of 4000 nautical miles, reach a top speed of 20 knots and take 8 people. Filling the tanks might require some flexibility: methanol is widely available at ports all over the world, but not from filling stations for yachts. Coming alongside a tanker and getting the crew to fill the catamaran tanks is a skill that adds to the skippers maritime competence.


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