No more mysteries about marine biofuels – your top six questions answered

Biofuels are an interesting alternative for the marine industry. What are biofuels? How are they made? What do you need to know about them? Your questions answered!

Biofuels are an interesting alternative as the marine industry explores future fuel options. What are biofuels? How are they made? What do you need to know before deciding if they’re right for your operations? This article answers all these questions and more.

Where do biofuels come from?

While fossil fuels are derived from finite, non-renewable resources like crude oil and natural gas, biofuels are produced from renewable biomass. Biofuels can be made from things like vegetable oils, animal waste, crop residues, sewage from wastewater treatment and food waste from industry and households.

When people talk about marine biofuels, they’re usually referring to liquid fuels like biodiesel and renewable diesel, but biofuels come in gaseous form too. 

Biodiesel is primarily made from crops, with the type of crop varying according to geographical region. Common sources include rapeseed in Europe, soya in the Americas and palm crops in Asia. Both liquid biodiesel and biomethane gas can also be produced from industrial waste streams such as waste from the pulp and paper industry. The EU categorises biofuels as liquid or gaseous transport fuels and includes bioethanol in this category.

When people talk about marine biofuels, they’re usually referring to liquid fuels like biodiesel and renewable diesel, but biofuels come in gaseous form too.

Kai Juoperi, Wärtsilä


What are the most common biofuels? How are biofuels made?

The three most common biofuels are:

  • HVO (hydrotreated vegetable oil), also known as renewable diesel
  • FAME (fatty acid methyl ester), also known as biodiesel
  • bioethanol

This article focuses on three fuels that are considered most relevant for shipping: HVO, FAME and bioLNG, which is liquefied biomethane produced from biomass. 

HVO is made by taking vegetable oils and fats and hydrotreating them. Hydrotreatment means removing the oxygen from the raw material in a chemical reaction using hydrogen to produce renewable diesel. HVO is available in its pure form or as a blend. The European standard EN 15940 describes the requirements and test methods for HVO. 

FAME is the most commonly used biofuel quality in shipping and, like HVO, can be derived from various vegetable oils, used cooking oil or animal fats. It is made using a process called transesterification, which converts the fatty acids to biodiesel in a reaction with methanol in the presence of a catalyst. FAME is available as a pure product or as a blend – for example as B20, which contains 20% v/v of FAME mixed with fossil diesel. The European standard EN 14214 describes the requirements and test methods for FAME. 

BioLNG can be produced by liquefying biomethane made from biogas, which can be produced from a wide variety of organic feedstocks. These include animal waste, crop residues, sewage, and food waste. There are two ways to make biomethane:

  • by upgrading biogas produced through waste fermentation to remove CO2 and other contaminants
  • through the thermal gasification of solid biomass followed by methanation


Are biofuels carbon neutral?

The short answer to this question is probably not completely, but it depends entirely on the raw materials and processes used to manufacture them. The European Renewable Energy Directive (RED) describes the percentage reduction in carbon intensity of biofuels compared to fossil fuels.

As with other alternative fuels the carbon neutrality of biofuels needs to be viewed from the perspective of the whole value chain. For example, growing crops to make biofuels requires cultivation, irrigation and harvesting – and then there is the energy consumed during the manufacturing process itself. As a rule of thumb, however, biofuels can reduce overall carbon emissions by something in the region of 40–80% from a well-to-wake perspective.

The International Maritime Organization (IMO) is currently drafting regulation that will shift the focus away from tailpipe emissions towards lifecycle CO2 emissions. This should drive real change in the industry and encourage the adoption of biofuels and other sustainable fuels.

Heikki Korpi, Wärtsilä


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Learn more about future fuels and their carbon neutrality:

Deep-dive Q&A article on methanol

Deep-dive Q&A article on LNG

Deep-dive Q&A article on ammonia

From well-to-wake, biofuels can cut carbon emissions by around 40–80%.

Kaj Portin, Wärtsilä


Will biofuels replace fossil fuels?

From a technical perspective there is no reason why not. FAME is the most commonly used biofuel quality in marine applications, and its quality is comparable to fossil distillate fuel, though minor differences can be seen in various physical and chemical properties.

From an engine point of view, HVO works nearly as well as fossil diesel. This means that it can be used as a direct replacement, or drop-in fuel, without modifying existing engine, fuel supply and storage technologies.

BioLNG can also be used with existing engine, fuel supply and storage technologies. The passenger shipping company Destination Gotland has been operating with bioLNG in its fuel mix for some time and ultimately plans to operate on 100% bioLNG in the future.

All biofuels that meet established standards are compatible with Wärtsilä engines. However, before switching you should check that your engine’s materials and fuel-system components are compatible. You will then be able to use the same vessel bunkering arrangements for biofuel storage and supply.

HVO, FAME and bioLNG can all use the same bunkering facilities as diesel and LNG fuels to some extent. This is a benefit over other alternative fuels such as methanol, ammonia and hydrogen, which require further infrastructure investments.

So, what’s limiting the uptake of these fuels if proven systems, equipment and infrastructure all exist? In short, it is lack of incentives for using them, which is in turn causing a shortage in both demand and supply. Compared to fossil-based alternatives the production volumes of biofuels are small.

BioLNG can use the same bunkering facilities as LNG, so there’s no need to invest in different infrastructure.

Anders Siggberg, Wärtsilä

The following International Energy Agency figures from 2022 put the production volumes into perspective:

  • Biodiesel (FAME): around 45 billion litres, equal to 1.5 exajoules of energy
  • HVO: 12 billion litres, equal to 0.4 exajoules of energy

To put these figures into perspective, international shipping consumed around 8.7 exajoules of energy in 2021 according to the IEA.
Even though today’s production volumes are small, the European Biogas Association expects bioLNG production to grow to between 40 and 120 exajoules by 2030.


Can I blend my own biofuels?

As a shipping operator, when you do get your hands on your biofuel, blends can be a way forward. Increasing the volume of biofuel you use in your fuel mix is one way to reduce the CO2 footprint of your vessels – but be sure to follow the recommendations of your fuel supplier and equipment manufacturers. This will help you to avoid problems: while some biofuels can easily be blended with fossil fuels, others can be more challenging.

Following the recommendations of your fuel supplier and equipment manufacturers is the best way to avoid problems.

Jussi Mäkitalo, Wärtsilä


What do I need to think about if I want to start using FAME?

There are seven things to consider when thinking about adopting FAME, and some of these may come as a surprise to you.

  1. Potentially higher NOx emissions – NOx emissions can be around 10–12% higher with FAME than with fossil distillate fuels.
  2. Lower energy content – The energy content of FAME is around 13% less than that of fossil distillates, meaning you need to burn more onboard to get the same amount of energy.
  3. Price – Just like other future fuels, liquid and gaseous biofuels are more expensive. Biodiesel can cost up to twice as much as traditional fossil fuels.
  4. Water content and microbial growth – Reducing the water content of biodiesel is also more challenging than with fossil diesel. FAME can lead to increased microbial growth that can contaminate the fuel. Its long-term storage potential may also be limited by oxidation. 
  5. Fuel specification – Choosing the right fuel specification for the climatic conditions is critical. If you’re operating in colder climates, you’re going to need a fuel specification that’s quite different than those created for hotter or more humid regions.
  6. Component compatibility – Check that your new biofuel will not have any adverse effects on things like gaskets and sealing materials in your fuel system. FAME has characteristics that may degrade rubber and other metals. Wärtsilä engines or fuel supply systems all have fully compatible components.
  7. Storage – FAME should be stored in dedicated tanks. If the tanks previously contained other fuels they should be thoroughly cleaned before bunkering FAME. FAME is a powerful solvent that will loosen any deposits or sludge inside the tanks, and these can clog an engine’s fuel filters and fuel separator.

Biofuels are an interesting option as the maritime industry looks for effective ways to decarbonise. If the fuel is available and the supply infrastructure exists on the routes where your vessels operate, this can help you to reduce your environmental impact significantly. And if you operate with Wärtsilä engines and fuel supply systems the good news is that they are compatible with any biofuel, gas or liquid, that meets established standards.

Do you operate vessels on LNG? Excited about what switching to bioLNG could do for your decarbonisation efforts? Then take a look at why bioLNG means it’s full steam ahead on Destination Gotland’s quest to decarbonise.

Written by
Charlie Bass

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