Regulations spark interest in fuel homogenisers

As the European Union tightens its regulatory grip, shipowners and operators have sought alternative technologies to comply with these measures whilst maintaining operational efficiency.

Technologies like fuel additives, fuel homogenisers, and water-in-fuel emulsions offer shipowners a comprehensive solution to these challenges by optimising fuel performance, reducing harmful emissions, and lowering compliance costs.

The most stringent regulations are the EU ETS and the Fuel EU Maritime initiative which impose limits on CO₂ emissions and fuel carbon intensity.

EU ETS is the cornerstone of the EU’s efforts to reduce CO₂ emissions across all sectors, including shipping. Extended to cover maritime emissions in January 2024, the EU ETS requires shipping companies to monitor, report, and pay for their CO₂ emissions. The system applies to voyages within the European Economic Area (EEA) and 50% of emissions from voyages between the EEA and non-EEA ports.

EU ETS operates on a cap-and-trade basis, where companies are allocated emissions allowances or purchase additional credits, known as EU Allowances (EUAs), to cover their emissions. The price of EUAs has ranged between €80 and €90 per tonne of CO₂ in 2024, and as the cap tightens, prices are expected to rise. Shipping companies are incentivised to adopt emissions-reducing technologies to lower their fuel consumption and reduce the number of EUAs they need to purchase.

EU ETS focuses on emissions from fuel combustion, measured using a “tank-to-wake” approach. This straightforward method calculates emissions based on the amount of fuel burned during a ship’s operation, directly linking fuel efficiency to compliance with emissions targets.

Wake-up call for shipping

Fuel EU Maritime, however, sets progressive limits on the carbon intensity of maritime fuels. Unlike the EU ETS, which measures emissions from fuel combustion, the Fuel EU Maritime regulation takes a “well-to-wake” approach, covering the entire fuel lifecycle from production to consumption. This comprehensive framework aims to incentivise ship operators to adopt low-carbon fuels, such as biofuels, hydrogen, ammonia, as well as synthetic fuels improve fuel efficiency, and implement advanced emissions-reduction technologies.

It also imposes penalties for non-compliance, driving the industry to explore innovative solutions to meet the increasingly stringent emissions targets, but adoption of the well-to-wake model is highlighting the overall cost the green versions of the alternative fuels available to the maritime industry. They are still a long way from becoming mainstream, mainly due to the cost of producing the totally green versions, availability, and infrastructure, as well as safety and storage issues which can create a dilemma for the shipowner.

In order to comply with the new regulations, shipowners may need to take a longer term view before committing to these ‘alternative’ fuels by maximising the benefits of the current range of fossil fuels readily available worldwide and even consider blending fossil fuels with the likes of biofuels.

How fuel homogenisers work

Fuel homogenisers (pictured), specialised fuel additives, as well as water-in-fuel emulsions are re-emerging as key technologies that can help the maritime sector meet these challenges. By optimising fuel combustion and reducing emissions, these technologies help ship operators to comply with EU regulations while improving fuel efficiency and reducing costs.

Fuel homogenisers are mechanical high shear devices that condition fuel by breaking down large fuel droplets into smaller, more uniform particles. This process improves fuel atomisation, which enhances combustion efficiency and reduces emissions. Fuel homogenisers are particularly effective with heavier fuels like Heavy Fuel Oil blends (VLSHFO) but also with Marine Diesel Oil (MDO), which often contain impurities and have high viscosities, and also biofuels.

Marine fuels (HFO and MDO) can contain impurities, such as large and long-chain asphaltene particles, water, sludge, or other contaminants that can affect combustion efficiency and have an adverse effect on engine combustion.

Inside the homogeniser, the fuel passes through the narrowing gap between a rotor and stator. The high-speed rotor generates strong centrifugal and frictional forces which grind down the larger particles in the fuel, reducing the size of asphaltene clusters, breaking emulsions, and homogenising fuel. The rotor also creates localised cavitation, where vapour bubbles form and collapse violently in the liquid. This process helps break up fuel impurities and water into fine droplets, ensuring a more uniform and stable fuel mixture.

As a result of the mechanical forces, the homogeniser reduces the size of fuel particles and any water droplets to the micron or sub-micron level (typically between 1 and 5 microns). This fine dispersion is crucial for improving the combustion characteristics of the fuel. If water is present, it will be evenly dispersed within the fuel as a micro-emulsion. This prevents water droplets from causing localised hotspots in the combustion chamber, which could lead to corrosion or incomplete combustion. The reduction of asphaltene clusters improves the flow characteristics of heavy fuel oils and reduces the risk of clogging or uneven combustion.

Once the fuel is fully homogenised the fuel particles and any water content are evenly distributed. The fuel becomes more stable, less prone to separation, and more suitable for efficient combustion.

The finer fuel particles burn more completely, reducing unburnt fuel residues, black smoke and particulate matter (PM) NOx, SOx and enhancing engine efficiency. By ensuring a stable and homogeneous fuel mixture, the homogeniser helps optimise engine performance, leading to better fuel efficiency and reduced wear on engine components.

Combining homogenisers, additives, and water-in-fuel emulsions

Looking at fuel additives as a stand-alone technology, the industry has cleaned up its act over the last 10 to 15 years, and while there are still some sceptics and some claims of ‘snake oil’, the simple fact is that fuel additives do work, all be it to varying degrees.

While some additives are claimed to be more effective than others, these differences are usually due to the fuel type (HOF, ULSHFO, or MDO) and dosage ratio which can range from 1:200 to 1:50,000. Essentially most of them are very similar using a combination of detergents, antioxidants, corrosion inhibitors, organic surfactants, dispersants, combustion improvers, detergents, anti-foulants, metal-organic catalysts, detergents, and stabilisers. The fuel additive industry is reported to be worth almost $10 billion and expected to rise, suggesting its popularity is increasing.

Many shipowners are realising that by combining fuel homogenisers with targeted or specially blended fuel additives the compound effect of the benefits can lead to a significant reduction in fuel consumption and emissions, particularly black exhaust smoke and PM’s. This is a win-win by reducing fuel costs, and significantly improving the environmental impact of using readily available and cost-effective fossil fuels.

Taking the concept further, the combination of homogenisers with specific fuel additives (or stabilisers) and water to create a WiF (Water-in-Fuel) emulsion mix is gaining popularity and has been shown to be a very effective way of significantly reducing emissions, particularly NOx, while improving fuel efficiency. As with homogenisers and additives, there is also the additional payback in reduced maintenance in fuel pumps, injectors, and in the exhaust system.

Persuading marine engineers to blend 15-20% water into their fuel, when they have spent most of their careers trying to keep it out, can be a challenge, but it offers an effective way to improve combustion efficiency and reduce emissions. The main concerns are usually the potential of ‘free water’ in the fuel system which could cause significant damage to the engine.

However, the water in emulsion fuels is not present in free or bulk form but is finely dispersed in the fuel as tiny micro- to nano-sized droplets encapsulated in the fuel and are vaporised during combustion. The fine dispersion of water means that there is minimal risk of water coming into direct contact with metal surfaces in the fuel system or combustion chamber. The additives or stabilisers also help to maintain the homogenous mix and stop any stratification.

The key phenomena during the combustion process is the micro-explosion. The water encapsulated within the fuel droplet reaches its boiling point (100°C) much earlier than the surrounding oil, which requires significantly higher temperatures (typically 300-400°C). As the water vaporises, it generates steam within the droplet, with a rapid increase the internal pressure of the droplet, and pressure exceeds the surface tension holding the droplet together, resulting in the micro-explosion just before TDC (Top Dead Center), which can add to the pressure on the power stroke. The disintegration of the droplet into smaller particles also commonly referred to as the secondary atomisation, and as the many smaller droplets have a larger surface area-to-volume ratio, which enhances the fuel-air mixing, it makes it easier for the fuel to evaporate and combust more efficiently.

Future-proofing maritime operations

By integrating fuel homogenisers, fuel additives, and water-in-fuel emulsions, shipping companies can move closer to achieving substantial improvements in fuel efficiency and emissions reduction. Each technology addresses different aspects of fuel optimisation, creating a comprehensive system for improving operational performance and compliance with EU regulations.

The EU ETS and Fuel EU Maritime regulations impose stringent limits on CO₂ emissions and fuel carbon intensity. By adopting fuel homogenisers, additives and emulsions, ship operators can reduce CO₂ emissions through improved combustion efficiency. This directly reduces CO₂ emissions, allowing operators to earn carbon credits under the EU ETS. Water-in-fuel emulsions and fuel additives help operators stay within the carbon intensity limits set by the Fuel EU Maritime regulations.

By lowering emissions, operators can reduce their exposure to carbon taxes and potentially sell excess carbon credits.

The introduction of the EU ETS and Fuel EU Maritime regulations has placed the maritime industry under unprecedented pressure to reduce emissions and improve fuel efficiency. Technologies like fuel homogenisers, fuel additives, and water-in-fuel emulsions offer a comprehensive solution to these challenges by optimising fuel performance, reducing harmful emissions, and lowering compliance costs.

Investing in these technologies is essential for future-proofing maritime operations, achieving regulatory compliance, and contributing to the broader decarbonisation goals of the global shipping industry.