LR’s Yildiz Williams Lead Marine Consultant of Maritime Performance Services looks at the potential of biofuels and biofuel blends.
As the industry looks to prove the technical and commercial viability of fuels like ammonia, hydrogen and methanol, and at the same time ensure the safe application of electro-fuels, LR’s Yildiz Williams Lead Marine Consultant of Maritime Performance Services look at the potential of biofuels and biofuel blends. Despite the current IMO impediments to their use, can these increasingly available fuels play a vital role in helping shipping move faster to a carbon-neutral future?
Biofuels as a term covers a wide range of fuel types produced from an extensive array of biomass source materials and production processes. Biofuels already play a minor role as a maritime fuel, either as a direct replacement of existing petroleum derived distillate or residual fuels, or as a blend component with such fuels. The key point, unlike most of the other currently projected future marine fuels, is that these biofuels can generally be used in existing engines without the need for modifications and within the existing marine fuel supply infrastructure and onboard storage, handling and treatment systems.
Furthermore, the CO2 emitted is derived from terrestrial carbon, not from fossil carbon which has otherwise been sequestrated in the earth’s crust for millions of years1 . In the future, biofuels have the potential to be used as the pilot fuel necessary for zero carbon fuels such as hydrogen, ammonia, methanol or certain electro-fuels where those are to be used in combustion engines. Indeed as a recent IEA study indicated, the use of biofuels, in all their various forms, are projected to increase from their current low baseline to some 10% of the total by 2030 then to 20% by 2050 as part of the maritime industry’s move to a multiple fuel type future.
But despite biofuels displacing fossil derived carbon emissions there is the issue over the nitrogen oxides (collectively known as NOx) exhaust gas component. This is a concern, as NOx are a significant pollutant, with impacts on people’s health and environment. NOx have been the focus of particularly tight controls in, for example, automotive applications where it has been found that there can be increases in NOx emissions with the use of biofuels; but then automotive engines are fundamentally different in virtually every respect to marine type engines.
The regulatory treatment under MARPOL Annex VI of biofuels is different to that of traditional petroleum derived marine fuels. NOx emissions from non-emergency only use marine diesel engines over 130 kW are controlled by regulation 13 of Annex VI. This requires marine diesel engines to demonstrate compliance with the relevant NOx emissions standards under specified reference conditions (fuel type used – a petroleum derived distillate, ambient conditions, engine operating conditions etc) in accordance with the IMO’s NOx Technical Code. This is done by ‘one-off’ testing at the engine builder’s test bed of a few selected representative engines – thereafter all engines as represented by the respective tested engine are free to use any petroleum derived fuel oil without further emission testing.
In contrast, for fuels from non-petroleum sources, which of course includes a wider range of fuel types other than just biofuels, regulation 184.108.40.206 of Annex VI requires that each engine is instead required to meet the relevant regulation 13 limit value when actually operating on that fuel, in this case the particular biofuel, as used. A further complicating factor is that under the existing regulation 18 requirements of Annex VI, it is the fuel supplier who required to issue a declaration (as part of the bunker delivery note which is mandated for every consignment of fuel supplied to a ship) in which they are to state that the biofuel supplied is complied with this NOx restriction. A requirement which is totally outside their capability to confirm.
The effect of this difference in regulatory treatment is that currently the use of biofuels at sea are generally under trial exemptions as provided for under regulation 3.2 of MARPOL Annex VI. Those trials either being simply to assess the usability of particular biofuels or biofuel blends or more detailed trials performed by or on behalf of the shipowner, under which the NOx emissions are also assessed. However, onboard exhaust emission trials can never replicate test bed testing, as recognised by IMO. Furthermore, the need to carry out sea trials defeats the goal of creating a ‘drop-in’ fuel. The actual factors which affect NOx performance are not just fuel related. Other factors include biofuel sourcing and processing; the engine design and operating settings together with load and operating conditions which all play a part. If biofuel uptake is to grow, the shipping industry and the IMO must use the experience from those trials that have been undertaken to find a standardised, repeatable way of using biofuels that is realistic and does not add to uncertainty or administrative burden.
So, what have we learned from biofuels trials so far?
Lloyd’s Register (LR’s) Maritime Performance Services team undertakes to support shipowners undertaking sea trials of new and in-development technologies to establish performance, safety and compliance with applicable regulations. In the case of biofuels, we have now carried out several projects and trials, which encompass:
- Development of a detailed project delivery plan to capture the required exhaust emissions and other necessary data from the use of multiple fuel blends over an extended period of sea operations.
- Trial support, including obtaining flag state exemptions and procurement of exhaust emission analysis equipment and assessment of existing capabilities in terms of measurement of engine power and individual engine fuel consumption rates.
- Carrying out risk assessment for safe operation on the biofuel or biofuel blend to be used.
- Direction and remote assistance of exhaust emission trials, a task complicated by the Covid-19 pandemic having precluded the ‘hands-on’ support that may otherwise have been provided.
- Calculation and reporting of mass basis NOx and other exhaust emission rates from the raw data as captured
- Trial evaluation reports covering the findings and context under which those have been obtained.
In summary we are now able to draw some initial overall findings for the biofuels and biofuel blends trialled to date:
- A typical one engine / one fuel trial programme takes around one day to perform, not counting the necessary preparation time to get the required fuel into the engine’s service system. During that day the ship’s engineers need to be totally focussed on the trial programme and therefore not available for other duties. The need to operate across the load range in order to determine the NOx emission value precludes main engine trials being undertaken in voyage controlled or other high traffic areas.
- Weather or other factors may prevent a planned trial from being undertaken as intended.
- NOx emission values are generally within allowable limits, subject to experimental tolerances and comparable to those when using conventional petroleum derived residual type fuels.
- NOx emissions tend to be more increased at the lower loads with much less effect, or indeed improvements, at the normal operating loads.
- Carbon monoxide (CO) emissions, as an indicator of incomplete combustion, generally significantly reduced across the load range.
- Tank to wake CO2 emissions per tonne of fuel are decreased, typically between 2.5% and 6.0%, due to the lower carbon content.
- Tank to wake CO2 emissions per unit of energy content (kg/GJ) are generally found to be comparable with those from petroleum fuels due to the respective energy contents.
- Specific fuel consumption tends to be increased by less than that which would be indicated from the energy content of the fuels indicating better combustion performance i.e. fuel efficiency.
- Engine settings did not need to be adjusted so these biofuels or biofuel blends can be used as a direct replacements (or ‘drop-ins’), for conventional petroleum derived fuels.
- In general ships did not have any significant operational problems with storage, handling, treatment and usage onboard.
So far, so good. But inevitably there are challenges and limitations. A lot depends on the specific situation in which the fuel is being used and the multitude of influencing factors, so the results of a limited number of trials do not provide the confidence to generalise at this point.
The current regulatory regime is geared to carrying out bespoke trials as required, but it does not provide a long-term scalable solution. Also, it is important to note that direct exhaust emissions monitoring on the existing bases is unrealistic for ships operating in commercial conditions due to the operational uncertainty which results, additional costs and operational overheads. Paradoxically the existing regulation 18 requirements of MARPOL Annex VI actually works to favour petroleum over non-petroleum derived fuels.
More broadly, it is of course crucial to also consider the complete fuel supply chain. Emissions when burning such fuels onboard is part of the picture, but the environmental and social impact of feedstocks, fuel production, refining and distribution to ports must also be considered to understand the full impact of using such fuels. The current IMO regulations only consider operational (i.e. tank to wake) emissions, whilst the true impact of a fuel can only be ascertained through full lifecycle (or well to wake) analysis.
The work of the industry in emissions testing of biofuels so far has been an extremely useful learning exercise, not just for NOx compliance but also when considering CO2 emissions, but primarily just how difficult such trials are to undertake. We have established that biofuels have potential to have a small but beneficial impact on tank to wake CO2 emissions that can be immediately implemented. Now we need to address the wider environmental questions, including:
- Will biofuels be available at the scales needed for the shipping industry and other hard-to abate sectors that will need access to this?
- Is there enough sustainable biomass feedstock?
- Should CO2 be distinguished as coming from fossil or non-fossil carbon?
- Are the lifecycle GHG emissions (considering all factors, including indirect land use change) better than the fuels they are looking to replace?
- Are there any other unintended consequences?
The Lloyd’s Register Maritime Decarbonisation Hub are working on practical solutions to these and many other questions related to neutral carbon shipping.
1. Existing IMO regulations including The Energy Efficiency Design Index (EEDI) and Fuel Oil Data Collection System (DCS) do not take this into account.