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Drop-in alternative fuels

Alternative drop-ins or alternative diesel fuels, defined here as fuels that are functionally equivalent to diesel fuel and are able to substitute diesel fuel with no or minimal infrastructure or engine changes. These included Gas-To-Liquid (GTL) and biofuels, such as Hydrotreated Vegetable Oil (HVO), Fatty Acid Methyl Esters (FAME), and Pyrolysis.

Much of the existing bunkering infrastructure on the Thames could be transitioned to biofuels or GTL with relatively minimal changes. However, some biofuels can be acidic, so require additional modifications to storage and engines to ensure their safety in use. Both GTL and HVO is already offered on the Thames.

The PLA has done a trial on one of our vessels, Kew, with two different types of alternative drop-ins fuels – GTL and HVO. During the trial, the exhaust gas was collected and analysed to evaluate the environmental benefits.  A post-trials engine inspection was also performed to appraise any unintentional consequences. The combination of the exhaust monitoring, engine inspection, and desk-top based greenhouse gas emissions helped the PLA to make an informed decision on switching from ultra low sulphur diesel to lower emissions fuel across our fleet.

FAQs related to our trial

Did the use of alternative diesel fuels cause any damage to the Kew’s engine?

No changes in the engine calibration were made prior the trial on Kew and no physical or visible operational issues, including no blockages and no signs of fuel breakdown, were experienced during the trials.The post-trials engine inspection also indicated no additional servicing was required and identified no significant wear and no signs of cylinder glazing, no signs of damage due to changing of combustion timing related to the higher cetane number, and reduced soot deposition on the piston crowns, valves and injector nozzles.

Did the use of alternative diesel fuels increase the fuel consumption rate on Kew?

No. The fuel consumption rate with ULSD, GTL, and HVO fuels were found not to be significantly different during the trial.

What are the environmental benefits of alternative diesel fuels?

Our exhaust gas monitoring demonstrated a reduction in nitrogen oxides (39-56% for GTL and 51-78% for HVO) and particulate matter (50-93% for GTL and 76-99% for HVO) emissions when operating with GTL and HVO relative to ULSD at all engine speeds.Using the UK government conversion factors, the use of HVO can reduce the greenhouse gas emissions associated with an organisation’s activities as the carbon dioxide emitted during combustion is deemed to have been offset by the absorption of carbon dioxide during growth of the biomass that forms the biofuel.

Read the full alternative diesel fuels report >>

Download the full alternative diesel fuels report >>

Read the alternative diesel fuels summary >>

How is the exhaust monitoring methodology compare with the legislative method for engine certification?

The exhaust monitoring reports pollutant level as a proportion of total exhaust gas volume while the legislative methods reporting of pollutant level on a per power out basis. The exhaust monitoring is used to assess the effect of a specific intervention on an in-service vessel and cannot be used for certification or checking regulatory compliance.

Page updated 2/2/2022