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How GPS Marine embraced environmental challenges for the win

By John Spencer, Director, GPS Marine

At GPS Marine we first became aware of the movement towards the maritime sector being encouraged to drastically improve its environmental performance in early 2019, as a result of attending a series of workshops organised by Port of London Authority pursuant to the launch of its clean air strategy.

As a business for which a significant part of its trade is moving goods by barge on the rivers Thames and Medway, the environmental benefits associated with water transport had long been an important marketing tool, and it came as something of a shock to be faced with the reality that we needed to up our game in order to be able to maintain the high ground in terms of the environmental benefits of transporting freight by water rather than by road (or rail). As with most challenges to the status quo, the important thing was to embrace the challenge and find a way to make it work for us.  

The Port of London Authority workshops in 2019 set out not only the authority’s aims and objectives, but also challenged vessel operators to join the journey and provided a significant amount of basic information about what was then technically possible to reduce emissions and environmental impacts resulting from the operation of vessels.  

Much of what was put forward as purportedly being possible to reduce emissions from vessels was impractical due to factors such as the size and types of our vessels, lack of supporting infrastructure, the nature of our operations and, not least, the costs involved in implementing the technologies.  

This applied to options such as the installation of exhaust gas scrubbers, electrification of our vessels, conversion to hybrid technology and, initially, the adoption of alternative fuels, with LNG, LPG, ammonia, hydrogen and biodiesel being put forward as options. The remaining options put forward were selective and passive catalytic converters (SCR and CR), and diesel particulate filters (DPF). 


We decided to investigate installing catalytic converters and diesel particulate filters as well as the possibility of using biodiesel in place of marine gas oil. Although it soon became apparent that the capital costs associated with retrofitting post-combustion technology across the fleet would be extremely challenging, we went ahead and ordered an SCR system for one of our single-engine 1200 BHP tugs, and subsequently we acquired catalytic reducers for another 1200 BHP tug; with two 600 BHP main engines, the capital cost of the systems was £125,000 for the SCR system and £100,000 in total for the two catalytic converters. We also investigated installing DPFs in these vessels, but it was immediately apparent that there was insufficient space in the engine rooms for the catalytic converter systems and DPFs. 

Whilst waiting for the SCR system to be delivered we began investigating biodiesel because we were aware that while the SCR and CR systems would reduce NOx emissions, they could do nothing to reduce carbon emissions. We began by speaking to inland ship and tug operators in Europe who we knew had been using biodiesel in their vessels, and we were immediately made aware of numerous serious problems that they had all suffered whilst using biodiesel, such as a propensity for microbial contamination, filter clogging caused by the formation of carboxylic acid compounds, a tendency for the methyl esters in biodiesel to absorb moisture from the air, a tendency for the fuel to stratify, short shelf life, poor cold flow characteristics and solvent-like properties that can cause the failure of nitrile seals and pipes.  

We also learned that burning FAME in diesel engines often resulted in higher NOx emissions compared to when burning fossil diesel or fossil MGO. It was only through further investigation that we came to understand that biodiesel is a generic term that covers both fatty acid methyl ester (FAME) and hydro treated vegetable oil (HVO). Effectively these are first-generation and second-generation forms of biodiesel. 


Upon making investigations into the differences between HVO and FAME, it became clear that HVO was a form of biodiesel that suffered from none of the problems associated with the first-generation biodiesel known as FAME. We learned that at a molecular level, HVO molecules are indistinguishable from molecules of fossil GTL (gas to liquid) fuel, a top-of-the-range diesel like fossil fuel. Both GTL and HVO contain no aromatic molecules, but instead are comprised entirely of long chain paraffinic molecules, causing these fuels to have a higher cetane number than fossil diesel and so to burn much more readily and much more cleanly.  

HVO has the added advantages of not being hygroscopic, not supporting microbial growth, having an almost infinite shelf life, and not affecting nitrile seals and pipes. We learned that HVO is a direct drop-in replacement for fossil diesel and MGO, and that when burning HVO particulates and NOx components of diesel exhaust are significantly reduced, the SOx component is eliminated completely. Most importantly, however, is the fact that the carbon contained in HVO molecules was only removed from the atmosphere very recently (ie when the plant from which the HVO was produced was growing).  

Therefore, when burning HVO instead of fossil fuels, we would not be adding to the net carbon in the atmosphere; effectively we would only be recycling carbon. The fact that Neste produced HVO is warranted to contain 0% palm oil and is produced from waste cooking oils was a further incentive to trial HVO in one of our vessels.  


In summer 2020, the decision was taken to trial the use of HVO in one of our tugs, the GPS Vincia.  

This tug had been the subject of a complete overhaul, including the complete rebuilding of her main engine, which had included fitting a new crankshaft, all new crankshaft bearings, several new cylinder liners, pistons and cylinder heads, and this tug did not trade between the completion of the overhaul work and the start of the HVO trial.  

The trial of HVO using the GPS Vincia was commenced in August 2020, and very soon the decision was taken to try to use HVO in the entire fleet of tugs operating on the Thames.  

Using HVO in place of fossil MGO delivered all the benefits of the post-combustion technologies without any of the capital cost of the equipment, and without any of the huge costs associated with renewing exhaust systems in stainless steel, and completely rearranging the engine rooms of existing tugs to accommodate very large catalytic converters, Ad-Blue tanks and the electronics necessary to support an SCR type system.  


We had learned, however, from the trial with the GPS Vincia that loading fuel from trucks was a logistical nightmare. This was primarily because of the limited number of wharves that were prepared to allow truck to tug bunkering to take place, and the difficulty of ensuring that both tug and truck were at the same place at the same time.  

In order to overcome this problem, a small self-propelled tank barge was purchased and completely refurbished to enable it to load HVO at the Stolthaven oil terminal and transport and deliver it to our fleet of tugs as and when required on the rivers Thames and Medway. When this vessel entered service in spring 2021, it was immediately possible to change the entire River Thames tug fleet to exclusively use HVO, and this was done during March and April. 

Since changing the fleet to HVO, we have not noticed any increase in engine repair and maintenance costs. The fuel has been used in small high-speed diesels, high-speed mechanical and electronic injection engines, as well as in medium-speed four-stroke and two-stroke engines. Fuel consumption has either been unchanged or slightly reduced across the fleet.  

The only challenge that we have faced following the change from MGO to HVO has been that clients have been unwilling to accept any increases in cost arising from our use of this low-carbon alternative to fossil MGO.   

Although it was possible to absorb the increased costs associated with using HVO in 2021 and 2022, the recent increases in interest rates and cost increases more generally, which have been the result of high inflation, combined with a reduction in the volume of trade following the pandemic and the trend towards working from home, have all combined to make continuing to bear the full burden of increased costs associated with using low carbon fuel ourselves ever more difficult to justify and sustain. 

Published On: 08/02/2024 14:00:00


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