HVO: kind to the climate, good for mtu engines
Posted on June 29, 2023 by Lucie Maluck
Is that really true? Rolls-Royce engineers conducted a detailed investigation. The results were impressive.
“HVO is entirely compatible with diesel engines, is similar in its chemical composition to fossil diesel and is therefore a drop-in replacement for it.” That's the claim you'll find on the websites of fuel manufacturers. But is it true? Can Hydrogenerated Vegetable Oil – or HVO for short – a paraffinic fuel, be used to power mtu engines without any compromise to power delivery or service life?
The theoretical explanation is convincing: HVO is synthetic diesel – pure and simple. Unlike the fossil fuel, it does not contain pollutants such as aromatics or naphthenes – precisely the elements in conventional fossil diesel that generate particulate emissions.
The service life of engine components remains unchanged
After years of testing, that claim has been found to be true. “We can already give the green light for most mtu engines,” confirmed Arnd Lierhammer, HVO expert in the Rolls-Royce engineering team. He and his colleagues examined the components of mtu engines that had run at least 3,000 and in some cases up to 9,000 hours on HVO. The results were more than pleasing. “Used in the engine versions we have approved so far – which is in fact the majority of mtu engines – HVO does not shorten the service life of individual engine components,” said the HVO expert unequivocally. In fact, his estimate is even optimistic: “We're looking at whether some engine components run with HVO will actually have a lower maintenance requirement.”
HVO means lower fuel consumption
Fuel consumption does not increase when the engines are run on HVO. That surprised even the experts, since the energy density of HVO is actually lower than that of fossil diesel. “We were expecting fuel consumption to be 5% higher,” conceded Lierhammer. In actual fact, there is a slight decrease in mass-related fuel consumption with HVO. That is because HVO, since it does not contain pollutants, combusts more cleanly than fossil diesel, which suggests almost better utilization of the energy contained in the fuel.
Better CO2 balance; particulate and nitrogen oxide emmissions fall
Another issue that interested the Rolls-Royce engineers was pollutant emissions. Once again, there were pleasing findings. Engines powered by HVO produce significantly lower particulate emissions than those running on fossil diesel. “We're talking about reductions of over 40%,” said Lierhammer. That is explained by the absence of aromatics in HVO, which in fossil diesel are the cause of particulate emissions. Nitrogen oxide emissions are also up to 8% lower.
The local CO2 emissions generated by engines running on HVO are comparable to those produced by fossil diesel. However HVO is made from renewable raw materials which are not specially manufactured to make it. They consist of animal and vegetable waste and residue, for example fat for deep-frying. The plants used to produce these already extracted CO2 from the atmosphere while they were growing. That CO2 is returned to the atmosphere when the fuel is combusted in the diesel engine, making HVO almost neutral in terms of its carbon balance. The further 10% saving in CO2 that is needed to achieve full climate-neutrality is attributable to fuel production and transport i.e. to the upstream chain.
“We've examined engine components that have run a total of more than 120,000 hours on HVO. The conclusion we draw from those investigations is crystal clear: HVO can be used without hesitation in most mtu engines,” said Arnd Lierhammer with absolute conviction. His message is clear: “Tank HVO – it's your fast track to greater sustainability.”
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