That’s among the findings of a study carried out for the Department for Transport by the Low Carbon Vehicle Partnership (LowCVP), supported by the LowCVP’s newly formed commercial vehicle working group.
The report recommends that the government should continue to support the development of gas vehicle infrastructure and gas-powered vehicles, particularly dedicated gas, while increasing the supply of low carbon/renewable methane as a sustainable fuel to realise these benefits.
An earlier study, in 2012, recommended increasing the use of methane and, ultimately, biomethane as a fuel for HGV operations. Last year, LowCVP was asked to test the latest methane trucks to assess the performance of Euro 6 vehicles and identify the GHG impacts.
LowCVP’s managing director Andy Eastlake says: “This work shows that powering heavy vehicles with natural gas – and particularly biomethane – does have the potential to make a significant contribution to cutting emissions from this hard-to-tackle sector of road transport.”
Key findings from the latest LowCVP study include:
- The Euro 6 dedicated gas vehicles tested exhibit very low levels of methane slip, typically adding less than 0.5% to the overall GHG impact compared with the CO2-only case.
- The only aftermarket dual-fuel system tested (converting a Euro 6 diesel truck to diesel and natural gas operation) exhibited high levels of methane slip – sufficient to increase GHG emissions by 20%.
- The aftermarket dual-fuel (diesel/CNG) conversion of a Euro 5 vehicle exhibited high levels of methane slip, enough to increase GHG emissions by 20-30%.
- The research has not yet been able to disprove the hypothesis that Euro 6 diesel trucks typically emit quite high levels of nitrous oxide (N2O). Further evidence is needed to quantify this.
- Euro 6 dedicated gas vehicles emit lower levels of NOx emissions than diesel counterparts. The same is true if only NO2 emissions are considered. Emissions of carbon monoxide and hydrocarbons, however, were typically higher.
Stakeholders have indicated that effective catalysis of methane is possible, as is more effective in-cylinder methane combustion. Two current Innovate UK/OLEV-funded projects are developing new retrofit dual-fuel systems, finishing in 2019. At least one OEM is developing its own dual fuel (diesel-methane) system, with availability anticipated towards the end of 2017.
The testing indicates that the transition to Euro 6 has, for diesel HGVs, been effective in cutting overall NOx emissions by over 98% when compared to Euro 5 vehicles. A further move to Euro 6 dedicated gas increases the magnitude of that reduction in NOx emissions to at least 99%.
The study also suggested that there is potential for GHG savings from dual-fuel diesel/LPG conversions.
The LowCVP has increased its activities in the commercial vehicle sector in recent months with the re-establishment of its commercial vehicle working group: click the link below for more on this.