However, most participants also believe that alternatively-fuelled trucks will decline without further financial support to bridge the gap to larger-scale commercialisation of the associated technologies.
Those are among key findings from the two-year £23.4 million LCTT, which concluded last year but has only just seen the official report published.
The new report shows that economic performance of the dual-fuel diesel and L/CNG (liquefied/compressed natural gas) and gas trucks varied widely according to fleet operations and choice of technology.
The main contributors to disappointing results were the reducing cost of diesel throughout the trial period and the “large engine efficiency loss apparent in some dual-fuel systems”.
A gas fuel price of 20p below the diesel price was shown to allow average gas trucks (across dedicated and dual-fuel) to achieve payback within three to four years – suggesting that this differential is critical to the uptake of such alternative fuels.
However, the report finds that “the current lack of a clear business case” is a major implementation barrier to fleets, vehicle/system suppliers and L/CNG station suppliers.
Turning to environmental performance and, in particular, CO2 emissions, the report finds variable performance across the trialled technologies.
The best performing dual-fuel systems offered CO2 savings of up 10% TTW (tank to wheel) and 6% WTW (well to wheel), with the biofuel blend having a significant impact.
That said, dedicated gas vehicles and some of the diesel/gas dual-fuel systems operating only on L/CNG showed an increase in CO2 emissions against their diesel comparator vehicles.
The only outstanding success concerned the dual-fuel diesel/UCO (used cooking oil) trucks, which delivered an 86% TTW and 84% WTW emission saving.
The report also reveals that dedicated gas trucks running on a 15% biomethane blend achieved real-world emission savings of 11% TTW and 10% WTW.
The big problem, however, is methane slip – unburnt emissions from the tailpipe – with the report indicating that “relatively large amounts” of methane were present in the exhaust gas stream of dual fuel diesel/gas vehicles (not the dedicated gas trucks designed from the ground up to burn methane).
Methane slip meant that the dual-fuel trucks affected ran with higher total greenhouse gas emissions than conventional diesel trucks, because of the much higher GWP (global warming potential of methane than CO2.
The government’s report says this highlights the need for a better evaluation of the total GHG and air quality effects of different technologies under real-world driving conditions “before policy is set in favour of certain technologies”.
Policies should also take into account how the environmental impact of retro-fit technologies (which are sold without evidence of Euro emissions compliance) are managed and enforced, states the report.
As for overall environmental performance, two of the LCTT consortia provided results of independent air quality emissions testing and these indicate that performance was generally improved by using dual-fuel diesel and gas systems.
One system showed reductions in all air quality pollutants (CO, NO, NO2, PM, NOx) while the other indicated an emissions reduction in some pollutants, but set against increases in CO and with variable PM (particulate matter) performance.