Question to the Department for Transport:

To ask the Secretary of State for Transport, what comparative assessment he has made of the effect on the environment of vehicles using (a) diesel and (b) liquefied petroleum gas.

The Department for Transport assesses a number of different fuels in terms of a range of environmental impacts including air quality and greenhouse gas emissions. A number of initiatives are underway to encourage cleaner, lower carbon fuels.

The Renewable Transport Fuel Obligation was amended to increase rewards for suppliers of biopropane from April 2015, following a consultation which considered the potential benefits of alternative fuels, including biopropane, in delivering greenhouse gas savings. Biopropane is the term commonly used to describe liquid petroleum gas (LPG) derived from production processes that use biomass as the feedstock.

The Department for Transport and Low Carbon Vehicle Partnership also established a Transport Energy Task Force which considered the potential of Liquefied Petroleum Gas (LPG) in meeting our greenhouse gas reduction targets, alongside other alternative fuels, last year.

While no formal assessment of the air quality impact of LPG has been made, DfT and Defra officials met with representatives of the LPG industry during the consultation on the UK Air Quality Plans in 2015. Industry data shows that retrofitting older diesel cars and vans to run on LPG can reduce emissions of NOx (oxides of nitrogen) and particulate matter whilst producing CO2 (carbon dioxide) emissions between those of equivalent diesel and petrol engines.

Birmingham City Council were awarded £500,000 to enable the conversion of older black cabs from diesel to LPG as part of the 2014 Clean Vehicle Technology Fund (CVTF) grant scheme. As part of this funding, emissions will be measured before and after conversion.

As part of the Department’s Heavy Goods Vehicle emissions testing programme, the Low Carbon Vehicle Partnership is testing a dual fuel (diesel / LPG) retrofit conversion to a Euro VI truck, as well as gas and diesel comparators. Vehicle tests are currently underway and we expect to publish the results later this year. On 30th June, the Department launched an HGV accreditation scheme for retrofit technology to enable equipment manufacturers or vehicle operators to conduct robust, repeatable and reliable tests to validate the impact on fuel consumption and emissions under a range of operating conditions.