Environmental Study Urges 'Caution' When Replacing Clean Diesel Trucks With Natural Gas Vehicles

June 2, 2015

A new study published by the Diesel Technology Forum, a nonprofit aimed at raising awareness about the importance of diesel engines, fuel and technology, said that switching from diesel to natural gas in heavy-duty trucks could worsen and accelerate negative climate impacts unless methane leakage can be lowered. 

The study also outlined the need for increased data and new policies to lower methane leakage in order for natural gas heavy-duty trucks to have a possible environmental advantage over new and future clean diesel trucks.

The study – “Influence of Methane Emissions and Vehicle Efficiency on the Climate Implications of Heavy-Duty Natural Gas Trucks” - was conducted by scientists at the Environmental Defense Fund (EDF) and Columbia University’s Lenfest Center for Renewable Energy and published today in the journal Environmental Science and Technology.

The report concludes:

“Our results show that under our reference case assumptions, reductions in CH4  (methane) losses to the atmosphere are needed to ensure net climate benefits on all time frames when switching from diesel to natural gas fuel in the heavy-duty sector.

By combining such reductions with engine efficiency improvements for natural gas HDTs (heavy duty trucks), it may be possible to realize substantial environmental benefits. However, until better data is available on the magnitude of CH4 (methane) loss, especially for in-use emissions, the precise climate impacts of a switch remain uncertain in this sector. Therefore, policymakers wishing to address climate change should use caution before promoting fuel switching to natural gas.

Furthermore, diesel engine efficiency is likely to improve in the future (particularly as a result of current and upcoming HDT standards), and if this occurs without similar improvements in natural gas engine efficiency, a growing spread between these engines could worsen the impacts of diesel to natural gas fuel switching. Fleet owners and policymakers should continue to evaluate data on well-to-wheels CH4 (methane) losses and HDT efficiencies and work to ensure that the potential climate benefits of fuel switching are realized.”