Buses more carbon-hungry than planes, says research

Diesel buses running during off-peak periods are more carbon-consuming than airplanes on a per-passenger basis, according to a new report published in Environmental Research Letters.

The paper, entitled 'Environmental assessment of passenger transportation should include infrastructure and supply chains' was produced by researchers at UC Berkeley.

Traditional methods for assessing carbon emissions from transport tend to focus on emissions at the tailpipe, they said, which can lead to inaccurate results that inform policies such as CAFE standards. Instead, they advocate a more holistic approach by using a lifecycle analysis (LCA) that takes more aspects of transportation into account.

The LCA examines not just the operational aspects of transportation, but also takes into account inactive operation, including idling time in cars, taxiing in airplanes, and the use of lights and HVAC systems in trains. It also looks at the infrastructure needed to support a mode of transportation, and the production of fuel to power the vehicles.

"For example, the construction of an airport runway requires direct energy to transport and place the concrete, and indirect energy to extract and process the raw materials," said the researchers.

When all aspects of the LCA are combined, off-peak diesel buses by far exceeded other modes of transport in both energy consumption and greenhouse gas production.

The disparity between off-peak and on-peak buses was significant. On-peak buses were the most economic on a per-passenger basis, in both energy consumption and fuel consumption, highlighting the importance of rider occupancy in the findings.

Conventional gasoline pickups, SUVs and sedans were the second, third, and fourth-most energy-hungry and greenhouse gas-emitting modes of transport. They were more energy-hungry and greenhouse gas-emitting than small, medium and large airplanes.