Lewis M. Fulton, co-director of the NextSTEPS Research Program at ITS-Davis, is guest editor of a special section of the March issue of Energy Policy, “Decades of Diesel,” with Lee J. Schipper, a respected transportation energy policy researcher who passed away in August 2011.
Fulton wrote the introduction and finished a paper that he and longtime friend and colleague Schipper had started together, their third in a series.
“Dazzled by Diesel? The Impact on Carbon Dioxide Emissions of the Shift to Diesels in Europe through 2009,” finds that while diesels have gained substantial market share in European countries, they have delivered very little net emissions reductions or energy savings.
“I felt compelled to finish the important work that Lee started and get it published to make sure that this information got out,” Fulton said. Diesels are a big topic in Europe, where they have captured roughly 55 percent of the new car market.
The numbers are telling. A diesel version of any given car may have as much as 35 percent lower fuel use per kilometer and up to 25 percent lower CO2 emissions than the gasoline model. But the story is not so simple, Fulton explains.
“Diesel cars have certainly improved technologically and are more efficient on a matched pairs basis,” he says. ‘Matched pairs’ means the same or similar model with diesel versus gasoline engine.
“But people are choosing bigger, more powerful diesel cars and driving them farther,” he continues, perhaps because of the cheaper cost of fuel for diesels – what’s known as a rebound effect. “The result is we’re seeing very little net energy or CO2 benefit from the shift to diesels.”
As a result, on average, new diesels bought in Europe in 2009 had only 2 percent lower CO2 emissions than gasoline cars, a smaller advantage than in 1995.
The story is complicated by a so-called self-selection effect, where people buy larger diesels and drive them farther because they already had plans to drive a larger car or drive farther. In this case, which is not a rebound effect, the choice of diesel saves fuel.
“But separating these effects is very difficult,” Fulton acknowledges.
The results point to a need to look beyond technology and examine consumer purchase and driving behavior, he said.
The special section includes six other papers, five of which examine trends in various EU countries and one on diesel use in the United States.
“Together these papers provide a wealth of data and analysis on the status and history of dieselization – in the EU and here,” Fulton said.
• One study found that Belgium had the highest diesel market share in Europe in 2009 and concludes that the country’s fuel tax subsidy policies, which favor diesel over gasoline, have led to net social costs and lost tax revenue to government.
• Another paper concludes that Swedes may buy diesels not so much to lower fuels costs but rather to cut CO2 emissions.
• One paper argues for stringent emissions standards and enforcement so that the black carbon (a greenhouse gas) emitted from diesel exhaust doesn’t undermine the climate benefit from efficiency gains.
“It’s been great fun to read all the excellent work. The volume explores many complex questions and contributes to this interesting and important topic,” Fulton said.
Schipper, Lee and Lewis Fulton (2013) Dazzled by Diesel? The Impact on Carbon Dioxide Emissions of the Shift to Diesels in Europe through 2009. Energy Policy in press
Fulton, Lewis (2013) Introduction to Energy Policy special issue “Decades of Diesel”. Energy Policy 54, 1 – 2
Schipper, Lee and Lewis Fulton (2010) Disappointed by Diesel? Impact of Shift to Diesels in Europe through 2006. Transportation Research Record: Journal of the Transportation Research Board 2139, 1 – 10
Schipper, Lee, Céline Marie-Lilliu, Lewis Fulton (2002) Diesels in Europe: Analysis of Characteristics, Usage Patterns, Energy Savings and Co₂ Emission Implications. Journal of Transport Economics and Policy 36 (2), 305 – 340