Decarbonizing Your Ride for a More Stable Climate: Scientists Measure the Climate Benefits of Alternatives to Petroleum Fuels

(National Science Foundation) Transportation produces a sizable amount of greenhouse gas emissions, largely by using petroleum to power internal combustion engines. Alternatives –- for example, organic materials such as grasses to produce fuels or electricity –- could avoid petroleum use altogether.

Now, a team of scientists at the Great Lakes Bioenergy Research Center, a partnership between Michigan State University and the University of Wisconsin–Madison, has examined biofuel crops grown in Michigan and Wisconsin to test their potential to mitigate global warming when used for ethanol or electricity. The paper is published in Environmental Science and Technology.

In a field experiment at the National Science Foundation's Kellogg Biological Station Long-Term Ecological Research site and the University of Wisconsin’s Arlington Research Station, the team measured the potential for biomass crops to mitigate climate change by powering ethanol or electric vehicles.

"This study is an important step forward in what has been a long-running debate about the potential benefits of biofuels," said John Schade, a program director in NSF's Division of Environmental Biology. "The results highlight how long-term fundamental research in ecosystem science can benefit society in sometimes unexpected ways."

Before this research, scientists lacked evidence to say how much and by which means biofuels should reduce carbon emissions caused by petroleum-burning vehicles, according to Phil Robertson of MSU, senior author of the study.

"Despite being grown on very different soils and with natural climate variability, all crops we tested had a significant mitigation capacity," said lead author Ilya Gelfand of Ben Gurion University of the Negev, Israel. READ MORE

Excerpt from Environment Science and Technology: Climate mitigation scenarios limiting global temperature increases to 1.5 °C rely on decarbonizing vehicle transport with bioenergy production plus carbon capture and storage (BECCS), but climate impacts for producing different bioenergy feedstocks have not been directly compared experimentally or for ethanol vs electric light-duty vehicles.

A field experiment at two Midwest U.S. sites on contrasting soils revealed that feedstock yields of seven potential bioenergy cropping systems varied substantially within sites but little between. Bioenergy produced per hectare reflected yields: miscanthus > poplar > switchgrass > native grasses ≈ maize stover (residue) > restored prairie ≈ early successional.

Greenhouse gas emission intensities for ethanol vehicles ranged from 20 to −179 g CO₂e MJ^–1: maize stover ≫ miscanthus ≈ switchgrass ≈ native grasses ≈ poplar > early successional ≥ restored prairie; direct climate benefits ranged from ∼80% (stover) to 290% (restored prairie) reductions in CO₂e compared to petroleum and were similar for electric vehicles.

With carbon capture and storage (CCS), reductions in emission intensities ranged from 204% (stover) to 416% (restored prairie) for ethanol vehicles and from 329 to 558% for electric vehicles, declining 27 and 15%, respectively, once soil carbon equilibrates within several decades of establishment.

Extrapolation based on expected U.S. transportation energy use suggests that, once CCS potential is maximized with CO₂ pipeline infrastructure, negative emissions from bioenergy with CCS for light-duty electric vehicles could capture >900 Tg CO₂e year^–1 in the U.S. In the future, as other renewable electricity sources become more important, electricity production from biomass would offset less fossil fuel electricity, and the advantage of electric over ethanol vehicles would decrease proportionately. READ MORE

Excerpt from Biofuels Digest: The study attacks the idea that “electric vehicles could increase emissions”, suggesting that “we’ve seen a lot of discussion about this recently”. But, how much is there, really.

People who question the value of electric vehicles almost never say that they increase emissions, per se. What they do say is:

1. Plug-in electric vehicles reduce emissions far less than many people think they do. The myth really is of a zero-emission vehicle, since electric cars simply emit their pollution elsewhere, instead of through the tailpipe.

2. The push for plug-in electric vehicles almost invariably trades on this idea of sharply reduced emissions, when there are more conventional technologies that cost a lot less, involve almost no change in infrastructure or the purchase of a new car, and reduce emissions more than many electric vehicles do.

3. A plug-in electric vehicle is only as green as its grid, and there are countries with such a dependence on coal that a shift to electric vehicle adoption could, in fact, slow efforts to reverse climate change.

4. A rapid conversion to plug-in electric vehicles would require a substantial increase in a) fossil electricity generation or b) intermittent renewable sources such as solar or wind — a slower conversion allows for a safer build-out of grid resources.

Instead of tackling the big issues, the study authors invent a non-issue and report that, “The new research from the universities of Exeter, Nijmegen – in The Netherlands – and Cambridge shows that in 95% of the world, driving an electric car is better for the climate than a petrol car.”

Of course, almost no one drives a pure “petrol car” any more. New renewable fuels have far lower levels of emissions, and can in fact be carbon negative. Trucks operating on renewable diesel have typical emissions 70 percent lower than those operating on fossil fuels. READ MORE