May 16, 2007
The gist of a recent press release regarding research into alternative fuels for reducing the environmental impact of transport and helping us head towards a sustainable transport system said that there is basically no single alternative fuel that could provide all the answers. The research in question, published in the International Journal of Alternative Propulsion drew up a league table of alternative fuels that placed petrol (gasoline) and diesel at the bottom in terms of their negative environmental impact, closely followed by hybrid liquid gas driven vehicles. Surprisingly, at the top of the league table was the use of hydrogen fuel cells running on hydrogen obtained from converted methane. Surprising because one would assume that the use of methane, or natural gas, would have such an environmental impact as to push it down the league table and moreover be unsustainable.
The study’s authors, Karl Høyer of Oslo University College, Norway and Erling Holden of the Western Norway Research Institute, do concede, as is mentioned in the press release, that there is no alternative fuel that is 100% sustainable and has a zero carbon footprint. That is perhaps inevitable. However, there is research being undertaken that would suggest that natural gas is not the limited fossil fuel we might think. Indeed, there are vast reserves that are apparently produced by bacterial activity that might feed the league-topping fuel cells mentioned in Høyer and Holden’s paper.
One commentator, John Zerbe of the USDA Forest Service, in Madison, Wisconsin, was not convinced that the Høyer and Holden league table was valid at all. This is what he had to say on the matter:
“I think the most significant conclusion from the Norwegian scientists’ work is that currently there is no consensus regarding sustainable transport development. They obviously considered the relative importance of energy use, carbon dioxide emissions, and nitrogen oxide pollution differently than I would have. There is no way that I would rank fuel cell powered vehicles using hydrogen gas obtained from natural gas methane at the head of the list.”
Granted, fuel cell powered vehicles should be efficient. Chevron has stations that dispense hydrogen made, mostly, from natural gas. So, energy use with the fuel cell vehicle powered by hydrogen should be good and there is probably no nitrogen oxide pollution.
However, until Chevron has some experience, it is hard to know what the hang-ups will be. Use of fossil natural gas will certainly be bad for global warming. It is already conceded that hydrogen isn’t amenable to long distance transportation. So Chevron makes hydrogen close to where it is being used. Imagine the difficulties in filling a fuel tank on a vehicle with 5000 psi hydrogen. It seems impossible that they could prevent all leaks, and hydrogen at 5000 psi is probably more prone to explosion than gasoline or diesel at atmospheric pressure.”
Zerbe suggests that the best well-to-wheel evaluation would have to take into account a complete lifecycle analysis. Energy use would certainly be important in such an analysis, but a lifecycle analysis could be weighted so that generally more acceptable limitations, such as the unsustainable nature of fossil fuel natural gas is considered a more negative factor.