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Science Matters by David Suzuki The automotive world has recently reached an interesting crossroads. On one hand, there's the rampant popularity of sport utility vehicles (SUVs). Virtually every car manufacturer on the planet now produces at least one version of these trucks – which are some of the heaviest, most inefficient passenger vehicles ever made. Yet at the same time, some of the most fuel-efficient cars ever mass-produced are also due to roll off the assembly lines this year. These cars use a combination of a small gasoline engine with an electric motor powered by a battery that never needs to be plugged in. A computer decides which motor to use to get the best fuel efficiency. This "hybrid" system reduces greenhouse gas emissions by 40 per cent and also greatly reduces the air pollutants that cause smog. Both Toyota and Honda will be selling these vehicles in Canada by this summer, and Ford isn't far behind. Most auto-makers are also working on hydrogen fuel cell-powered vehicles that could reduce emissions even more. Massive amounts of money have been invested in this technology and working prototypes of a variety of fuel cell vehicles were paraded around autoshows this year. Often dubbed "zero-emission" cars, these vehicles don't burn their fuel the way conventional internal combustion engines burn gasoline. Instead, they run on pure hydrogen, which they convert directly to electricity without combustion. The only thing coming out of the tailpipe is water vapour and heat. The fuel cell is considered the first viable alternative to the internal combustion engine, which we've used in cars for more than a century. Purely electric vehicles have been available for decades, but they've never become very popular because their batteries are heavy and need frequent recharging. Fuel cell vehicles, on the other hand, are on the verge of commercialization, with manufacturers keen on mass-producing them within five years. On the surface, fuel cell vehicles seem like an ideal solution to the problems that gasoline-fuelled cars cause, like greenhouse gas emissions and smog. However, pure hydrogen does not exist in nature. It's plentiful in fossil fuels and water, and can be removed from these compounds by breaking them down into their components. Unfortunately, that process can create greenhouse gases and other emissions. So instead of polluting from the tailpipe, fuel-cell vehicles could just push the problem upstream to where hydrogen is produced. Depending on the method of production, the emissions could stay virtually the same and only the location of their source would change. That hardly sounds like a solution. Hydrogen can be produced without any emissions, but only if it is made from electricity generated by renewable sources like solar and wind power. Unfortunately, these are not yet widely available on a commercial scale. The only way to find out which of the current methods of producing hydrogen creates the least emissions is to conduct a "full-cycle analysis," which considers the pollutants created at all levels of the fuel's production and consumption. A recent full-cycle analysis by the David Suzuki Foundation and the Alberta-based Pembina Institute for Appropriate Development found that the greatest reduction in greenhouse gas emissions could be achieved by stripping hydrogen from natural gas – a process called reforming. This would reduce emissions by nearly 70 per cent. Using gasoline to produce hydrogen, on the other hand, would reduce emissions by just 20 per cent – less than the reduction offered by the new hybrid vehicles. Making hydrogen from natural gas also has the added advantage of not requiring major infrastructure changes. Service stations on natural gas lines could create hydrogen on site and we could pump it directly into vehicles, just like we fill our gas tanks today. Fuel cell vehicles are indeed a promising technology, but if they are going to reduce air pollution and climate change, the hydrogen they use must be produced cleanly. To discuss this topic with others, visit the discussion forum at www.davidsuzuki.org. (Science Matters is a regular feature by writer, geneticist and television host David Suzuki.)

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