The idea bank: California 'GOLD' RUSH

Automakers often modify existing vehicles to meet PZEV requirements. Typically, modifications include the addition of an electric air pump injecting air into the exhaust manifold for several seconds after a vehicle cold starts. Also, a PZEV vehicle will generally have a redesigned catalytic converter that is located closer to the engine and contains additional precious metals – platinum, palladium and rhodium. Automakers "will have to sell ZEVs to consumers at some point," Anna Gromis, an air pollution specialist for the California Air Resources Board says. "It may not happen until they determine warranty requirements and durability. It's a goal we're working toward. Soon the requirement will get so big it will make sense to get out of the demo phase."

As the demands on vehicle emissions systems continue to rise, manufacturers are seeking more efficient or economical ways of meeting these requirements. Honda spokesman Chris Martin explains, "Efforts are being made to reduce the amount of precious metals in catalytic converters. We need to clean up emissions to higher levels but we want to do that with fewer precious metals." Martin notes that most catalytic converters today contain platinum — and because that is also a key ingredient in fuel cells, the price for it is very high. "You'll see companies, including Honda, trying to reduce the amount of metals used in their catalytic converters."

Platinum isn't easy to replace, notes Richard Holliday, head of industrial applications for the World Gold Council. Automakers, he says, "use platinum because it's very durable under pretty severe conditions you get coming out of the engine — things like copper and aluminum just aren't durable enough." Platinum, he explains, is thought to be uniquely able to initiate a reaction that causes hydrocarbons and particulate matter to break down into less harmful components, including water.

He notes, however, that startup company Nanostellar has come up with a new catalytic converter formulation that uses gold in combination with platinum. While declining to provide specifics, Holliday says, "Commercial introduction is not far away." Initially the new formulation will be used on diesel vehicles, which operate at lower temperatures than gasoline engines, but according to Holliday, the second generation of the technology will be expanded to a wider range of vehicles.

Traditionally, heavy-duty vehicles have faced less stringent emissions requirements than passenger vehicles. Nevertheless those requirements continue to become more and more demanding — and meeting them is particularly challenging.

"The larger the capacity of the engine, the more exhaust it creates and the more challenging it is to rapidly treat it in the exhaust system," notes Tim Dummer, segment marketing manager and business development leader for transportation advanced sensors for GE Sensing and Inspection Technologies. "If you look at how manufacturers are trying to solve it, on the diesel side they're focusing on exhaust gas re-circulation, diesel particulate filters and selective catalytic reduction. Over time, as you get to the tough regulations for 2011 and 2012, you get to a point where you have to use all three."

Increasingly manufacturers are relying on on-board sensors from companies like GE to provide temperature, pressure and other data, which they use to dynamically optimize emission controls. Ultimately some passenger vehicles also may require sensors to meet emission system requirements, Dummer predicts.