An option for slower ferries, such as those used in the Alcatraz route, is to use an Australian vessel design that is primarily powered by wind and solar. The boat, called a Solar Sailor, is currently the toast of Sydney, and is aesthetically gorgeous. Not only does it slip along at 11 knots without any diesel fumes or noise, the wakes are very small and I imagine it wouldn’t cause any disruption to wildlife. In fact, birds like to ride on it, too!

You are advocating that the City of Vallejo make the new ferryboat it will build soon "clean" by using CNG or LNG engines. But environmental and safety issues related to these technologies are not yet fully understood. Should the safety of ferryriders be put at risk?

Vessel safety should never be neglected. Fortunately, the US Coast Guard’s Office of Marine Safety in Washington, DC tells us that they are optimistic enough about CNG and LNG ferries that the Coast Guard has approved several demonstration vessels including one ferry. And a Norwegian car ferry propelled by natural gas is already in use in Scandinavia. Obviously, it’s important to move forward as fast as possible without compromising safety in any way.

You’re calling for a "no new diesel" policy on San Francisco Bay. Hasn’t the environmental performance of diesel engines remarkably improved, with emissions cut up to 90% overall?

Marine diesel doesn’t even come close to a 90 percent reduction, unless the marine version of a catalytic converter is used. But these devices, called SCR, are very expensive, require tremendous maintenance, and entail that either ammonia or urea be injected into the exhaust. We could joke about where to find that urea supply, but seriously, we should be concerned about dumping either of these pollutants into the marine environment without more study. Using the cleanest possible marine diesel without SCR will only get emissions reductions of about 40 percent — a level that is still many times greater than single passenger cars! For these reasons, we maintain that the only practical option is natural gas.

Many experts believe that the long-term solution to marine pollution is fuel cell technology, which is at least a decade away from being ready for prime time. Aren’t diesel engines unavoidable until then?

No. As I mentioned, natural gas powered vessels are the interim solution — and according to the Interagency Task Force, we could be riding in the world’s first fuel cell powered ferry as soon as 2003!

Your report criticizing the environmental performance of ferryboats got, well, a boatload of attention when it was released last year. Did you expect the reaction you got?

The marine industry has never been subject to regulation or review by the EPA until just recently, and so I imagine our preliminary study was pretty shocking for them. I think they’re beginning to overcome their denial and constructively tackle the problems of how to make a ferry, per passenger, as clean as an automobile.