I liked working with Shell and the Chinese Government and other groups on energy, but it can get frustrating keeping all your thoughts in-house. I wanted to put a piece on the New York Times op-ed page, and noticed that they liked articles that began with some sort of question or quiz; they also liked articles that identified powerful, long-term trends. It was easy enough to write a piece on natural gas policy that fitted in.
         The piece got a large response. What effect it has, though, will depend on how the wider political landscape shifts... D.B.

 LONDON  - IN the early 1600's, the Flemish alchemist Jan Baptista van Helmont planted a willow sapling and measured its weight as it grew. After five years the tree weighed 169 pounds.

 Where had the solid bulk of wood come from? Not from the soil, which had lost only two ounces in all that time. Rather, Helmont's measurements led to the discovery that a tree's new wood comes from tiny bits of carbon that float in the air, in the form of carbon dioxide.

That simple insight tells us a great deal about the problems that bedevil American energy policy. Coal and oil ultimately derive from ancient vegetation that soaked up carbon in the planet's primeval atmosphere. Breathe in car exhaust or the air near a coal plant today and you are inhaling the earth's ancient geologic atmosphere, in the form of carbon that accumulated over millenniums. But the carbon dioxide we release as we burn fuel builds up in the air, leading to global warming.

 The good news is that not all fuels store the same amount of ancient carbon. And the United States can have a cleaner, low-carbon energy future if it makes greater use of a low-carbon fuel -- namely, natural gas. The advent of natural gas was a major advance in the history of energy use, but American regulations have held the United States back from embracing its full benefits.

 From the Middle Ages until well into the Industrial Revolution, humans depended on solid sources of energy -- like wood, peat or coal -- that were inherently high in carbon. The carbon from the original vegetation that made up these solids tended to burn inefficiently, emitting much carbon dioxide and soot. The late 1800's ushered in the era of liquid energy, especially petroleum, which burns more efficiently, producing less carbon. For that reason, and because liquid fuels are easier to distribute, petroleum rather than coal became the fuel of choice.

 A third class of fuel -- energy gases -- emerged in the mid-1900's. The most important of these was natural gas, which has far less polluting carbon and even more clean hydrogen in it than oil. It seemed inevitable, as gas began its rise, that the new fuel would be substituted for older, less efficient ones. But then, in the late 1970's, something happened. The rise of natural gas slowed, while the decline of coal abruptly halted.

 Legislation passed by Congress was to blame. The Fuel Use Act of 1978, supported by the coal companies, blocked the use of natural gas for utility and industrial power. The newly restricted American market could not absorb all the natural gas that was then available, and so the natural gas industry collapsed in the 1980's. Drilling rigs were mothballed, and many of the nation's natural gas specialists left the industry in search of better jobs.

 The Fuel Use Act was repealed in 1987, and the industry began to recover nearly a decade later. But as a result of the years of slow growth, as well as the loss of expertise, production still has not reached anywhere near the level possible. Only 18 percent of American electricity is generated from natural gas -- a number that has barely increased over the last decade, and which stands in striking contrast to Britain's nearly 30 percent, let alone Singapore's more than 60 percent.

 This summer's omnibus energy bill does little to remedy that. Instead it strongly supports coal-generated electric plants. Only taxpayer subsidies can keep the carbon emissions from that archaic fuel pouring skyward. And President Bush has ensured that Environmental Protection Agency guidelines allow the coal industry to cut down entire mountains in the eastern United States. The resulting coal mining boom is likely to last for decades, given the cycle of investment. It will also increase the likelihood that the United States will remain the biggest contributor to global warming.

 Luckily, there's an easy way to get America out of this fix. Making it slightly more costly for energy generators to emit carbon dioxide would quickly lead them to turn toward low-carbon natural gas. Indeed, a consortium of Northeastern states is working on price incentives to that end. The result would be less soot and fewer other pollutants -- as well as a lot less ancient carbon sent billowing into our planet's rapidly filling atmosphere.