The drive for energy independence is rooted in three concerns. First, we are vulnerable to oil disruptions. Second, our energy demands generate national security entanglements. And third, we face rising emissions of climate-altering carbon dioxide.

Politicians have been calling for American energy independence for over thirty years. In 1973 U.S. foreign oil imports were at 33 percent of total consumption. Today they are 58 percent, and may reach 70 percent by 2020. Despite this, we’ve made progress.

Since our Bicentennial, the U.S. economy has grown by 126 percent, while energy use has increased by only 30 percent. These gains come from a combination of advances in technology and an evolution in our economy. We’ve moved from energy-intensive manufacturing to services and information technology.

Petroleum meets about 40 percent of U.S. energy demand. Almost all of it is consumed by the transportation sector. So when we talk about energy independence, we mean finding alternatives to gasoline, diesel, and jet fuel.

Wind, solar, hydro, and nuclear power generate electricity. Hence, their contribution lies in displacing greenhouse gas emissions from coal- and natural gas-fired power plants. (A single quarter-ounce pellet of uranium generates as much energy as 3.5 barrels of oil, 17,000 cubic feet of natural gas, or 1,780 pounds of coal.)

Every modern society (and all those that strive to be) requires large amounts of petroleum. Canada, Iceland, Sweden, and Norway consume more per capita than the U.S. does. Likewise, Western Europe uses 30 quadrillion Btu worth of petroleum annually. The U.S. uses 39. And last year, for the first time, Asians used more oil than North Americans.

Will a decrease in the price of oil spur reform of corrupt Arab regimes? Probably not. Recall our enemies managed quite well in 1999 when oil was $9 a barrel. Terrorism is cheap. The reality is that the lowest-cost, easiest to extract oil is in the volatile Middle East. This is depressing, for it implies that oil revenues used to fund terrorism are nearly impossible to disrupt.

Low prices will increase, not decrease, our dependence on foreign oil, as they derail investments in higher-cost alternatives. For example, Governor Schweitzer’s plans to turn Montana coal into liquid fuel won’t survive a fall to $35 a barrel.

Currently, half of our electricity is generated with coal. It’s the least expensive and most accessible of our domestic fuels. But it also is the dirtiest, producing the most pollutants and carbon dioxide per unit of heat. (Coal-fired power plants annually produce about 2.5 billion tons of CO2. Automobiles are second at 1.5 billion tons.)

According to forecasts by the Energy Information Administration, U.S. demand for electricity will increase 50 percent by 2025. This implies 350,000 megawatts of new generating capacity -- hundreds of new power plants -- will have to be brought online.

In the real world, there are no solutions, only trade-offs. Here’s a big one: coal, our cheapest, most abundant energy source is also the dirtiest. Uranium, our cleanest, may be the most expensive, if we consider all the costs, e.g., storage and security.

Since the beginning of human history we’ve expanded and diversified our energy sources. This has transformed society. In the middle of the 19th century, America was an agrarian nation. Wood was our chief source of Btu. A hundred and fifty years later, most Americans live in urban centers and we are the world’s largest producer. We’re also the biggest consumer of fossil fuels.

The U.S. has centuries’ worth of coal, from which we can make practically unlimited amounts of electricity. There are billions of barrels of oil locked up in the tar sands of Canada and South America. They are just coming online. North America has enormous deposits of uranium, but perhaps we lack the political will to fully employ it. Few doubt that some day, when technological advance brings prices down, we’ll harness the sun and the wind in meaningful amounts.

The issue we face is not one of absolute energy scarcity. The real questions are: What prices are we willing to pay and what environmental trade-offs are we willing to accept to meet energy demands?