In 2001, the United States used 97,100,000,000,000,000 (that's quadrillion) Btu of all forms of energy.

That breaks down to 39 percent petroleum-based products; 24 percent natural gas; 23 percent coal; 8.2 percent nuclear; and 5.8 percent renewable energy.

Of the renewable energy forms, hydropower from rivers and lakes was No. 1, at 41 percent. But would you be surprised to know that burning of wood was No. 2, at 39 percent? And more recent data indicate that biomass has overtaken hydropower as the leading source of renewable energy.

Ethanol, biodiesel, and windpower made up only 0.21 percent of the energy consumed in the United States in 2001, but these, too, have seen significant growth. Ethanol production nearly doubled to 2.81 million gallons in 2003 and biodiesel production rose from 500,000 gallons to 20 million gallons.

With the United States as the world's dominant consumer of energy, policymakers are seeking ways to expand domestic production through development of alternative fuels and energy-saving technologies.

But it has been spit in the ocean in terms of this nation's appetite, and the United States' dependence on imported oil has increased rather than declined. This demand, combined with turmoil in the key Mideast petroleum nations, is further exacerbated by China's competition for energy to support its mushrooming industrial economy.

The report from the recent conference, “Agriculture as a Producer and Consumer of Energy,” sponsored by the Farm Foundation and USDA's Office of Energy Policy and New Uses, highlights the chasm that exists between what's consumed and what can realistically be expected to be produced from alternative sources.

In 2002, U.S. farm production consumed approximately 1.7 quadrillion Btu of direct and indirect energy, about 1.7 percent of total consumption.

As a source of energy, experts say, agriculture can't be expected to meet total U.S. needs. But it can make an important difference as part of a portfolio of diverse energy sources.

This will hinge on the economics of production, distribution, and use relative to fossil fuels. Significant growth will also depend partially on government assistance. Federal subsidies for ethanol are already in place, and many states also offer incentives. That has not been the case for biodiesel, but recent legislation will help subsidize that product.

These subsidies are not without criticism from certain lawmakers and anti-agriculture groups. They conveniently overlook, though, that almost every form of fuel has had some kind of government subsidy. Lord knows how many billions in tax breaks have gone to oil companies. Without subsidies, renewable fuels would be playing against a stacked deck.

For three decades, critics have charged that it takes more energy to produce ethanol than is derived from the fuel. More efficient production has pretty much eliminated that objection, and there is the additional consideration that any extra cost would be justified in terms of increased energy independence and environmental advantages.

But ethanol would have to come from sources in addition to corn. If every single kernel of the yearly U.S. corn crop (average 10 billion bushels) were used, the ethanol produced would replace only about 14 percent of imported oil.

The challenges are many, and time's a'wasting.