With U.S. gasoline prices hovering near $4 a gallon and the unrest roiling the Arab world, attention is focusing on alternatives to oil. Just last week, President Barack Obama ordered U.S. agencies to switch to smaller cars, preferably alternative fuel and hybrid models, to reduce the federal government's energy footprint. Discussions are under way on fracking -- releasing oil and natural gas from rock formations -- and whether it's wise to expand the nuclear power industry in light of the disaster at Fukushima, Japan. And the dickering continues in Congress over whether to expand offshore drilling. We've been here before. Repeatedly. Think the 1970s oil embargo by the Organization of Petroleum Exporting Countries and 1979 energy crisis, as well as the more recent oil speculation that helped produce the global recession of the last few years. The darlings of the alternative energy debate long have been wind, solar and biofuels. But how practical is it to replace oil consumption? Scientist/futurist Chris Martenson says it's not. In "The Crash Course: The Unsustainable Future of Our Economy, Energy, and Environment," alternative fuels even some combination of all forms -- cannot replace world oil consumption -- 30.8 billion barrels in 2009. Martenson calculates it would take more than 6,800 nuclear reactors, nearly 6 million 1 megawatt wind towers and 13 million acres covered by solar photovoltaic panels, or more than 16 billion acres of farmland (about 135 percent of the total amount of agricultural land in the world) converted to soybean biofuel production. "A prevalent and hopeful line of thinking found all across the political spectrum suggests that we will simply transition away from oil onto some combination of nuclear energy, decreased oil consumption, and/or alternative energy sources, such as solar, wind or even algae biofuels," Martenson said in a recent release. "[However] none of them individually or in combination can ever completely plug the gap left by oil's slow departure." Martenson, who says he gave up a high-paying executive job with a Fortune 300 company and a big house in Mystic, Conn., for a more rural existence in western Massachusetts, predicts nuclear and coal energy will become more major players along with alternative energy, but the reality is we'll have to learn to operate on less energy. The World Coal Association says 49 percent of electricity produced in the United States comes from coal and estimates indicate U.S. deposits would last 300 years at the current rate of consumption. The U.S. Energy Information Association puts the cost of generating electricity from coal at less than $2.36 per million British thermal units as of February, compared with $3.27 per MMBtu overall from all sources. Wind energy last year accounted for 2.5 percent of electricity production worldwide, with some countries seeing as much as 21 percent, according to Wikipedia. The concept is not new. Wind power has been used for milling grain and pumping water for centuries as well as powering ships. Solar power received scant attention until the 1980s although it did help power the 1958 Vanguard satellite once the vehicle's chemical battery was depleted. But by 2008 solar energy accounted for less than 0.02 percent of electricity production. Part of the problem is that photovoltaic cells just aren't that efficient and make electricity production four times as expensive and requiring nearly 10 times as much land as that produced with coal. Hopes are biofuels can provide a quarter of transportation fuels by 2050. But there's a ways to go. In 2008, biofuels provided only 1.8 percent of the world's transport fuel. Americans are not entirely oblivious to the situation, but a recent Gallup poll indicated we prefer energy development to green concerns by a 50 percent to 41 percent margin. At the same time, they say the government should encourage production from alternative sources by reducing monetary support and incentives for the oil and gas industries -- cost pass-throughs that likely will show up at the pump. Both Obama and Vice President Joe Biden have been pushing public-private partnerships to advance alternative energy development. "Now, more than ever, America's future competitiveness depends on our ability to innovate and our capacity to live up to our rich history of technological advancement," Biden said during a visit to the National Renewable Energy Laboratory in Golden, Colo., earlier this month. Obama has emphasized his support for production of alternative car batteries by visiting the Allison Transmission plant in Indianapolis. "Allison Transmissions is also part of the ultimate solution to high gas prices. We know there are no quick fixes to this problem," Obama said in a subsequent Saturday morning address. "In the short term, we're doing everything we can to boost safe and responsible oil production here at home -- in fact, last year, American oil production reached its highest level since 2003. "But over the long term, the only way we can avoid being held hostage to the ups and downs of oil prices is if we reduce our dependence on oil. That means investing in clean, alternative sources of energy, like advanced biofuels and natural gas. And that means making cars and trucks and buses that use less oil."