The Sierra Club, the country's leading grass-roots environmental organization, has spent a year trying to figure out what it thinks about liquefied natural gas, so far without success. And therein lies a parable about politics and policy that explains a lot about the current stalemate in national energy policy.

Like most environmental groups, the Sierra Club would prefer that we meet our energy needs through conservation and stepped-up use of renewable resources such as solar and wind power. But with home heating bills set to climb as much as 50 percent this winter and some cold-weather states facing the very real possibility of rationing natural gas supplies, even most enviros concede the need to boost supply.

Enviros, in fact, can take some credit for the current gas shortage. For years, they've fingered oil- and coal-fired power plants that are leading culprits behind acid rain and global warming. But so many utilities rushed to build cleaner gas-burning plants that demand has now badly outstripped supply.

The readiest source of additional domestic supply -- offshore drilling -- is hotly opposed by environmentalists as too risky to marine ecosystems. Instead, they prefer to tap the huge reserves that remain under Alaska's North Slope. They're willing to override their genetic disposition to tampering with the Alaskan wilderness and support a new (non-liquefied) gas pipeline along the trans-Alaskan highway through Canada to the Lower 48. But the pipeline would require a $20 billion investment that even Big Oil is unwilling to make.

Which leaves us natural gas in its liquefied form, which must be transported from abroad in cargo ships and unloaded at coastal terminals that change the liquid back into gas.

There are already six such facilities in the United States, including one at Cove Point in Calvert County, and the industry estimates that it will need as many as a dozen more. Fourteen proposals have already received federal approval, 20 have been proposed, and probably 10 more are in the works.

With all those to choose from, you might think that the Sierra Club would have identified the ones it could support. But with a few notable exceptions -- the expansion at Cove Point being one -- you'd be wrong. It would appear that for the Sierra Club, LNG has become the energy source to be supported in principle, but rarely in practice.

Go to the Web site of the Los Angeles chapter of the Sierra Club, for example, and you'll learn why any of three proposed terminals would be frighteningly dangerous and costly to electricity customers while making the nation even more dependent on foreign fuel.

In Louisiana and Mississippi, the Sierra Club chapter warns of tens of thousands of innocents who would be burned to a crisp if there were ever an explosion and fire at any of the LNG terminals proposed for the Gulf Coast.

On the East Coast, the Sierra Club's Delaware chapter has come out against BP's plan to build an LNG terminal in the Delaware River. In its April newsletter, the New York chapter lists eight environmental catastrophes that would befall the region if Shell were allowed to build a floating terminal 25 miles out in the Long Island Sound. And in Boston, the Sierra Club is leading the charge against a proposal by AES to build an LNG terminal on a small, unused and largely unusable island at the mouth of Boston Harbor.

The grass-roots politics of all this is easy to understand. For years, environmental groups have successfully opposed power plants, utility lines and offshore drilling by tapping into the not-in-my-back-yard instincts of anyone living near such projects. Now, when an LNG proposal comes along, the response is almost reflexive. Local residents see the need to gussy up their NIMBYisms with environmentalist garb, and local enviros are happy to oblige.

Back at Sierra Club headquarters, however, officials are still struggling to reconcile the knee-jerk opposition of local chapters to just about every energy infrastructure project with the political imperative to confront the realities of Republican rule and soaring energy prices.

"We are very conscious that we need to articulate what we are for as well as what we are against," says David Hamilton, who oversees energy policy issues for the Sierra Club in Washington.

Recently, a number of environmental groups were able to put aside their reflexive NIMBYism to support controversial wind-farm proposals off Cape Cod and San Francisco. And some environmental leaders have become so alarmed by the pace of global warming that they have even indicated a willingness to reopen the debate over nuclear power.

My guess, however, is that unless more enviros figure out how to prioritize their issues and engage in the kind of trade-offs and compromises needed to recapture the political center, their once vaunted movement runs the risk of falling further into irrelevancy.

Steven Pearlstein will host an online discussion at 11 a.m. today at washingtonpost.com. He can be reached at pearlsteins@washpost.com.

The liquefied natural gas plant at Cove Point, Md., owned by Dominion Resources, is one of six such facilities in the United States.