The damage is far less severe than the Valdez fiasco two decades ago, which dumped some 11 million gallons of oil into waters off Alaska’s Prince William Sound. But it necessitated the temporary closure of the Sabine waterway, the Texas ship channel serving refineries that process 6.5 percent of US capacity.

The spill, which also left an acrid, sulfurous stench hanging over the area, is a grim reminder of the vulnerability of America’s energy lifeline to disasters, man-made or otherwise. It also calls unwelcome attention to the industry at a time when the Environmental Protection Agency (EPA) is on the warpath. It’s also worrisome for ExxonMobil (NYSE: XOM), the company that chartered the vessel.

At this point, prevailing legal opinion is the company will not be held responsible for the spill. How it will play in the court of public opinion will be critical, however, as ExxonMobil attempts to win federal regulatory approval for a groundbreaking takeover of North American gas producer XTO Energy (NYSE: XTO).

The key issue with this deal concerns the process of drilling for natural gas known as hydraulic fracturing, or “fracking.” When the two companies announced the agreement, analysts quickly noticed ExxonMobil had secured itself an out–it could exit the deal should US regulators impose economics-changing restrictions on fracking, which involves injecting water mixed with a small amount of chemicals at high pressure into rock to free up gas.

Scrutiny of fracking techniques has grown in recent years due to concerns that the chemicals injected could contaminate water supplies. The issue has taken on particular political importance in New York State, which contains within its borders promising areas of the Marcellus shale deposit.

At the federal level, legislation was introduced in June that would require frackers to meet EPA standards under the Safe Drinking Water Act. This proposal, in turn, provoked an outcry from the industry, which noted that adhering to new standards would boost costs at each well by $100,000 and could reduce drilling in the US by 20 percent. Fracking is now used at more than 90 percent of US wells.

The prospects for draconian new standards look considerably less likely now that Republicans have acquired a 41^st vote in the US Senate. In fact, several leading Democrats this week made comments praising the economic and environmental benefits of replacing coal with natural gas, which emits no particulate matter, mercury pr acid rain gases, and less than half the carbon dioxide (CO2) of coal. Most positive for ExxonMobil were comments from House Energy and Commerce Committee Chairman Ed Markey (D-MASS), who called the deal “a $41 billion bet on what America’s energy future will be,” adding “I think that’s a smart bet.”

The main risk now for the ExxonMobil-XTO Energy tie up and fracking overall is the EPA’s ongoing review of the practice. As the EPA showed last year when it categorized CO2 a potentially harmful gas, the agency under Lisa Jackson is no shrinking violet when it comes to tackling controversial issues with tough regulations. New CO2 regulation, for example, is expected this spring, even as the issue of cap and trade appears to be hung up indefinitely in Congress.

A major move by the EPA against fracking could cause ExxonMobil to walk away from the XTO deal and wound a number of natural gas producers. But given the support of many in Congress for fracking–particularly politicians from states enjoying the fruits of gas drilling–it appears more likely the agency would go for something less controversial, such as requiring companies to reveal what chemicals they use in fracking.

Meanwhile, passage of major Congressional legislation to encourage more development and production of natural gas in the US appears to have gained steam from the election of Scott Brown to the US Senate. Chances of passing CO2 regulation in the form of a federally mandated cap-and-trade system, already slim before the Brown vote, appear virtually nil, at least for 2010. But financial and regulatory incentives for renewable energy are as alive as ever and will almost certainly be part of any legislation encouraging greater use of natural gas this year.

The District of Columbia and 36 states–including all the major ones–now have mandates in place requiring utilities to derive a set percentage of output from renewable-energy sources. Utilities and their regulators are hard at work spending the dollars to make that happen.

The renewables boom is even more explosive abroad, where China is fast becoming the globe’s most prolific producer of wind power. And a growing number of countries–including Canada–have imposed CO2 regulations with real bite.

The bottom line: We may not know exactly what political developments will shape the great energy debate in the US. But global investment in natural gas and renewable energy in all its forms will continue to rise for some time to come. And that spells opportunity for investors in a wide range of areas, from natural gas and energy efficiency to wind, solar, tidal and nuclear power.

All of these industries are well represented in Portfolio 2020. We’ve already realized substantial profits in many of our positions. Amazingly, this has been during a time of major global economic weakness.

That has very bullish implications as the economy gradually cycles back to strength this year. And it’s why all investors should take advantage of market weakness in early 2010 to build positions in our favorite stocks.

Roger S. Conrad is chief strategist of Portfolio 2020.