The Deepwater Horizon disaster has fouled the Gulf of Mexico with unprecedented amounts of leaking crude; devastated coastlines and marine life; and left industries all along the Gulf in bad shape. It's hard to imagine even the slimmest of silver linings for a catastrophe of this magnitude. Still, even the worst crises can create opportunity for determined Fools.

In response to our call for questions on The Motley Fool's Twitter feed, Foolish follower @OfMany2 asked: "Any thoughts regarding defensive or safe investments related to the oil spill disaster? Solar, wind, cleanup companies?"

We posed this question to an armada of Fools, asking them to suggest stocks that might benefit from cleaning up BP's mess in the Gulf, shifting the U.S. away from its oil addiction, or guarding against future disasters. Remember, these aren't highly refined recommendations -- just ideas to kick off your own further research.

Defensive, shmefensive
Alex Dumortier, Fool contributor
The economic impact of the Deepwater Horizon oil spill on the solar and wind energy industries is nil, absolutely, and shouldn't therefore enter into any decision to invest in companies in these sectors.

As far as defensive or safe investments are concerned, I think you should consider that these qualifiers need not be synonymous with "no direct exposure to the spill." "Defensive" and "safe" are more a function the price you pay for a stock, in relationship to the value you are receiving. If the stock is cheap enough, even a company with a multibillion-dollar exposure can prove to be a safe investment.

If you're looking for investment opportunity related to this incident, I think you have to be willing to wade into the center of the oil slick, as it were. In a disaster receiving this level of attention, it would be very surprising if the stocks of the companies most closely linked to the fiasco did not become undervalued – perhaps very substantially -- at one point or another.

I think there is a good case to be made that the current stock prices, Transocean (NYSE: RIG), which owns the Deepwater Horizon rig, and Anadarko (NYSE: APC), which has a 25% stake in the discovery that includes the Deepwater Horizon site, more than compensate investors for the economic impact of the spill. I think this is likely even for BP.

However, in order to profit from these situations, investors must have the temperament to withstand price volatility in the near term, and be patient enough to hold the stocks through what could be long periods of underperformance.

This investment really cleans up
Mike Pienciak, Fool contributor
My oil-spill related stock pick is hardly unknown. Given the controversy surrounding its oil dispersant Corexit, shares have fallen roughly 12% since the sinking of the Deepwater Horizon rig. But that's no reason to avoid Nalco Holding (NYSE: NLC), a leading supplier of water treatment and efficiency improvement services to industrial and institutional markets.

First off, it appears to me that the environmental hullabaloo over Corexit is overdone. The product is approved by the Environmental Protection Agency (EPA). According to Nalco, it biodegrades "rapidly" and does not contain human carcinogens or reproductive toxins. Furthermore, a federally funded committee of independent experts recently gave a thumbs-up to the use of dispersants.

According to Nalco's most recent comment, Corexit sales have amounted to $40 million, or 1% of estimated 2010 company revenue. However, that figure could soon rise precipitously -- U.S scientists just recently raised their flow estimate on the busted BP well by 50%.

As for the bigger picture, Nalco's high percentage of recurring revenue offers investors a relatively defensive play on the growing global need to conserve water and properly treat wastewater discharge. Nalco also has exposure to enhanced oil recovery and clean (or "cleaner") coal markets. Oh, and did I mention that Warren Buffett's Berkshire Hathaway (NYSE: BRK-B) is a major shareholder?

Even so, given Nalco's sales to the manufacturing and refining industries, the company's results will partially fluctuate with the business cycle. So with signs that the U.S. economy could be headed for another fall, I recommend buying only an initial position at current levels, then waiting to see how the 2011 economic scene is shaping up.

The nuclear option
Anders Bylund, Fool contributor
It's not exactly a secret that fossil fuels make a less-than-ideal source of energy for the human race. The Deepwater Horizon disaster only reinforced the dirty and dangerous downsides to oil exploration and extrication. Unfortunately, green alternatives remain years away from being a viable source for enough energy to replace fossil fuels.

As a result, I believe that this cloud of dispersed oil has a uranium lining. Public opinion shifts with highly visible events like the oil spill or Three Mile Island. This time, it's swinging in favor of nuclear energy. In my view, it's about time. Three Mile Island happened more than three decades ago, right around the release of nuclear-disaster epic The China Syndrome. Panic was nearly guaranteed to ensue.

Now, it's time to look at nuclear power as a relatively clean, safe, and efficient energy medium again. According to the World Nuclear Association, 16 licenses to build 24 new reactors in the U.S. have been submitted since mid-2007, and the oil spill could provide the final straw to break the nuclear camel's stigmatized back. When construction gets moving, much of the business will go to reactor element builders. That's a very select group of companies. And for investors, the selection is even narrower: Toshiba and Areva only trade on the Pink Sheets in the U.S., but General Electric (NYSE: GE) is both easy to buy and tremendously cheap right now.

Sure, General Electric is far from a pure play on nuclear energy, saddled as it is with other unrelated businesses. But if I were to invest in one stock based on BP's oil spill, GE would be it.

Attack of the oil-eaters
Brian Orelli, Fool contributor
My roundabout pick might benefit more from the next oil spill than from this one. Still, bear with me; I think this technology is worth keeping an eye on.

Cleaning up the mess in the Gulf with oil-consuming bacteria seems like the logical step. Bacteria are generally safer than chemicals, work for cheap, and create offspring to further the cleanup -- no romantic music required.

Bacteria to do the job are being developed, but they need to be optimized to work in harsh environments and consume as much oil as possible. Combining those traits is possible, but a new technique developed by Craig Venter's Synthetic Genomics could make it a heck of a lot easier. Last month, Synthetic Genomics produced an organism with a synthetic genome created by scientists. Put the right genes on the chromosome, and it should be possible to create bacteria capable of breaking down large amounts of oil with great efficiency.

Synthetic Genomics isn't a public company, but you can get a piece of the company through Life Technologies (Nasdaq: LIFE), a producer of scientific tools, which recently took an equity stake in Synthetic Genomics. Life Technologies plans to spend $100 million this year developing synthetic biology tools for researchers. Pick-and-shovel companies like Life Technologies are a nice defensive play, since they'll make money even if synthetic biology doesn't strike gold for a while.

The best policy
Selena Maranjian, longtime Fool contributor
As the Gulf disaster sadly demonstrates, many companies -- and entire industries -- often don't want to think about the risks they face. But the business of insurance companies is all about calculating risks, taking them on prudently, and being properly compensated for that peril.

My favorite insurance company is Warren Buffett's Berkshire Hathaway. In addition to providing a variety of insurance services, from individual auto policies to massive reinsurance for major disasters like the BP spill, Berkshire also embraces a host of other sturdy businesses in industries as diverse as candy, jewelry, furniture, paint, and railroads.

In his 2006 letter to shareholders, Buffett noted, "We remain prepared to lose $6 billion in a single event, if we have been paid appropriately for assuming that risk. We are not willing, though, to take on even very small exposures at prices that don't reflect our evaluation of loss probabilities." In contrast, BP doesn't even know exactly what kind of financial hit it will eventually take, and it doesn't seem to have been prepared to prevent or effectively respond to the disaster that happened.

Buffett's focus on long-term performance over short-term ups and downs means he'll take on huge risks other insurers won't touch. And with the consequences of a major unanticipated disaster now clearly visible in the Gulf, it's a safe bet that more companies like BP will be eager to sign up for a little extra protection themselves, which could ultimately mean more business for Berkshire's reinsurance arm.

Shale and fare well
Tim Beyers, Fool contributor
No investing maxim's more gut-wrenching than this: Disaster sometimes makes for opportunity. A federally mandated moratorium on deepwater drilling in the wake of the Gulf of Mexico spill could open the way for exploration of natural gas in shale deposits throughout the U.S. and Canada. That, in turn, could lift the fortunes of Dawson Geophysical (Nasdaq: DWSN).

Subscribers to our Motley Fool Hidden Gems service will recognize the company, which has been a recommendation since 2005. In recent years, depressed natural gas prices have reduced demand for its seismic technology. (Think of it as an X-ray for finding deposits buried in the earth.)

The risk here is that we've seen no sustainable evidence of a lasting rebound in natural gas prices. We have only history (this is a cyclical business), momentum (gas prices are up more than 22% since June 1, according to the Associated Press), and the possibility of a federal boost in the wake of the Obama administration's offshore drilling crackdown.

I like the odds of the Feds taking action. I also like that Dawson's stock is valued at no premium to its trailing 12-month revenue, which to me looks like the price reflects the idea that there's little to no growth left in the underlying business. To me, that's too pessimistic. That's why I added Dawson to my Motley Fool CAPS portfolio this morning.

We want your questions!
Thanks to OfMany2 and the other Fools who've sent us questions thus far. We'll be answering more of them in the days to come. If you've got a question about investing or personal finance, we'd like to help you. Tweet your queries to us @themotleyfool, or post them in the comments below!

Berkshire Hathaway is a selection of both Motley Fool Stock Advisor and Motley Fool Inside Value. Dawson Geophysical got the nod from Motley Fool Hidden Gems. Both Berkshire and Dawson are Fool holdings. Try any of our Foolish newsletter services free for 30 days.

Selena Maranjian owns shares of Berkshire Hathaway, but none of the other contributors hold any financial position in any of the stocks they wrote about. Fool online editor and lead Tweeter Nathan Alderman owns shares of Dawson Geophysical, but isn't invested in any other stocks mentioned here. The Fool's disclosure policy always looks on the bright side.