Do we really need to keep pushing the frontiers in the search for oil? Must we venture into ever deeper and more dangerous waters, and into areas on land where technical challenges and political risks are rising? Some leading multinational energy companies evidently believe there may be a promising alternative much closer to home — algae, that slimy scum, often green or brown in color, that grows abundantly in oceans, along seashores, and in lakes, rivers and ponds, basically anywhere there is sunlight.

Exxon Mobil Corp said in 2009 that it would invest $600 million over the next five or six years trying to produce fuels from algae comparable to those refined from conventional crude oil. On July 14, it opened a greenhouse facility in California to grow and test algae.

Algae biofuels have several attractive features for investors and consumers. Unlike other biofuel sources such as corn, soybeans and sugar cane, algae do not compete with our food supply. Nor are they linked to the cutting and burning of tropical forests, as palm oil is in Southeast Asia. And because algae absorb huge amounts of carbon dioxide, the main greenhouse gas from burning fossil fuels, they could help reduce global warming.