One day in the future, the Pacific Ocean could be home to kilometers of seaweed farms tended by submarine drones and waiting to be turned into fuel. This is the vision of Marine BioEnergy, a start-up backed by the Advanced Research Projects Agency–Energy (ARPA-E). The U.S. government agency is funding the company …. because it views the open ocean as a largely untapped resource for a new and potentially better source of renewable bioenergy.

About 5 percent of total U.S. energy use currently comes from biomass such as corn and wood, which are renewable and absorb carbon dioxide from the atmosphere through photosynthesis as they grow.

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Current bioenergy options in the U.S. are dominated by corn-based ethanol. But producing it uses a lot of land, fertilizer and fresh water, which creates other pollution problems and ties up finite resources.

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In order for bioenergy derived from macroalgae to become mainstream, researchers and companies need cost-effective ways to convert seaweed into usable fuel for commercial use. They will also need to create the technologies and techniques to farm macroalgae on a massive scale far out in the ocean, where conditions such as storm-driven waves can be brutal.

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