US start-up Marine BioEnergy is targeting the creation of seaweed farms in the Pacific Ocean as a source of biofuel. The company, which is being supported by the US government’s Advanced Research Projects Agency–Energy, aims to cultivate macroalgae on top of submarine drones and convert it into biogas and ethanol. The approach has advantages over corn-based ethanol, as it does not require land, fertiliser and freshwater. The technology for large-scale seaweed farms is, however, still in development and would require widespread automation in storm-ridden conditions. The ecological consequences of mass ocean farms also remain unknown.

Interest in seaweed biofuels spans more than a decade, with a number of start-ups in coastal nations like the UK and Chile investigating their feasibility. Asia is the only region where seaweed farming has led to widely commercialised products, such as seaweed-based cosmetics and gastronomy. In Europe, consortia like MacroFuels view seaweed as “building blocks” for biofuels and chemicals but rely on government funding.

Despite slow progress, macroalgal feedstocks are more sustainable than land-based feedstocks, with excellent carbon sequestration and fewer environmental trade-offs. Further studies are required before scaling-up the sector, with research suggesting that large-scale seaweed farming could outcompete marine life for nutrients.

The cultivation and processing of seaweed biofuels also face many technical challenges. Researchers need to identify streamlined but energy-dense strains of seaweed that can survive hostile waters out at sea. For the bioconversion process to produce adequate yields, enzymes that optimise sugar extraction must also be found.

Researchers stress that markets for high-value seaweed products need to be established before biofuels can really take off. While strong near-term growth is projected for seaweed markets, such biofuels are 100x costlier than traditional fuels. Seaweed farming is a very labour-intensive process, which will remain cost-prohibitive in Western markets. The next step could be to concentrate farms offshore, where economies of scale can more easily be achieved.

Source: Scientific American

https://www.scientificamerican.com/article/could-our-energy-come-from-giant-seaweed-farms-in-the-ocean/