Advanced BioFuels USA

Unlike land-based biofuels, such as corn and sugar cane, seaweed does not compete for land and fresh water with other food or non-food crops. What’s more, the US Department of Energy (DoE) has estimated that if enough algae could be grown as a biofuel to replace all petroleum-based fuel in the US, it would require less than 0.5 per cent of the area of that sprawling nation. That’s about half of the land area of Maine and around one-seventh of the area needed to harvest US-grown corn.

At the same time, seaweeds grow very quickly, have a high polysaccharide content – both crucial for biomass used in biofuel production – and could represent a colossal carbon sink, by absorbing carbon dioxide from the sea during photosynthesis.

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Ocean life is rough, and high capital and production prices mean algae costs more per unit mass than most land-based biofuel sources. Meanwhile, businesses have yet to find a cost-effective way to convert seaweed into a commercial fuel.

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At the heart of AtSeaNova’s technologies lie 2D textile cultivation substrates, ‘AlgaeTex’, a range of twines, ropes, sheets, ribbons and nets based on synthetic fibres such as nylon and polyester, as well as bio-fibres. Typically, most seaweeds are seeded on twine, nursed in a hatchery and then attached to thicker rope and deployed at sea. However, AtSeaNova’s substrates bypass the nursery and allow juvenile seaweeds to be directly seeded onto the textile structure using a binder, before being sent out to sea to grow.

According to Martínez (AtSeaNova business manager Adrián Martínez), the choice of substrate depends on seaweed type and growing conditions, with a view to nurturing the healthiest seaweed at the highest possible yield. “We developed sheets that can occupy more surface area in the sea than, say, ropes,” he says. “Our tests show these yield up to eight times more seaweed than your traditional long [rope] line.

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Working with Hawaii-based firm Makai Ocean Engineering, Sims (Neil Sims, head of aquaculture research and development business for Ocean Era) and colleagues are set to build a small, prototype wave-driven upwelling system, in which wave energy drives a pump that pulls up the deeper seawater, and nutrients, to the offshore seaweed array.

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At the same time, Ocean Era is pursuing that all-important problem of how to cost-​effectively convert seaweed into a commercial biofuel. Sims explains: “There’s a whole range of complex carbohydrates in seaweed, which are very difficult to break up – this is why it piles up on beaches and takes months and months to rot.”

Given this, the marine biologist is collaborating with other Hawaii- and US mainland-based researchers on adapting the microbiome of a seaweed-eating fish, Kyphosus, to improve the biodigestion of seaweeds. “We’re going to try to work out a more efficient means of macroalgae biodigestion,” he says. “It’s astonishing to me that people haven’t looked at this biological model before.”

California-based Marine BioEnergy is also getting ready to launch a macroalgae array in the open ocean, on the far side of Catalina Island, south-west of Los Angeles. However, instead of bringing the nutrients to the seaweed, this company is taking the seaweed – in this case, giant kelp – to the nutrients.

Marine BioEnergy co-founder and ex-Nasa Jet Propulsion Lab engineer Brian Wilcox decided that upwelling was incredibly capital-intensive, so instead devised a system to tow farms of giant kelp down to deeper waters using unmanned submarine drones. 

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Wilcox (Marine BioEnergy president and co-founder Cindy Wilcox) says that as of yet she and colleagues don’t know of any problems, and highlights that seaweed farms will be absorbing huge amounts of carbon dioxide from the ocean. She also points out that the seaweed could be sequestered to the ocean subduction zones to mitigate climate change and ocean acidification.

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Erin Fischell, an assistant scientist at the Woods Hole Oceanographic Institution (WHOI), points out: “Macroalgae needs to scale up to the point where it’s economically feasible for biofuel, and to do this we are going to have thousands of hectares of farms.”

As this happens, cultivators will need more and more data on, say, water-nutrient content and seaweed growth rates, which will raise the costs of today’s labour-intensive farms. Given this, Fischell and colleagues have been developing autonomous underwater observation systems for monitoring large-scale seaweed farms with minimal human intervention.  READ MORE