Groundbreaking technique turns rotting seaweed into biofuels 

Researchers at the University of Bath have developed a simple technique for creating biofuel and fertilizer from seaweed. 

Beyond producing sustainable fuels and chemicals, the new strategy could clean up beaches in the Caribbean and Central America.

Every year, millions of tons of rotting seaweed washes up on beaches throughout Mexico and surrounding regions.

The foul-smelling Sargassum seaweed that clogs up white sand beaches is partially fueled by fertilizer runoff. The annual invasion is devastating to ocean ecosystems and to the tourism and fisheries industries. 

In the current study, the researchers developed an inexpensive way to pre-process seaweed before converting it into bulk chemicals and biofuels.

Study co-author Mike Allen is a professor at the University of Exeter.

“Ultimately, for this to work it has to make financial sense,” said Professor Allen. “Processing marine biomass like seaweed usually requires removing it from the salt water, washing it in fresh water and drying it.”

“The costs of these processes can be prohibitively high. We needed to find a process that would pay for and sustain itself – something both economically and environmentally viable.”

“This work provides a crucial missing step towards a true salt-based Marine Biorefinery by establishing the initial fractionation step.”

The new process releases sugars that can be used to produce a palm oil substitute and prepares the leftover seaweed for hydrothermal liquefaction. This is a type of depolymerization process that converts wet biomass into bio-oil, which can be further processed to make fuel and fertilizer. 

Study first author Ed Jones is a PhD student at the Center for Sustainable Circular Technologies at the University of Bath.

“In contrast with existing pre-treatment strategies, we show that an entirely salt-based biochemical conversion route can work,” said Jones.

“For the first time this study demonstrates that, rather than a hindrance, the presence of saltwater can be helpful.”

Professor Christopher Chuck,  Director of the Center for Integrated Bioprocessing Research at the University of Bath, said the variety of products created by this process is a major strength. 

“The oil industry creates a variety of products including liquid fuel, plastics and fertilisers – and we can benefit from a similar flexibility,” said Professor Chuck. 

“We can simply alter the process conditions to produce larger or smaller amounts of specific by-products, allowing us to meet variable demand.”

Another major advantage of the strategy is the elimination of invasive seaweed. 

“Many countries in the Caribbean and Central America rely heavily on tourism, so the coronavirus pandemic and the ongoing Sargassum problem have put them on their knees,” said Professor Allen. “Last month more than 4 million tonnes of problematic seaweed washed up on their shores.”

The study is published in the Journal of Chemical Technology and Biotechnology.

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By Chrissy Sexton, Earth.com Staff