Seaweed Can be Invasive, but We Can Turn It Into Biofuels or Fertilizers

Since we’ve talked about invasive species for quite some time here, we all know now that any species can be invasive and harmful towards the environment. Today’s species will be seaweed.

Every year, there are millions of tons of rotting seaweed which gets washed up on beaches of Mexico and the Caribbean. What caused the bloom? Fertilizers that drifted into the sea from farming in the Americas are partly at fault here. As a result, Sargassum seaweed (which smells bad) devastates the tourism industry and harms fisheries and ocean ecosystems.

It’s a problem, no doubt. But thankfully there’s a solution. A research team led by the University of Exeter and the University of Bath, has developed a cheap and simple way to pre-process seaweed before making bulk chemicals and biofuels from it.

Biofuels made to be feasible financially

Professor Mike Allen from the University of Exeter and Plymouth Marine Laboratory said, “Ultimately, for this to work it has to make financial sense. 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.”

Using acidic and basic catalysts, the team devised a process that releases sugars that can be used to feed a yeast that produces a palm oil substitute. This method is also used to prepare the residual seaweed for the next stage of processing, called hydrothermal liquefaction.

This process subjects the organic material to high temperature and pressure, turning the seaweed into bio-oil that can be processed further into fuels, and high-quality but low-cost fertilizer.

sargassum seaweed by brewbooks Wikimedia Commons
sargassum seaweed by brewbooks Wikimedia Commons

“In contrast with existing pre-treatment strategies, we show that an entirely salt-based biochemical conversion route can work. For the first time this study demonstrates that, rather than a hindrance, the presence of saltwater can be helpful,” said Ed Jones, first author on the paper and PhD student at the Centre for Sustainable Circular Technologies at the University of Bath.

“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 Christopher Chuck, director of the Centre for Integrated Bioprocessing Research at the University of Bath and the project lead.

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

Killing two birds with one stone

You’d think that seaweed is the only problem in these shores, but let’s not forget about plastic. But don’t worry, any plastic collected alongside the seaweed will also be converted alongside the seaweed.

The inspiration came from Professor Allen’s 12-year-old daughter who helped collect seaweed samples for trial studies from the Devon coast. “It was Rosie who triggered a whole stream of research following the painstaking removal of plastic litter from the children’s seaweed samples by asking ‘Dad, can’t you just convert the plastics alongside the seaweed?'” said Professor Allen.

Also, by using the invasive seaweed, this program can bounce back the tourism industry around the area. Because as I stated earlier, Sargassum is a type of seaweed that doesn’t smell good, which deters visitors and damages the economy.

“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. Last month more than 4 million tonnes of problematic seaweed washed up on their shores,” said Professor Allen.

Seaweed invading the Gulf of Maine

Kelp forest by Gustavo Gerdel Wikimedia Commons
Kelp forest by Gustavo Gerdel Wikimedia Commons

Invasive seaweed doesn’t happen only in Central America. University of New Hampshire researchers have found that a species of shrub-like seaweed that has invaded the seafloor of the Gulf of Maine now dominates the seabed. This could potentially reduce the number of fish in the areas.

Researchers who has looked at decades of data and pictures of the ocean floor observed that warmer water temperatures caused by climate change are shortening the growing season of kelp, which thrives in colder conditions. As a result, invasive species known as Dasysiphonia japonica or “turf seaweed” began to invade the waters.

Jennifer Dijkstra, a research assistant professor at UNH’s Center for Coastal and Ocean Mapping, was the lead author of a paper about the findings. Dijkstra had previously authored a study showing the invasion of the turf seaweed, which is originally from Asia and is spreading north along the Northeast coast, in 2017 in the Journal of Ecology.

Dijkstra said that the new research mapped a much larger area of the seafloor. It showed that fish are looking for a habitat that provides continuous coverage over a large area, as opposed to the patchy coverage provided by the turf seaweed that is replacing other types of seaweed.

Similar to forests providing canopy to give animals some protection, kelp provides cover or concealment for fish species that utilize that habitat, according to Dijkstra.

“When you lose a kelp forest, it’s very similar to losing a terrestrial forest. It’s like going from a forested ecosystem to a shrubland . . . The canopy is important to species that visually assess their surroundings like fish,” she said.

Just like animals utilizing forests to hide, fish use the kelp to run away and hide from predators. The new study shows that there are fewer observed fish in the habitats with the turf seaweed. If there are any, they spend more time and energy seeking and defending their shelter.

It’s unknown whether the technology used to recycle Sargassum is applicable to this turf seaweed, because if it is, then the solution will be easier. Or, if possible, we can utilize biocontrol like the case below.

Sea urchins, savior of Kāne‘ohe Bay

sea urchin by 紫堂 Wikimedia Commons
sea urchin by 紫堂 Wikimedia Commons

Sometimes nature finds its way to balance things out, and that’s the case in Kāne‘ohe Bay, Hawaii. The Division of Aquatic Resources (DAR) is now planting native sea urchins (which was hatchery-raised) in the Waikīkī Marine Life Conservation District (MLCD).

Aquatic Invasive Species team from DAR has introduced the first of 100,000 native sea urchins (Tripneustes gratilla), to help control over 4 acres of invasive algae or seaweed.

I didn’t know this at first, but apparently sea urchins are important for Hawaiian aquatic life because they consume invasive seaweed. This seaweed has altered coral reef ecosystems by overgrowing and starving corals of light and can eventually kill the coral colony.

And when these urchins consume the seaweed, corals are able to regrow, which leads to fish, native seaweed (called limu), and invertebrates coming around the area and repopulate the places previously overgrown with algae.

This sort of natural method to combatting algae has been used in Kāne‘ohe Bay for over 9 years. It has worked well so far. Invasive seaweed used to dominate corals, but are now reduced to manageable levels, which has greatly reduced the impact to corals in the Bay.

“We hope to see the same level of success in Waikīkī , to improve coral habitat and expand healthy reef coverage in the most visible MLCD in the state,” said DAR Habitat Monitoring Coordinator Wesley Dukes.




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