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Good Thinking

New system could put dead seaweed to use as a source of power

By Ben Coxworth
May 06, 2013
New system could put dead seaweed to use as a source of power
Dead seaweed on a beach in the Spanish city of Alicante
Dead seaweed on a beach in the Spanish city of Alicante
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A diagram of the seaweed-treating system
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A diagram of the seaweed-treating system
Dead seaweed on a beach in the Spanish city of Alicante
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Dead seaweed on a beach in the Spanish city of Alicante

When it’s alive and in the ocean, seaweed serves as a habitat, spawning ground and food source for marine life. Once it gets washed ashore, however, it pretty much just rots. Typically, along beaches in tourist areas, that dead seaweed is simply gathered and taken to a landfill. Now, however, researchers from Spain’s University of Alicante have conceived of a new seaweed-removal system that has less environmental impact, and that allows the seaweed to be used as an energy source.

Normally, when dead seaweed is gathered off Spanish beaches, a lot of sand and sea water is gathered with it. This makes it quite heavy and bulky to transport, and causes it to take up a lot of space in the landfills.

Additionally, the salt content of the water limits its potential uses, while the beach gradually loses sand with each new load of seaweed that’s taken away – in some cases, sand from outside sources needs to be periodically brought in to replace what’s been removed.

The new system, however, would reportedly reduce the weight and volume of the gathered seaweed by up to 80 percent, in the form of less sand and seawater.

A diagram of the seaweed-treating system
A diagram of the seaweed-treating system

It would consist of a flatbed trailer-like wheeled platform, containing three linked hoppers. As it was wheeled along the beach, human workers would deliver loads of wet, sandy seaweed into the first hopper, where it would be swirled with pumped-in seawater. As that water subsequently flowed back into the sea, it would take the bulk of the sand with it.

The seaweed would then proceed into the second hopper, where seawater that had been desalinated using a solar-powered device would be used to rinse much of its salt content away. It would then go into the third hopper, where air heated via solar power would be used to dry it.

Finally, it would be compressed into bales or pellets. Among other possible uses, it is hoped that it could then be used as a source of biomass in power plants.

The research was led by Prof. Irene Sentana Gadea.

Scientists from Germany’s Fraunhofer Institute for Chemical Technology have also developed a process for converting waste seaweed into building insulation.

Source: University of Alicante (Spanish)

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Good ThinkingPowerWasteBiomassOceanEnvironmentally-friendly
13 comments
Ben Coxworth
Ben Coxworth
Based out of Edmonton, Canada, Ben Coxworth has been writing for New Atlas since 2009 and is presently Managing Editor for North America. An experienced freelance writer, he previously obtained an English BA from the University of Saskatchewan, then spent over 20 years working in various markets as a television reporter, producer and news videographer. Ben is particularly interested in scientific innovation, human-powered transportation, and the marine environment.

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13 comments
viffer
Nice cartoon and concept, but a stumbling block in this is the "seawater that had been desalinated using a solar-powered device". The quantity of water required for rinsing would be large compared to amount generated from a solar still. The whole process seems to be very energy intensive for something that is basically just a cosmetic issue.
Slowburn
If they can produce enough desalinated water to wash the salt out of the seaweed the worlds fresh water concerns just vanished.
Washing out the sand and removing as much as the water as practical on the beach are good ideas but unless they are dumping fresh water into the sea, they are going to need a salt tolerant incinerator or anaerobic digester if they want to use it as a fuel source.
Joe Blake
There is no mention of a "still" to give fresh water. Using a series of filters such as activated charcoal and reverse osmosis would only need the power to pump the water to be derived from the sun. We're not talking about human consumption here. The RO filters can be reverse flushed to extend their useable life and charcoal is fairly easily obtained.
Further, salt water is more conductive than fresh, which would then raise the possibility of using solar electricity to split the water into hydrogen and oxygen, then recombine to give pure water, when some of the heat from the combustion could be harvested for another use, perhaps in drying the weed.
Slowburn
re; Joe Blake
While reverse osmosis desalination can be less energy intensive than distillation there is no way that solar energy collected by that truck will produce enough fresh water for any meaningful reduction of salt content in the seaweed.
Your electricity to hydrogen to electricity and water idea is interesting but you will also be liberating chlorine which is rarely a good thing.
garyO
This is a ridiculous use of energy to make fuel for energy, it is surely not efficient if you add up all the costs. The vehicles, equipment, man power and transport costs alone might be enough to make this a non starter. And that's on top of the other issues raised already in this discussion. But there is, I believe, a much bigger issue 'hidden' in the text. Why are we dumping seaweed in landfill in the first place ? Where I come from seaweed from the beach is used as a very useful fertiliser and soil conditioner. Overuse can raise the level of salt in the land so it's not the sole product used. But, If a system similar to the one described could collect the weed, rinse it in seawater then macerate it followed by a high speed spin drying. That might provide a product that could be spread straight onto the land, no more processing needed. No need to remove all the sand either. Now that is efficiency, minimal input, maximum output. It would also save using a bunch of chemicals currently used for this job. IMHO
joeblake
@Slowburn, I see nothing in the text that says the solar collectors have to be on the truck. There appears to be what looks like 3 solar collectors of some sort on the truck, but I don't read Spanish, so I'm none the wiser.
However by the nature of their construction photovoltaic panels pack flat and a fairly large area of collector surface could be transported to the site on a separate vehicle. Further, there is no reason why some solar collectors could not be assembled the previous day on site, and then when the day's work is finished, moved to the next site, and so forth. Maybe the vehicles themselves could have some electrical propulsion using electricity generated etc.
My main reason for commenting however was to show that there was more than one way of tackling the problem, not just solar distillation.
As for the chlorine problem, what is to stop the chlorine recombining with the sodium to give salt again? Surely the processes of splitting and recombining the components of NaCl won't BOTH consume more energy than they consume.
Slowburn
re; Joe Blake
Additional vehicles means additional cost, and the illustration shows 3 tiny panels of solar collectors. Some of the sodium will combine with oxygen. I would say this needs to be cost effective but it is a green energy project.
ezeflyer
Bad idea. Seaweed washed onshore traps sand, forms a hard composite berm that buttresses the shore and prevents the waves from washing in and eroding the beach. It also provides vital nutrients for the shore vegetation that helps restore and build the beach as well as cover and food for crabs, birds and other shoreline organisms. Seaweed and driftwood are one of nature's ways of building seashore and should be left in place. Beach raker tractors compact the sand and cause erosion. They crush turtle nests and destroy the shoreline ecology. The seashore is a living thing, not just a sandbox for tourists. Plastics washed onshore should be picked up and recycled until the time countries begin to charge recycling taxes to make plastic containers unprofitable and force manufacturers to go back to reusable containers.
Joe Blake
@ ezeflyer, Whilst I would agree with you on some points, the idea nevertheless has merit. Invasive water born plants such as water hyacinth and salvinia can literally choke a stream with vegetation, and clearing these waterways is very expensive in time, money and resources. The Brisbane river has been invaded in the past. Utilising this technology might make it possible for the plants themselves to be the feedstock for fuel to help run the clearing operations. The weeds could bear the seeds of their own destruction.
Don Duncan
ezeflyer:
You had me until you got to the taxes and force. The free market solves all problems. No force needed. No theft (tax) needed. For example, baby seals are clubbed to death because the govt. forbids ownership until the seals are dead and then awards ownership to the killer. If ownership of the live seals were allowed, they could be bought and protected.
The market is not an unexplained miracle. It's working is based on the fact that reason and voluntary interaction is superior to force and fraud.
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