Science

Turning up the heat to make kelp a viable source of biofuel

Turning up the heat to make ke...
Sugar kelp yields a lot of bio-oil – if you put the heat on (Photo: NOAA)
Sugar kelp yields a lot of bio-oil – if you put the heat on (Photo: NOAA)
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Sugar kelp yields a lot of bio-oil – if you put the heat on (Photo: NOAA)
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Sugar kelp yields a lot of bio-oil – if you put the heat on (Photo: NOAA)

Biofuels may indeed offer a greener alternative to fossil fuels, but they do raise at least one concern – crops grown as biofuel feedstock could take up farmland and use water that would otherwise be used to grow crops for much-needed food. That's why some scientists have looked to seaweed as a feedstock. Kelp is particularly attractive, in that it's abundant and grows extremely quickly, although its fuel yields haven't been particularly impressive. That could be about to change, however, thanks to a newly-developed hydrothermal process.

Khanh-Quang Tran, an associate professor at the Norwegian University of Science and Technology (NTNU), has been experimenting with heating kelp very quickly. More specifically, Tran and his team put a slurry of kelp biomass and water in sealed drinking-straw-like vessels known as quartz capillary reactors, then heated those reactors to 350º C (662º F) at a rate of 585º C (1,085º F) per minute, and held them at that temperature for 15 minutes.

A variation on a process known as hydrothermal liquefaction, the technique resulted in 79 percent of the biomass being converted into bio-oil. A previous UK study also explored the hydrothermal liquefaction of the same type of kelp (Laminaria saccharina), although it didn't incorporate the rapid heating aspect. In that case, the yield was only 19 percent and the oil was harder to refine, plus the addition of a chemical catalyst was required. No catalyst is necessary with the NTNU system.

Although it has so far only been demonstrated on a small scale, Tran has plans to test his process in a large-scale reactor, and is looking for industrial partners to help finance the research. He also believes that with some more finessing, he can increase the yield beyond 79 percent – it's worth noting that the net energy gain would presumably be somewhere below that number, as a significant amount of energy would be consumed generating the required heat.

Keeping that in mind, scientists at California's Bio Architecture Lab are taking another approach to seaweed-derived biofuel. They've engineered a microbe that can extract all the major sugars in seaweed, and convert them into renewable fuels and chemicals.

A paper on the Norwegian project was recently published in the journal Algal Research.

Source: NTNU

8 comments
Freyr Gunnar
> Kelp is particularly attractive, in that it's abundant and grows extremely quickly, although its fuel yields haven't been particularly impressive. That could be about to change, however, thanks to a newly-developed hydrothermal process. How does that compare to good ol' oil in terms of cost, energy density, and land use? And will it be competitive within the next twenty years? https://deepresource.files.wordpress.com/2013/02/globalpeakoilforecast.jpg
Slowburn
How does the process work on grass clippings?
Paul Robertson
Concentrated solar produces more than enough heat for this process. Net energy cost negligible. Heat waste producing industry also a possibility as a partner. How about comparing the cost of an industrial application of this kind of alternative energy with the cost of climate change mediation projects like the creation of dykes around New York. Those are the real questions in a climate change world. Not how it compares to petrol.
Fretting Freddy the Ferret pressing the Fret
It's grown in water obviously, so there is little land use. Also, there is no fertilizer, or consumption of water. It avoids use of important resources.
arationofreason
What is the energy yield vs process energy ratio?
Anthony Valenti
"Concentrated solar produces more than enough heat for this process. Net energy cost negligible." Really? You know this... how? Where will this concentrated solar energy plant be located? Please tell me you will no harm the critical habitat of the coastal horned spotted frog. How will the harvesting be done? Rowboat? I think not. How will the materials be transported to the various sites? Bicycle? Not likely. How will the materials that go into the processing plant be produced and assembled? The correct answer is "something powered by the internal combustion engine". "Heat waste producing industry also a possibility as a partner." Poor grammar aside, this is a viable line of thinking. "How about comparing the cost of an industrial application of this kind of alternative energy with the cost of climate change mediation projects like the creation of dykes around New York." And the answer is '[BZZZZ] Wrong!'. The validity of your comment requires a cause and effect relationship between non-alternative energy and an as yet unproven theory. Here is the problem with the low-information "global cooling ... erm, global warming .. dang, I mean global climate change" crowd who are so eager to jump on every idea regardless of the practicalities. You forget to consider second-order effects, the 'non-green' parts of the process and the law of unintended consequences. If people were truly concerned about the environment as opposed to being good little drones supporting the political and financial power grab that is the modern global cooling / global warming / global climate change movement you would focus on the reduction of pollution while working within the reality of our economic system.
StWils
I can see how this could readily be industrialized with the externally supplied energy coming from solar, wind, wave, or ocean current sources. And, yes, the whine about oil or gas prices does not compare to the cost of levees, flow gates, barriers or rebuilding a city. The next major avenue for research pursuit & inclusion should look at possible resource contributions from municipal sewage. Can the kelp be fed processed sewage as a fertilizer? Existing technology can have floating solar towers conducting concentrated light with solar tubes far down in the water column to locally increase the rate of growth and limit the "acreage" of coastline needed. It would be great processed sewage can then be an available resource provided to the kelp as needed to limit the demands on the ocean. It not good enough to just push biofuel growth off of arable land whilst imagining that the oceans are an endless resource.
kevinwebb47
The sea has hidden lots of energy sources adding seaweed in the list which releases bio crude from the kelp. Fast hydrothermal liquefaction is the only method used to heat the sugar kelp and produce bio oil but need more methods to make it almost 99% from 79%. As our global temperature is changing very rapidly we need more biomass in order to sustain in future. It is good to hear that efforts are being made to mime the natural processes to produce oil and I honestly appreciate Professor Tran for his endless efforts in saving our energy resources. Thanks for such an insightful post. It is really surprising that it has additional features of growing but in sea.