Shrimp Shells are not Only for Plastic Now, but Also Batteries

I’m sure you’ve read or seen the news of researchers turning to shrimp shells in order to replace oil-based plastics. Well, science has taken us to another level of recycling: shrimp shell-based batteries.

Spanish researchers and other collaborators at the Massachusetts Institute of Technology (MIT) had done a project together and it shows that chitin from shrimp shells is in fact able to produce electrodes for vanadium flow batteries. You can see the results of their work in ACS Sustainable Chemistry & Engineering.

Francisco Martin-Martinez, a chemical engineer and one of the authors, stated, “We propose to produce these vanadium flow battery electrodes from chitin, a material from shrimp shells, which, in addition to carbon, contains nitrogen,”

“Vanadium redox flow batteries, unlike lithium batteries used in the automotive industry, do not provide high energy density, but do provide a large volume of energy storage at low cost, which makes them ideal for storing energy from renewable sources such as solar and wind power, whose energy production is intermittent.”

Martin-Martinez is an expert in the development of bio-inspired materials, and he stated that carbon electrodes are usually used to facilitate the flow of electrons from one side of the battery to the other.

“We have produced these electrodes from chitin, a material from shrimp shells. Chitin is a polysaccharide, similar to cellulose, which is found in the exoskeleton of crustaceans and insects,” he said.

What’s so special about chitin

According to Martin-Martinez, chitin contains both carbon and nitrogen “which is incorporated into the structure of the electrode during the production process, improving its performance.” This parameter has been characterized in detail by the authors in the paper.

Moreover, the team has proven the benefits of nitrogen in the chemical structure of the electrode. It facilitates the transfer of electrons between from the vanadium ions.

The researcher stated that there are other carbon electrodes that can yield a better performance, but Martin-Martinez stated that the key to this project was to produce such electrodes from a waste material, which was chitin from shrimp shells in this case.

He added that chitin has good performance, plus it’s low cost and sustainable as a material. Electrodes of this type are principally made from carbonized polyacrylonitrile, a synthetic polymer. Therefore, producing them from a waste product, according to Martin-Martinez, is a more sustainable alternative.

“These electrodes from shrimp waste could also be applied in supercapacitors, electrochemical devices that provide a very high energy density, and even in desalination processes, although we have focused on vanadium redox flow batteries,” said Martin-Martinez.

Now, since I’m not a scientist, I don’t know what Martin-Martinez means in simple English (if you know it, do leave a comment below so that the others can understand). What I know is that there is another use of shrimp shells for a better, more eco-friendly life in the future.

Green chitin production

Speaking of chitin, there’s another discovery or advancement relating to its production. Scientists at Nanyang Technological University, Singapore (NTU) have developed a green way to create chitin. They use prawn shells and discarded fruit as materials and ferment them to create the substance.

Now, Chitin has a lot of uses in the food industry, like food thickeners and stabilizers, as well as anti-microbial food packaging. Everything’s good about them, but not he production/extraction.

The current method to chemically extract chitin from marine waste costs a lot of money and consumes large amounts of energy. It can also lead to chemical by-products that may be discharged in industrial wastewater. That is why NTU scientists have developed a more sustainable method.

There are roughly six to eight million tons of crustacean waste generated annually around the world, with 45 to 60% of shrimp shells discarded as processing by-products. Simply put, there will be no shortage of shrimp waste (given that we don’t overharvest them or marine economy stays healthy).

Professor William Chen, Director of the Food Science and Technology program at NTU, said, “The huge amount of shrimp waste has sparked industrial interest as it is an abundant source of chitin. However, there is a problem in the extraction method, which is both unsustainable and harmful to the environment,”

“Our new method takes crustacean waste and discarded fruit waste and uses natural fermentation processes to extract chitin. This is not only cost-effective, but also environmentally-friendly and sustainable, and helps to reduce overall waste,” said Prof Chen, who is also the lead researcher.

The researchers from NTU tested ten sources of common fruit waste like mango, apple peels, and pineapple cores in various fermentation experiments. They found that fruit waste has enough sugar content to power the fermentation process that breaks prawn shells down into chitin.

Then, they used something called x-ray diffraction technique to determine the atomic and molecular structure of the chitin created using the new method and its level of purity was measured using a crystallinity index.

And, the result is satisfactory. Extracted chitin samples from shells fermented using fruit waste had about a crystallinity index of 98.16%. In contrast, commercial chitin samples gave an index of 87.56%.

graphic made by Vicente Neto Wikimedia Commons
graphic of chitin and chitosan  made by Vicente Neto Wikimedia Commons

It turns out that fermentation using sugar content from fruit waste produced higher quality chitin than the commercial one. The more sustainable method wins this case.

“Our research has led to not only higher quality chitin but a more sustainable and environmentally-friendly process too. While the various types of fruit waste produced good results, the sugar from the pomace of red grapes had the best performance,” said Prof Chen.

“This is also a cost-effective method for industry-scale operations, which could be of potential interest to wineries looking to reduce and upcycle their waste,”

“This research also echoes NTU’s translational research focus, which aims to develop sustainable innovations that benefit society and industry and create a greener future,” he went on.

If well-utilized, NTU’s findings could have a significant impact in the food industry.

Managing Director of Integrated Aqua Singapore Pte. Ltd., Loo Yuen Meng, said, “The latest innovations developed by Prof William Chen from the Food Science and Technology program at NTU, is an excellent example of how the expertise from an institute of higher learning can be applied to improve operational efficiency of the food industry while reducing food processing waste,”

“Through a simple fermentation process, the high-value chitin and chitosan recovered from the prawn shells are environment-friendly, and the products can be re-connected back to the food industry.”

More possibilities with shrimp shells

The NTU research team has left chitin to undergo further stages of fermentation, and the researchers found that they could ferment chitin further into chitosan.

Chitosan can be used as a growth enhancer in plant fertilizers, or as a controlled drug delivery system in pharmaceutical treatments.

Since there are more possibilities, the NTU researchers are exploring ways to use chitosan to enhance previous research innovations such as food packaging created using soybean residue or Okara. This could lead to the development of a more durable cellulose film with anti-microbial and anti-bacterial properties.



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