If someone tells you about garbage, what comes into your mind immediately? Perhaps plastic bags, newspapers, bottles, and the like? They may be waste materials or unwanted things that you throw away but those are classified as rubbish.
Garbage is highly putrescible while rubbish is not. Garbage is mostly decomposable food waste. To name a few: peelings of potato, radish, and squash; unusable portions of cabbage, pechay, and kangkong; fish gills and entrails; and leftovers after meals.
Two of the most common leftovers are the shells of crabs and mussels. Both are considered biological waste and they are typically discarded in landfills.
The blue swimming crab (BSC) – called lambay or masag in Bisaya – is one of the most in-demand crabs due to its sweet, nutty flavor. The shells and appendages make up 60% to 70% of the total weight of the BSC. This means that for every ton of crabs processed in a day, some 300-400 kilos of shells are dumped.
However, the shells should not go into waste. Three Filipino scientists – Efren G. Gumayan, Ian Ken D. Dimzon, and Raphael A. Guerrero – have managed to convert an extract from crab shells into a bioplastic that can be used to make optical parts known as diffraction gratings.
“Repurposing crab waste as a raw material for bioplastic components shows promise, with shells having chitin content of 10% to 72%, suitable for chitosan extraction,” they wrote in a paper that was published by Applied Optics.
The authors – Efren G. Gumayan, Ian Ken D. Dimzon, and Raphael A. Guerrero – have managed to convert an extract from crab shells into a bioplastic that can be used to make optical parts known as diffraction gratings.
“Diffraction is the bending of light around an obstacle,” explained Dr. Gumayan, who is from the Ateneo de Manila University (ADMU). “A diffraction grating is an optical component that redirects light in specific directions based on its color. The surfaces of CDs and DVDs, with their small micrometer-sized structures, can act as diffraction gratings, resulting in the colors seen on the discs.”
The outer skeleton of crabs contains chitosan. “We wanted to find an alternative use for crab shell waste, and decided to find out if chitosan from crab shells could be used as a biodegradable replacement for silicone, which we have previously used in our lab to make diffraction gratings,” said Dr. Guerrero, also from ADMU.
“Gratings made of chitosan are biodegradable and environmentally friendly while also being very inexpensive since crab shells are generally considered waste,” Guerrero pointed out. “By showing that useful optical components can be made from materials typically considered waste, we hope to help improve sustainability in optical manufacturing and reduce the amount of seafood waste that requires disposal.”
This science breakthrough is good news for those involved in crab raising. “The conversion of shell waste into a valuable product should increase income for the local crab meat industry,” Dr. Gumayan said. “This added value to crab shells will hopefully improve the economic status of crab fishermen and their families.”
Aside from its economic benefits, it is also good for the environment. “Using crab shells as the raw material for bioplastic will reduce the amount of waste generated by the seafood industry, and increase sustainability for the environment,” Dr. Guerrero said.
Meanwhile, approximately 31-33 percent of the total weight of mussels are shells. The shells should never go into garbage disposal; it just can’t handle them. However, some people add whole shells to their garden beds or compost pile. The only thing is that the shells break down slowly. To break down faster, some people put them in a sack and pound them with a hammer.
But there is probably a better way of doing it. That’s what the project, “A Valorization of Agri-Fishery Materials Using Opportune Science (AVAMOS): Nanomaterials from mussel shells for agri-aquaculture applications,” is doing.
With funding from the Philippine Council for Agriculture, Aquatic and Natural Resources Research and Development (PCAARRD), the University of the Philippines Visayas project is set to generate mussel shell waste processing innovations that are anchored on green nanotechnology and circular economy.
“Traditionally, mussel processing mostly focuses only on the meat, leaving behind a substantial quantity of shells,” notes Rizza B. Ramoran of Science and Technology Media Services. “However, these discarded shells hold great potential as raw materials for nanomaterial production for application in aquaculture and agriculture.”
Now in its first year of implementation, the project collects discarded food waste from random households in Iloilo province. Procured mussel shells are pulverized and used as nanomaterials that have an adsorption capacity twice over available technologies.
The mussel shells are repurposed and pulverized to serve as valuable resources such as, feedstocks, mulch, aquarium decorations, fertilizers, and other uses.
“Aiming to promote sustainability and zero-waste management, the waste mussel shells generated from these projects will be utilized by the AVAMOS project,” Ramoran reported.
One good thing about the innovative waste valorization strategy is that it helps reduce solid waste accumulation in communities and foster a healthier environment.
In addition, the production of these nanomaterials opens doors for the development and commercialization of innovative products with potential economic benefits.
