A material derived from the shells of crustaceans has the potential to offer a plentiful and eco-friendly alternative to numerous plastics around the world.
This material, known as chitosan, is a durable variant of chitin, which experts regard as “the second-most abundant organic substance on the planet.” Chitosan is used as medicine and in drug manufacturing. The fibrous substance, according to WebMD, can help reduce the fat and cholesterol the body absorbs from foods.
Chitin is a robust polysaccharide present in the exoskeletons of crustaceans. Common examples of edible crustaceans include shrimp, prawns, lobsters, crabs, and crayfish. The chitin shells of shrimp are treated with an alkaline substance, particularly sodium hydroxide.
The United Nations Food and Agriculture Organization (FAO) reports that over 7.9 million tons of crustaceans, mostly shrimps and prawns, are harvested annually through fishing or aquaculture for human consumption.
In Cebu City, researchers from the University of San Carlos (USC) are turning shrimp waste into bioplastic with potential use for packaging. This chitosan-based material could make the waste another revenue source.
As a background of their study, the USC team found that the processing of frozen shrimp meat for export results in significant waste, primarily in the form of shrimp heads and shells, which are subsequently disposed of in local landfills at a cost.
According to the Philippine Statistics Authority, the Philippines is a significant exporter of shrimp. The country’s average annual production of shrimp and prawns is estimated at 60,000 metric tons, representing 2.65% of the overall aquaculture output. The Philippines primarily exports shrimp to Japan, South Korea, and the United States.
In response to this challenge of shrimp wastage, Dr. Maria Kristina Paler, the project leader, and her team have outlined the necessary industry specifications for packaging materials. These specifications include essential attributes such as barrier properties to enhance shelf life, printability of films, strong lamination, and effective heat-sealing capabilities.
To meet these requirements, the team developed chitosan films incorporating organic or clay nanofillers. These films were subjected to testing and demonstrated promising potential as alternatives to single-use plastic coverings.
The project was supported by the Southeast Asian Regional Center for Graduate Study and Research in Agriculture (SEARCA) through its Grants for Research toward Agriculture and Innovative Solutions (GRAINS).
Dr. Glenn Gregorio, SEARCA director, commended the USC project team for seeking solutions to transform industries affecting the agriculture sector. “Innovations, which aim to reduce waste and protect our planet, are critical toward achieving sustainable production and consumption,” he said.
Dr. Gregorio added that the “breakthrough could help reduce plastic waste from the shrimp industry and contribute to a cleaner environment.”
The Philippines, an archipelago comprising about 7,641 islands, ranks among the leading contributors to plastic waste in marine environments. It is essentially immersed in plastics.
“The Philippines produces around 2.7 million tons of plastic waste each year. Most of it ends up in landfills, dumps, our rivers and our water supply systems. However, about 20% ends up in our oceans,” Environment Secretary Maria Antonia Yulo was quoted as saying during the Earth Day celebration last year.
“When the rains come,” she added, “we are literally swimming in them.”
In Luzon, three Filipino scientists – Efren G. Gumayan, Ian Ken D. Dimzon, and Raphael A. Guerrero – have managed to convert an extract from the shells of blue swimming crabs 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 with the Department of Chemistry at 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.”
According to the three researchers, using crab waste as a source for bioplastic components is promising, as the shells contain chitin levels ranging from 10% to 72%, which is appropriate for the extraction of chitosan.
Chitosan is extracted from the outer skeleton of crabs. “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 but with the Department of Physics.
Dr. Guerrero said the gratings made of chitosan are biodegradable and environmentally friendly. “They are also very inexpensive since crab shells are generally considered waste,” he added.
“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,” Dr. Guerrero pointed out.
This science breakthrough is good news for those involved in crab raising in the country. “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.”
The Philippines is the fourth-largest producer of blue swimming crabs and the third largest exporter of this species to the United States, according to the Seafood Watch. In 2020 alone, experts in the US were valued at $45 million.
“The blue swimming crab is a significant sub-sector of marine fisheries in the Philippines,” wrote Josette Emlen Genio, sustainable market consultant at Sustainable Fisheries Partnership. “In 2015, the country produced close to 26,000 metric tons of crabs, most of which are processed into crab meat.”
The shells and appendages of blue swimming crabs make up 60% to 70% of the total weight. This means that “for every ton of crabs processed in a day, some 300-400 kilos of shells are dumped,” Genio said.
All these wastes end up in landfills and some into the sea.
Aside from its economic benefits, the findings of the study also showed it is 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.
