Scientists believe that shrimp shell crab shells are of great value as a renewable resource

: In developing countries, discarded crab, shrimp and lobster shells are often dumped in dumps or oceans. In developed countries, the processing costs are high. But these shells actually contain useful chemicals: proteins, calcium carbonate, nitrogen, and shells (a cellulose-like polymer). The potential value of these shells to the chemical industry is often overlooked. Writing in the journal Nature, scientists should find sustainable ways to refine crustacean shells, and governments and businesses should invest in this rich and inexpensive renewable resource.scientists should find sustainable ways to refine crustacean shells, and governments and businesses should invest in this rich and inexpensive renewable resource.Photo credit:
Bert Folsom
/
Alamy Worldwide produces 6 million to 8 million tons of discarded crab, shrimp and lobster shells each year, including 1.5 million tons in Southeast Asia alone. Although 75 per cent of a tuna weighs, only 40 per cent of a crab's meat is eaten.in developing countries, these discarded shells are often dumped in garbage dumps or oceans. In developed countries, the processing costs are high. In Australia, for example, a ton of processing costs $150.these shells actually contain useful chemicals: proteins, calcium carbonate, nitrogen, and shells (a cellulose-like polymer). The potential value of these shells to the chemical industry is often overlooked. Writing in the journal Nature, scientists should find sustainable ways to refine crustacean shells, and governments and businesses should invest in this rich and inexpensive renewable resource.promising,estimate that dried shrimp shells are worth about $100 to $120 a tonne. It can be ground up for animal feed additives, bait, fertilizer or shell production. Of course, the return on this recycling is not much higher than agricultural waste: corn stalks and straw used to burn heating or refine chemicals sell for $50 to $90 a tonne.crustacean shell contains 20% to 40% protein, 20% to 50% calcium carbonate and 15% to 40% shell. What can these ingredients do?protein is excellent animal feed. For example, shrimp shells contain all the essential amino acids and have nutritional value comparable to soy rice. Currently, these proteins cannot be used because of the damage caused by the processing process. But with the rapid development of animal husbandry, crustacean shells from Southeast Asia can be converted into protein-rich animal feed. The World Bank estimates that its annual market value exceeds $100 million.carbonate is widely used in the pharmaceutical, agricultural, construction and paper industries. At present, it mainly comes from geological sources such as marble and limestone. Although these sources are extremely rich, they can contain heavy metals that are difficult to remove. And the calcium carbonate in these shells allows the body to absorb better, for example as a pharmaceutical ingredient. Perhaps food-derived pills are more acceptable than rock-based pills.
Ning Yan
, a professor of green chemistry at the National University of Singapore, says the market price for calcium carbonate coarse molecules is about $60 to $66 a tonne, mostly in construction, dyes, fillers and soil treatment. Ultra-fine particles used to improve rubber and plastic properties can cost up to $14,000 a tonne. Even if the crustacean shells of Southeast Asia are used only as coarse-particle calcium carbonate, they have a market value of nearly $45 million.is a line polymer and the second-richest natural biopolymer (first, cellulose) on Earth. It is found in the exoskeleton of fungi, plankton, insects and crustaceans and produces about 100 billion tons of crustaceans each year. Currently, this polymer and its water-soluble derivatives (shell polysaccharides) are used only in very few industrial chemical fields, such as cosmetics, textiles, water treatment and biomedicine. As a result, scientists say, the potential is enormous.other biomass, shells contain nitrogen, which is important for modern life. For example, nitrogen-containing organic compound pyridoxine is essential for best-selling drugs such as zopiclone and valentine, while power plants use
ETA
to isolate carbon dioxide. According to a 2014 survey by
Grand ViewResearch
, a U.S. market research firm, nitrogen-containing chemicals have considerable market space, consuming 2 million tons of
ETA
per year and generating annual sales of approximately $3.5 billion.other hand,
Yan
that industrial preparation of nitrogen-containing compounds involves fossil fuels and energy-intensive industries. First, nitrogen must be converted into ammonia by the Haberbos ammonia method, but the process is inefficient and accounts for 2 to 3 percent of global energy consumption. Consuming 1 mole of nitrogen requires 3 moles of hydrogen from fossil fuels.processing is more complex and costly. For example, the production of
ETA
requires six steps: the preparation of hydrogen from coal or natural gas, the separation of nitrogen from the air, ammonia synthesis, the production of ethylene from a crude oil cracking reaction, the conversion of ethylene into epoxy, and the conversion of epoxy into
ETA
.researchers say shell
a
stable starting point for ETA production. Carbon, nitrogen and oxygen have been trapped in polymers to produce eTA
in
. Moreover, five other chemicals can be derived in a single step. Chemistry Challenge
Xi Chen
, a researcher in the Department of Chemistry and Molecular Bioengineering at the National University of Singapore, notes that the current method of extracting chemicals from abandoned crustacean shells is inefficient and unethical. "This requires the separation of different components, a process also known as fractionation."
hydroxide
remove proteins, and calcium carbonate is mainly broken down with hydrochloric acid, which is a corrosive and dangerous solution, Chen said. , in order to prepare shell polysaccharides, the relevant personnel need to use a 40% concentration of sodium hydroxide solution to treat the shell. It takes more than 1 ton of water to produce 1 kg of shell polysacchar sugar from shrimp shells. , the result is that the cost of high-quality shells rises to $200 a kilogram, even though the original material is cheap. In addition, the industry's refined shell is used less: about 10,000 tons per year. At the same time, the number of existing shell equipment is also very low.
Yan
that the conversion of shell or shell polysaccharose into other chemicals can also cause more problems. is a crystalline material that prevents reagents from approaching the polymer chain easily. Under harsh reaction conditions, these chains can easily experience side effects, forming numerous complex complex complex compounds. In response, the separation of biological substring products is often very difficult. , these challenges are no greater than converting wood biomass into biofuels and other chemicals, which took 20 years to commercialize from the laboratory, " he said. "
Chen
said. the use of shell fertilizers to build a profitable and sustainable industry requires creative chemistry. It requires a sustainable separation method that separates proteins, calcium carbonate and shells, and avoids the use of corrosive and dangerous reagents and reduces waste. , however, new approaches are emerging. For example, researchers in Mexico and the United Kingdom proposed a lactic acid fermentation process for shell preparation. The process converts 30 to 50 kg of shell waste in a single reactor. Researchers in the UK, US and China have developed a bacterial blend that consumes protein and breaks down calcium carbonate. Protein hydrolytes and calcium lactic acid are by-products and can be used to produce animal feed and calcium supplements. , scientists at the University of Pennsylvania have found that discarded crab and shrimp shells are likely to be key to extending the power supply of water sensors, the life of microbial fuel cells. They used a pillow-like electrode made of carbon fiber cloth to study a variety of crustaceans, including shells. Electrodes are placed in seafloor sediments or suspended in water for naturally occurring microorganisms to maintain physical strength by swallowing shells, moving downstream, causing charge to flow. The researchers tested two different sizes of shells and found that both fine-grained and coarse-grained shells increased the power production capacity of marine microbial fuel cells without adding organic food to the bacteria. work is another option may be to design and use ionic liquids. This liquid dissolves carbohydrate polymers and extracts shells. Shell polymers produced in this way have long chains and a high molecular weight and can be made into fibers or films that can be used as wound dressings or water treatments. researchers also need to explore the physical, solvent-free way to isolate the chemical composition of crustacean shells. Ball grinding (placing material in a metal ball in a rotating cylinder) finely grinds shells and breaks crystals. The combination of chemistry and mechanical force has proved to be very effective. For example, wood can be broken down without heating using ball grinding and acidic catalysts.
Yan
and
Chen
wrote that while technologies such as ball milling have been used to refine wood biomass, little attention has been noted about their potential for shell waste. , however, nitrogen
chemicals
such as ETA derivatives or furans are being developed. Researchers say it will take at least five years to scale up and another 10 years to commercialize. Future research will need to explore research routes from shell to other chemicals to increase product yields through improved catalytic action and pre-treatment. "We recommend the development of a shell waste refining process pipeline, just as wood biomass can be separated and converted into different products in a set of equipment." "
Yan
said. New methods are being developed in Europe for processing shell-rich fishery industry waste and producing integrated solutions for fine chemicals. these advances require efforts and are driven by public concerns about energy security and climate change, as well as financial support from governments and the chemical industry. Shell waste bio-refining will provide new business opportunities in Southeast Asia and other places.