Seashells can be a valuable resource and a range of industries are now looking at how they can be used, not just to improve profitability but also sustainability. Mined calcium carbonate is used in a range of industries such as construction materials, food supplement, pharmaceutics, animal feed, plastic production, and others but seashells offer a natural alternative. The top potential uses for seashells include use in:
- Poultry nutrition;
- Water purification;
- Reating toxic waste;
- Oganic fertiliser;
- Construction material.
A natural product they are collected from locations such as the Caspian sea.
- “Seashells from the Caspian Sea area contain natural aragonite and mineral structures and are the rich sources of calcium”.
In addition to natural sources such as the Caspian, mussel and other seashell farming is a fast-growing industry around the world driven by increased demand for protein and seafood. However, this increase in shellfish production also generates a large amount of shell waste which is becoming a significant environmental problem in some countries.
Using Seashells for Poultry Nutrition
Global egg production has grown by 24% over the last decade, and there is a need for sustainable feed sources for the poultry industry. Laying hens have a high demand for calcium, especially during peak egg production when calcium output is at its greatest. Calcium Carbonate makes up 94% of the eggshell composition and laying hens, in particular, require calcium supplements to maintain the strength and quality of eggshells, and several studies have shown the benefits of using seashells as a calcium source in the diets of laying hens. For egg producers, a well-developed shell is an important aspect of product quality. Currently, ground limestone and seashell are the common sources of calcium for laying hens, researchers have also investigated the potential of whelk shells. Particle size is an important factor in the availability of calcium from different sources, and it has been found that a larger particle size or lower in vitro solubility may increase calcium retention for layers.
- “The use of crushed seashells as a calcium supplement has been shown to improve egg quality compared with other sources of calcium”.
A study comparing blends of fine limestone along with large limestone, eggshell and seashells found that eggs from layers fed the supplement containing seashell had an increased calcium content within the eggshell.
Feed Innovation Services have compared seashells, Oyster shells and limestone. In their report it was concluded that seashells remained stable during a longer time period compared to the coarse limestone and oystershells. The fine limestone reacted immediately, followed by a sharp increase in pH value. This indicates a more gradual solubility in an acidic environment of the Morgan Agro seashells compared to limestone and oyster shells. Feed Innovation Services also noted, that can be hypothesized that the more gradual solubilization of the seashells will lead to a longer retention time in the gizzard, and a better egg shell quality due to a more stable calcium supply in the small intestine.
Calcium supplementation can also improve the performance of broiler chickens, and it has been found that using seashells as a supplement source can lead to increased feed intake compared with birds fed with supplements from other calcium sources.
The lack of clean drinking water is a major public health problem in developing countries. However, seashells can play a role in water purification and providing clean drinking water in many communities. Conventional purification methods include chemical precipitation, coagulation, flocculation, ion exchange, membrane filtration, activated carbon and high-cost technology (such as the use of carbon nanotubes). There are different methods of tertiary treatment, and one of the most effective is the photocatalysis of water to remove any final trace contaminants. This process normally uses titanium dioxide, which is expensive and not affordable in many developing country situations.
By replacing this with material from the calcium derived from seashells called hydroxyapatite – which can also be found in teeth and bones – researchers are aiming to significantly reduce the cost of water treatment by reusing a renewable unwanted waste product. Naturally available materials including mollusk shells, called biosorbents, can clean up contaminated water at the same efficiency, but with little impact on the environment and human health. Wastewater could be treated using seashells leftover from restaurants, hotels, commercial farming and other foodservice outlets, according to research by scientists at Bath University. This could provide “significant” savings if the system can be scaled up to industrial level.
Treating toxic waste
Contamination of soil with heavy metals is a worldwide problem. Mine and smelter discharges, sewage irrigation and sludge application to agricultural land, as well as gaseous emissions from industrial processes, are some of the major sources of heavy metal contamination in soil. The toxicity of these heavy metals may affect soil quality and agricultural productivity and ultimately becomes a hazard to human and animal health.
Effective treatments of industrial waste streams and toxic spills containing heavy metals depend on the rapid removal of high concentrations of metal ions. Here we describe such a method using minimally-processed waste mollusk and crustacean exoskeletons.
- Compared to calcium carbonates of geologic origin, biomineralized shell materials exhibit extremely rapid sequestration of metal ions: a 10,000 mg L−1 Pb solution, for example, can be reduced to less than about 0.5 mg L−1 in five minutes using the comminuted clamshell, while at higher initial concentrations, both clam and seashell can extract almost twice their weight of Pb.
In Ireland, toxic and environmentally damaging leachate is the product of municipal solid waste disposal in landfill systems. Currently, 51% of landfill leachate (LFL) produced in Irish landfill sites is discharged directly into sewer mains with 48% being treated in increasingly overloaded regional wastewater treatment plants. These discharge and treatment options are inadequate and costly and pose risks for both public and environmental health.
Onsite treatment of leachate in Ireland is uncommon (<1%), but represents a viable and sustainable alternative to current practices. A study assessed the effectiveness of using a fixed-bed column system to treat LFL. This system combines both bioremediation using materials such as seashells and adsorption. The research has shown that the system is capable of reducing the concentration of ammonia, phosphate and nitrate from leachates.
Fertilizer and Soil Amendments
Organic farming is a fast-growing segment of the farming industry, driven by consumers desire to reduce the reliance on chemicals in food production. Seashells can be a useful component of natural or organically certified fertilizers and soil amendments and can contribute to reducing the reliance on synthetic fertilizers in food production. Calcium is an essential element needed for the growth and development of plants being an important factor for cell wall and membrane stability and also playing a role in many developmental and physiological processes, including the response of plants to biotic stress.
Shells are a calcium-rich resource that can be used to produce calcium oxide (lime), which can be used to improve acidic agricultural soils and increase calcium content. Studies have found that the composting of the seashell increases the utility of seashell as a liming material for crop cultivation.
In developing countries where concrete is widely used, the high and steadily increasing cost of concrete has made construction very expensive. The high cost of conventional building materials is a major factor affecting housing delivery in the world. Use in construction also encourages the reduction of extraction of natural stone, such as granite and marble.
It has been shown that while seashells have been used as a replacement for both cement and aggregate, there is still a lack of data on durability, as well as the actual influence of seashell powder as a cement replacement. Despite the reduction in the workability and strength, it is suggested that seashell waste could still be utilized as a partial aggregate at a replacement level of up to 20% for adequate workability and strength of concrete for non-structural purposes.
Seashells are a renewable resource making an important contribution to developing a circular economy in a wide range of industries ranging from agriculture to construction and can help make a positive contribution to food security and sustainability.
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Source: Morgan Agro
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