Sericulture – the practice of rearing silkworms to produce silk – is often viewed purely through the lens of its primary output: the shimmering silk thread. But at every stage of this industry, from growing mulberry trees to reeling silk off cocoons, a significant volume of secondary materials is generated. These materials, commonly called by-products, are not simply waste to be discarded. They carry real economic potential, and learning to recognise and utilise them is what separates a profitable sericulture operation from one that leaves value on the table.
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What exactly is a by-product?
In agriculture and industry, a by-product is any secondary output that arises during the production of a primary commodity. It is not the intended goal of the production process, but it emerges as a consequence of it. In sericulture, silk thread – drawn from the cocoon – is the primary product. Everything else generated in the process of cultivating mulberry, rearing silkworms, and reeling silk qualifies as a by-product.
Research published in Current Research in Green and Sustainable Chemistry confirms that a large amount of sericulture by-products, spanning the entire chain from silkworm cultivation to post-cocoon technology, can add significant value to the seri-economy. These are not marginal outputs. In many cases, the volume of by-products generated exceeds the volume of silk itself, and their combined economic value can make a decisive difference to farm profitability.
Where do by-products arise in sericulture?
By-products are produced at each of the three main stages of silk production: mulberry cultivation, silkworm rearing, and silk reeling. Understanding where they come from is the first step toward knowing how to use them.
By-products from mulberry cultivation
The mulberry plant (Morus spp.) is cultivated primarily to supply leaves as feed for silkworms. However, the plant generates considerably more material than just the leaves that end up in the rearing shed. According to a comprehensive 2025 review in the International Journal of Research in Agronomy, the pre-cocoon stage produces large quantities of pruned branches, stems, roots, unfit leaves, and fallen fruits. These residues can be directed toward compost, vermicompost, livestock feed, herbal preparations, and nutraceutical extracts.
Mulberry fruits, leaves, bark, roots, and wood are rich in bioactive substances such as flavonoids, polyphenols, and alkaloids – compounds with anti-inflammatory, anti-microbial, and antioxidant properties that make them relevant to functional foods and pharmaceutical preparations. Pruned branches that cannot feed silkworms can serve as fuel or be converted into organic material through composting. Research from Tamil Nadu Agricultural University demonstrated that compost made from silkworm litter and pupal waste was richer in nutrients than conventional farm yard manure, and its application significantly increased mulberry leaf yield.
By-products from silkworm rearing
Once silkworm rearing begins, several types of waste accumulate rapidly. These include leftover mulberry leaves, rearing bed refuse, larval moult skins, dead larvae, and – most significantly – silkworm litter, which is the mixture of faecal matter, uneaten leaf fragments, and rearing debris that builds up on the rearing trays throughout the larval period.
Studies indicate that silkworm faecal matter is rich in undigested phytochemicals, dietary fibres, and bioactive compounds from mulberry leaves, making it valuable as a potent organic fertiliser and pharmaceutical material. When processed through composting or vermicomposting, rearing waste significantly improves soil health and crop yield. A field study conducted in Mandya district, Karnataka found that farmers who composted their sericulture waste generated net returns of approximately Rs. 10,695 per acre per year, while simultaneously reducing their dependence on chemical fertilisers.
Research on sericulture waste management in Karnataka has estimated that converting approximately 12-15 metric tonnes of waste generated per hectare annually through composting can increase farmer income by up to 40% while reducing input costs and enhancing soil fertility.
After silk reeling, the silkworm pupae – the transformed stage of the silkworm inside the cocoon – remain as one of the most commercially important by-products. Silkworm pupae are high in both protein and oil, making them suitable for use as animal feed, in cosmetics, and in pharmaceutical applications. Their high protein and unsaturated fatty acid content also positions them as a sustainable alternative to conventional animal protein sources. Pupal powder has been incorporated into protein supplements, bakery products, and fish feed with documented results – fish fed diets supplemented with silkworm pupal meal have shown significantly improved growth rates.
By-products from silk reeling
The reeling process – where continuous silk filament is unwound from cocoons in hot water – generates a distinct set of by-products. Not all cocoons are suitable for reeling. Pierced or cut cocoons, which are unsuitable for continuous reeling, are used in handicrafts, decorative art, spun silk production, and the manufacture of composite materials. Reeling waste – floss silk, noil, and short fibres – is repurposed into spun yarn, nonwoven fabrics, upholstery, and insulation.
Two silk proteins produced during reeling deserve particular attention: fibroin and sericin. Fibroin forms the structural core of the silk thread and accounts for 70-75% of silk protein. Sericin is the gum-like coating that binds the fibroin filaments together, making up 25-30% of the silk protein content. In conventional textile processing, sericin is washed away during degumming and discarded – often into wastewater. This represents a significant loss.
Sericin has been recognised as a potential biomaterial due to its biocompatibility, biodegradability, anti-inflammatory, antibacterial, antioxidant, and photoprotective properties. It can be formulated into hydrogels, films, sponges, foams, and particles for applications in tissue engineering, wound healing, and drug delivery. Its use in cosmetics – specifically in creams and shampoos – increases hydration, elasticity, and anti-aging effects, making it commercially relevant to the personal care industry. The moisturising power of sericin also supports its use as a therapeutic agent for wound healing and protection against ultraviolet radiation.
Sericin’s recovery and reuse, rather than disposal, is now understood to carry both environmental and commercial value. Wastewater from silk degumming that contains discarded sericin contributes to environmental pollution – recovering and processing that sericin instead converts a pollutant into a marketable ingredient.
Why by-product utilisation matters for sericulture
The significance of by-products in sericulture goes beyond supplemental income. Valorising sericulture by-products enhances the economic value of the entire industry and improves the livelihoods of rural populations by creating additional income through waste management and circular bioeconomy practices. When sericulture is viewed not as a single-product industry but as a multi-output system, the economics change considerably.
Each stage of production that would otherwise generate disposal costs instead generates sellable material. Silkworm litter that would require removal and dumping becomes organic fertiliser that reduces chemical input costs. Pupae that would be discarded after reeling become a protein source for the poultry or aquaculture sector. Sericin that would be discharged as wastewater becomes a raw material for cosmetics or biomedical products. With appropriate processing technologies and market development, sericulture by-products can support a zero-waste industry model that creates rural entrepreneurship opportunities and strengthens the bio-circular economy.
For students and practitioners of sericulture, understanding what a by-product is – and where each one originates – is the foundational step. The by-products themselves are diverse, their applications span agriculture, food, pharmaceuticals, cosmetics, and materials science, and their combined value can rival or exceed that of silk in certain production contexts. Recognising them as resources rather than residues is what makes modern sericulture both economically viable and environmentally responsible.
What do you think? Given that by-products like silkworm pupae and sericin have applications in pharmaceuticals and cosmetics, should more investment go into processing infrastructure for small-scale sericulture farmers? And which by-product – mulberry residues, silkworm litter, or silk proteins – do you think holds the greatest untapped potential for rural income generation?
References
- https://www.sciencedirect.com/science/article/abs/pii/S2589014X2030236X
- https://www.agronomyjournals.com/special-issue/2025.v8.i8S.3644
- https://www.extensionjournal.com/article/view/1619/8-2-31
- https://www.agronomyjournals.com/archives/2025/vol8issue8S/PartF/S-8-8-42-306.pdf
- https://www.extensionjournal.com/article/view/2536/8-10-21
- https://www.researchgate.net/publication/361843089_ECO-FRIENDLY_APPROACH_FOR_SERICULTURE_WASTE_MANAGEMENT_AND_NUTRIENT_ENHANCEMENT_USING_VERMICOMPOSTING_TECHNOGY_TO_IMPROVE_SOCIOECONOMIC_STATUS_OF_KARNATAKA_A_REVIEW
- https://www.extensionjournal.com/article/view/2323/S-8-8-11
- https://pmc.ncbi.nlm.nih.gov/articles/PMC9699483/
- https://pmc.ncbi.nlm.nih.gov/articles/PMC5124675/
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