DIVE DEEPER:

• Silk is a historic fibre, with evidence of silk garments found in China dating back 8,500 years.

• China remains the dominant geographical force behind silk. In 2020, 63% of all silk was produced in China, followed by India, which has a market share of 33%.

• Approximately 109,111 tonnes of silk was produced in 2020, with production volumes doubling between 1990 and 2019. However, there was a 50% decline between 2015 and 2020.

• Although silk production makes up less than 0.2% of the global fibre market, the International Sericultural Commission estimates that around one million workers are employed in the silk sector in China, while in India the silk industry employs 7.9 million people.

• Labour intensity and the time needed to produce silk – the wait for larvae to hatch, grow and produce silk can take up to eight weeks – means a high price. In 2021, the price of mulberry raw silk in India was INR 2,562 (USD 32) per kilogram, versus approximately USD 1.41 per kilogram for cotton.

• Like leather, many of the environmental concerns around the production of silk have been linked to the Higg Index, which gave it a score of 681 per kilogram, higher than almost any other fibre. The score indicated that silk was 30 times worse than polyester in terms of environmental impact, however it did not take into account the renewability of resources at the start-of-life and biodegradability at end-of-life. The use of the index has been paused pending an independent review on data and methodology.

• While synthetic alternatives are fossil fuel-based and exist in the environment for hundreds of years, sericulture is a natural process. Albeit, one which has been industrialised.

• Most silk is farmed and like all farming, it can have environmental impacts, including freshwater eutrophication, water usage and ecotoxicity. These can come from humidity and temperature control, the use of steam and hot air, water use, fertilisation, and pesticide use.

• Due to different cultivation practices, impacts vary from region to region and farm to farm. One LCA study of gambiered caton silk established that the majority of carbon emissions come from silkworm breeding and reeling, while an LCA of Indian raw silk production found that environmental impact came mainly from cocoon production, particularly fertilisation. Assessment of individual facilities and supply chains is paramount to create a true picture of where impacts lie and where they can be mitigated.

• The larvae used in sericulture are typically fed mulberry leaves. Mulberry trees are known for their positive environmental impact, such as the ecorestoration and bioremediation of degraded and polluted land, carbon sequestration, and combating desertification.

• Silk production is much smaller than cotton and synthetic fibres, with annual production just dipping into the hundreds of thousands of tons as opposed to 27 million tons of cotton and 68 million tons of synthetics. This inherently limits its impact and comparatively, it often performs better – some lifecycle analyses have found that silk is 1000 times more efficient in its energy formation than polyethylene, for example.

• There are multiple standards for preferred silk, including the Indian National Programme for Organic Production (NPOP), the Organic Content Standard (OCS), the Global Organic Textile Standard (GOTS), Certified Wildlife Friendly and the World Fair Trade Organization (WFTO). The Recycled Claim Standard (RCS) can be applied for recycled fabrics and fibres, like Mantero’s Resilk.

• Material innovations include Bolt Thread’s Microsilk, which is made from spider silk. So far it has been used to make dresses, hats, ties and activewear but it is not yet a fully commercial operation.