Context: A team from Stanford University and a Nepal Based NGO is attempting to develop a low-cost decentralised and environmentally sustainable method of producing sanitary napkins from Sisal leaves. The objective is to meet the growing demand for low-cost and environmentally friendly menstrual hygiene products.
About Sisal
- Sisal is a xerophytic succulent plant, known for its ability to store water and thrive in drought-prone areas.
- Sisal has thick sword-like leaves that grow up to 2 m long which are covered with a waxy layer.
- The lifespan of a sisal plant is about 7-10 years, during which it produces 200-250 usable leaves.
- Each leaf has about a thousand fibres that can be used to make ropes, paper, cloth, and highly absorbent material.
- Sisal plant is a native of Mexico.
- Sisal is well adapted to arid and semi-arid regions of India. It grows mainly in Odisha, Jharkhand, Maharashtra, Western West Bengal and some parts of Bihar and many southern states where annual rainfall varies between 60-125 cm and temperature 40-45 degree celsius.
- Global production: Brazil is world’s largest producer of sisal fibre followed by Tanzania, Kenya, Madagascar, China, Mexico and Haiti.
- Current uses of Sisal:
- Sisal leaves have been used for making paper, twine, cloth and carpet.
- Mezcal: Sisal plant is used to make Mezcal which is a distilled alcoholic beverage.
- Researchers have reported that sisal leaves are highly absorbent and retentive. Absorption capacity of sisal leaves is higher than those found in commercially available menstrual pads.
Benefits of Sisal in Making Sanitary Napkins
- Water Efficiency: Sisal cultivation requires less water compared to cotton industries, contributing to water conservation.
- Environmental Impact: Sisal is less environmentally damaging than cotton, making it a more sustainable choice for sanitary napkin production.
- Substitute for Cotton-CMP: Replacing cotton-CMP (Chemical Pulp) with sisal fluff pulp could enhance the environmental sustainability of sanitary napkin production in the long term.
- Timber Alternative: While timber could be an alternative to cotton, it is viable only in regions with an "endless supply of sustainably harvested forests."
- Distributed Manufacturing: The concept of "distributed manufacturing" supports the environmentally sustainable production of sanitary napkins, allowing for a more widespread and eco-friendly manufacturing process.
- Addressing Access Issues: Utilising sisal in sanitary napkin production contributes to addressing the lack of access to menstrual products, fostering an "open-source framework" for menstrual hygiene solutions.
Process of Making Sustainable Absorbent Material from Sisal
- The process begins by feeding sisal leaves into a decorticator, a machine that mechanically separates the fibres.
- In the next step, a process known as delignification dissolves lignin, a water-repelling polymer in plant cell walls, leaving behind highly absorbent cellulose fibres, substituting the traditional wood-to-wood pulp process known as the Kraft process.
- While effective, the Kraft process generates volatile and toxic by-products, causing air and water pollution.
- In the environment, researchers identified two organisms proficient in converting wood to wood pulp: termites and wood-rot fungi.
- The termite guts house an incredible consortium of organisms, including microbes of various shapes and sizes, which delignify wood through a process not completely understood by scientists.
- Peroxyformic acid, an important compound in this process, selectively removes lignin while preserving the structure of cellulose microfibers.
- Treatment with peroxyformic acid allows for the compound's reuse over several cycles, and it decomposes into water and carbon dioxide at the end of the process, requiring no neutralising chemicals and minimising environmental damage.
- The amount of CO2 released during the breakdown of peroxyformic acid is minuscule compared to the total CO2 in the overall analysis.
- After treating the sisal fibres with peroxyformic acid, the process proceeds by washing them first with a solution of dilute sodium hydroxide and then water.
- The result is a wet pulp that is then dried and mechanically blended to obtain a dry mass called fluff pup. This fluff can be used in place of cotton in sanitary napkins.
Increasing Demand and Lack of Access of Sanitary Pads
- Increasing Use: There has been a significant rise in the number of people using hygienic methods, such as sanitary napkins, tampons, and menstrual cups, to manage menstruation in India.
- Limited Access: Despite promising growth, access to menstrual hygiene products remains limited for around 500 million people worldwide. For example, in rural India, only 42% of adolescent women exclusively use hygienic methods to manage their periods.
- Rising Cost: A key barrier to making menstrual hygiene products, like sanitary napkins, accessible is the rising cost of raw materials and distribution.
Problem of Safe Disposal and Unsustainable Use of Sanitary Pads
- Increasing Waste: According to a United Nations Population Fund report from 2022, Patna alone discards 9.8 billion sanitary napkins every year. Another estimate from a 2022 study placed the monthly quantity of discarded sanitary napkins in Chennai at 27 million.
- Problem of Dioxin: Single-use sanitary napkins contain dioxin, a persistent environmental pollutant and a carcinogen, putting users at risk of cancer. The International Agency for Research on Cancer (IARC) classifies dioxin as a “known human carcinogen.”
About Dioxins
- Belong to the so-called “dirty dozen” - a group of dangerous chemicals known as persistent organic pollutants (POPs), covered by the Stockholm Convention.
- Found throughout the world in the environment, they accumulate in the food chain, mainly in the fatty tissue of animals (Bioaccumulate).
- Mainly by-products of combustion and industrial processes but can also result from natural processes, such as volcanic eruptions and forest fires.
- These are unwanted by-products of a wide range of manufacturing processes including smelting, chlorine bleaching of paper pulp and the manufacturing of some herbicides and pesticides.
- More than 90% of human exposure is through food, mainly meat and dairy products, fish and shellfish.
- Has been associated with a range of toxic effects, including chloracne; reproductive, developmental and neurodevelopmental effects; immunotoxicity; and effects on thyroid hormones, liver and tooth development. They are also carcinogenic.
Potential Alternatives
- The absorbent material in sanitary napkins currently comprises a combination of wood pulp and synthetic superabsorbent polymers (SAPs). To address environmental and health concerns, efforts are underway to reduce the use of SAPs and substitute them with cellulose-based nanofibers.
- Additionally, plant fibres, such as those derived from banana plants, have been employed to synthesise absorbent materials. However, banana plants are highly sensitive to drought, making them less sustainable for producing sanitary napkins in arid or semi-arid and drought-prone regions. Access to hygienic menstruation is particularly critical in countries located in the tropics, which often face drought-related challenges.