Unlike clay, which is difficult to recover completely once immersed, Plaster of Paris can be recycled if idols are collected from fixed immersion sites instead of flowing rivers
Plaster of Paris (PoP), chemically known as calcium sulfate hemihydrates (CaSO4.½H2O), is obtained by heating gypsum (CaSO4.2H2O) at controlled temperatures and has been in use for more than 10,000 years across civilisations. According to Material Safety Data Sheets (MSDS), gypsum is non-toxic, non-combustible, and safe for human use. It is widely applied in construction, medicine, and dentistry, proving its biocompatibility. This information challenges the widespread perception that PoP idols are inherently harmful to the environment. In contrast, clay (shadu) idols, often projected as eco-friendly, are not necessarily free from impurities. Natural clay is seldom pure and may contain heavy metals and minerals such as silica, manganese, and magnesium. These elements, when leached into waterbodies, would increase water hardness, can also affect aquatic life and drinking water quality. Hence, the assumptions that clay idols are always safer and non-polluting are not backed by scientific logic.
The cultural and religious sentiments around the immersion of idols of Lord Ganesh originate from the story where Goddess Parvati creates Ganapati from the dirt of her own body. The symbolic message is clear that life originates from the earth and eventually dissolves back into it, representing the spiritual idea of moksha. It reminds us that idol-making and immersion should respect the same cycle of nature, returning the material harmlessly back to the earth. Yes, PoP idols do not dissolve completely or immediately after immersion. Instead, they undergo a slow process of weathering and gradual disintegration. As a result, sometimes the fragments often float or wash ashore, creating distress among devotees who consider it disrespectful to see Ganapati idols broken and scattered. When PoP idols are immersed in water, the surface begins to react with the water, forming fine cracks and softening over time. This leads to slow flaking, weakening of structural strength, and eventual disintegration. Unlike clay idols, which readily absorb water and break down quickly, PoP idols resist dissolution and therefore degrade at a much slower pace.
PoP idols, when produced with quality control, offer several practical advantages. They are lighter than clay, making transport and logistics easier and more economical, especially for large idols during festival seasons. Their strength and durability surpass those of clay, ensuring safer handling during installation and processions. Moreover, gypsum is recyclable. Once a PoP idol has been used, the set material can be recovered through controlled heating and converted back into usable gypsum powder. This property holds immense potential for sustainability, provided a systematic recycling infrastructure is put in place. Unlike clay, which is difficult to recover completely once immersed, PoP can be recycled if idols are collected from artificial tanks or fixed immersion sites instead of flowing rivers. This way, the material can be recovered and reused for making new idols, creating a sustainable cycle. I still remember how, as children, we would collect the disintegrated clay from local waterbodies days after immersion and use it to make small molds just for fun.
The concern that PoP idols release heavy metals into water lacks strong scientific grounding, as pure gypsum is widely used in medical science without toxicity issues. Any contamination is more likely a result of poor manufacturing practices or use of unsafe decorative paints and additives, not the PoP itself. The gypsum itself is chemically stable and non-toxic. This issue of paints and additives is not exclusive to PoP idols. The clay idols are equally vulnerable to contamination when coloured with synthetic paints or decorated with metallic powders. Thus, the real environmental concern lies in the external substances applied during idol finishing, not in the core material, whether gypsum or clay. If recycling units are established to collect, process, and reuse materials from immersed idols, any environmental impact of PoP could be significantly reduced, turning a perceived liability into an opportunity for sustainable innovation.
There is a big hype about water pollution during the festival season, often attributed solely to PoP idols, but the reality is much broader and more concerning. The larger issue lies in immersing idols along with plastic bags and other non-biodegradable. Also, beyond festivals, untreated sewage, industrial effluents, detergents, and domestic waste are routinely released into rivers and lakes. The most troubling aspect is that even educated individuals, despite being aware of the consequences, continue to engage in these practices, mostly due to habit or convenience. Thus, water pollution is not just about PoP idols; it is a reflection of human negligence and misuse of natural resources, making it a far more serious environmental concern that demands collective responsibility and sustainable practices.
A promising startup model can unite idol makers, recyclers, and communities to build a circular economy around Ganapati idols. Collection systems at immersion sites, combined with recycling facilities, can ensure that the sacred remains of idols do not desecrate rivers while also recovering raw material for reuse. Such an initiative would address the dual challenge of maintaining religious sentiments and reducing water pollution, while also creating economic value. Ultimately, this approach harmonises tradition with modern environmental responsibility, ensuring that the celebration of Ganesh Chaturthi remains both spiritually fulfilling and ecologically sustainable. Jai Ganesh!
(Dr Mithil S Fal Desai is Assistant Professor in Chemistry (contract) at Shree Mallikarjun and Shri Chetan Manju Desai College