A choona or lime factory in Kodungallur, Kerala informed Beauty Without Cruelty that the primary source of choona (calcium carbonate) other than mining (limestone) was from marine organisms, i.e. sea shells or kakka in Malayalam.

These living shells or marine animals are collected mainly by women from sea shores and backwaters of Kerala. The collection of kakka is a common occupation in the coastal belt of the Arabian Sea covering places like Kollam, Alappuzha and Ernakulam districts.

The flesh of the live creatures inside the shells is scooped out and sold for a good price in the meat market, whereas the shells are sold to the choona factories in the region which pick up huge quantities.

At these factories the shells are mixed with charcoal and baked in a kiln. The foul smell during baking is because the shells have a thin membrane-like coating. Twenty-four hours later the shells are transformed into ithil – the local name for choona or calcium hydroxide.

Choona is mainly utilised as edible lime, an ingredient used in paan, as an insecticide (particularly on tea estates), for whitewashing walls and as a cleaning agent in waste water treatment systems.

Production of Sipo chuna in Odissa

Ganjam is where the lime industry of Odissa is situated. Marine mollusc shell lime preparation which is indigenous and crude, is much preferred because shell lime putty remains okay for 2 months, whereas the stone lime becomes hard within 2-3 weeks.

The lime produced from the shells of molluscs is called sipo chuna in Odissa. By heating shells quick lime is produced. Hydrated lime is the reaction of this quick lime with water. If more water is added, it becomes dahi chuna or milk of lime i.e. lime putty.

Different types of mollusc shells (bivalves) like khola sipo, gondhi sipo, pati sipo and genda (snails) are utilised – snails being the most. Locals collect these shells. The method of collection and lime preparation has been passed down over generations.

The burning unit or klin (bhati and chula) that is specially constructed in the open (although surrounded by settlements resulting in harmful pollution for people who live there) in an east-west direction for burning mollusc shells also has a fan, and wheel; and then there is the slaking pit (kunda). The charcoal used is collected from kewda and liquor distilleries or by burning forest wood.

Lime is very corrosive to human skin and the burning, slaking and packing need to be carefully handled. Shells and charcoal are washed and usually mixed in a ratio of 2:1 for lime putty and 1:1 by volume for dry hydrated lime (powder lime). However, the highest amount of charcoal is used for khola sipo due to its thick and large shell size. Gondhi and genda consume more charcoal than pati sipo due to their hard, compact shells. A single burning takes 3 to 4 hours.

For 100 kgs wet lime about 48 kgs of shells are required; and for 100 kgs of powder lime about 117 kgs of shells are required.

Lime of shell origin is used for white washing – the demand for lime putty is decreasing as people prefer to use distemper.

Khola and gondhi are the shells mainly used for preparation of items put in the mouth (since they can cause damage) like gudakhu (a pate of tobacco leaf, lime and some sweetening agent), nasa (snuff powder of tobacco leaf and lime), khoini (tobacco leaf and lime), and paan (betel leaf, lime and other ingredients).

It is also used as an agent to increase the alkalinity of fishponds, as a water purifier in dug wells and for hygienisation of sewage sludge, as well as an ingredient in the preparation of cement and bleaching powder.