Papermaking process in current context of mill closure

Amrit Goswamee

(amritg_2007@rediffmail.com)

Although an early form of paper had existed since the 3rd century BC, Cai Lun, a court official of the Eastern Han Dynasty of China occupies a pivotal place in the history of paper for his development of certain paper-like sheets for writing purposes using a pulp made from macerated tree barks, hemp wastes, old rags and fish-nets in 105 AD. The Chinese paper making process spread to the Islamic world after the battle of Talas and then to Europe. With gradual development and the addition of different types of machinery in Europe and the US, it has reached the present state of the art paper technology that involves a chemical process known as the 'Kraft Process'. The raw material used is lignocellulosic materials bamboo or other softwood. Lignocellulosic materials are composed of three components viz- lignin, cellulose and hemicelluloses. In the Kraft process followed in our paper mills, cellulose is separated by delignification using alkali and sodium sulfide at above 175oC to make pulp which is then bleached using chlorine, dried and then given different shapes of paper. This process breaks down the macromolecule lignin into a mixture of monomeric, dimeric or higher units of fragmented aromatic molecules in the form of black liquor, a reserve of gold in a torn quilt for several values added chemicals but flared up as the energy source for the running boiler. The whole process entails several steps but releases several harmful odorous solid, particulate and gaseous pollutants and substantial liquid wastes causing groundwater pollution, leading to health problems in the surrounding area of the paper mills. In a health camp organized by a medical team from CSIR-NEIST, Jorhat at Jagiroad, it was observed that people in the nearby areas of Nagaon Paper Mill have been suffering from different serious health issues. Thus, sustainability of the paper mills using Kraft Process became a challenge as the environmental issue is now a condition sine qua non, no matter whether the industry is running on profit or not as sooner or later it was sure to come under closure, for the Government of India has already identified the paper industry as one of the major polluting sectors. Because, in the current context of climate change and the COP-26 agenda, India's commitment to a 50% reduction of carbon emission by 2050 and net-zero emission by 2070 can only be achieved by taking drastic measures in many sectors. As per IPCC sixth assessment report released on 27 February last, major cities of India will encounter dangerous levels of heat and humidity with sea-level rise flooding and there will be intolerable conditions if carbon emissions are not eliminated, The report refers that a wet-bulb temperature of 31oC is extremely dangerous for human while a value of 35oC is unsurvivable for more than 6 hours even for healthy persons. In 2012, the Principal Scientific Adviser of PMO, as a Green Chemistry Initiative

convened a meeting at IIT, Mumbai on 7 March under the chairmanship of the Director, IIT, Mumbai with the concerned officials of Central Pollution Control Board, paper industries, distillery industries, a few other polluting industries and research institutes having R&D units on paper to discuss the long-term and short-term measures that can be taken up to combat pollution created by such industries. Before that, considering the pollution aspect and the process mutatis mutandis of the paper mills, CSIR-NEIST, undertook an integrated network project for a bio-pulping process that involves less energy along with four other CSIR laboratories in the country sharing responsibilities of different activities as a suitable alternative to Kraft Process through microbial delignification of lignocellulosic materials using suitable wood-decaying microbes isolated by the institute from the biodiversity hotspot NE region in the 12th five-year plan. Such commercial bio-pulping processes have been developed in Finland and also in the US. The black liquor that would be generated in the entire process was proposed to utilize for isolating the value-added aromatics such as vanillin required in the confectioneries, preservatives such as syringol, auxiliaries for replacing systems in leather industries etc, the demand in the country against which are met through import substitution only. While presenting this long-term measure initiative of CSIR-NEIST in the IIT, Mumbai meeting, the members present in the forum highly acclaimed it. The work on this project was also progressing well with time on cellulose separation and isolation of value-added chemicals such as vanillin etc., from bamboo as per programme using selected microbial species with simultaneous bio-reactor studies and publication of results in high impact factor peer-reviewed international journal. It must be noted that for upscaling a process from its bench scale to the commercial scale, a lot of data are required to be generated for which sufficient time is required. However, with the fortuitous constitution of NITI Ayog replacing the planning commission by the Government of India in 2015 the project at the later stage had to be closed in the midway. Alternative to bamboo-based cellulose paper avoiding Kraft Process papers is also produced from the herbivorous animal poop of elephants and rhinoceros which is mostly fibrous cellulose by blending it with seasonally available non-wood fibres or shredded textile wastes. But the paper quality is not as desirable. It is China again that invented paper two millennia ago made a breakthrough to re-invent non-cellulose based paper in the 21st century sustainable in the present context called stone paper from calcium carbonate. It is prepared by grinding calcium carbonate into a fine powder and then heating it with non-toxic high density polyethene resin that glues the stone elements together in an 80:20 ratio finally after drying, a proprietary coating is given to enhance printing quality. This future stone paper has a density of 1.0-1.6 g per cubic centimetre, the texture is somewhat like that of the outer membrane of a boiled egg, photodegradable but not biodegradable, has its surface smoother, flame resistant, durable, waterproof, absorbs less ink and is lighter. The advantages of stone paper are that it is an easy source of raw material, needs no water and harsh chemicals in its process, can be recycled, reduce carbon dioxide generations, does not pollute waterways and rivers with toxic effluents and most importantly save cutting trees and reduce deforestation.