Finding eco-friendly ways of making paper

In an interview Anupam Kumar, a junior scientist in Physical Chemistry, Pulping and Bleaching Division, at Central Pulp and Paper Research Institute in India with Chemical Today magazine speaks at length about the various innovative researches happening with non-conventional raw materials which hold the potential to make this industry more cost effective and environment friendly.

Overview of your current research.

My research group focuses on developing papermaking cellulose from agro forestrybased novel wood species and nonconventional raw materials such as grasses, agro and agro-industrial residues through environmentally benign pulping and bleaching processes at laboratory and pilot plant scales. We are also researching on integrating pulp and papermaking processes to biofuel and dietary fibre production along with transforming solid wastes generated during pulp and papermaking to biochar for energy, soil and water applications.

Recently, we got involved in design and development of pilot plants for bagasse depithing, black liquor desilication and heattreatment. Preparation of activated carbons, development of pressure swing adsorption based refrigeration technology andadsorptive wastewater treatment is other research areas in which we are engaged since long. We are also into data collection and use response surface methodology, artificial neural network and multicriteria decision-making methods in our research.

Research technology used for the pulping and bleaching research.

Currently, our research laboratory is running several pulping and bleaching based research projects sponsored by government and industries. Our major thrust is on exploring the utilisation of rice straw for production of different grades of pulp through various environment friendly pre-treatment, pulping and bleaching technologies; improvement in selectivity of oxygen bleaching; increase in brightness ceiling of agro residue pulps in cost effective manner specifically for wheat straw; and ozone treatment of indigenous raw material pulp for better bleachability and quality of effluent.

India is a major rice producing country and generates plenty of rice straw. But despite the feasibility of rice straw to produce pulp and paper, there is no single mill in India which runs completely on rice straw. This is due to several technological constraints. To develop a complete technology package for producing pulp and paper solely based on rice straw is the greatest challenge for us. We are also engaged in the evaluation of novel raw materials for pulp and paper; designing and investigating energy efficient single and dual stage pulping processes; developing new elemental and total chlorine free short bleaching sequences; and appraisal of new chemicals and additives for pulping and bleaching. All the researches are being carried out in our research laboratory with the primary motive to benefit Indian pulp and paper industries.

Use of sustainable chemical materials for research

General chemicals used in pulping and bleaching research are: sodium sulphide, sodium hydroxide, sodium sulphite, sodium carbonate, anthraquinone, potassium hydroxide, organosolvents (cooking chemicals); diethylenetriaminepentaacetic acid, ethylenediaminetetraacetic acid, hydrogen peroxide, ethanol, methanol (pretreatment chemicals); chlorine water, chlorine dioxide, hydrogen peroxide, sodium hydroxide, oxygen, sodium silicate, magnesium sulphate, diethylenetriaminepentaacetic acid, sodium hypochloride, potassium hypochlorite (bleaching chemicals) etc. Various chemical companies are manufacturing different types of solid and liquid additives these days which are used as cooking and bleaching aids.

Recently our research laboratory completed several projects on an evaluation of effects of additives on pulping and bleaching characteristics of hardwood and agro-residues. These were sponsored by Solenis Singapore Pte Ltd (Singapore), Tata Chemicals Innovation Centre (India), Cornell Brothers Co India Pvt Ltd (India), Singhania Chemicals Corporation (India), Rishabh Metals and Chemicals Pvt Ltd (India) etc.

A benefit of Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) to selecting raw materials.

Selection of suitable raw materials is extremely decisive for pulp and paper industry since raw materials influence the overall quality and economics of papermaking process. Generally, for woody raw materials, selection is made in terms of age and species.

At the time when government has framed National Agroforestry Policy, paper mills had to depend on social and agroforestry for meeting the wood demand. Deciding which tree species should be grown up to what age is of greater significance from sustainability point of view. The general approach for selecting suitable age and species of a tree for pulp and paper include analysis of wood characteristics; cooking experiments; and pulp and paper characterisation.

However, implementing these steps consume a great quantity of time, manpower and chemicals. With an intention to make this raw material selection process shorter, simpler and cheaper, we adopted multicriteria decision-making methods specially TOPSIS and SAW methods. Under this approach, we focus only on beneficial and non-beneficial wood characteristics, assign weights to each characteristic, calculate composite scores and finally rank them according to their preferences for pulp and papermaking. The preliminary results achieved through these methods were found in confirmation of those published in the literature. We are further exploring these methods to make suitable selections among different woody/agro/ grass based raw materials, pulping methods, coating formulations etc.

Technologies used in mechanical and chemical pulping process.

Though mechanical pulping provides higher yields and less pollution load, its higher energy intensity is the greatest drawback. Hence, the main thrust in mechanical pulping is to reduce specific energy consumption. Several measures such as improvements in refiner efficiency, heat recovery, low consistency refining, advancements in chemical thermos mechanical pulping (CTMP) etc. are being taken into consideration. We have recently completed a research project on CTMP of a hardwood sponsored by JK Paper Limited, Gujarat and the results found were encouraging.

Currently, we are running another research project on CTMP of a different hardwood sponsored by ITC Life Sciences and Technology Centre, Bangalore. Latest advancements in chemical pulping include a use of pulping additives, alcohol based solvent pulping, enzymatic pulping, adoption of pre-treatment technology, design and control modifications in continuous and batch digesters, improved heat recovery, integrating pulping process to the biorefinery, use of radiation etc.

Challenges in the pulp bleaching research process.

Pulp bleaching is done through conventional, elemental chlorine free (ECF) and total chlorine free (TCF) processes. Conventional bleaching process uses elemental chlorine, ECF process uses chlorine dioxide while TCF process uses not any chlorine-based chemicals. Conventional bleaching process leads to higher pollution load in comparison to ECF and TCF processes; however, ECF and TCF processes generally do not provide that level of brightness to the pulp as that of the conventional process. Hence, the biggest challenge in pulp bleaching research process is to achieve greater brightness with lowest pollution load.

In India, big mills are adopting ECF technology after installation of oxygen delignification system, while small mills are still following conventional bleaching sequence. In India there are two or three mills which have completely switched over to ECF bleaching technology, much more are on their way to adopt ECF bleaching process, but a use of TCF bleaching technology is still rare. Implementation and establishment of efficient oxygen delignification, ozone and enzymatic bleaching processes for agro pulps are still a greater challenge in India.

Other challenges in pulp bleaching research processes include lowering chemical and biological oxygen demand discharges, reducing colour in bleach effluent and increasing a higher percentage of recycled process water.

Advantages of your material usage for research compared to other researches.

We focus mainly on industrial research rather than academic research. Our research laboratory generally takes up research projects to cater to the needs of pulp, paper and allied industries. The process technology, pulp and paper materials are also developed on demand of national and international agencies, industries, universities and research institutes. These are our scoring points over traditional research.

Strategy to commercialise the research technology.

Major pulp and papermaking companies in India and overseas, work in collaboration with our research laboratory to commercialise the technologies. We developed pulping and bleaching technologies for producing paper from palm oil empty fruit bunches and wheat straw in collaboration with Eko Pulp and Paper, Malaysia and Prairie Pulp and Paper, Canada respectively and these technologies are successfully being used for commercial production. We worked on developing pilot-scale technologies for liquor extraction from hardwood and for producing pulp and paper from agrifibres in association with ITC Life Sciences and Technology Centre, Bangalore. We are awaiting their trial at mill scale. Recently, we conducted a commercial plant trial at Madhya Bharat Paper Mills Limited, Madhya Pradesh taking jute core as raw material. The trial was based on our laboratory scale findings and has garnered hope for utilisation of jute core as a potential raw material in the Indian paper industry.

In future, we are planning to extend our research on the development of cellulose-based biofuels, chemicals, packaging products and nano materials.

Challenges faced while conducting research.

Scientific and technical challenges of a research project motivate to work on it. However, there are several challenges that slowdown the pace of research. Some of the prominent challenges include reluctance of majority of pulp and paper industries to participate in active research, retaining the research team i.e. research fellows and project assistants for a considerable period due to temporary nature of these assignments and complex procurement process of instruments and research accessories.

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