Black liquor

Agro-based pulp and paper: technological inability?

 
Last Updated: Sunday 28 June 2015

Black liquor

-- The case of India's agro-based pulp and paper mills is representative of most small and medium enterprises (SMEs) operating in the country: low on resources, low on motivation to turn clean, and therefore, low on efficient, non-polluting technology.

Numbering about 300, these mills together produce about one-third (2.0 million tonnes) of the total paper manufactured in the country. But on an average, these paper mills produce less than 50 tonnes of paper per day (tpd). This insignificant individual capacity restricts these mills' access to technology that can treat the vast quantities of effluent -- called black liquor -- which they generate: there is no economically feasible chemical recovery process available for mills with capacities below 100 tpd.

It is a problem that has a spiralling impact. In the absence of a chemical recovery process, these mills discharge the pulping chemicals laden with lignin as effluents. The pollution generated by them is about 60 per cent of the total load from the Indian pulp and paper sector, and six times more than that generated by a wood-based plant for equivalent production. In fact, the agro-based segment faces the prospect of closure of its mills on account of its enormous contaminating capacity. This would destroy a potential source of employment from natural resources. According to the Indian Agro and Recycled Paper Mills Association, India currently has about 15-20 million tonnes of rice and wheat straw, which can yield about 3-4 million tonnes of paper annually -- enough to curtail India's gargantuan paper import bills drastically. But this conversion cannot be effected without a chemical recovery process that is suited to the small-scale agro-based pulp and paper mills.

Industry has limited options to scramble out of this mess. It can either develop a recovery system that is customised for agro-based mills, increase capacity to install the existing technology, shift to wastepaper as the resource base, or close shop. The first choice, besides being least-cost, also has the advantage of access to cheap raw material and value addition to an otherwise low-value but vital rural resource. But has industry reached out for it? Only haltingly, as the few initiatives in this direction show (see box: Lone rangers).

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