Towards zero emission pulp and paper production: the BioRegional MiniMill

Growing demand for paper is putting pressure on the World's forests, and although paper made from agricultural residues could meet global demand five times over, today less than 10% is made using these resources. The primary reason for this is the absence of cost effective, small-scale (～10,000 tonnes per annum), environmentally sound pulping technology. The BioRegional MiniMill was developed in response to this problem. The MiniMill is a modular, regional scale, sustainable pulping process designed for straw and other non-wood feedstocks. The MiniMill innovates in two key areas: (i) preparation, feeding and pulping of straw using a twin screw extruder to reduce energy use, produce pulp in a shorter time and improve pulp quality, and (ii) the inclusion of a small-scale black liquor chemical and energy recovery system, based upon novel fluidised bed technology. The MiniMill is projected to be cost competitive at less than one-tenth the size of the smallest conventional wood-based pulping mill. As with conventional pulp mills, the MiniMill recovers enough renewable energy from the effluent to power the mill and qualifies for carbon emissions credits in accredited countries. In this work we report on some of the key research and development activities, at laboratory, pilot and semi-industrial scale, that have underpinned the design and development of the MiniMill. The ultimate goal of the project is to make available a technically and economically viable process for small-scale cellulose pulp production, that will facilitate the uptake of alternative uses of wheat straw, hemp or flax into the market place.