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BioRegional MiniMills - mini pulp mill technology for agricultural crops and residues - NF0607

The BioRegional MiniMill is a new technology which will process locally-available agricultural crops and residues, such as wheat straw, to make cellulose pulp for paper. The MiniMill is a modular continuous paper pulping and effluent recovery process which is expected to be cost-competitive with traditional large pulp mills, at less than a tenth of the scale and using 50% less energy. Using locally-available resources such as wheat straw, hemp, flax and miscanthus would bring environmental benefits (of reduced transport and reduced pressure on overseas forests) and economic benefits for farmers and the paper industry. The paper industry would like a locally-available pulp, and straw and other agricultural crops can produce a quality paper-making fibre. Agricultural crops and residues are bulky and so best pulped locally on a small scale, but to date there has been no clean technology to do this on a small scale.In 1997, a company, BioRegional MiniMills (UK) Ltd, was formed to develop such technology, the MiniMill, led by environmental charity BioRegional Development Group and including the World Wide Fund for Nature (WWF) and five UK paper companies, Sappi, James Cropper, Inveresk, Curtis Fine Papers and Tullis Russell. The MiniMill is designed to operate on the smaller scale required and to get the best results from straw and other agricultural crops and residues. In an almost completely closed loop process, it will recover the energy and chemicals from the effluent produced from pulping for reuse in the process, making the mill almost completely self sufficient in renewable energy derived from the effluent. It also advances the state of the art with processing that improves the quality of the straw pulp while reducing pulping time and energy, water and chemical use. The new elements of the MiniMill have been robustly tested at laboratory scale and semi-industrial scale (1) and international patents are pending with the priority date of August 2001. Independent experts have reviewed the technology and confirmed it’s technical and economic feasibility (2) (3). The project is now at the final development stage. The main objective of this research is to operate the new elements of the equipment at full industrial scale and carry out a work programme to optimise the process, products and supply chain, determine the environmental, economic and technical characteristics and complete the final research and development work. The intention is that after this stage there will be sufficient information and confidence to go on and build the first full-scale MiniMill. This project is relevant to Defra policies as it is developing a process for non-food use of crops, and through this final research and development phase will remove the technical barriers to commercial scale implementation of the straw and other non-wood pulp production in the UK. The project will assess the MiniMill process, product and supply chain in environmental, economic and technical terms, including; a life cycle assessment, pulp quality development programme, market study and final economic costings.Introduction of a technically and economically viable method of small-scale cellulose pulp production will facilitate the uptake of non-food uses of wheat straw, hemp or flax in the market place. Of the ten million tonnes of straw generated annually in the UK, research and discussions with farmers and straw merchants have shown (4) that four million tonnes of waste straw is not used for other purposes and could be collected for use in pulping. The market potential for high quality straw pulp in the UK is likely to be as a substitute for up to 20% of the imported wood pulp market. This would require 12 MiniMills, each using 75,000 tonnes of straw or a total of 900,000 tonnes, putting £27 million into the agricultural economy and generating pulp to a value of £131 million per annum. In addition, there is potential to make a bio-based plastic substitute or perhaps even textiles from the cellulose pulps produced, further increasing the potential market scope.It is intended that the project results will be publicised at appropriate conferences during 2005-6 and in the trade press and UK and international media, and that the project will lead to the construction of the first full-scale MiniMill in the UK in 2007. The technology would also be of great use in developing countries such as China and India, where small mills pulping agricultural residues have produced most of the paper requirement but have been forced to close mainly because there has been no treatment for the black liquor effluent.
1.Optimise the twin screw extruder for continuously feeding and pulping fibres, test and measure the effect of different operating conditions in the new pulping system and determine the optimum pulping regime with particular regard to pulp quality.

2.Determine a non-chlorine bleaching regime for straw pulp and produce bleached paper samples

3.Develop, through a planned matrix of trials, optimum operating conditions for the black liquor effluent treatment energy and chemical recovery technology.

4.Determine the optimum method for reducing or eliminating build up of sodium silicate scale on process equipment.

5.Carry out a Life Cycle Assessment of the MiniMill to inform the development of the technology and the supply chain at an early stage.

6.Identify and report on industry attitudes to straw and other non-wood paper to identify and address any issues which may affect the succesful uptake of non-wood paper pulp in the UK.
Project Documents
• Abstract : NF0607 - Project Summary   (2551k)
Time-Scale and Cost
From: 2004

To: 2006

Cost: £380,471
Contractor / Funded Organisations
BioRegional MiniMills (UK) Ltd
Arable Farming              
Fields of Study
Non-Food Crops