Process Integration and Intensification: Challenges and Opportunities in Renewable Bioproducts Including Pulp and Paper

The forest bioproducts industry today includes the pulp, paper, composite and allied chemical and other manufacturers. This segment of the US and North American manufacturing industry has been globally competitive for much of the last century because of the abundance of high quality forest resources as raw materials and highly optimized large scale processes such as the chemical recovery system in pulp mills. The focus of the industry upto now has been primarily on producing low cost cellulose fiber and fiber based products including building materials. This is a mature commodity industry with high capital costs and low profit margins. With increasing cost of raw materials and labor and operational efficiency and leveling the technology playing field for conventional fiber based products, the forest industry is increasingly looking to expand the revenue streams and profitability. As pulp and paper mills and forest products manufacturing units evolve into integrated forest biorefineries, they will produce a broader spectrum of chemicals and materials with higher value. The evolution towards diversification of products and materials while pursuing higher value and economic profitability presents tremendous challenges and opportunities for process integration and intensification. We expect process intensification to result in more compact, modularized processing and converting operations serving to improve profitability while better utilizing the raw material and energy inputs.

With significant expertise in the understanding, logistics, handling and processing of lignocellulosic biomass and sustainable forestry practices, the forest industry has much to offer in contributing to the future development of sustainable bioeconomy. The RAPID Renewable Bioproducts technical focus area is formed with the goal to develop, demonstrate and deploy innovative approaches and solutions of process intensification in the pulp and paper and other biobased industry improving energy efficiency, increasing productivity, improving environmental performance, minimizing waste and better utilization of waste streams, and the development of novel value added bio-products diversifying the product spectrum to enhance revenue. It is proposed to deploy a wide range of process intensification technologies based on membranes, reactive processes and advanced novel separations for pulping, bleaching, black liquor and chemical recovery, papermaking processes, reduction and better utilization of wastes, biorefininig including thermochemical, biological and biochemical processesand development of value-added bioproducts.

Specifically, the pulp and paper area will specifically aim to address the key goals of increased value through modularization and intensification of processes to increase energy efficiency, doubling energy productivity via reductions in capital costs and operating costs, enabling cost effective deployment of new technologies in existing manufacturing sites, and improved work force by focusing on better education of students. The project efforts will strive to address the strategic goals for the pulp and paper industry developed by Agenda 2020: to reduce the total input energy by 25%, increasing fiber yield by 5% on oven dry (O.D.) basis, reducing BOD/COD of effluents by 25% and reduction of the industry’s overall capital intensity by at least 25%.

Kraft pulp mills and bleaching operations alone consume an estimated 562 trillion Btu. From the Agenda 2020 analysis, it is projected that breakthrough next generation pulping and bleaching technologies offer the potential for saving approximately $950 million per year in energy and raw material costs alone. Other specific metrics have been proposed and these include achieving energy savings in the pulping process of up to 10%, a target to increase the pulp yield by 4-6%, increasing the extent of delignification (targeting up to 15% increase in lignin removal) and obtaining an improved pulp strength and bleaching response. Eliminate scaling in chemical recovery and heat and mass transfer operations thereby improve the overall heat and mass transfer rates and energy consumption.

About 7% of pulp and paper energy usage, or nearly 164 trillion Btu, is used to remove water from black liquor in U.S. Kraft mills. It is estimated that integrating membrane-based black liquor concentration technology has the potential to reduce annual energy costs by $2–$3 million typical for a typical 2,000 TPD mill.

It is estimated that paper drying alone consumes about 20% of the total energy consumed by pulp and paper industry. It is targeted to increase the moisture content going into the drying stage to approximately 60-65% solids from the current 40-45% solids; increase the drying rate by about 10%; decrease the energy consumption in the pressing and drying section by about 10%. The above target, if successful, could save 80 trillion Btu per year in the United States, or $240–$400 million.

Process water usage in pulp and paper manufacturing is another key area. Here the target goal is to reduce the water usage by 50% by focusing on reducing water use and reuse during papermaking on the paper machine and reusing effluent water back in the manufacturing process.

Another key component as part of an integrated biorefinery is aimed at improved utilization of biomass feedstock and waste streams from pulp and paper manufacturing including the development of cellulose nanomaterials and value-added bioproducts. This is aimed at addressing the strategic goal of producing additional revenue and improving the overall economic viability and sustainability of the pulp and paper industry.

Working closely with the pulp and paper industry it is important to integrate the learning from the research and demonstration projects in undergraduate and graduate curriculum specifically in courses in the areas of pulp and paper engineering, process engineering, biomass chemistry and conversion, reaction engineering, separation process principles, unit operations laboratory, and engineering design. In addition it is critical to incorporate appropriate technology developments in outreach and continuing education efforts including certificate programs geared towards industry professionals and workforce training and development.

RAPID working together with Agenda 2020 and the pulp and paper and other biobased industry, academia and national labs is well positioned to address these challenges using a strategic integrated approach involving key technical and application focus areas. Pulp and paper area is fortunate to have established academic institutions and national labs bringing significant expertise and research and development capabilities including pulping, bleaching and paper making unit operations, biomass characterization and conversion equipment, wide spectrum of analytical characterization and instrumentation including physical testing for pulp and paper, pilot scale pulping and bleaching equipment, black liquor characterization and separation, paper machines and biorefining processing capabilities and waste water treatment capabilities. In addition through our industrial partners’ larger scale pilot and commercial scale processing equipment can also be used for large scale demonstration and commercialization.