Evaluating the Life Cycle Environmental Performance of Chemical‐, Mechanical‐, and Bio‐Pulping Processes

Introduction

Pulp and paper manufacturing constitutes one of the largest industry segments in the United States in terms of water and energy usage and total discharges to the environment. More than many other industries, however, this industry plays an important role in sustainable development because its chief raw material – wood fiber – is renewable. This industry provides an example of how a resource can be managed to provide a sustained supply to meet society’s current and future needs. The objective of this work is to present streamlined environmental LCA between chemical (kraft–sulfate), mechanical (or thermomechanical), and biopulping processes. This LCA would help us to evaluate the industry’s current experience and practices in terms of environmental stewardship, regulatory and nonregulatory forces, life cycles of its processes and products, and future developments.

The pulping industry has been traditionally using mechanical or chemical pulping methods, or a combination of the two, to produce pulps of desired characteristics. Mechanical pulping accounts for about 25% of the wood pulp production in the world today. Mechanical pulping, with its high yield, is viewed as a way to extend the forest resources. However, mechanical pulping is electrical energy–intensive and yields paper with less strength compared to that produced by the chemical pulping process. These disadvantages limit the use of mechanical pulps in many grades of paper. Chemical pulping accounts for about 75% of the wood pulp production in the world. This process produces paper with very high strength. However, the process has the disadvantages of being capital‐ and energy‐intensive, giving relatively low yields, producing troublesome waste products, and producing by‐products that are of relatively low values.

A new technology that offers a biopulping process with the potential to ameliorate some of these problems is being tested on a commercial scale. Biopulping treats wood chips with a natural wood‐decaying fungus before mechanical pulping and can save substantial amounts of electricity, significantly reduce the amount of air pollutants (including CO₂ and some odor‐causing total reduced sulfur compounds) and water pollutants (BOD, COD, TSS) compared with conventional pulping, improve paper quality, and enhance economic competitiveness.

The USEPA’s TRACI (USEPA 2003) model was used to assess the chemical, environmental, and human health impacts attributed to three pulp and papermaking processes. The results obtained from the biopulping process indicate a significant reduction in environmental and human health impacts. The biopulping process proves to be more sustainable in terms of economic advantage, and environmental and human health benefits.