Environmental Life Cycle Assessment of a Swedish Dissolving Pulp Mill Integrated Biorefinery

Abstract

Summary The pulp industry plays an important role in the structure of the European economy and society. The production of pulp has been traditionally considered an important source of pollution due to the use of large amounts of chemicals, fuels, and water and its intensive energy consumption. Currently, this situation is changing due to the potential use of biomass to produce value‐added products, which minimizes environmental impacts and increases sustainability. This article uses life cycle assessment (LCA) to identify and quantify the environmental impacts associated with a Swedish softwood‐based biorefinery where total chlorine‐free (TCF) dissolving cellulose is produced together with ethanol and lignosulfonates. The system was defined according to a cradle‐to‐gate perspective—that is to say, from forest activities to the output of the biorefinery mill. According to the results, forest activities associated with the production of soft roundwood play a minor role in all the environmental impact categories under study. In contrast, the production of chemicals consumed in the cooking and bleaching stages, the sludge treatment generated in the wastewater treatment plant, and the on‐site energy production system were identified as the elements that negatively contribute the most to all impact categories. The production of steam from biorefinery wastes, biogas, and methanol in external boilers reduces the environmental impact in all categories. Specific actions associated with the reuse of wastes and improved gas treatment systems would improve the environmental profile of this production activity.

Environmental Impact Assessment of Forest Operations and Pulp Manufacture

“…Nevertheless, this situation is changing due to the potential of wood biomass as a renewable source to produce value added products as well as energy and chemicals, minimizing environmental impacts, increasing sustainability and making this sector competitive and becoming less dependent on crude oil. In fact, this biorefinery not only produce cellulose but also other value co-products from waste streams such as lignosulfonates and ethanol (González-García et al 2011c). …”

“…The study under assessment (see Fig. 18.6) included all the industrial activities related to the production of dissolving cellulose in a Swedish biorefinery and corresponding co-products obtained in the mill: ethanol for chemical uses and lignosulfonates (González-García et al 2011c). Thus, this study covers the whole cycle of the pulp mill from raw materials production (including industrial plantation activities -Sect.…”

“…The softwood logs directly delivered from the industrial plantations are debarked, chipped and fed to batch digesters to cook the cellulose adding the acid cooking (with HSO 3 and SO 2 ). Subsequently, the resin content of the washed cellulose is reduced by means of an internal de-resination, where the resin is solubilized by alkali (González-García et al 2011c). The following stage is the bleaching of cellulose in two stages in a completely close-loop bleaching sequence with a final peroxide bleaching step.…”

“…Inventory data for the cellulose mill system were obtained from average annual data of on-site measurements (González-García et al 2011c). These inventory data were completed, when necessary, with bibliographic resources and literature (González-García et al 2011c).…”

“…The third stream (52 % of solids) is sent to the lignosulfonate plant, where is dried and converted into fine dried powder (lignosulfonates). The fourth stream (remaining effluents) is sent to the wastewater treatment plant (WWTP) where under a first anaerobic and a second aerobic steps, biogas is produced and sludge used as soil conditioner (González-García et al 2011c). …”