Uncovering energy use, carbon emissions and environmental burdens of pulp and paper industry: A systematic review and meta-analysis

The pulp and paper industry, which provides cellulose pulp and paper, bio-based energy and chemicals, is one of the largest energy consumers, greenhouse gases (GHG) and pollutant emitters among manufacturing industries. Although the environmental impact of the pulp and paper industry has been extensively studied, life cycle assessment (LCA) results have not yet reached a consensus. By means of a systematic review and meta-analysis, this article contributes to the quantification and harmonization of the life cycle environmental impacts of pulp making and paper making systems. Based on the screening of 45 cases of paper making and 18 cases of pulp making, we found that 1 t of paper results in about 950 kg carbon dioxide (CO2) equivalent (CO2-eq) GHG emissions on average. However, there are distinct differences between countries and pulp and paper categories. The dominant factor influencing GHG emissions is energy use. In paper making, the pulp making process is responsible for 62% of energy use, 45% of GHG emissions, 48% of acidification potential, and 49% of eutrophication potential. The kg CO2-eq emissions of three different types of pulp were as follows: Kraft, 508 kg CO2-eq/t; chemi-mechanical, 513 kg CO2-eq/t; and recycled pulp, 408 kg CO2-eq/t. Excluding emissions from electricity and steam production, the convergence of carbon emissions is observed within the same categories of pulp. Straw-based pulp caused far more environmental impact than any other type because of the intensive inputs in agricultural activities as well as in the pulp making process. This research highlighted the inconsistencies in functional units, system boundaries, and methodologies and carbon neutrality assumptions in different LCA studies of pulp and paper making. Future studies should focus on the environmental impact of straw-based pulp making, system boundary unification, and calculation of biogenic carbon emissions.