Biotechnical methods for improvement of energy economy in mechanical pulping

Forest industry is a notable user of electric power in Finland. The main reason for this is mechanical pulping, which is very energy intensive. Energy savings in mechanical pulping will also affect indirectly emissions of greenhouse gases (GHG). The aims of the study were to a) study the potential for energy savings and reduction of GHGs by implementation of biotechnical methods in mechanical pulping, b) estimate their cost-efficiency and c) assess the environmental impacts of their adoption into TMP production using the LCA methodology. Two different biotechnical methods were considered, namely fungal pretreatment of chips (biopulping) and enzyme-aided refining, both of which have shown marked potential for energy savings in mechanical pulping. Biopulping has been studied intensively, but without experience in mill scale. Enzyme-aided refining was developed during 1990s in collaborative projects and the method has been succesfully verified in mill scale trials. Cost-efficiency, adoption and effects on emissions of GHGs of the biotehnical methods as compared with other competing technologies were estimated by the EFOM model. Two different scenarios extending to 2030 were used. In the optimistic scenario the new cleaner biotechnologies develop rapidly and they are adopted effectively into use, whereas in the realistic scenario new technologies reducing greenhouse gas emissions penetrate rather slowly into the energy and industrial systems. The results showed that enzyme-aided refining was very competitive as compared with alternative methods and it has a potential of being largely applied in mechanical pulping. Biopulping, which is technically more difficult to control and also more expensive to invest and operate, could be largely adopted according to the optimistic scenario in 2020. It is shown by the LCA study that implementation of the biotechnical methods would reduce total emissions of GHGs. Acidifying emissions from production of bleaching chemicals would, however, increase due a need of extra bleaching for biopulped chips, but the portion of acidifying emissions from the total emissions were assumed to be low. Effects on wastewater loadings arising from the application of biotechnology were not assessed in this study due to lack of relevant data.