Life cycle assessment of raw materials for non-wood pulp mills: Hemp and flax

Abstract

At the present time, there is a remarkable increasing interest for using non-woody fibres as raw materials for pulp mills. The present study aims to identify and quantify the environmental impacts associated with the production of hemp and flax fibres for speciality paper pulp by using the Life Cycle Assessment (from now, LCA) methodology. One ton of fibre entering the pulp mill was used as functional unit in both systems. Inventory data for the foreground system (agricultural inputs and outputs) were obtained directly from growers (Spanish plantations and expert advisors) and combined, when necessary, with bibliographic sources. Data for the background system such as production of chemicals and pesticides, machinery or electricity were taken from the Ecoinvent database. The CML baseline 2000 methodology was selected to quantify the potential environmental impact associated to the crops. Specifically global warming (GWP), acidification (AP), eutrophication (EP) and photochemical oxidant formation (POP) were evaluated. In addition, two flow indicators were considered: energy (EU) and pesticide use (PU). Production of hemp fibre reported higher values for all the impact categories analyzed. On the contrary, flow indicators were more intensive in the flax scenario due to irrigation and pesticide consumption. LCA tool aided to identify the hot spots, so that a proposal for upgrading alternatives to reduce environmental impacts could be made. Production and use of fertilizers as well as the stage of scutching were identified as the hot spots in both crops; in addition, harvesting has also significant contribution in hemp production and irrigation regarding the flax scenario. Future work will be focused on the study of non-wood fibre processing in order to get a complete picture of the non-wood pulp life cycle.