Environmental sustainability of bioethanol production from waste papers: sensitivity to the system boundary

The production of bioethanol from various waste papers (newspaper, office paper, magazine and cardboard) was evaluated from an environmental standpoint. 'Cradle-to-grave' (or 'well-to-wheel') analyses were performed using a Life Cycle Assessment (LCA) approach with the aims of identifying the key drivers of environmental impact in the bioethanol supply chains and of comparing the environmental footprints of various bioethanol supply chains with those of conventional petrol. Base cases (bioethanol production from various waste papers) and two state-of-the-art cases including pretreatment of office paper by dilute acid (DA) and of newspaper by an oxidative lime (OL) process were constructed using laboratory data, expert consultations, literature values, and simulation in AspenPlus (TM) software. Contribution analysis showed enzyme production needed for hydrolysis of the papers to be the main contributor to the environmental profiles for bioethanol in the base cases. The production of process heat and hydrochloric acid respectively were the main contributors to the bioethanol environmental profiles for office paper-to-bioethanol with DA pre-treatment and newspaper-to-bioethanol with OL pre-treatment. Overall, bioethanol produced from newspaper, magazine paper and cardboard was found to have a lower environmental impact than the conventional transport fuel petrol. However, this conclusion is significantly affected by the system boundaries used for the analysis. When an expanded system boundary is applied to consider virgin and recycled paper production as the potential consequential effects within the bioethanol and petrol systems respectively, office paper-derived bioethanol systems emerge as the most environmentally favourable over petrol.