Waste paper and cardboard is a potential resource for producing bioethanol. In this work, bioethanol production processes from various waste papers (newspaper, office paper, cardboard and magazine) using two enzyme alternatives (Celluclast 1.5L supplemented with Novozyme 188 and Cellic Ctec 1) were evaluated from technological, economic and environmental standpoints.
Laboratory experiments were conducted to analyse the composition of the waste papers and to assess the carbohydrate yields from enzymatic saccharifications at relatively high-solids loading (15% w/w). Kinetic models were adapted for the glucan and xylan hydrolyses in this study and were validated by experimental data. The kinetic models provide further insights on enzymatic hydrolysis at high-solids loadings and predictions of the enzymatic digestibilities of the four types of paper. The experimental data, together with published data, were applied in process design models using the simulation software ASPEN PLUSTM to explore the techno-economic aspects of potential conversions of waste papers to bioethanol. The mass and energy flows and the pollutant emissions estimated from the process simulations were used in life cycle environmental analyses (LCAs) to provide insight on the potential environmental pros and cons of converting waste papers to bioethanol.
This research has demonstrated that several pathways to bioethanol production from waste paper are economically and environmentally competitive with conventional petrol as a transport fuel. They can also offer environmentally favorable or neutral profiles when compared with the alternative waste paper management options of recycling or incineration with energy recovery. Simplistic, general assumptions that converting waste paper to bioethanol is either ‘good’ or ‘bad’ are not supported by this research. Instead, this study has demonstrated that detailed techno-economic and environmental profiling work, such as that carried out here, is essential to identifying the most beneficial approaches to developing valuable and environmentally favorable production of bioethanol from waste papers.