Recycling of Paper Mill Biosolids: A Review on Current Practices and Emerging Biorefinery Initiatives

In a rapidly urbanizing global society, the issue of solid waste management has become even more challenging in recent times. Manufacturing of paper, an integral part of human civilization, generates a substantial amount of effluent sludge, which invariably needs extra monetary resources to dispose-off in millions of tons annually around the world. Currently, most of the widely practiced disposal options, landfilling and incineration, invariably pose serious environmental risks to immediate neighborhoods as well as to society at large. Recent stricter environmental legislations and general public awareness have been forcing paper producers to follow a sustainable approach in dealing with residual biomass generated at their facilities. At the same time, reducing waste at source and recycling have become an integral part of waste management of some responsible companies and governments of the industrialized world have also taken a number of initiatives in this regard. This review presents a holistic overview on current practices in dealing with paper sludge and their environmental and economic implications. Also presented is a comprehensive discussion on emerging biorefinery trends leading to value- added utilization of primary, secondary and mixed biosolids originating from effluent treatments plants, especially from paper mill operations.