Evaluating land application of pulp and paper mill sludge: A review

Keywords Pulp and paper mill sludge; Land spreading; Waste management; Soil health; Soil ammendment Highlights * Land spreading paper pulp mill sludge (PPMS) offers economic and environmental benefit. * Characteristics and utility of PPMS vary with treatment level (primary vs secondary). * Co-application of N sources can prove beneficial in some cases. * Routine analysis and robust regulation prevent adverse outcomes from PPMS use. * Longer term studies on soil chemistry and ecology effects are warranted. Abstract It is estimated that >400 Mt of board and paper are produced globally per year, and that 4.3--40 kg (dw) of sludge like material, pulp and paper mill sludge (PPMS), is generated for every tonne of product. PPMS are now more widely reused in agriculture as a soil amendment due to their high organic content of 40--50% by weight, perceived low toxicity and possible liming capabilities. Within this review article historic and recent literature on PPMS land spreading are combined with knowledge of European and UK regulation to explore the benefits, potential impacts and viability of land spreading PPMS. The review reveals that risks relating to potential N immobilisation in soils post-application can be readily mitigated, if desired, by coapplication of an N source, or even pre-treatment of sludge via composting. The benefits to crops have been demonstrated emphatically, while negative ecological impacts under typical field application rates have not been observed to date. The case is therefore strong for continued land application of the material as an environmentally responsible and sustainable use option. However, there are currently gaps in the literature regarding longer-term implications of PPMS applications in agriculture and in regards to the possible presence of emerging contaminants in some PPMS materials, both of which have been identified as areas that merit further research. Author Affiliation: (a) School of Geography, Geology and the Environment, Keele University, Keele, ST5 5BG, UK (b) 4R Group, Control House, A1 Business Park, Knottingley Road, Knottingley, WF11 0BU, UK * Corresponding author. Article History: Received 11 July 2021; Revised 24 February 2022; Accepted 27 May 2022 Byline: Tomi Turner [t.turner@keele.ac.uk] (a,*), Rebecca Wheeler (b), Ian W. Oliver (a)