Greenhouse gas emissions following biosolids application to farmland: Estimates from the DeNitrification and DeComposition model Okenna Obi-Njoku a , Michael Yongha Boh a , Ward Smith b , Brian Grant b , G.W. Price c , Naseer Hussain d , Joann K. Whalen d , O. Grant Clark a, ⁎ a Department of Bioresource Engineering, McGill University, 21111 Lakeshore Road, Ste-Anne-de-Bellevue, QC H9X 3V9, Canada b Agriculture and Agri-Food Canada, 960 Carling Ave, K.W. Neatby Building, ON K1A 0C6, Canada c Department of Engineering, Faculty of Agriculture, Dalhousie University, PO Box 550, Truro, NS B2N 5E3, Canada d Department of Natural Resource Sciences, McGill University, Macdonald Campus, 21 111 Lakeshore Road, Ste-Anne-de-Bellevue, Quebec, QC H9X 3V9, Canada HIGHLIGHTS • DNDC is tested for the first time in a biosolids-amended Canadian agro- ecosystem. • Corn is grown using digested, composted, and alkaline-stabilized bio- solids. • N 2 O emissions are highest from treat- ments receiving digested biosolids. • CO 2 and N 2 O emissions, SOC, and corn yields are simulated using DNDC. • Simulation of biosolids-induced early- season soil respiration needs to be im- proved. GRAPHICAL ABSTRACT ABSTRACT ARTICLE INFO Article history: Received 12 October 2021 Received in revised form 1 February 2022 Accepted 2 February 2022 Available online 8 February 2022 Editor: Huu Hao Ngo Municipal wastewater sludge may be processed into biosolids and applied to farmland for crop production, rather than be disposed of in landfills. Biosolids supply plant nutrients and increase soil organic carbon but also contribute to the production of greenhouse gases (GHGs). Computational models must therefore be refined to estimate the contribution of these gases to national GHG inventories. The DeNitrification and DeComposition (DNDC) model was evaluated for processes regulating crop growth, GHGs and soil C&N dynamics to determine its suitability for informing policy decision-making and advancing Canada's GHG inventory. Three years (2017–2019) of data were collected from repli- cated corn (Zea mays L.) plots in Quebec, Canada. The plots received 120 kg of available N ha -1 y -1 in mesophilic an- aerobically digested biosolids, composted biosolids, alkaline-stabilized biosolids, urea, or combinations of these, while control plots were left unfertilized. Treatments receiving digested biosolids emitted more nitrous oxide (N 2 O) during the growing season than other treatments, while carbon dioxide (CO 2 ) emissions were similar between treatments. After calibration, DNDC estimates were within the 95% confidence interval of the measured variables. Correlation co- efficients (r) indicated discrepancies in trends between the estimated and measured values for daily CO 2 and N 2 O emis- sions. These emissions were underestimated in the early and mid-growing season of 2018. They were more variable from plots fertilized with composted or alkaline-stabilized biosolids than from those with digested biosolids. Annual N 2 O emissions (r = 0.8), crop yields (r = 0.5), and soil organic carbon (r = 0.4) were modelled with higher accuracy than cumulative CO 2 emissions (r = 0.3) and total soil N (r = 0.1). These findings suggest that DNDC is suitable for estimating field-scale N 2 O emissions following biosolids application, but estimates of CO 2 emissions could be im- proved, perhaps by disaggregating the biosolids from the soil organic matter pools in the decomposition subroutines. Keywords: Biosolids DeNitrification and DeComposition model Crop yield Greenhouse gas Biogeochemical process modelling Land application Science of the Total Environment 823 (2022) 153695 ⁎ Corresponding author. E-mail address: grant.clark@mcgill.ca (O.G. Clark). http://dx.doi.org/10.1016/j.scitotenv.2022.153695 0048-9697/© 2022 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv