Greenhouse gas emissions following biosolids application to farmland: Estimates from the DeNitrification and DeComposition model

Okenna Obi-Njoku; Michael Yongha Boh; Ward Smith; Brian Grant; G W Price; Naseer Hussain; Joann K Whalen; O Grant Clark

doi:10.1016/j.scitotenv.2022.153695

Greenhouse gas emissions following biosolids application to farmland: Estimates from the DeNitrification and DeComposition model

Sci Total Environ. 2022 Jun 1:823:153695. doi: 10.1016/j.scitotenv.2022.153695. Epub 2022 Feb 8.

Authors

Okenna Obi-Njoku¹, Michael Yongha Boh¹, Ward Smith², Brian Grant², G W Price³, Naseer Hussain⁴, Joann K Whalen⁴, O Grant Clark⁵

Affiliations

¹ Department of Bioresource Engineering, McGill University, 21111 Lakeshore Road, Ste-Anne-de-Bellevue, QC H9X 3V9, Canada.
² Agriculture and Agri-Food Canada, 960 Carling Ave, K.W. Neatby Building, ON K1A 0C6, Canada.
³ Department of Engineering, Faculty of Agriculture, Dalhousie University, PO Box 550, Truro, NS B2N 5E3, Canada.
⁴ Department of Natural Resource Sciences, McGill University, Macdonald Campus, 21 111 Lakeshore Road, Ste-Anne-de-Bellevue, Quebec, QC H9X 3V9, Canada.
⁵ Department of Bioresource Engineering, McGill University, 21111 Lakeshore Road, Ste-Anne-de-Bellevue, QC H9X 3V9, Canada. Electronic address: grant.clark@mcgill.ca.

PMID: 35143794
DOI: 10.1016/j.scitotenv.2022.153695

Abstract

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 replicated corn (Zea mays L.) plots in Quebec, Canada. The plots received 120 kg of available N ha^-1 y^-1 in mesophilic anaerobically 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 (N₂O) during the growing season than other treatments, while carbon dioxide (CO₂) emissions were similar between treatments. After calibration, DNDC estimates were within the 95% confidence interval of the measured variables. Correlation coefficients (r) indicated discrepancies in trends between the estimated and measured values for daily CO₂ and N₂O emissions. 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 N₂O emissions (r = 0.8), crop yields (r = 0.5), and soil organic carbon (r = 0.4) were modelled with higher accuracy than cumulative CO₂ emissions (r = 0.3) and total soil N (r = 0.1). These findings suggest that DNDC is suitable for estimating field-scale N₂O emissions following biosolids application, but estimates of CO₂ emissions could be improved, perhaps by disaggregating the biosolids from the soil organic matter pools in the decomposition subroutines.

Keywords: Biogeochemical process modelling; Biosolids; Crop yield; DeNitrification and DeComposition model; Greenhouse gas; Land application.

MeSH terms

Agriculture
Biosolids
Carbon
Carbon Dioxide / analysis
Denitrification
Farms
Fertilizers / analysis
Greenhouse Gases*
Methane / analysis
Nitrous Oxide / analysis
Soil

Substances

Biosolids
Fertilizers
Greenhouse Gases
Soil
Carbon Dioxide
Carbon
Nitrous Oxide
Methane