Radioactivity in future phosphogypsum: New predictions based on estimates of ‘Peak P’ and rock phosphate resources

Willey, Neil; Timbs, Patrick

Abstract

Global food supplies currently depend on producing inorganic P fertilisers from a finite reserve of rock phosphate (RP). P fertilisers are themselves significant pollutants but their production from RP also leaves a phosphogypsum (PG) by-product that is sufficiently radioactive that its reuse is restricted. PG is mostly accumulated in open ‘stacks’ that make up a significant proportion of all Technologically Enhanced Naturally-Occurring Radioactive Material (TENORM) waste. Using lower and upper estimates of current RP reserves, historic production, and Hubbert's logistic function-based ‘peak theory’, lower and upper boundaries for possible RP production were predicted to the year 2100. The ‘low’ boundary scenario had a production peak of c.350 Mt/a RP in c.2050 followed by a steep decline. The ‘high’ boundary scenario had a production peak of c.1200 Mt/a RP in about 2090. Future trends in P demand for food production were used to predict a possible, demand-driven, RP production scenario until 2100 which peaked at a demand of c.620 Mt/a RP and was within possible production boundaries. An RP:P ratio of 5.62:1 and PG:P fertiliser ratio of 4:1 was used to calculate that this predicted demand-driven scenario would ultimately produce nearly 350 Mt/a of PG and a cumulative total of c.30 Gt by 2100. Average PG activity concentrations of 226Ra (650 Bq/kg), 210Po (300 Bq/kg) and 230Th (100 Bq/kg) give a total of c.30 PBq radioactivity in this by-product. Humanity is faced with a phosphorus dilemma – if the low production scenario unfolds it threatens food security but if predicted demand for P is met from RP the environmental challenges arising from P fertiliser use will be profound and exacerbated by a significant radioactive waste challenge. The estimates reported here show that studies of environmental radioactivity have a role to play in debates about P resources and global food security.

• Journal Article Type: Article
• Acceptance Date: Jan 24, 2022
• Online Publication Date: Feb 3, 2022
• Publication Date: Apr 30, 2022
• Deposit Date: Nov 7, 2023
• Publicly Available Date: Feb 4, 2024
• Journal: Journal of Environmental Radioactivity
• Print ISSN: 0265-931X
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 244-245
• Article Number: 106828
• DOI: https://doi.org/10.1016/j.jenvrad.2022.106828
• Public URL: https://uwe-repository.worktribe.com/output/11415756