Phosphorus cycling in Montreal's food and urban agriculture systems

Geneviève S Metson; Elena M Bennett

doi:10.1371/journal.pone.0120726

Phosphorus cycling in Montreal's food and urban agriculture systems

PLoS One. 2015 Mar 31;10(3):e0120726. doi: 10.1371/journal.pone.0120726. eCollection 2015.

Authors

Geneviève S Metson¹, Elena M Bennett²

Affiliations

¹ Department of Natural Resource Sciences, McGill University, Sainte Anne de Bellevue, Montreal, Quebec, Canada.
² Department of Natural Resource Sciences, McGill University, Sainte Anne de Bellevue, Montreal, Quebec, Canada; McGill School of Environment, McGill University, Montreal, Quebec, Canada.

Abstract

Cities are a key system in anthropogenic phosphorus (P) cycling because they concentrate both P demand and waste production. Urban agriculture (UA) has been proposed as a means to improve P management by recycling cities' P-rich waste back into local food production. However, we have a limited understanding of the role UA currently plays in the P cycle of cities or its potential to recycle local P waste. Using existing data combined with surveys of local UA practitioners, we quantified the role of UA in the P cycle of Montreal, Canada to explore the potential for UA to recycle local P waste. We also used existing data to complete a substance flow analysis of P flows in the overall food system of Montreal. In 2012, Montreal imported 3.5 Gg of P in food, of which 2.63 Gg ultimately accumulated in landfills, 0.36 Gg were discharged to local waters, and only 0.09 Gg were recycled through composting. We found that UA is only a small sub-system in the overall P cycle of the city, contributing just 0.44% of the P consumed as food in the city. However, within the UA system, the rate of recycling is high: 73% of inputs applied to soil were from recycled sources. While a Quebec mandate to recycle 100% of all organic waste by 2020 might increase the role of UA in P recycling, the area of land in UA is too small to accommodate all P waste produced on the island. UA may, however, be a valuable pathway to improve urban P sustainability by acting as an activity that changes residents' relationship to, and understanding of, the food system and increases their acceptance of composting.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Agriculture*
Food Analysis*
Phosphorus / chemistry*
Quebec
Urban Health*

Substances

Phosphorus

Grants and funding

This work was supported by National Science and Engineering Research Council Alexander Graham Bell scholarship (http://www.nserc-crsng.gc.ca/students-etudiants/pg-cs/bellandpostgrad-belletsuperieures_eng.asp) to GSM and National Science and Engineering Research Council Discovery grant (RGPIN 327077, http://www.nserc-crsng.gc.ca/professors-professeurs/grants-subs/dgigp-psigp_eng.asp) to EMB. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.