Brownfield Remediation: Solutions for Urban Agriculture

Executive Summary
(Version français)

Urban agriculture is an important emerging field because of its positive implications for urban food security, community development, and urban environmental conditions. However, community groups pursuing urban agriculture face many obstacles. Soil contamination is a major barrier to potential agriculture projects in urban areas, as most urban soil is below agricultural soil standards, and food cannot be grown in contaminated soil because of the associated human health risks. Unused, contaminated lands in urban areas known as 'brownfields' have great potential as sites for urban agriculture if remediation can be successfully undertaken. Though many soil remediation techniques exist, they are of varying practicality for community groups attempting the remediation of brownfields for urban agriculture.

The goal of this project is to evaluate several physical and biological soil remediation techniques for use by community groups using the following criteria: accessibility, cost, time, ability to bring soil up to agricultural standards, and environmental effects. Our specific research questions were as follows:

What are the initial steps a community group should follow before beginning a remediation project?
What are the various soil remediation techniques that can be used to achieve these soil quality requirements?
What are the pros and cons of available remediation techniques for use by community groups for the purpose of urban agriculture?
What can we learn from case studies of past remediation attempts undertaken by community groups for this purpose?

The research team consulted academic journals, sources from the Quebec, Canadian, and US government, and conducted interviews with academics, Montreal city officials, representatives from remediation companies, and community group members to answer these questions. It was determined that although soil standards exist at several levels of government, community groups should follow the most stringent ones, as they are liable for any contamination of the food produced in their gardens. The research team also explored resources available for determining the land use history of a proposed garden plot and for soil testing, which will enable a community group to determine the levels of contamination present in the soil. Sources of subsidies were also researched.

Four physical remediation methods were evaluated: excavation, geotextiles, soil washing and soil vapor extraction. Of these methods, excavation was determined to be the most appropriate option for community groups, as it can ensure complete contaminant removal in a very short time frame. Other techniques were deemed too technical and costly for use by community groups, and had negative environmental consequences. Of the biological remediation techniques (microbial remediation, phytoremediation, fungal remediation, and composting), microbial remediation was selected as most effective for community groups, as it has very low associated costs and can be effective in a relatively short timeframe. Other techniques were less accessible, took longer to implement, and had varying degrees of effectiveness in bringing soil up to agricultural standards. It should be noted that these are only general conclusions; selection of a remediation technique must be done on a case-specific basis, since variance in the level and spectrum of contaminants in the soil, the soil's properties, and the available timeframe and budget will all determine the appropriateness of each technique for the urban agriculture project.

Finally, the research team recognizes that the field of soil remediation for urban agriculture is quite young, and some techniques that are not presently applicable may have a promising future.