Theme: 3. Sustainability

Topic Area: 3b. Water and Air Quality Technologies

Background/Objectives:

Throughout the world metals and other chemicals in groundwater can produce unacceptable risk to receptors. Traditional methods of remediation typically use ex situ removal, treatment, and disposal resulting in large negative impacts on climate and sustainability. The climate negatives include energy consumption, use of virgin material, and landfilling. Recently, innovative in situ methods of remediation have been developed, somewhat reducing negative impacts to climate. Currently, major additional positive climate mitigation is being achieved in environmental remediation due to the incorporation of the concepts of the circular economy. For example, the application of circular economy can greatly mitigate negative climate effects of environmental remediation while boosting sustainability when compared to using virgin material. In addition to climate mitigation the use of repurposed rather than virgin material can result in jobs for local workers and often associated environmental justice benefits. Two metals sites will be discussed in the presentation; the history of the sites is similar with industrial processes resulting in releases of metals to groundwater. Each site has been determined by regulators as having an unacceptable risk to human health or the environment. For a U.S. site the metals addressed are cobalt and hexavalent chromium, and for the Costa Rica site the metal is molybdenum. At both sites, increased severity of rain events and global warming concerned regulators that slugs of dissolved metals would negatively impact sensitive receptors. The main objective of the presentation is to highlight the climate mitigation advantages of applying the circular economy in environmental remediation.

Approach/Activities:

Focusing on in situ technologies rather than traditional ex situ remediation can greatly reduce negative climate impacts. The work to develop in situ technologies for both subject sites has passed from theory through bench stage to full-scale application. Work at both sites commenced with consideration of inorganic and organic geochemistry with biochemistry, microbiology, and biology with the concept of non-reversible capture of cobalt, molybdenum and hexavalent chromium. In all cases, a simple inorganic or organic approach did not meet remediation goals whereas biogeochemistry was successful. During all the work the details of the theory and application of the circular economy were considered. The final solutions were heavily scored by application of the circular economy. The concept of upcycling – a process in which used materials are converted into something of higher value in their second life – was of particular importance as use of this repurposed material provided the most positive climate mitigation and sustainability value.

Results/Lessons Learned:

Application of the circular economy has been successful in maximizing the mitigation of climate change at environmental remediation sites. Understanding and applying the concepts of the circular economy should be standard for all environmental remediation. Data expected by the time of the presentation will include savings in energy, material, and landfill capacity.

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Dale Haigh