Though the remediation of Superfund and brownfield sites protects the environment by removing harmful contaminants, the cleanup process itself can produce a significant environmental footprint. Remediation often involves technologies and heavy-duty construction equipment that is powered by fossil fuels and emits air pollution. How can we reduce the environmental footprint of the remediation process at these contaminated sites?
Bioremediation, a process that uses living organisms to break down pollutants and convert them into less toxic forms, offers a cleanup method that is both environmentally friendly and cost-effective. First commercially used in the 1970s, bioremediation is a branch of biotechnology that employs biological mechanisms to produce useful products and processes or to solve industrial or environmental problems. Despite some limitations, bioremediation has great potential to reduce the environmental impacts of contaminated site cleanups.
Bioremediation of contaminated soil is either done in situ, meaning treated on site, or ex situ, where the soil is treated after being removed from the site. There are several different organisms that can be used for bioremediation, including fungi, bacteria, and plants. These organisms can be supplemented with nutrients, carbon sources, electron sources, or enriched cultures of microorganisms to accelerate the rate of natural degradation of contaminants. The use of plants for bioremediation is called phytoremediation, in which wild and genetically modified plants absorb contaminants through their roots and accumulate them into biomass.
Bioremediation has been successfully used to clean up more than 100 Superfund sites across the United States. The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) of 1980 established EPA’s Superfund program, allowing the Agency to respond directly to known releases of hazardous substances at “Superfund” sites. In addition, EPA assists state and local governments with the remediation of brownfields, sites that may also contain hazardous pollutants. Currently, more than 450,000 brownfields exist throughout the United States.
The environmental impact of the remediation process has increasingly gained attention over the past two decades. In 2009, EPA launched its Superfund Green Remediation Strategy, which recognizes the range of negative environmental impacts from contaminated site cleanups. EPA’s current green remediation approach aims to reduce energy use, the exhaustion of natural resources, and emissions of air pollutants and greenhouse gases from Superfund site remediation. As part of this approach, EPA has published a series of Green Remediation Best Management Practices (BMPs), including bioremediation as a recommended BMP.
As a cleanup method, bioremediation offers an environmentally friendly approach compared to traditional remediation technologies. Bioremediation draws on natural processes without adding any foreign or toxic chemicals to the site, creating few, if any, waste byproducts. Unlike physical and chemical methods of cleanup, bioremediation does not disrupt the site’s natural habitat. Furthermore, since natural organisms degrade contaminants into simple compounds that pose little or no threat to the environment, polluted soil and groundwater can be treated on site, or in situ. As a result, there is no need to remove and transport contaminants away from the site, which saves energy and money and reduces the risk of oil spills. Thus, compared to other methods, bioremediation is also more cost-effective as it requires less equipment, labor, and energy.
Despite the numerous benefits of bioremediation, the technology has drawbacks that have limited its use for site cleanups. A major complication of bioremediation is its sensitivity to environmental conditions such that site conditions must allow for microbial activity in order for treatment to work. This requires a delicate balance between temperature, pH level, moisture content, and other factors. Another issue is the length of time typically required for treatment. Compared to other remediation methods, bioremediation treatment periods are typically longer, ranging from months to even several years. As such, in-situ bioremediation is not ideal for emergency remedy cases requiring “fast cleanup.” Moreover, considering the growing backlog of Superfund cleanups, bioremediation’s lengthy treatment period must be weighed against the efficiency offered by conventional methods.
Many studies in the field of bioremediation address these limitations. Scientists have experimented with bioremediation techniques in a variety of ways in order reduce treatment time and improve site applicability. For soil contamination, the alterations include improving oxygen supply, adding in materials such as biochar (charcoal produced from plant matter), and combining different techniques such as bioaugmentation and biostimulation, which have proven to effectively reduce treatment time. Regarding site-specific limitations, further research and field studies are necessary to expand bioremediation’s applicability. This research will drive future advances in the field of bioremediation, leading to increased adoption of the technology.
In the next three years, the global bioremediation market is expected to be valued at $186 billion, more than double its value in 2018. Given its environmentally friendly approach and cost-effectiveness, this technology will continue to play an increasingly significant role in environmental remediation. As research continues and adoption accelerates, bioremediation will further reduce the environmental footprint of contaminated site cleanup.
For more information on biotechnology, and to browse a database of other biotechnology products and applications, visit ELI’s Future Bioengineered Products Database.