Among the 1200 wastewater treatment plants which have begun producing natural gas in the United States, few have set their sights on attaining energy neutrality and even fewer are funnelling power back into the grid. In September 2015, Stickney announced its aims to do both, with the goal of becoming energy neutral by 2023.
Anaerobic digestion describes the process by which bacteria are used to break down wastewater components to form natural gas. It is not a novel technology. Its use has become widespread in Europe over the past decade; however its adoption has been slow to grow across the Atlantic.
According to the Water Environment Research Foundation (WERF), an independent research organisation, drinking and wastewater plants are amongst the greatest municipal guzzlers of energy. These account for over a third of public sector energy use in the US, and 45 million tons of greenhouse gases a year.
Conveniently, the energy contained in wastewater is greater than that required to treat it. Some estimates suggest that the energy stored in sewage could be as high as two to ten times greater as that needed to process it (WERF). Incorporating organic waste has additionally been found to increase the gas produced by digesters, giving way to alternative waste processing avenues for wastewater treatment plants.
The wastewater treatment plant in Gresham, Oregon was the first to become energy neutral in the United States in 2012. This milestone was met by incorporating oil and grease residues disposed by local restaurants are mixed with wastewater, multiplying the production of natural gas. Ambitious goals have also been set by sewage treatment agencies in Virginia, as well as in Colorado. In the latter State, public services, such as trash disposal trucks and buses are increasingly being fuelled by these natural gas gains.
What are the implications?
Technological shifts such as producing natural gas from waste water allow us to reframe our conceptions of what constitutes 'waste' and 'resources'. Illinois, Oregon, Virginia and Colorado are blazing the trail, however other States may soon follow suit given the revenue potential of repurposing waste streams.
Energy neutrality is not only cost effective for wastewater processing plants, but enables these public services to become more independent to the fluctuations of the energy prices, and develop a new revenue stream. By becoming a producer of fuel, these plants can curb greenhouse gas emissions and avoid other more aggressive extraction practices, such as fracking - which is increasingly wreaking havoc on natural environments in the US and elsewhere.
Natural gas produced through wastewater will not single-handedly revolutionise the energy sector but it is a significant piece of the puzzle to creating more sustainable cities. According to Energy Vision the potential for natural gas production garnered through organic waste too could also drastically reshape energy production and consumption in the country. If the entire nation’s organic waste were collected, natural gas could replace approximately 50% of the diesel fuelling US transportation.
Anaerobic digestion may prove to be even more promising in less economically developed countries, where wastewater treatment is rare due to financial and infrastructural barriers. Wastewater in cities such as Dhaka in Bangladesh and Dar Es Salaam in Tanzania continues to be indiscriminately discharged into surface water bodies. By turning pollutants into profits, the costs of water, sanitation and electricity services could not only decrease, but the services would become more sustainable.
Image credit: Chris Bentley
NPR (01Jan. 2016) From Poop To Power: Colorado Explores New Sources Of Renewable Energy.
CleanTechnica. (05 Aug. 2015) Heh. Your Butt Could Help The Clean Power Plan.
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Used to Useful (23 Sept. 2015) Wastewater Treatment Innovators Focused on Zero Waste.
The New Yorker. (Apr. 2015) The Arrival of Man-Made Earthquakes.