Secret Cash Stash Discovered in Sewage Treatment Plants

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columbia engineering researchers find way to save money, reduce greenhouse gas emissions at sewage treatment plantsA national research team headed by the Columbia University Engineering School has found that sewage treatment plants in the U.S. could save $100 million per year in electricity costs with a few simple tweaks to cut down on emissions of nitrous oxide, a powerful greenhouse gas. An emissions credit system to motivate the upgrades would create another $600 million in incentives, and some of the larger plants could make even more money by generating more energy than they consume, potentially enabling sales to the electricity grid.

Nitrous Oxide and Sewage Treatment Plants

Last year, lead researcher Kartik Chandran of Columbia Engineering reported that sewage treatment plants emit nitrous oxide at far greater volumes than previously thought. Nitrous oxide – not to be confused with harmless nitrogen gas –  is a greenhouse gas almost 300 times stronger than carbon dioxide, so in terms of global warming management there is a strong incentive to upgrade U.S sewage treatment plants. Until now, the question has been whether there is a direct economic incentive for the upgrades.

The Nitrous Oxide Problem

Ironically, the problem of nitrous oxide emissions has worsened in recent years with the introduction of a step in the wastewater treatment process that is intended to protect waterways, by reducing the amount of ammonia in treatment plant discharges. The direct economic benefits of ammonia reduction are tangible in terms of drinking water quality, the improvement of commercial fishing and related industries, and recreation. As more treatment plants introduce this step, called biological nitrogen removal, the nitrous oxide problem is bound to worsen.

The Nitrous Oxide Solution

Chandran’s new recent study confirms that a cost effective solution is at hand. Chandran proposes a system of carbon dioxide emissions credits that could be used to offset the upgrade of treatment plants to reduce nitrous oxide emissions, since a more efficient process would consume less energy. The upgrades would involve existing technologies that would also help to reduce the amont of nitrogen discharged into waterways.

Sewage Treatment Plants as Community Value Centers

Improvements in efficiency would also help to enhance the energy resource potential of wastewater treatment plants, and Chandran is working on that aspect as well. Treatment plants already produce usable energy in the form of sewage biogas that can be used onsite or sold to the commercial grid. Hydrokinetic energy in the waste stream is another potential. Often covering large footprints in relatively remote areas, treatment plants can also be suitable sites for wind farms and solar power installations. Meanwhile, new energy efficient processes are helping treatment plants to cut down on their use of grid-supplied energy.

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Tina Casey

Tina specializes in advanced energy technology, military sustainability, emerging materials, biofuels, ESG and related policy and political matters. Views expressed are her own. Follow her on LinkedIn, Threads, or Bluesky.

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