Sewage treatment could aid in combatting climate change while generating new revenue, according to new research.
Published in the journal Nature Sustainability, the research from Princeton University concludes that municipal sewer plants offer a major option for capturing carbon dioxide and other greenhouse gases.
“The water industry could play a big role in tackling climate change,” said Jason Ren, senior author and professor of Civil and Environmental Engineering. “It is a very exciting idea because people always think about energy or transportation, but water has not been considered as a major factor in carbon reduction.”
Recent research has looked into how wastewater can capture enough carbon to offset the emissions generated to power the equipment used in sewer plants. It has been found that as well as offsetting the emissions of the plant, extra carbon could be absorbed by pumping it into the sewage as it moves through the sewer plant.
“If you consider it as a resource, you could convert part of the waste material including CO2 into products,” Ren said. “You could actually make money.”
A common approach, according to a Princeton University statement, is for sewer operators to use pipes to pump carbon dioxide gas into the sewer water in the plants. Various techniques would then be used to convert the gas into carbonate minerals, biofuels or a sludge-based fertiliser called biochar.
The article in Nature Sustainability reviewed a range of techniques, including microbial electrolytic carbon capture, microbial electrosynthesis, microalgae cultivation, biochar production.
Through analysing the potential environmental and economic benefits of such operations, they determined that millions of tonnes of CO2 could be captured and utilised, in turn allowing billions of dollars of revenue to be generated in major CO2 emitters such as the US and China.
The team stress that such concepts are still in their infancy. Substantial work still needs to take place to bring them into practice.
"Wastewater treatment is one of the largest energy users and greenhouse gas emitters of a municipal spreadsheet," said Jerald Schnoor, an engineering professor at the University of Iowa, who was not involved in the research, in a statement.
"Technologies exist at pilot scale to achieve zero carbon and energy footprints, but they are not proven to be scalable or cost-effective at the current time. As the country now embarks on 'green infrastructure' initiatives, as being discussed by the new Congress, this should be a high priority."