The International Panel on Climate Change has used University of Queensland research to update its National Greenhouse Gas Inventories Guideline for the first time in 13 years.
UQ’s Advanced Water Management Centre has spent a decade researching greenhouse gas emissions from wastewater systems, both in lab-scale and full-scale, in close collaboration with its many utility partners.
Based on this research, the IPCC guidelines significantly updated the default emission factors for nitrous oxide in one type of domestic wastewater treatment plants.
AWMC Director Professor Zhiguo Yuan said wastewater handling could contribute extensively to greenhouse gas emissions from utility operations.
“IPCC default emissions are not one size fits all,” Professor Yuan said.
Previously, insufficient data meant the IPCC guidelines had under estimated default emission factors for nitrous oxide in full-scale domestic wastewater treatment plants with step-feed.
“In 2015-2016 we published research from a full-scale study with SA Water that showed nitrous oxide emissions correlate directly with influent nitrogen load. Our research outcomes have been considered in the accounting guidelines, and have contributed to the emissions factor tables.”
The inclusion of new research means new factors cover the most widely used treatment processes globally, providing a more accurate accounting benchmark.
Professor Yuan said UQ’s research had also influenced updates to the guidelines for two other greenhouse gas emissions in the wastewater sector – methane and carbon dioxide.
“In the original guidelines, IPCC had no recommendations for methane emission from sewer systems due to lack of information,” he said. “Evidence is emerging that the methane formed in sewers is not insignificant. Our new research will help quantify the emissions and can provide a benchmark for calculation instead of just raising awareness.”
New data also shows that wastewater contains an appreciable amount of fossil carbon, thought to be derived from petroleum-based products.
These non-organic carbons contribute to a large percentage of the carbon dioxide produced in the treatment process.
“Our research from 2013 shows that these fossil carbons come from cosmetics, pharmaceuticals, food additives and other commercial and domestic sources,” Professor Yuan said. “Countries that have higher levels of fossil carbons in their wastewater should definitely be taking this into account when evaluating their emissions.”
He said future improvements to the IPCC guidelines should include a method for estimating non-biogenic emissions associated with wastewater treatment operations and wastewater discharges.
The guidelines were updated following a recommendation from the Task Force on National Greenhouse Gas Inventories considered refinements from scientific and technical advances that have occurred since 2006.