McGill engineering researchers have introduced an open-source model that makes it easier for experts and non-experts alike to evaluate greenhouse gas emissions from U.S. natural gas supply chains and yields more accurate results.
Lead author Sarah Jordaan, an associate professor in McGill University's Department of Civil Engineering, said the work, published in Cell Reports Sustainability, responds to a long-standing challenge.
"Natural gas supply chains are complex and are often studied using life cycle assessment (LCA)," Jordaan said. "Due to the complexity, LCAs can be challenging to develop and implement."
The new model, called SLiNG-GHG, calculates carbon dioxide and methane emissions released during transmission, distribution and ocean shipping. The team of researchers initially developed it for the U.S. National Petroleum Council at the request of the U.S. Secretary of Energy.
Methane emissions often underestimated
Methane, a potent greenhouse gas, is one of the biggest sources of uncertainty in natural gas life cycle assessments.
"Methane emissions are released across natural gas supply chains. These leaks are highly uncertain and not well modelled in LCAs," Jordaan said.
In the study, SLiNG-GHG results were anywhere from 23 per cent lower to 316 per cent higher than methane estimates typically used in LCAs, which are extrapolated from data from a representative sample of devices and published in "bottom-up" government inventories.
"Bottom-up inventories often underestimate emissions compared with direct measurements. This discrepancy can undermine market credibility and public trust in greenhouse gas reporting," she said.
To build the model, the researchers reviewed more than 2,200 publications and harmonized data from the 16 studies that met rigorous quality criteria. They then constructed material-balance equations to track gas flows and estimate emissions through each stage of the supply chain.
"The model empowers policymakers, regulators, investors and civilians to better evaluate emissions from natural gas supply chains," Jordaan said.
About the study
"Democratizing life cycle assessment by developing a streamlined model of greenhouse gas emissions from U.S. natural gas supply chains," by Sarah Marie Jordaan and collaborators, was published in Cell Reports Sustainability.
