Several major sources of greenhouse gas (GHG) emissions, including manholes and old landfills, “go under the radar” of the City of Montreal, worries a study by the McGill University. Approximately 2130 tons of methane would not be measured annually by the municipality.
According to the report led by Professor Mary Kang, from the Department of Civil Engineering at McGill University, Montreal excludes three powerful emitters of methane from its greenhouse gas reports: old landfills, vents sewer and natural gas leaks.
The annual methane emissions produced in Montreal from these three sources are significant. In 2020, they “totalled 2,130 tonnes,” says the research team, which took more than 600 samples over an entire year in different areas of Montreal. Annual methane emissions from historic landfills “were 901 tonnes, which is the highest among the three source types we measured,” it also notes.
Moreover, these 901 tons of methane per year “place historic landfills as the second largest source of methane in Montreal, preceded only by municipal solid waste emissions,” insist the researchers in their report.
“Our goal is to highlight that there are several sources of methane production that are not known, and on which we are not necessarily working,” explained to The Press postdoctoral researcher Sébastien Ars, who participated in the study. “We have targets to reduce our emissions, but if we don’t take them all into account, it’s a bit counterproductive”, he judges.
25 times more harmful
Mr. Ars also recalls that methane “is a gas with a warming power 25 times greater than CO2 “. “In other words, one molecule of methane has the same warming power as 25 molecules of CO2. In the short term, it is therefore more important to reduce methane emissions to achieve its zero emission goals and really fight against climate change,” he says.
His research group also fears that the lack of monitoring of methane sources will make it more “difficult” for the Plante administration to achieve carbon neutrality by 2050. The city is also aiming for a 55% reduction in emissions. of GHGs by 2030.
In the study, we learn in particular that “25% of methane emitters are contained in downtown Montreal, between Ville-Marie and Plateau Mont-Royal”. In this sector, there are approximately 800 manhole covers per square kilometer, the highest rate in the metropolis.
In total, the researchers estimate that approximately “155,000 remaining manhole covers are not counted” by the City of Montreal, which according to them highlights “the importance of collecting information on the different sources of methane for the implementation of mitigation strategies adapted to each situation”.
In the office of Mayor Valérie Plante, we ensure that we are deploying “unprecedented efforts to ensure that Montreal becomes carbon neutral, whether through our efforts in the various mobility sectors or the carbon neutrality of all buildings in the territory from here. 2040”.
“Greenhouse gases from landfilling are already accounted for in the City’s inventory. […] Although certain figures put forward in the study are not currently included in the inventory of GHG emitted by the City, it is estimated that they represent a marginal source of approximately 0.3%. Nevertheless, we will take the time to analyze this study and assess whether improvements can be made to the methodology used,” says press officer Catherine Cadotte.
Crucial role of cities
The study also estimates that cities are responsible for “about 20% of global methane emissions caused by human activity” today. These municipalities, says Mary Kang, “are well placed to reduce methane emissions because they face fewer political challenges than larger bodies like provinces, states, territories and countries.”
Too often, “municipal greenhouse gas reports underestimate emissions and tend to be based on only a few measures in place elsewhere, making it difficult to develop actionable mitigation strategies,” says she asks in passing.
James Williams, a doctoral student who is also one of the authors of the study, asserts that “old landfills have the greatest potential for reducing the volume of methane emissions”. The complexity, he points out, however, is that these sites “incur the most onerous mitigation costs, unless you focus only on the landfills with the highest emissions.”
“When it comes to emissions from natural gas leaks, if we prioritize the repair of high-emitting industrial meters, we can greatly reduce mitigation costs and emissions. The same does not apply to residential meters: by prioritizing these, we will only obtain small reductions at increased cost,” he concludes.