This text is part of the special Quebec engineering booklet
A research team from McGill University has shown that Montreal’s landfills and manholes emit large amounts of methane. However, the City of Montreal’s reports on its greenhouse gas (GHG) emissions do not take this into account.
Prior to 2020, McGill University Department of Civil Engineering Assistant Professor Mary Kang and her team focused on measuring methane emissions from oil and gas operations. However, the pandemic has greatly reduced their ability to travel. The team therefore fell back on a project that had started on a very small scale in 2019: measuring methane emissions from old landfills, sewers and natural gas distribution networks on the island of Montreal.
“We carried out 615 individual measurements in these locations, which are among the four largest sources of methane emissions in Montreal,” explains Mary Kang. She is the chief author of an article based on this research, which was published in the scientific journal Environmental Science and Technology and whose main author is doctoral student James Williams.
The City of Montreal is aiming for carbon neutrality by 2050 and has adopted a plan comprising 46 measures to achieve this. It also prepares reports on GHG emissions in its territory, to measure its progress. However, it does not take into account the methane produced by old landfills and sewers. “It is not the only city to underestimate the methane emissions on its territory, admits Mary Kang. In Canada, Toronto conducted a study on this subject a few years ago, but most Canadian cities instead rely on estimates from other countries, which do not give an accurate picture of the situation. »
A powerful global warming factor
Methane is thought to be responsible for around 30% of global warming since pre-industrial times and is growing faster than at any time since it was first measured in the 1980s, according to the United Nations Program united for the environment. Data from the US National Oceanic and Atmospheric Administration indicates that atmospheric methane continued to rise during pandemic-related lockdowns in 2020.
Over a period of 20 years, its warming effect is more than 80 times more powerful than that of CO2. Cities produce about 20% of global methane emissions that come from human activity.
Work by the McGill University team showed that old landfills on the island of Montreal emitted an average of 901 tonnes of methane in 2020, with a peak recorded at 1,541 tonnes. This stems in particular from the putrefaction of the organic matter found there. These are the places with the greatest potential for reducing emissions, but at the highest cost. The sewers generated an average of 786 tonnes of methane, with a peak recorded at 2602 tonnes. These emissions could be mitigated at lower cost, but the solutions to achieve this are not yet commercially available.
Natural gas distribution facilities emitted 451 tonnes of methane on average in 2020, peaking at 843. Increasing the frequency of repairs to plug leaks in this network would be a quick and effective way to reduce these methane emissions. at a relatively modest cost.
Misleading estimates
The measurements made in the McGill University study are based on a very small sample. For example, the 136 sewers observed in the study represent 0.03% of all sewers in Montreal. “Other measurements will therefore be necessary to have an even more precise idea of the quantities of methane generated by these facilities,” says Mary Kang. But our work shows that the City of Montreal must take these sources of methane emissions into account when calculating its GHG emissions, if it really wants to achieve its objectives. »
Especially since estimates based on data from abroad do not necessarily correspond to our situation. “For example, emissions from old landfills and sewers are largely dependent on weather, soils and atmospheric processes, which vary from place to place on the planet,” explains Mary Kang. It is therefore essential to measure what is really happening in our own cities. »
This special content was produced by the Special Publications team of the Duty, pertaining to marketing. The drafting of Duty did not take part.