Air pollution is a threat to public health affecting both developed and developing countries, causing seven million deaths every year according to the WHO. More than 90% of the global population live in regions where pollution is above levels considered harmful for human health. Emergent economies are hit the hardest, as the problem gets particularly worrying where air quality regulation struggles to keep pace with rapid urbanisation and industrial development, usually sustained by massive combustion of fossil fuels and coal in particular.

Attention to the issue has been revived in the midst of the COVID-19 pandemic. On the one side, cleaner skies seen around the world as a consequence of total or partial lockdowns have been considered a silver lining to the pandemic. Beyond meaningful short-term results in these months, however, the slowdown in economic activity cannot (and should not) be considered a feasible solution to poor air quality in the longer run. On the other side, scientists have also been studying the “boost” effects of several pollutants – such as PM10, PM2.5 and NOx – whose high concentration in urban and industrialized areas like northern Italy or eastern and central China might have favoured the spread of the virus at greater distances and might have increased the exposure and severity of COVID-19 symptoms. 

PM2.5, sulphur oxides and nitrogen oxides are the main responsible for the most widespread impacts of air pollution, either directly or once transformed through chemical reactions in the atmosphere. As several of the core causes (and core remedies) of poor air quality do lie in the burning of fossil fuels, gas might play a role where it replaces more polluting sources, primarily coal and secondly oil.

The combustion of natural gas indeed results into lower air pollutant emissions compared to coal and oil. It releases very little particulate and sulphur emissions into the air and currently accounts for only around 10% of global NOx emissions. These features make it an ally in the fight to curb the health impacts of poor air quality in a number of contexts and timeframes.

Switching to gas as we know it cannot provide a long-term solution and will therefore need to be supplemented by decarbonization solutions, including CO2 capture and storage. In the meantime, its role should be considered case by case in its regional, infrastructural and market complexity. In specific timeframes, sectors and countries, using gas can bring significant air quality benefits, especially where quick wins for emissions reductions are possible, i.e. where there is the potential to switch to gas using existing infrastructure. 

Gas has indeed growingly played a role in addressing local air quality problems, pushed by different reasons and touching upon different sectors. Using gas to reduce pollution has become a matter of priority for China since 2014. In the country, demand for gas has strongly risen in the last two years as a result of a push for a coal-to-gas switching in urban areas: a key part of the effort to make China’s skies blue again is indeed that of reducing the use of coal-fired boilers - seldom equipped with adequate pollution controls - in industrial facilities and in residential buildings. In the residential sector, 27 million households were connected to the gas grid in 2005-16 and 7 million in 2017-18 alone. The growth in gas use also concerns other sectors, as transport, part of the battle against air pollution that includes restrains on heavy-duty diesel vehicles. Despite this increase, the share of gas in electricity generation is still low, 3.6% of total power generation.

In the United States, emissions from coal fell drastically in 2018, largely because of gas displacing coal, and this contributed improving air quality. The regulation of air pollutants including SO₂ and NO_X is now reinforcing the trend for moving to natural gas in the electricity sector. The push for gas in the US, however, has mainly to do with the remarkable rise of shale gas in the country, thus underpinning large-scale switching from coal to cheap gas.

Some megacities have in the past bet on gas. Istanbul, recording the busiest traffic and highest population in Turkey, is certainly one noteworthy case. The city has grown from 2 million people in ‘70s to around 15 today. Urbanization, migration and socio-economic development have contributed to an expansion of the built-up areas and industries in the city and the suburbs, raising worrying environmental concerns. From the ‘70s, Istanbul switched from oil to coal for domestic heating and industry, experiencing significant PM and SO₂ growth. A gas distribution company (IGDAS) was then established to install the necessary infrastructure to distribute gas to residents and in 1992 the city administration banned lignite. By 1998, natural gas was supplying around half of the residential heating needs in the city and the industry has also started to switch fuels, with significant impacts on air pollution. 

The current crisis has severely hit the gas market, already characterized by conditions of oversupply, causing low consumption and prices. One might consider that efforts for limiting pollution and climate change are deprioritized globally as a result of the current crisis, a context which could result into less efforts to switch to gas where considered helpful. Policy support to gas is however in most cases part of plans that go beyond the current market phase. By virtue of its greater air quality attributes in comparison with coal or liquid fuels, the near-term prospects might remain strong. 

Even if there are obviously lower-emission and lower-cost alternatives to gas that are key to decarbonisation (starting from RES and efficiency measures), the role of gas is recognized under scenarios consistent with the Paris Agreement – such as the Sustainable Development Scenario (SDS) – in certain countries and timeframes, to push more polluting fuels out of the system. For example, coal- to-gas switching contributes around 8% of the emissions savings in IEA’s SDS relative to the Stated Policies Scenario (STEPS), also helping to improve air quality as it contributes to the 50% reduction in coal-based sulphur dioxide and particulate matter emissions until 2025.

To take advantage of all the benefits of gas, the wider environmental consequences must however be more strongly considered, in particular the indirect emissions relatable to producing, transporting, processing gas or coal (mainly CO₂ and methane). These emissions are again highly variable across regions, supply chain routes, processes, and equipment, but IEA considers that natural gas operations result in around 40 Mt of methane globally today – thus having an important environmental impact that must be minimised in the near-term. 

Margherita Bianchi is a researcher at IAI, where she works in the “Energy, climate and resources” program. Among her previous experiences she worked at the European Parliament, in the Task Force of the Italian G7 Presidency, and at UN Environment.