The relationship between atmosphere-warming greenhouse gas emissions and health-harmful air pollution is well-established: the same activities that generate carbon emissions also tend to emit health-harmful air pollutants, some of which also fuel global warming.
But researchers in the hot, humid tropical city-state of Singapore have found another link: when outdoor air pollution spikes, electricity use rises too — as residents became more likely to seal themselves indoors, run the air-conditioning and crank up air purifiers — which in turn drives up carbon emissions produced in supplying the electricity.
About 95 per cent of Singapore’s electricity is generated using natural gas, according to the country’s Energy Market Authority.
The study, conducted by Associate Professor Alberto Salvo at the National University of Singapore and published in the Journal of the Association of Environmental and Resource Economists in July, found that overall electricity demand grew up 1.1 per cent when PM2.5 (fine particulate matter smaller than 2.5 micrograms) concentrations rose by 10 micrograms per cubic metre (μg/m³).
The study examined utility meter readings of 130,000 households – a 1-in-10 random sample of all households in Singapore – from 2012 to 2015. The same household’s energy consumption was examined over time and compared with concurrent PM2.5 measurements from the air-monitoring network.
But the increase was not uniform.
The study found that PM2.5 levels had a larger percentage impact on electricity demand as household income and air conditioning access increased – when PM2.5 increased by 10 μg/m³, electricity consumption rose by 1.5 per cent in more expensive, private apartment dwellings (condominiums), compared to a 0.75 per cent rise in one- to two-room apartments.
The 1.5 per cent increase in electricity consumption is equivalent to running the air-conditioning unit for another 10 hours per month. At the time of study, 14 per cent of one- and two-room apartments had air-conditioning, compared to 99 per cent of condominium apartments.
“Urban areas in developing Asian nations are home to an expanding base of energy consumers, with energy supply likely to remain carbon intensive for decades in the absence of major technological or regulatory shifts. Understanding what drives energy demand across the socioeconomic distribution of Singapore households can provide insight on the future energy demand of urban populations in the region’s cities as incomes rise. This is important for policymakers when forecasting and influencing future emissions paths in the context of climate change,” said Associate Professor Salvo.
Forty per cent of the developing world’s population lives in the tropics, and PM2.5 pollution ranges between 20 and 200 μg/m³. However, only 8 per cent of the tropics’ three billion people currently have air conditioners, compared to 76 per cent in Singapore.
“This study shows that households care about the quality of the air that they breathe, revealed through their spending on utilities, in particular, to power air-conditioners. Cleaner urban air will reduce energy demand, as households engage in less defensive behaviour, and this helps to mitigate carbon emissions,” Associate Professor Salvo said.
“At the same time, lower-income households are less able to afford such defensive spending on utilities. This observed inequality in defensive behaviour may also exacerbate health inequalities, especially in developing countries. Overall, this research can contribute towards longer-term forecasting of energy demand as developing Asian countries face the twin issues of a rising urban middle class exposed to air pollution, and the need to cope with climate change,” he added.
That need to cope with higher temperatures is likely to be another factor affecting electricity demand for cooling in the highly-urbanised island state, locking it into a vicious cycle and emphasising the need for less carbon intensive cooling options, passive design and cleaner electricity generation.
The highly urbanised island is heating up twice as fast as the rest of the world – at 0.25 degrees Celsius per decade – according to the Meteorological Service Singapore; one researchers projected that the amount of energy used to cool Singapore would grow by 73 per cent between 2010 and 2030.
In 2018, air-conditioning accounted for up to 40 per cent of the electricity bill for the average household, according to the National Environment Agency.
“When I was growing up in the 60s, the hottest month in Singapore was about 27 degrees Celsius on average,” said former Minister for the Environment and Water Resources Masagos Zulkifli in 2019, adding, “that is now the average temperature of the coolest months in this decade, and our hottest days exceed 34 degrees.”
From here, Associate Professor Salvo said he would continue to explore – with a focus on Asia – how households respond to environmental harms and what such responses reveal about their preferences for environmental quality.
Based on a press release by the National University of Singapore: Air pollution drives residential electricity demand
Banner photo by the Climate and Clean Air Coalition