Household heating and cooking accounted for 40 per cent of Delhi's PM 2.5 pollution in December 2020 and January 2021, according to a new study.

Though recent assessments on the use of biomass in Delhi are not available, a large number of homeless people burn firewood and waste to keep themselves warm in winters.

"The contribution to PM 2.5 from the residential sector (including domestic cooking, space heating, water heating, and lighting) was as high as 40 per cent in December 2020 and January 2021," the Council on Energy, Environment and Water (CEEW), a Delhi-based not-for-profit policy research institution, said in a study report.

Delhi is estimated to have 1.5 lakh to two lakh homeless people. According to the Delhi Urban Shelter Improvement Board, as of January 2021, as many as 319 shelter homes had been created with a boarding capacity of 19,116 people.

"However, these shelter homes can accommodate only around 10 per cent of the homeless population in Delhi, which leaves a sizeable portion of the city's homeless population exposed to the elements.

"This population, therefore, is forced to use firewood/biomass fires to keep themselves warm during winters. Waste is also burnt for warmth and disposal purposes, which also contributes significantly to the pollution burden of the national capital," the CEEW said.

According to the study, a relatively longer stubble-burning period and unfavourable meteorological conditions were primarily responsible for Delhi's worsening air quality in winters last year.

It also said that emissions from 11 coal-fired power plants in the National Capital Region accounted for just seven per cent to the Delhi's PM2.5 pollution on an average between October 2020 and January 2021, while vehicles contributed 14 per cent.

The findings are significant considering the Delhi government had recently moved the Supreme Court seeking closure of coal-fired power plants using outdated polluting technology in the vicinity of the city.

On April 1, the Union Environment Ministry had issued a notification with amended rules allowing thermal power plants within 10 kilometers of the National Capital Region (NCR) and in cities with more than 10 lakh population to comply with new emission norms by the end of 2022.