They say that there are 9000 restaurants in Delhi that use coal. Flyash particulate matter emission is large. Average consumption is 30kg/day. Coal and flyash are the largest contributor to PM 10 (particulate matter less than 10 micron in diameter) and PM 2.5 (particulate matter less than 2.5 micron in diameter) in summers.
"... a study by IIT Kanpur has identified coal-fired tandoors in restaurants and hotels of the Capital as one of the contributors of particulate matter.
The study was commissioned by the Delhi government in 2012 and a draft report, which has been submitted to the government, recommends that such restaurants shift to electric or gas-based appliances.
The ‘Comprehensive Study on Air Pollution and Green House Gases (GHGs) in Delhi’ analysed several sources that contribute to Delhi’s hazardous air, including vehicles, power plants, industries, traffic, local power generation, hotels and open burning of municipal solid waste (MSW). ..."
"... “A careful examination shows that about 67 per cent reduction of PM10 (2,142 kg/day) and PM2.5 (1,083 kg/day) emission from this source can be achieved by stopping uses of coal. It may be seen that coal and flyash are the largest contributing sources in summer and this action is expected to reduce ambient air concentration by 2.7 µg/m3 and 2.9 µg/m3 in PM10 and PM2.5 respectively,” the report states. ..."
Find this at http://indianexpress.com/article/india/india-news-india/tandoors-burning-of-solid-waste-adding-to-dirty-delhi-air-iit-study .