Where Asia's smog comes from: burning fields and burning rubbish

Late October in northern India has a smell. Farmers in Punjab and Haryana finish the rice harvest, then set fire to the stalks left standing in their fields. Within days a brown haze settles over towns and cities, Delhi among them. If you live downwind, you taste it before you see it.

Fields on fire
NASA's Earth Observatory describes crop burning as the main source of the haze over northern India, especially in Punjab and Haryana, where farmers grow rice and wheat. The practice is recent. Combine harvesters became popular in the 1980s and leave stalks several inches tall. According to NASA, burning is the quickest and cheapest way to clear that debris before farmers plant wheat.

A NASA Goddard scientist told the observatory that without cheap, easy alternatives, farmers have little reason to stop. NASA also reported that, based on its Aqua satellite, fires in the Indo-Gangetic Plain rose about 300 percent between 2003 and 2017. The smoke does not stay near the fields. NASA researchers found that particles and gases regularly travel several hundred miles.

Rubbish on fire
Fields are one source. Garbage is another. A 2014 study led by Christine Wiedinmyer of the US National Center for Atmospheric Research, published in Environmental Science & Technology, estimated that about 40 percent of the world's waste, some 1.1 billion tons, burns in open piles. The authors found that open burning releases more pollution than regional and global inventories show.

Scientific American, reporting on the study, said trash fires account for as much as 29 percent of global human-caused emissions of small particulate matter. The same report gave open burning about 10 percent of mercury emissions and about 40 percent of polycyclic aromatic hydrocarbons. These figures cover the whole world and date from 2014, so treat them as an estimate of scale rather than a count for any one Asian city.

A season with a calendar
The burn follows the harvest. In 2018, NASA reported, fires began in early October near Amritsar, and by the end of the month large numbers burned across Punjab and Haryana. Burning typically peaks in the first week of November. A NASA Goddard scientist, Hiren Jethva, said at the time that fire counts and PM2.5 levels in New Delhi were rising together.

That timing matters if you live in the region. The stalks go up in smoke over a few weeks, and the cities downwind absorb the particles over the same few weeks.

Rubbish fires have no season. They burn whenever the pile gets large enough to be a nuisance.

What the smoke does to people
The World Health Organization estimates that outdoor air pollution caused 4.2 million premature deaths worldwide in 2019. About 89 percent of those deaths occurred in low- and middle-income countries. WHO also reports that 99 percent of the world's population lived in places that did not meet its air quality guidelines that year.

The Wiedinmyer study adds a climate figure: carbon dioxide from trash burning is about 5 percent of total global CO2 emissions. WHO names open incineration of solid waste among the practices that cleaner options can replace. Where burning cannot be avoided, it says, combustion technology needs strict emission controls.

Two waste streams, one match
Look at the two fires side by side. Rice straw is biomass. Household and commercial rubbish is municipal solid waste. Both pile up on a schedule, both cost money to move, and both burn for free. NASA's scientist put the farmer's side of it plainly: cheap alternatives are missing. The same logic applies to a dump where nobody collects the waste.

Any fix has to give straw and rubbish a use that pays for itself, so that nobody needs to light them. That means equipment a village or a district can afford, move and run, and a product someone wants to buy. Energy fits that description.

Nexus Biofuel Inc., based in Kelowna, British Columbia, converts waste streams, including biomass and municipal solid waste, into usable energy. Its equipment is portable and economical, and it avoids incineration. The company aims to cut reliance on fossil fuels, reduce greenhouse gas emissions and create jobs. Because the equipment is portable, the processing can go to the waste, which suits waste that is expensive to haul. A waste stream that produces energy has a buyer, and that gives a farmer or a city a reason to keep the match in the drawer.