Open burning and Asia's smog

When the fire is the disposal plan: open burning and Asia's smog
Picture a farmer in northern India at the end of the rice harvest. The field is full of stubble, the next crop goes in within weeks, and a match is the fastest way to clear the ground. Now picture a city edge in another country where uncollected household waste piles up and someone sets it alight to shrink the heap. Neither person wants dirty air. Both are solving a disposal problem with the only tool within reach.

What the research says about farm fires
Burning crop residue gets much of the blame for the haze that settles over Delhi each autumn, and the science is more cautious than the headlines. A 2025 study by Akash Biswal and colleagues, published through the Royal Society of Chemistry, modeled how much fine particulate matter (PM2.5) in the Delhi region came from crop residue burning in Punjab and Haryana. The authors put the share at 18 percent in 2022, 16 percent in 2023 and 9 percent in 2024.

The authors also note that the 2024 drop may be partly a measurement gap. Farmers may have shifted burning to the evening, when satellites are less likely to detect fires, and sensors in rural Punjab still recorded high PM2.5. The study shows how hard it is to assign a fixed share of a city's smog to one source. It does not show that the fires are harmless.

Burning waste adds a second fuel
Farm residue is one fuel. Household and commercial waste is another. A review commissioned by Engineering X, a body founded by the Royal Academy of Engineering and Lloyd's Register Foundation, and carried out by the University of Leeds with the International Solid Waste Association, found that about half a billion tonnes of municipal solid waste (24 percent of the world total) is never collected. Another 27 percent is mismanaged after collection. The review says much of this waste ends up burned in the open.

The same review says open burning harms the health of tens of millions of people, and that the true number is unknown because few places measure it. It also lists persistent organic pollutants among the emissions, along with compounds linked to cancer and to developmental and immune damage. The world's 11 million waste pickers work closest to these fires.

What the air costs people
The World Health Organization estimates that outdoor air pollution caused about 4.2 million premature deaths worldwide in 2019. Its fact sheet, updated in October 2024, adds that 99 percent of the world's population lived in places where air quality fell short of WHO guideline levels that year. Those totals cover every source, from traffic to power plants to fires. Open burning is one contributor among many, and no source cited here splits the total by cause.

For a family in a smog-bound city, the cause matters less than the result: closed windows, sick days and children kept indoors. A parent checking an air quality app before school drop-off lives with the numbers above, whether the smoke came from a field, a rubbish heap or a tailpipe.

Why bans alone do not work
Governments can prohibit burning, and several have tried. A ban leaves the original question unanswered, though. What does a farmer do with the stubble, and what does a city do with waste that trucks never reach? The Leeds review makes the same point from the other side: ending open burning would add as much as a billion tonnes of waste that someone has to treat and dispose of. That waste needs a destination, and the destination needs to be affordable and close to where the waste starts.

Large plants take years and heavy capital to build, and they need reliable roads and collection routes. Many of the places with the worst burning have neither.

Nexus Biofuel's role
Nexus Biofuel Inc., based in Kelowna, British Columbia, works on this gap. The company converts waste streams, including biomass and municipal solid waste, into usable energy with portable, economical equipment that avoids incineration. Because the equipment moves, it can go to the waste instead of waiting for the waste to reach a distant facility. Nexus Biofuel aims to cut reliance on fossil fuels, reduce greenhouse gas emissions and create jobs in the communities it serves. Giving farmers and cities a use for their residue and waste other than fire is the problem this technology is built to address.