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The world is burning useful waste, and cleaner alternatives are needed
When we talk about clean air, the conversation usually turns to traffic: exhaust fumes, congestion, school runs and the air people breathe on busy streets. That focus is understandable because road transport remains one of the most visible sources of poor air quality in everyday life. But Clean Air Day should also draw attention to a less visible question: why are useful materials still being burned as waste? Clean air is about more than traffic Around the world, huge quantities of leftover straw are still treated as waste to be cleared quickly, with rice straw one of the clearest examples. More than 700 million tonnes of rice straw are produced globally every year, and around 80% is burned. That contributes directly to air pollution and greenhouse gas emissions, while also destroying material that could have value. At Aston University’s Energy and Bioproducts Research Institute, researchers are exploring alternatives to open burning of crop residues, including whether materials often treated as waste could instead become useful sources of energy, fuels or bioproducts. This matters because the clean air debate needs to look beyond transport. How we manage waste, land and energy also plays a part, and agricultural residues should not automatically be seen as rubbish to be burned. In many cases, they could be resources with real value. Why burning crop waste matters The World Health Organization describes air pollution as one of the greatest environmental risks to health, estimating that ambient outdoor air pollution caused 4.2 million premature deaths globally in 2019. Much of that risk comes from exposure to fine particulate matter, which is linked to cardiovascular and respiratory disease and cancers. That is particularly relevant when residues are burned in the open, as smoke and fine particles can travel beyond the field where burning takes place, affecting nearby communities and wider air quality. There is a practical issue as well as an environmental one. If burning is the fastest and cheapest way to clear land, it can easily become the default, which is why any cleaner alternative has to work for farmers and communities in practice. It is not enough to tell people to stop burning; they need practical alternatives that make sense economically and locally. Turning waste into cleaner alternatives Biochar and bioenergy are two examples of how waste crop material can be treated differently. Instead of being burned in the open, residues can be converted into useful products or sources of renewable energy. Biochar can also offer practical benefits for farmers when it is produced and applied appropriately. Studies have shown that addition of biochar to the soil can improve its structure, help retain nutrients and, in some cases, reduce the need for synthetic fertilisers, which will lower associated emissions and economic demands. The water-holding capacity of biochar can also support crops during dry periods, potentially reducing irrigation demand in drought-prone seasons. Work connected to rice straw has shown that cleaner alternatives to burning can produce measurable environmental benefits while supporting local economies. Community-scale rice straw bioenergy systems, for example, can avoid 2.7–3.5 tonnes of CO₂ equivalent emissions per hectare each year, while creating fuel savings and reducing post-harvest losses for rice farming communities. Research and interviews have shown that farmers and local stakeholders are willing to participate in these transitions when alternatives are designed around their needs and priorities. During community engagement activities, participants consistently highlighted cleaner air as an important benefit, not only for environmental reasons but also because of concerns about the health impacts of smoke and the financial burden of illness. For many households, avoiding respiratory problems and expensive hospital bills was seen as just as important as generating additional income from agricultural residues. That matters because cleaner air is linked to more than one policy area. Transport is important, but so are farming, energy and waste. Research can help identify what works, where the trade-offs are, and how promising ideas can move beyond the lab. It can also support industry, policymakers and local partners to develop alternatives that are practical rather than theoretical. For policymakers, the lesson is that air quality cannot be improved by focusing only on the most visible sources of pollution. Transport matters, but so do homes, industry, farming, waste and energy systems. There is no single answer. Agricultural residues vary, local conditions vary, and technologies need to be assessed carefully, but cleaner air will require better options than burning. Clean Air Day should prompt us to ask why useful materials are still being burned in the first place. If we want cleaner air, we need to reduce what we burn and get smarter about what we waste. This article was written by Dr Samuel Sogbesan and Thea Mae Baltazar from Aston University’s Energy and Bioproducts Research Institute. (Photo by Sandie Peters on Unsplash)
