Come October, the India’s capital begins its annual battle with smog – a toxic cocktail of automobile and industrial emissions, construction dust and a generous splash of smoke from burning crops. Burning is the quick and economical means by which farmers get rid of post-harvest waste.
Is there a better way to dispose of this waste? Yes, say a team of researchers from Harvard who have fashioned the crop residue into air-cooling panels called Green Screens. The screens are a win-win: they help to cool homes during sweltering summer days and use up crop waste, which would have otherwise been burned by farmers and contributed to air pollution in and around New Delhi.
The Green Screen was developed by an interdisciplinary team of designers, scientists and policy experts during a course at Harvard University, aimed at creating viable solutions to intractable problems facing developing countries. Founder Gina Ciancone is a design student; Alex Robinson and Ramya Pinnamaneni are global health practitioners; and Dan Cusworth is an atmospheric chemist.
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Together, they have been working on, refining, the idea since fall 2017. In October 2018, the Green Screen mock-up passed a technical evaluation at the NASA Johnson Space Centre in Houston, Texas, where engineers checked how effective it was at cooling space.
“We aim to have a final prototype ready to test for proof-of-concept in a select number of households in New Delhi by March 2019,” Robinson said.
A March 2018 study by Dan Cusworth and others that quantified the impact of agricultural fires on Delhi’s air pollution was the springboard for Green Screen. By comparing fine particulate matter (PM2.5) concentrations before and after the crops are burned, the study estimated that almost half of all particulate pollution in Delhi during October-November was due to upwind agricultural fires.
To compare, models from the Centre-run System of Air Quality and Weather Forecasting (SAFAR), a research-based initiative that monitors air quality in metros across the country, attribute 30-40% fine particulate matter pollution to stubble burning. Gufran Beig, its project director, said, “It is the greatest need of hour that technology should be developed to curb this source.”
Cusworth and his collaborators also used atmospheric transport computer simulations to identify specific regions upwind of Delhi from where burning contributes most to Delhi air pollution. The Green Screen team is using this information to make connections with farmers from these regions and source crop residue from them, for maximum potential impact in reducing air pollution.
Successfully sourcing the agricultural waste will be the team’s primary challenge, says Venkatraman Srinivasan, who studies eco-hydrology at the Indian Institute of Technology Madras. “Harvesting the waste is labor intensive and not very economical, which is why farmers choose the easy option of burning them. The government has pushed mechanised harvesters, but with small land size, this is difficult and has not been successful so far,” he cautioned.
How this will affect the teams plans to scale up production in the future remains an open question at the moment.
The Green Screen is made by converting the agri-waste into bio pulp and assembled onto a square-shaped panel about 4” thick. The screens can be thought of as a more efficient version of [bamboo and vetiver grass curtains. Funnel shaped holes in the panel are designed to allow hot air passing through to be compressed into cooler wind.
Additionally, an attached scrim of vegetation can be watered and it provides further cooling as the water vaporises. With both these cooling methods, the Green Screen can bring indoor temperatures down by about 6°C. “It is a simple but nifty design, using conical holes to achieve cooling,” said Satyanarayanan Seshadri, an assistant professor in the department of applied mechanics at IIT Madras. He develops cleaner sources of heating for process industries, and he expects that the design could work well in hot, dry areas.
Srinivasan agrees – but expects the design to work best in well-ventilated, instead of crowded, areas.
While the exact amount of agricultural waste needed to optimise the impact of Green Screen is still being worked out, early projections show that 100 screens can be produced from one tonne of bio pulp, preventing one tonne of carbon dioxide from escaping into the air.
The team expects the screens to have a particularly positive impact on the environment of urban slums – places that are most vulnerable to extreme heat and dangerous levels of pollution. Light-weight and portable, the Green Screen can be easily attached by a hinge system to voids and gaps that commonly act as windows in urban slum houses. When it is ready to be sold, the cost is expected to be as low as Rs 350, about 1% the cost of a conventional air-conditioner.
But first, the product has to be tested in the field. The researchers have partnered with two not-for-profit organisations – Chintan, an environmental advocacy NGO in New Delhi, and the UK-based WIEGO – who will work with them for proof-of-concept testing.
“Harvard reached out to us. The project makes a lot of sense to us and aligns well with our mission,” said Chitra Mukherjee, head of operations and programs at Chintan. “It is a good concept, a sustainable means to transform waste that causes harm into something that can benefit poor and marginalised communities,” she added.
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Between March and May 2019, the screens will be installed for free in select households in Gazipur and Bhalswa. Each such household will be fit with digital thermometers to log the temperature at regular intervals and log it in a central database. Other sensors will also monitor PM2.5 levels.
Finally, the team itself plans to conduct a door-to-door survey to capture qualitative indicators and better understand the broader impact of Green Screen on household productivity, health outcomes and wellbeing. If all goes well, the team will begin to source stubble and establish production capabilities locally after June 2019. After another phase of pilot testing, they hope to scale up production and diversifying design options for the screen the following year.
A combination of design research, data analysis, needs assessment and engineering have gone into making this zero-electricity panel that promises to mitigate, at once, the harmful effects of air pollution and extreme heat.
Harini Barath is a freelance science writer based in New England, USA.