Search for a good hearth

While cook stoves in India are becoming fuel-efficient, they are not improving air quality, finds study

By Manupriya
Published: Sunday 30 November 2014

Search for a good hearth

Around 780 million people use solid cooking fuels, including wood, like this woman in Tamil Nadu

To think that something as basic and age-old as cooking is also a cause of air pollution and diseases, is not easy. Our traditional chulhas burn biomass and release small particulate matter and carbon monoxide (CO) in the air. The Indian National Census 2011 shows 780 million people use solid cooking fuels.

In the Global Burden of Disease 2010 assessment done by the World Health Organization (who), around 1.04 million premature deaths and 31.4 million disability-adjusted life years were attributed to household air pollution resulting from solid cooking fuels in India, accounting for 6 per cent of the national disease burden. For the last 25 years, the Indian government has run and supported initiatives to build solid fuel-based stoves with lesser emissions. In 2009, the government started the National Biomass Cookstoves Initiative (NBCI). Till today, it has approved 17 cook stove models for domestic use. But till date, their impact on reducing air pollution has not been assessed.

A unique study

A study published this October in the journal Eco Health by a group of scientists in India and the US has looked at some advanced cook stoves for their ability to improve air quality in communities where they are used. The study is unique since not only did it measure the level of pollutants in the houses where the advanced cookstoves were used, but also surveyed extensively to assess the acceptability of these stoves in the community and identified the challenges faced by their real users.

Six commercially available models of cook stoves were selected for the study—three models of natural draft-rocket stoves (Envirofit-B1200, Envirofit-G3300 and Prakti-Leo), a natural draft micro gasifier stove (Philips-Natural Draft) and two models of forced draft micro-gasifier stoves (Philips-HD4012-Forced Draft and Oorja). The stoves were distributed in seven villages in three districts of Tamil Nadu and Uttar Pradesh between May 2010 and December 2011. The study was conducted in three phases. In Phase I, baseline measurements of pollutants over a period of 24 hours in the kitchen were made, when chulhas were in use. Phase II and III were conducted one month and six months after the test stoves were installed.

Of the six stoves that were studied, none came close to meeting air pollution guidelines prescribed by the WHO. The stoves did not even meet interim standards (see interview). Using advanced stoves reduced the requirement of fuel by 30-40 per cent but the time spent near the stove remained either unchanged or increased in comparison to traditional stoves. The rocket stoves allowed charging the stove with the required quantity of fuel for a full meal, whereas the Phillips and Oorja stoves required re-charging within a single meal period. This resulted in spending ever more time close to the stove.

Surprisingly, the stoves with best impact on air quality were found to be least customised for usage in rural settings. For example, the Philips-HD 4012 Forced Draft stove was the only one to show statistically significant reduction in PM 2.5 (62.7 per cent) and CO (78 per cent) but was very cumbersome to use. Clearly, user requirements were not understood well enough before designing the stoves.

`The problem lies not just in stoves but in solid fuels themselves'
Kalpana BalakrishnanKalpana Balakrishnan, director, WHO Collaborating Center for Occupational and Environmental Health, Sri Ramachandra University, Chennai, who was part of the study, talks about the research and the way ahead
What are the WHO-prescribed emission guidelines for cook stoves based on solid fuel?

The guideline value for exposure to fine particulate matter (PM2.5) is 10 microgram/m3 (annual mean). WHO also provides three interim targets (such as 35 followed by 25 and 15 microgram/m3 (annual mean) for PM2.5) to gradually reduce health risks from a high level of pollution and assess progress towards achieving the guideline values. Achieving even the interim standards appears far-fetched for now.

What does your study reveal?

Of the six commercially available stoves we tested, none came close to meeting the World Health Organization (WHO) air quality guideline values. In fact, none of them consistently achieved even the interim standards. We would like everyone, including manufacturers in the field, to realise that the focus in designing these stoves should not be limited to improving efficiency, but be extended to making them clean enough to attain the health benchmark for air quality over a period of long-term usage. The study has also highlighted the key role of household-level factors. For instance, a single pot stove is often not enough for a household's basic meal requirements. This forces people to use the old stoves in addition to newer ones and air quality inside the house does not improve. Quality of fuel is another critical matter. Sometimes the fuel may not be well-chopped, may be wet or just be of the wrong type - all leading to greater inefficiency in burning. Also, exposures in excess of guideline values may be experienced even in clean fuel households located in communities using solid fuels.

Which stove was found to be the best?

The per cent reduction in mean concentration of PM 2.5 over a 24-hour period ranged from 8.5 to 62.5 per cent for different stoves. Philips-HD 4012 Forced Draft stove was the only one to show statistically significant reduction (at 62.5 per cent). The Oorja Forced Draft gasifier stove produced 20 per cent reductions but both were far from WHO air quality guidelines and reported to be cumbersome to use.

Are technical bottlenecks stalling us from building stoves that achieve WHO-prescribed emission levels?

The problem lies not just in the stoves but also in solid fuels themselves, that burn very inefficiently. Our technological knowhow does not allow us to build a stove in the Rs 2,000-Rs 3,000 bracket that burns fuel efficiently enough to match WHO standards. In trying for greater efficiency, the costs often shoot up. Till a breakthrough in clean technology occurs, the need of the hour is to move to cleaner fuels like LPG and electricity.

How can the government better implement schemes like the National Biomass Cookstove Initiative (NBCI)?

The NBCI was constituted to provide technologies that are comparable to LPG or other clean fuels. But we have found that cook stoves currently approved based on improvements in efficiency, cannot help attain WHO standards of air quality. Although India has been a pioneer in looking at more energy-efficient stoves, the aspect of health benefits of a cleaner fuel and stove have not been central in these discussions. There is now an increasing momentum to start evaluating stoves based on their health impact. This will change the course of things.

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