Pellet-fuelled cookstove cuts pollution and saves lives

A new pellet-fuelled cookstove has been found to reduce harmful air pollutants by around 90 per cent, an advance that could prevent millions of premature deaths.  

New cookstove design makes use of compressed wood pellets and reduces air pollution by about 90 per cent (Pic: Andy Grieshop, NC State)

According to the World Health Organisation (WHO), over three billion people in low-and middle-income countries rely on solid fuels – such as wood and charcoal – burned in inefficient and highly polluting stoves for cooking and heating, resulting in around four million premature deaths per year. WHO add that the same pollutants, including black carbon, negatively impact climate change.

The new design was evaluated during a Rwandan field study by a team from North Carolina State University (NC State).

“There have been numerous attempts to develop cleaner cookstoves for use in developing countries, but while they’ve often done well in lab testing, they’ve had disappointing performance when tested in real-world conditions,” said Andy Grieshop, an associate professor of environmental engineering at NC State and corresponding author of a paper on the work. “However, we found that the pellet-fed stoves performed well in the field. We saw drastic cuts in pollutant emissions.”

According to NC State, the pellet-fuelled stoves rely on battery-powered fans to burn the pellets efficiently, reducing pollutants. The stoves come with solar panels for recharging the batteries, making long-term use feasible in off-grid areas.

The researchers worked with residents in Rwanda, monitoring air emissions when people prepared food using conventional wood fires, which are common in rural areas; when using conventional charcoal-burning cookstoves, which are common in urban areas; and when using the new pellet-fuelled cookstoves.

The researchers tested for air pollutants including fine particulate matter (PM), carbon monoxide, and black carbon, a large fraction of which comes from domestic heating and cooking and contributes to climate change.

“For the most part, we saw pollutant levels across the board cut by 90 per cent or more using the pellet-burning stoves,” Grieshop said in a statement.

The researchers found that mean reduction in PM emissions from pellet-fuelled stoves was 97 per cent compared to wood fires and 89 per cent compared to charcoal cookstoves.

The pellet-fuelled stoves are the first cookstoves that have met the International Organisation for Standardisation’s (ISO) highest standard – Tier 5 – for carbon monoxide emissions. The stoves also met targets for carbon monoxide set by WHO, though they fell slightly short of the PM emission target.

“The ISO standard was developed with lab testing in mind, and we got these results in the field, which is remarkable,” Grieshop said.

“The only exceptions we found to these emission cuts were when a pellet stove was used improperly,” Grieshop said. “For example, when people used sticks or other materials to start the fire instead of kerosene, as suggested by the manufacturer, we found higher emissions in roughly 10 per cent of the 59 pellet stove research tests. But even the worst performance from a pellet stove was comparable to the best performance from a wood or charcoal cooking test.”

NC State said the results are promising, but the real challenge will be whether the pellet-fuelled stove concept can be scaled up. Test results showing how effective the pellet-fuelled stoves are at reducing air pollution are new, but the concept of introducing new cookstoves is not.

“The stoves we tested are essentially provided for free by a company that makes money by selling the necessary wood fuel pellets,” Grieshop said. “Anecdotally, we found in Rwanda that the cost of the pellets was comparable to the cost of the charcoal people buy for their cooking needs. However, right now, the fuel pellets are made using sawdust waste from timber operations. We just don’t know to what extent that is scalable.”

The paper, “Pellet-fed gasifier stoves approach gas-stove like performance during in-home use in Rwanda,” is published in Environmental Science & Technology.