The case for aerated stoves in rural homes

Own Correspondent

ROMA – DR Mosotho George, a chemist and senior lecturer at the National University of Lesotho (NUL), has made discoveries that revealed a need for better aerated stoves for use in Lesotho.

George, working with his students, discovered dangerous chemicals emitted during the burning of cow dung for household warming and cooking.

That is because poor burning of cow dung (lisu and likhapane in Sesotho), coal and wood, may generate smoke which contains chemicals that are called Polycyclic Aromatic Hydrocarbons (PAHs).

Lisu is the plural of compressed dried cow dung while likhapane is a plural of uncompressed dried cow dung.

These strange materials are assumed to have potential to cause cancer and can interfere with the hormone system in human bodies.

What exactly are these PAHs? These are materials made up of carbon and hydrogen atoms. When any carbon (organic) material is burned in a situation where there is insufficient air, the carbon atoms tend to come together and form ring structures of carbons complemented only by hydrogen atoms or in the extreme they form soot (mooa in Sesotho).

More interesting is how George got interested in PAHs.

“This work was actually inspired almost 17 years back when I took my newly born daughter home, some rural village on the feet of Thaba-Telle where I was born, to see her grandparents and be welcomed customarily,” he says.

His daughter was welcomed warmly in a home where the burning of lisu and likhapane in a poorly ventilated environment was never a concern.

“The sight of some black particles oozing with mucus out of my daughter’s tiny nostrils in the morning sparked a thought in me? What impact does this soot have on the poor babies’ health? However, by then my appreciation of the PAHs was not as much as it has been recently.”

As he attended many conferences and read a lot of literature about chemistry and health, that thought came back once more, many years later.

What effect does burning of lisu and likhapane have especially given that the people who rely on them as a source of fuel are already the least endowed in terms of resources?

In his observations, burning lisu and likhapane often happens in poorly ventilated huts, usually without any windows, as was the case in his home and to make matters worse, with doors closed to prevent excess wind current.

This already suffocates the fuel material even more, thus leading to the production of these unwanted materials.

It was time for George and his students to plan the experiment. As a scientist, he started with a guess, an educated guess (they like to give it a colorful name called hypothesis).

The educated guess was that PAHs are produced in a place suffocating with little air and oxygen.

On the basis of that supposition, they planned their “experiments to use a material that would allow for poor supply of air” while at the same time just igniting the fuel.

“Those who have been in a house where lisu are used would agree with me that these do not produce flame (ha li etse lelakabe, li hlena feela) as the material is being burned, and with a strong persistent stench,” George says.

“So we tried to mimic this situation.”

George then went deeper into the world of chemistry.

“We obtained a Schlenk tube (some tube that looks like a test tube but with a narrow side-arm towards the mouth). In this tube we placed some finely ground mass of different fuel materials: coal, lisu, likhapane, and wood.”

Thereafter they ignited the materials using firstly a technique called solid-phase micro-extraction, and later the supported solvent micro-extraction to trap these PAHs for subsequent analysis using a gas chromatograph.

Solid-phase micro-extraction uses a tiny fibre, about the size of a strand of hair coated with a plastic-like material. This device is able to trap most organic materials for further analysis.

On the other hand, supported solvent micro-extraction uses a tiny hollow membrane fibre that is filled with an organic solvent that can dissolve any organic compounds for further analysis.

So what did they find? Of the three fuel materials commonly used, lisu, likhapane and wood, only one PAH was obtained in lisu and one compound that could not be identified. Likhapane and wood did not produce any of these materials.

If you know both lisu and likhapane, you will testify that likhapane are more porous and lighter than lisu which are more compact – compacted dung cake, hence they differ in terms of their ability to hold air. Lisu hold less air and are difficult to dry completely, and that leads to poor burning.

More work will still need to be done to confirm and improve the results.

However, “the importance of these results is far-reaching for public health in a country already plagued by health challenges.

“We need to engage both the Ministries of Health and Energy about advocating for and improving “lipaola” (a makeshift stove made of perforated iron sheet container or tin) rather design better stoves that can burn these materials efficiently and direct the smoke out of the house through the chimneys,” George says.