Conversion to clean-energy fuel is a priority for cooking among Peru's rural communities. This is for two reasons: because of the adverse health effects of indoor smoke from biomass-burning stoves (see Nature 509, 548–551; 2014) and because using tropical hardwoods as fuel is accelerating deforestation in the Amazon.

The only viable source of clean fuel for rural communities in the Peruvian Amazon is natural gas, which has to be extracted and transported across the Andes, imposing prohibitively high running costs.

A pyrolysis cooking stove offers another solution. Its combustion design (see go.nature.com/e7j8q1) makes it superior to the biomass-burning stoves you describe. For example, it cooks faster than an open fire but consumes half the amount of wood, generates half the smoke and can run on low-grade fuel such as small twigs and leaf litter.

At US$180 per unit, it is costly compared with the $15 stoves that you discuss, but the price incorporates training, monitoring and education to ensure that the stove is properly used. It is also a simple matter to convert these stoves to burn natural gas, should that become more economically viable.