The first thing that strikes you as you enter the Makomboki Tea Factory is the air. It's clear, absent of the dark smoke that billows from the boilers of Kenya's other tea factories.

Of the 66 tea factories under the management of the Kenya Tea Development Authority, Makomboki is the only one that doesn't use firewood in the processing of its tea.

Instead, the factory has switched to a greener, cheaper fuel: briquettes made of biomass byproducts that would otherwise be treated as waste.