Cogenerating electricity from charcoaling: A promising new advanced technology

This article presents a technical review of the status of the charcoal cogeneration technologies. Cogeneration of electricity from charcoal production is an emerging technology, with promising worldwide application. When charcoal is produced through traditional slow pyrolysis batch cycle processes, about 50% of the original firewood energy is lost through the pyrolysis gases. These gases are made of condensable and non-condensable portions. The condensable fraction consists of an energy-rich mix of compounds that can be extracted through condensation. The non-condensable fractions consist of flammable gases such as CO, H2 and CH4, which can used to produce heat and power, either using steam cycle systems, or other technologies such as Stirling engines or even ECGT (External Combustion Gas Turbines). Several companies in Brazil, France, Denmark and Australia are currently pursuing the development of charcoal cogeneration. To overcome the usual instability in the availability of energy from pyrolysis gases when charcoaling in batch cycles, most companies are developing charcoal production units that cluster several charcoal kilns together, operating them in a staggered sequence, in order to stabilize the energy output from the system. Furthermore the usage of complementary fuels such as biomass residues or other petroleum fuels is investigated, to help stabilize cogeneration and increase power output. As this technology develops, it could offer several benefits including entrepreneurial opportunities, livelihood diversification and increased incomes in rural areas for charcoal entrepreneurs, as well as reduction of greenhouse gases emissions and additional renewable energy capacity. Sub-Saharan Africa, the leading charcoal production region in the world, suffers acute deficits in electricity access, and could benefit from this technology. However to enable such technology to flourish in the future, an appropriate legal framework and business model should be specifically developed for each country.

► Traditional charcoal making through batch pyrolysis loses 50% of feedstock energy. ► Losses occur because high-energy pyrolysis gases escape unutilized. ► Pyrolysis gases could be used to cogenerate heat and electricity. ► The technology reduces emissions of GHG, generates bio power, and boosts income.