Innovation in charcoal production: A comparative life-cycle assessment of two kiln technologies in Brazil

This paper presents a comparative analysis of environmental impacts in Brazil's industrial charcoal industry resulting from a shift from hot-tail kilns, which are the most common kiln used by the industry, to metal container kilns. Hot-tail kilns vent pyrolysis emissions directly to the atmosphere, but container kilns allow for easy capture of pyrolysis gases, which may be used as co-products, adding value to charcoal production and reducing environmental impacts through the displacement of other products and/or processes. This analysis uses hot-tail kilns as a reference scenario and considers four alternative scenarios using container kilns in which pyrolysis gases are utilized in different ways. We find that the container kilns improve environmental performance relative to hot-tail kilns across a range of indicators including greenhouse gas (GHG) emissions, water demand, energy-return-on-investment (EROI), Ozone depletion potential (ODP), photochemical oxidation (PCO), acidification, and eutrophication. GHG reductions range from 28% to 119% (10–43 ktons of CO2e per year) depending on the utilization of specific co-products. Water consumption declines by 25% consistently across all scenarios, and EROI improves by 24–157%. ODP also improves between 30% and 300%. However, container kilns do not show improvements in other impact categories: PCO increases by 20–58% while the potential for both acidification and eutrophication increase 20 to 40 fold. These increases in environmental impacts arise primarily from NOx and non-methane hydrocarbon emissions, which increase when charcoal production is coupled to cogeneration using pyrolysis gases and/or woodwaste. These additional emissions could be avoided with existing control technologies.

► Brazil is the largest charcoal producing nation using primarily hot-tail kilns.
► Metal “container kilns” are being tested as a more efficient alternative.
► Container kilns allow the use of pyrolysis gases for production of heat and power.
► LCA shows container kilns perform better in energy, GHG emissions, and water use.