Flame curtain kilns produce biochar from dry biomass with minimal methane emissions

Gerard Cornelissen, Erlend Sørmo, Ruy Korscha Anaya de la Rosa, Brenton Ladd

Research output: Contribution to journalArticlepeer-review


Flame curtain kilns have emerged as the preferred biochar technology for smallholders but reported methane emissions (30 g kg−1 biochar) have impeded carbon certification. Here, for flame curtain kilns we show almost no methane (0–3.6 g kg−1 biochar) emissions for dry (<15 % moisture) feedstock consisting of twigs and leaves. Wet feedstock (>40 % moisture) however generated significant methane (>500 g kg−1 biochar), underscoring that feedstock preparation is decisive for the carbon balance. Even for dry feedstock, both aerosol and CO emissions were significant (21–82 and 40–118 g kg−1 biochar, respectively). The data demonstrate that certification of low-tech biochar made from dry twigs and leaves should not be objected to on the grounds of methane. Careful selection of feedstock and potential after-combustion of the syn-gases are probably needed to avoid CO and aerosol emissions. More data are needed on methane emissions of other dry feedstocks.

Original languageEnglish
Article number166547
JournalScience of the Total Environment
StatePublished - 10 Dec 2023


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