Methane Emissions From Flame Curtain Pyrolysis (Kon‐Tiki)

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Abstract
Pyrogenic carbon capture and storage is increasingly recognized as a scalable carbon dioxide removal strategy. Flame curtain pyrolysis (Kon‐Tiki) enables decentralized biochar production, but its net climate benefit depends on the magnitude of methane emissions caused during production. Here, we compared emissions from flame curtain pyrolysis and open burning of crop residues, which is considered the baseline scenario in many cases. We tested five feedstocks across a range of moisture contents and continuously measured temperature and concentrations of CO 2 , CO, CH 4 , and C 3 H 8 in the flue gas. Emission factors were calculated via carbon mass balance, and regression analysis was used to identify drivers of the variability of methane concentrations. Kon‐Tiki pyrolysis resulted in lower CO and CH 4 emissions than open burning, particularly for wheat straw. Dry feedstocks (≤ 15% moisture) yielded low methane emissions (< 5 g kg −1 biochar), whereas moist feedstocks (≥ 25% moisture) produced up to tenfold higher emissions. Kon‐Tiki methane emissions were best explained by flue gas temperatures, showing an exponential decline of methane emissions with increasing temperatures. Overall, replacing open burning with Kon‐Tiki pyrolysis is a promising strategy to foster biochar production and reduce greenhouse gas emissions. Nevertheless, managing feedstock moisture and maintaining high temperatures are critical to minimize methane emissions and to enable Kon‐Tiki kilns to serve as an effective transitional technology for decentralized biochar production and carbon dioxide removal.

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