## 4 Conclusions  
The biomass types investigated in the present study, excluding the fine-grained ones (<2-3 cm), would represent a large opportunity for carbon sequestration upon the identification of a viable mechanism to incentivize biochar production by farmers using residues of maize, cacao, cassava, and similar crops. Flame curtain kilns are not suited for fine-grained feedstock because of the resulting flame quenching and subsequent aerosol and methane emissions. The low emissions of maize cob, grass, and sesame stem pyrolysis in flame curtain kilns documented here are important due to the relevance of these biomass residues in cropping systems in sub-Saharan Africa. In 2018, maize was the second most abundant crop in sub-Saharan Africa (93 million metric tons in 2018 [47]), after cassava (169 million metric tons in 2018 [47]), from which the stems also likely provide the same high-quality feedstock biomass that is similar to sesame stems and twigs, due to their similarity. Grass is abundant and accessible to most farmers in the region. The 33 million smallholder farmers in sub-Saharan Africa could potentially obtain at least 50 million tons of biochar feedstock from their maize cobs, cassava stems, and grass. Annually, this could potentially sequester 70-80 million tons of CO\({}_{2}\)-eq and improve 12.5 million ha of farmland (application rate 4 \(\mathrm{\,\,\,h^{-1}}\)) [48].  
The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app14219649/s1](https://www.mdpi.com/article/10.3390/app14219649/s1)]([https://www.mdpi.com/article/10.3390/app14219649/s1](https://www.mdpi.com/article/10.3390/app14219649/s1)), Figure S1: The setup of the flame curtain kilns in Gulu, Uganda; Figure S2: The devices deployed to monitor emissions; Figure S3: Using a rake to slightly lift newly added grass to allow enough oxygen access to combat all the synapses; Table S1: Raw data for pyrolysis of maize cobs; Table S2: Raw data for pyrolysis of sesame stems; Table S3: Raw data for pyrolysis of grass; Table S4: Raw data for pyrolysis of grass/twigs; Table S5: Raw data for pyrolysis of coffee husk.  
G.C.: Conceptualization; Data Curation; Formal Analysis; Funding Acquisition; Investigation; Methodology; Project Administration; Resources; Validation; Visualization; Writing--Original Draft. C.M.: Formal Analysis; Investigation; Writing--Review and Editing. A.O.: Formal Analysis; Investigation; Writing--Review and Editing. V.M.: Funding Acquisition; Project Administration; Writing--Review and Editing. J.T.: Formal Analysis; Investigation; Writing--Review and Editing. J.M.: Investigation; Funding Acquisition; Project Administration; Writing--Review and Editing. J.J.: Investigation; Funding Acquisition; Writing--Review and Editing. J.J.: Investigation; Funding Acquisition; Writing--Review and Editing. E.S.: Conceptualization; Formal Analysis; Methodology; Validation; Writing--Review and Editing. All authors have read and agreed to the published version of the manuscript.  
Financial support was received from Kijani Forestry (Gulu, Uganda), Export Trading Group (Amstelveen, the Netherlands), and the Norwegian Research Council (Grant Agreement 302713, NorGlobal \"ClimSmart--Climate-smart innovations in agriculture in Uganda: Improved food security, livelihoods and soil carbon\").  
Not applicable.  
Data Availability Statement: Data will be made available on request. All raw data can be found in Supplementary Materials.  
Author [PERSON] was employed by NGI but partly affiliated with Menon Economics. Author [PERSON] was employed by Export Trading Group (ETG). Author [PERSON] was employed by Kijani Forestry. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.