## 3 Results and Discussion
### Gas Emission Factors
NO\({}_{\rm x}\) emissions close to detection limits were observed for all biomass types (<0.13 g kg\({}^{-1}\) biochar; Table 2), probably explained by pyrolysis temperatures (<800 \({}^{\circ}\)C [7]) below those needed for the oxidation of ambient N\({}_{2}\) to NO\({}_{\rm x}\) (<1000-1200 \({}^{\circ}\)C [34]). \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Feedstock** & **\(n\)\({}^{\bullet}\)** & **CO\({}_{2}\)** & **CO** & **CH\({}_{4}\)** & **TSP** & **NO\({}_{\rm x}\)** & **CO\({}_{2}\)-eq. \({}^{\rm b}\)** \\ \hline \multicolumn{8}{c}{**g kg\({}^{-1}\) Biochar**} \\ \hline Grass & 17 & 5122 & 39 (33–47) & \textless{}5.5 \({}^{\circ}\) & 16 (13–24) & 0.13 (0.00–0.19) & 78 \\ \hline Grass + twigs & 19 & 4576 & 33 (27–60) & \textless{}5.5 \({}^{\circ}\) & 45 (31–72) & \textless{}0.006 \({}^{\rm d}\) & 66 \\ \hline Maize cobs & 21 & 3933 & 68 (56–107) & \textless{}5.5 \({}^{\circ}\) & 27 (17–40) & 0.07 (0.00–0.16) & 136 \\ \hline Sesame stems & 17 & 1197 & 28 (25–41) & 17 \({}^{\circ}\) & 14 (12–18) & 0.04 (0.00–0.07) & 481 \\ \hline Coffee husk & 4 & 2782 & n.d. \({}^{\rm f}\) & 179 (134–274) & 331 (287–356) & \textless{}0.006 \({}^{\rm d}\) & 4500 \\ \hline Twigs and leaves (10\% moisture) \({}^{\rm g}\) & 25 & 3633 & 101 (60–181) & \textless{}5.5 \({}^{\circ}\) & 62 (29–97) & 0.01 (0.00–0.03) & 202 \\ \hline Twigs (25\% moisture) \({}^{\rm h}\) & 190 & 3944 & 32 & 28.5 & 9.3 & 0.55 & 777 \\ \hline \hline \end{tabular}  
* \(n\) is the number of emission measurements on which the medians and IQRs were based. \({}^{\rm b}\) based on a 100-year GWP of 25 for methane [16] and 2.0 for CO [17]. CO\({}_{2}\) emissions are excluded here as the CO\({}_{2}\) had originally been taken up by the feedstock biomass. Methane emissions < 5.5 g kg\({}^{-1}\) biochar are set to zero in this calculation. \({}^{\rm c}\) \(<\)5.5 g kg\({}^{-1}\) biochar when setting measurements at each time point to LOQ/2 (0.0025%). \({}^{\rm d}\) \(<\)0.006 g kg\({}^{-1}\) biochar when setting measurements at each time point to LOQ/2 (0.05 ppm). \({}^{\rm e}\) approximate value based on one spike lasting around 30 s during quenching and averaged over the whole duration of the run (33 min). \({}^{\rm f}\) not determined due to sensor failure. \({}^{\rm g}\) from [PERSON], [PERSON] [19]. \({}^{\rm h}\) from [PERSON], [PERSON] [7].  
\end{table} 
Table 2: Emission factors (g kg\({}^{-1}\) biochar) of CO\({}_{2}\), CO, CH\({}_{4}\), TSP [aerosols, from particulate matter < 10 μm (PM\({}_{10}\))], the sum of nitrogen oxides (NO\({}_{\rm x}\)), and composite CO\({}_{2}\)-equivalents. Median values and interquartile ranges (IQRs—numbers in brackets) per run. Literature values on emissions from Kon-Tiki flame curtain kilns. Aerosol emissions (TSP; PM\({}_{10}\)) were in the range of 16-45 g kg\({}^{-1}\) biochar (Table 2) for all biomass types except coffee husk (331 g kg\({}^{-1}\) biochar), and significantly lower for grass and sesame stems (<25 g kg\({}^{-1}\) biochar) than for grass/twigs and maize cobs (>30 g kg\({}^{-1}\) biochar; sesame vs. grass/twigs, \(p\) = 0.003; sesame vs. maize, \(p\) = 0.04; grass/twigs vs. grass, \(p\) = 0.002; grass vs. maize, \(p\) = 0.02). All TSP emissions were slightly above values previously reported for both Kon-Tiki and other kilns (around 10 g kg\({}^{-1}\) biochar [7]), and in the same range as previously reported values for twigs + leaf litter (62 g kg\({}^{-1}\) biochar [19]). Aerosol emissions from coffee husk pyrolysis (331 g kg\({}^{-1}\) biochar) exceeded those for the other biomass types, indicating that aerosol emissions spiked in concert with methane emissions upon unintentional quenching of the flame curtain caused by the addition of this finely grained feedstock. This finding confirms our earlier suggestion that feedstock type, rather than moisture content, is decisive for aerosol emissions from flame curtain kilns [19].