## 3 Results and Discussion
### Gas Emission Factors
Earlier work showed higher ratios of organic to black carbon in green fuels (19.2 \(\pm\) 4.2) compared to dry wood logs (\(7.3\pm 1.9\)), indicating that more moisture in green biomass resulted in more smouldering-phase combustion and higher aerosol emissions [35]. Further, higher combustion temperatures in wood stove burns led to lower emissions [35]. This result corroborates earlier findings that pyrolysis of the currently studied green wastes resulted in higher aerosol emissions than dry woody twigs [19]. Our study thus confirms that fire intensity plays a role in aerosol emission patterns, with higher aerosol emissions for greener fuel types that burn with lower intensity (the non-woody feedstocks here and field underburns, green leaves, and branches in the work of [PERSON], [PERSON] [35]). The current data confirmed that Kon-Tiki kilns are not the cleanest kilns when regarding aerosol emissions, as the currently reported emissions factors were higher than those earlier reported for woody feedstocks in traditional kilns, retort kilns, and TLUDs (19, 11, and 7 g kg\({}^{-1}\), respectively [28]). Syn-gas combustion, such as in Pyreg and large-scale reactors, further reduces aerosol emissions (0.05-2.5 g kg\({}^{-1}\) biochar [36; 37]). Properties for the combustion analysis of biomass are usually classified into physical, chemical, and thermal properties [38]. Physical properties include density, porosity, and internal surface area. Twigs and sesame stems create a low density and large porosity at the flame curtain front, allowing for the full combustion of pyrolysis gases. Grass needs to be added with care and lifted at intervals with rakes to provide sufficient porosity (for oxygen penetration). Its advantage is its low density. Dense materials that form nonporous clusters, such as coffee husk, grains, and rice husk, are thus not ideal for maintaining the flame curtain, which is important for effectively combusting the pyrolysis gases. Important chemical properties for combustion are the composition of the biomass and the heating value of the volatiles it produces [38]. The higher lignin content of olive husk (50%) was found to result in a higher biochar yield in comparison with corncob (15% lignin) [39]. Lignin, generally more stable than cellulose or hemicellulose [40], will be completely decomposed at above 500 \({}^{\circ}\)C [41]. The lignin contents of grasses are typically 22-25% (of eight grass species studied [42]); of sesame stems, 22% [43]; and of woody materials typical for the Miombo forest biome, 15-16% [44]. Coffee husk contains up to 42% lignin, similar to the 42% lignin found in olive husk [45]. This indicates that a role in the pyrolysis process is played not only by particle size and biomass moisture content but also probably by lignin content, with denser, smaller, wetter, and high-lignin biomasses being the most challenging to pyrolyze with low emissions and high efficiency. The thermal properties of biomass include specific heat, heat of pyrolysis, and thermal conductivity. The caloric contents of all feedstocks are in the same range of 15 to 20 MJ kg\({}^{-1}\)[46]. Thus, the caloric content is probably not an important factor causing substantial differences in emissions between feedstocks. The effect of temperature and biomass grain size on biochar yield was also studied in a simple batch pyrolysis reactor [39]. A high temperature (>700 \({}^{\circ}\)C, similar to the temperature of a flame curtain kiln [4]) and smaller particles increased the heating rate, resulting in a decreased biochar yield. Composite CO\({}_{2}\)-equivalents were calculated on the basis of methane and CO emissions (Table 2), with a 100-year GWP of 25 for methane [16] and 2.0 for CO [17]. CO\({}_{2}\) emissions are excluded here as the CO\({}_{2}\) was the original source of carbon in the feedstock biomass. Most CO\({}_{2}\)-eq. emissions (60-500 g kg\({}^{-1}\) biochar) were well below the approximately 2000-2500 g kg\({}^{-1}\) biochar CO\({}_{2}\)-eq sequestered by biochar amendment to soil [33].