## 3 Results and Discussion
### Consequences  
This work marks the starting point for a more extensive database of emission factors for various feedstocks pyrolyzed in different kilns, especially artisanal methods such as Kon-Tiki flame curtain kilns. Such a database could provide a reliable inventory for the life-cycle analyses used to estimate the overall climate change impact of biochar production and soil amendment, which are typically used as scientific bases for carbon accreditation. The simple flame curtain kilns offer multiple advantages: (i) gas and aerosol emissions are relatively low compared to those of other low-cost biochar and charcoal production technologies; (ii) construction and operation are easier and more economical compared to more advanced kilns, and thus more suitable for developing country settings; (iii) pyrolysis is much faster (hours) than for most traditional and retort kilns (days). One of the most important results of this study is that the pyrolysis of two important and ubiquitous feedstocks, maize cobs and grass, does not result in higher emissions than that of woody twigs, provided that the biomass is sufficiently dry (<10-15% moisture) and provided that the operators are skilled enough to keep the flame curtain intact during the whole pyrolysis cycle. This notion implies that other ubiquitous coarser materials (larger than 5 cm diameter), such as coconut shells and cacao pods, can be converted into biochar in flame curtain kilns without methane emissions and with low aerosol and CO emissions. Uncertainties remain as to whether emissions are equally low for the pyrolysis of less dry batches of these biomass types (>25% moisture). We consider \"fine\" materials as those that will form dense layers that restrict gas flow and mixing of pyrolysis gases with oxygen in the flame curtain. The distinction between coarse materials that allow for correct operation and fine materials that disrupt the flame curtain will be more evident as data are collected on a larger variation of biomass feedstocks. From the current dataset and earlier investigations, it appears that fine grain-like materials with an overall diameter under 3-5 cm are not suitable for pyrolysis in flame curtain kilns. Also, the timing of the quenching process needs further investigation so that guidelines can be established for an optimal procedure to avoid methane spikes during the finalization of the pyrolysis process. Another limitation is the applicability of this work to more temperate regions as well as humid tropical areas, such as rainforests, where different feedstocks and weather conditions prevail. This study is most relevant for sub-Saharan Africa and regions with similar climates and crops. Additionally, there is a challenge in finding suitable pyrolysis technologies for finely grained feedstocks like coffee husks, rice husks, cacao husks, cashew shells, and other nut shells. Gasification with efficient syngas combustion in a heat engine presents a viable solution. However, emission factors for the simplest and most economical systems, such as those produced by Husk Power Systems(r) (Patna, India; Fort Collins, CO, USA), have yet to be published. The emission results in the present work demonstrate that certification of biochar made from dry maize, sesame, and grass biomass using low-tech pyrolysis should be encouraged. The fact that dry biomass is essential for a negative carbon balance is, however, an important complication in the humid tropics [19]. However, investment in technological upgrades that allow for the use of excess heat generated from the kilns to dry feedstocks could be possible through carbon credit financing to cover hardware expenses. In addition, soil pit flame curtain kilns should only be used when the soil is relatively dry. If not, much of the heat will be lost through evaporation of soil water, and as a result, the temperature in the kiln will be below optimal for high-quality biochar and possibly result in increased gas emissions.