## 1 Introduction  
Biochar is a promising tool for carbon dioxide removal (CDR) through pyrogenic carbon capture and storage (PyCCS) [1] which can also improve crop productivity [2] and bind soil contaminants [3]. For resource-poor smallholders in the tropics, cheap artisanal methods such as the \"Kon-Tiki\" flame curtain kilns are probably the most feasible for producing biochar in the foreseeable future [4]. Soil improvements in the longer term may not be a strong enough incentive for biochar making due to insecure land tenure arrangements and hand-to-mouth existence [5]. Carbon credits could create a more direct incentive for smallholder farmers to produce biochar, especially as a complement to the potential productivity benefits [1; 6].  
Flame curtain kilns have been adopted in many countries [4; 7; 8; 9; 10; 11; 12]. They are low-cost, can be operated on-farm, and can be used intermittently based on feedstock availability [9; 10; 13]. The most economical version is a simple, cone-shaped soil pit [10; 11]. During production, pyrolysis gases, most importantly methane, are combusted in the flame curtain above the pyrolyzing biomass. However, carbon certification platforms have been reluctant to include biochar from flame curtain kilns [14]. This reluctance may be related to concerns over emissions of toxic and/or greenhouse gases, including methane (CH\({}_{4}\)), carbon monoxide (CO), aerosols (smoke; PM\({}_{2.5}\) or PM\({}_{10}\)), nitrogen oxides (NO\({}_{\rm x}\)), and non-methane volatile organic carbon (NMVOC) [7]. Methane is a strong greenhouse gas with a 100-year global warming potential (GWP) of 25 [15]. While highly toxic, CO is a weak greenhouse gas, as it has been shown to be further oxidized to CO\({}_{2}\) in the atmosphere [16]. A GWP of 1.0 to 3.0 has been quantified for CO [17]. Aerosols can be both a driver and a dampener of global warming and annually cause millions of preliminary deaths from cooking on wood fires [18].  
Earlier, we documented that the pyrolysis of sufficiently dry twigs and leaves in flame curtain kilns led to almost zero methane, NMVOC, and NO\({}_{\rm x}\) emissions, as well as significant but acceptable CO and aerosol emissions (21-82 and 40-118 g kg\({}^{-1}\) biochar, respectively) [19]. An important remaining knowledge gap is the lack of emission data for other feedstocks. Of special importance are feedstock biomass types for which other uses are limited, such as maize cobs, grasses, and many husk types, and/or those that are left decaying in large mounds leading to methane emissions [20], such as rice and coffee husks as well as cashew and other nut shells. To this end, gas and aerosol emissions were quantified for the pyrolysis of maize cobs, sesame stems, grasses, twigs, and coffee husks in a conical soil pit Kon-Tiki flame curtain kiln in Gulu, Northern Uganda, as well as that of maize cobs and coffee husk in a 100 L metal Kon-Tiki container in Masaka, South-West Uganda. The current data are the first ones on non-woody biomasses in flame curtain kilns. They are important for life-cycle analyses (LCAs) of converting various ubiquitous biomasses into biochar using the simple and directly accessible flame curtain technology. Emission measurements are mandatory for a correct LCA of biomass conversion processes [21].