###### Abstract
Other functional groups such as carbonyl, phenolic hydroxyl, ether and hydroxyl, also contribute to CEC and hydrophobicity by acting as polar sites on an otherwise relatively non-polar and hydrophobic surface [17]. CEC depends on the amount of available surface and the density of charge on it, while the structure of a biochar determines its porosity and thereby its specific surface area (SSA); so CEC can be considered to be a combined effect of specific surface area, density of charge and porosity [18,19]. The porosity of a biochar determines its potentiality to interact with water and the nutrients it carries. The mesopores (i.e., diameters between 2 and 50 nm) are sorptive to liquids, while the macropores (i.e., >50 nm diameter) are retentive to plant-available water [20,21]. According to [PERSON] et al. [22], porosity of biochars largely consists of micropores, being possible to find exceptions with a higher number of mesopores [23], and microporosity depends heavily on feedstock. However, microporosity does not contribute to the additional plant-available water content (AWC) that a biochar can lend to a soil, so a higher SSA in a biochar amendment may not entail a higher AWC in the amended soil. [PERSON] et al. [1] purported that physical and chemical properties of a biochar are crucial to deliver benefits in a soil. However, those benefits rely on the intricate role of feedstock selection [6] and pyrolysis conditions (e.g., heating rate, holding time and temperature [7,8]). Additionally, once incorporated in a soil the biochar particle size [7] is of critical importance as well. A better understanding of this relation has been pursued by studying laboratory-produced biochars obtained from different source materials in different pyrolysis conditions [24]. Studies of adsorption on such biochars have been carried out with metal cations [25,26], soil-borne arsenic [27] and complex ions as nitrate, ammonium and phosphate [5,28]. The past years have seen increasing interest in laboratory produced biochars and lower interest in large-scale produced biochars. Advanced conversion systems allow precise control of operating conditions and, coupled with feedstock selection, permit customization of biochar physical and chemical properties [1]. This has led to a gap in current literature regarding quality control of biochar made by straightforward techniques commonly promoted for small scale agricultural environments, such as TLUD gasifier cook stoves [29,30]. In a TLUD stove, partial combustion of biomass allows production of heat, leaving behind residual biochar that can be incorporated along with the ashes into a soil [29; 31]. However, highly variable pyrolysis conditions may lead to unpredictable qualities in these biochars. This work discusses, in terms of their chemical and physical properties related to use in soils, the qualities of two biochars derived from _Guadua angustifolia_ bamboo and pinewood, produced in a commercially available TLUD gasifier cook stove. It seeks a better understanding of how the TLUD stove production process affects these properties. Additionally, this work strives to demonstrate the enhancement of the soil water retention properties of a compost soil amendment produced from the TPS, achieved by the addition of biochar. This work can be useful to researchers and technicians who are researching or promoting the use of biochars in developing countries, obtained by means of TLUD stoves and other similar low technology methods for soil remediation.