## 4 Conclusions  
We believed that the applicability of this study might include TLUD stoves along with other low technology low budget setups for the production of biochar, where the presence of air and variability of the charring conditions are inherent. The intrinsically high variability of charring conditions of TLUD stoves had more marked consequences for the bamboo feedstock, leading to greater variations in the properties of the bamboo biochars. Interestingly, bamboo biochars not only exhibited higher variability, but also higher quality in terms of CEC and AWC. AWC and CEC values were significantly different between the pinewood and bamboo biochars. The overall charring temperatures recorded for the bamboo feedstocks were lower and much more variable than for the pinewood feedstock. The BB1 biochar, with the lowest overall charring temperature and the shortest holding time, showed the highest CEC (19.97 cmolc kg\({}^{-1}\)) among all the biochars. The oxygen-to-carbon molar ratio O:C and ash content are potentially good predictors of hydrophobicity in biochars. Hydrophobicity of the pinewood biochars, though greater, was not a potential constraint after 800 s for the biochars tested. This study found overall improvements of 50% in AWC for the mixtures TPS with 10% biochar, and a 100% increase with 10% of the BB1 bamboo biochar. Given the promising results obtained with the bamboo biochars, more research needs to be undertaken relating types of feedstock and charring times and temperatures, to the crucial quality aspects of biochars, AWC and CEC.  
The following are available online at [[http://www.mdpi.com/2076-3417/10/2/507/s1](http://www.mdpi.com/2076-3417/10/2/507/s1)]([http://www.mdpi.com/2076-3417/10/2/507/s1](http://www.mdpi.com/2076-3417/10/2/507/s1)), Table S1: Relative timing effect (RLE) and potential limiting capacity (PLC) calculation of different biochar samples and replicates, Table S2: Volume of NaOH used to neutralize the remaining HCl (mL), Figure S1: Relative limiting effect (RLE) of biochars made of bamboo (BB) and pinewood (WB), Figure S2: Potential limiting capacity (PLC) of biochars made of bamboo (BB) and pinewood (WB).  
Conceptualization, F.M.-M., J.Q.-K.; Methodology, F.M.-M., D.S.-C., C.A.G.-G.; Formal Analysis, C.A.G.-G. and J.Q.-K.; Investigation, D.S.-C., F.M.-M.; Resources, F.M.-M., K.V.-M., C.A.G.-G.;  
Figure 5: Available water content at mixtures of TPS and twelve biochars made of bamboo and pinewood applying two doses (5% and 10% dry wt). Different letters show statistically significant differences between variables using Tukey’s test (\(p<0.05\)). Notice that the corresponding biochars in the mixture were denoted as \(x\)By, being \(x\) the feedstock source (B or W) and y the lot number (1, 2 or 3).  
Writing--Original Draft Preparation, F.M.-M.; Writing--Review and Editing, J.Q.-K., C.A.G.-G., K.V.-M. and D.S.-C.; Supervision, J.Q.-K. and K.V.-M.; Funding Acquisition F.M.-M., C.A.G.-G. All authors have read and agreed to the published version of the manuscript.  
This research was funded by Vice-rector of Research and Extension of the Instituto Tecnologico de Costa Rica (TEC), trough the project VIE 1460065 and by the national foundation FITACORI (Fundacion para el Fomento y Promocion de la Investigacion y Transferencia de Tecnologia Agropecuaria).  
We thank [PERSON], [PERSON] and [PERSON] (CEQIATEC) for helping with potassium and chloride analysis, [PERSON] from Universidad Estatal a Distancia (UNED) for providing the bamboo and technical support, [PERSON] (Master's degree of Medical Products) for help with TGA analysis, [PERSON] from (Laboratory for Wood Chemistry, Forestry of the Instituto Tecnologico de Costa Rica) for help with elemental analysis. Work supported by Xunta de Galicia [ED431F 2016/010 & ED431C 2016/008], MCIUN [RTI2018-094131-A-I00], AEMAT [ED31E 2018/08], Agencia Estatal de Investigacion (AEI) and FEDER funds. [PERSON] acknowledges to MINECO for a Ramon y Cajal Fellowship [RYC2014-15239].  
The authors declare no conflict of interest.