Fuel behavior prediction from thermal and physico-chemical characterization for African woods, energy crops and agro-residues for fuel switching in cookstoves

48 African biomass residues (woods, agro-residues, energy crops) were identified for their availability and fuel switching potential to replace fossil fuels in cookstoves. Samples were collected and characterized in terms of elemental composition, ash content, heating value and thermal behavior. The comparison to ISO 17225 recommendations and 4 reference fuels already studied in cookstoves (softwood, miscanthus, rice husk, shrubland pellets) aims to estimate their energy performance, associated emissions and char residue characteristics. Inorganic element ratios were calculated to empirically predict catalytic/inhibitor behavior of metals in thermochemical conversion (K/(Si + P)), K release in gas phase (Si/K), ash agglomeration (Si/(Ca+Mg); (Si + P + K)/(Ca + Mg)) and aerosols emissions (sum of K+Na+Zn+Pb). Residues from coffee, corn, sorghum, and rice were promising due to their availability and current lack of valorization route. However, their high nitrogen content, ash content and composition may lead to ash agglomeration issues and high nitrogen oxides and aerosol emissions. Agro-residues presented higher (Si+P + K)/(Ca+Mg) molar ratios, linked to a lower ash melting temperature but a mitigated K release to the gas phase due to high Si/K. Some agro-residues presented a high sum of K + Na + Zn + Pb (>10,000) coupled to a low Si/K ratio (<0.1), which may lead to higher particle matter emissions. A hierarchical clustering pointed out high heating value, nitrogen and total inorganic content as the main variables required to represent fuel diversity of the dataset. It also highlighted the importance of considering biomass physico-chemical properties rather that biological families to predict fuel behavior from the reference samples.