The thermal stability and decomposition kinetics of PLA/sisal biocomposites was discussed to evaluate the suitability of their use in energy recovery processes such as pyrolysis and combustion. The influence of the addition of sisal up to 30%wt, the presence of coupling agent, and the atmosphere of operation, i.e. inert or oxidative was discussed by means of multi-rate linear non-isothermal thermogravimetric experiments. All biocomposites showed a mean high heating value of 15 MJ/kg indicating their suitability for energy recovery processes. The thermal requirements of PLA/sisal decomposition were assessed in terms of onset decomposition temperature and apparent activation energy. A minimum of 240 °C and 174 kJ mol−1 in inert environment and 225 °C and 190 kJ mol−1 in oxidative environment ensured the feasibility of the reactions regardless the composition of the PLA/sisal biocomposites. The atmosphere of work lead to a greater amount of residue in case of pyrolysis reactions that would need further treatment whereas an oxidative atmosphere resulted in nearly zero final waste stream. The similar kinetics obtained for all samples regardless the amount of sisal or use of coupling agent eases the operability of energy facilities aimed of turning these biowastes into new fuels.