Biomethane potential test applied to psychrophilic conditions: Three issues about inoculum temperature adaptation

This study aimed to give lights for establishing a psychrophilic BMP test by three approaches for inoculum acclimation under 25 °C. The first test was run using stabilized mesophilic (25 °C) and psychrophilic (15 °C) inoculums to digest cellulose. Second was based on temperature acclimatization of inoculum just by time, from 30 to 10 and 20 °C. The third was running a consecutive BMP under psychrophilic temperatures (23 °C). Cellulose psychrophilic BMP using stabilized psychrophilic inoculum achieve similar results to those obtained at mesophilic conditions with stabilized mesophilic inoculum. Time acclimatization of inoculum improve BMP results respect non-adapted (from 0.47 to 055 Nm³ CH₄ kg⁻¹ SV at 20 °C, from 0.31 to 0.44 Nm³ CH₄ kg⁻¹ SV at 10 °C). Consecutive BMP under psychrophilic conditions shows better results for inoculum acclimatization to run assays at low temperatures. There is a need to develop and standardize a procedure to run psychrophilic BMP.