Thermal steam explosion pretreatment to enhance anaerobic biodegradability of the solid fraction of pig manure

The assessment of the biodegradability of thermal steam-exploded pig manure was performed compared to untreated samples. The pre-treatment was performed under different combinations of temperature and time, ranging 150–180 °C and 5–60 min, and used as substrate in a series of batch biochemical methane potential (BMP) tests. Results were analyzed in terms of methane yield, kinetic parameters and severity factor. In all the pre-treatment conditions, methane yield and degradation rates increased when compared to untreated pig slurry. An ANOVA study determined that temperature was the main factor, and the optimum combination of temperature–time of pretreatment was 170 °C −30 min, doubling methane production from 159 to 329 mL CH4/gVSfed. These operation conditions correspond to a severity factor of 3.54, which was considered an upper limit for the pretreatment due to the possible formation of inhibitory compounds, hindering the process if this limit is exceeded.