Improvement of anaerobic digestion of swine slurry by steam explosion and chemical pretreatment application. Assessment based on kinetic analysis

•A S/I ratio between 0.1–0.25 showed the best results using swine slurry as substrate.•Gompertz equation was able to fit all the BMP results with raw and pretreated substrate.•Steam explosion improved both the methane potential and the maximum production rate.•Weak alkali thermal pretreatment only enhanced the maximum production rate.

Swine slurry is generated in large quantities and anaerobic digestion may represent an appropriate process to both treat and revalue this waste as an energy source. Pretreatment processes aim to increase the anaerobic biodegradability of a specific waste. In this study, steam explosion and weak thermal-alkali pretreatments are evaluated. The first series of Biochemical potential (BMP) test is set to establish the best substrate/inoculum ratio conditions, and then other tests are carried out to assess the impact of these pretreatments on the methane potential and maximum production rate by using the modified Gompertz equation. The S/I ratio exerts an influence on the BMP results and the optimum ratio was found to be between 0.1–0.25 gVSs gVSI−1. Steam explosion leads to an improvement of both the methane potential and the maximum production rate at the highest severity conditions. Weak alkali thermal pretreatment improved the maximum production rate but affected negatively the methane potential of the substrate.