Long term alkaline storage and pretreatment process of cover crops for anaerobic digestion

The aim of this work was to study an innovative alkaline process on two cover crops. CaO load of 60 g.kgTS^-1 was implemented to combine the functions of storage and pretreatment. Lab-scale reactors were monitored for 180 days to assess the effect of this process on the physico-chemical properties of the biomass. From the first days, pH was not maintained in an alkaline zone and microbial fermentation activity was observed with the degradation of available carbohydrates and production of metabolites, CO₂ and H₂. High butyric acid accumulation was observed and mass losses of 18.1% and 9.0% of initial VS occurred for oat and rye, respectively. However, no methane potential loss was recorded in the short and long term and the crops were efficiently preserved. The pretreatment had no major impact on fiber solubilization, and no increase in BMP was obtained, which was attributed to the short duration of the alkaline conditions.