Ozonolysis of straw from Secale cereale L. for anaerobic digestion

•Taguchi statistical approach for rye straw ozonation is proposed.•Amount of straw, water, ozonation time and dose of ozone were chosen as operating factors.•The effect of ozonation on TS, VS, COD, VFA and RS was analyzed.•SEM and FTIR analysis were used to observe structural changes in ozonated and non-ozonated rye straw.•Anaerobic digestion of ozonized rye straw has been performed. The effect of different ozonation conditions on straw from Secale cereale (rye straw) pretreatment has been investigated. Using the Taguchi method, this study analyzed the optimum conditions for pretreatment of rye straw by ozonation. After 60min of rye straw ozonation the concentration of reducing sugars (RS) and volatile fatty acid (VFA), chemical oxygen demand (COD) were 7.4, 32.3 and 11.7 times higher, respectively compared to samples raw rye straw. The most effective rye straw ozonation occurred while using the highest amount of the rye straw (15g) treated with lower ozone dose (100gO3/m3) in the longest period of time (60min). For this variant of experiment the increment of methane production was 291.71dm3CH4/kgVS. Moreover, co-digestion of sewage sludge with addition of 20% ozonated rye straw allowed to obtain 269.1dm3CH4/kgVS. The positive effect of ozone on changes in the rye straw structure has been confirmed by SEM and FTIR analysis.