Impact of different types of pre-treatment on methane production of two agricultural substrates.

The aim of this study was to compare the effects of different types of pretreatment (thermal, alkaline, enzymatic and combination of them) on chemical composition and anaerobic biodegradability of ensiled sorghum forage and wheat straw. All the pre-treatments tested led to a solubilisation of fibrous fractions for both substrates. The highest lignin reduction, compared to untreated samples, was found at 100°C with 10% NaOH dosage (53% and 72% for wheat straw and sorghum, respectively). Under this pre-treatment condition a high hemicelluloses reduction yield was also found (63% for both substrates). The highest increase in methane yield (up to 29%), compared to the untreated substrate was observed at 40°C with 10% NaOH for sorghum. As for wheat straw, significant increases in methane yield were observed at 40°C with 10% NaOH (49%), at 100°C with 1-10% NaOH (55 and 75%, respectively), and after enzymatic pretreatment (40%).