Effect of total solids content on giant reed ensilage and subsequent anaerobic digestion

The effect of total solids (TS) content on giant reed ensilage and subsequent methane production by both liquid anaerobic digestion (L-AD) and solid-state anaerobic digestion (SS-AD) was investigated. Minimal loss of TS (about 1%), cellulose (1.2-2.4%), and hemicellulose (2.9-4.7%) was observed after 30 days of giant reed ensilage at TS contents from 25% to 40%. Ensilage with a TS content of 25% showed higher consumption of water soluble carbohydrates and extractives than those with TS contents of 30-40%, which was consistent with its higher production of organic acids and lower pH. Compared to non-ensiled giant reed, ensiled giant reed achieved up to 15% higher methane yield during AD. Ensiling giant reed at a TS content of 25% resulted in a lower glucose yield during enzymatic hydrolysis and lower methane yield during the subsequent AD, compared with ensiling it at TS contents of 30-40%. Compared to L-AD, SS-AD of non-ensiled or ensiled giant reed showed 12-18% lower methane yields, but about 2 times higher volumetric methane productivities.