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

• Ensilage of giant reed at total solids (TS) contents of 25–40% showed minimal TS loss.
• Giant reed ensiled at low TS content (25%) had higher lactic acid production.
• Ensilage of giant reed at TS contents of 30–40% slightly improved its sugar yield.
• Giant reed ensiled at a TS content of 40% obtained higher methane yields.
• Ensiled giant reed achieved 15% higher methane yield than non-ensiled giant reed.

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.

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