Figure 1From: Using the properties of soil to speed up the start-up process, enhance process stability, and improve the methane content and yield of solid-state anaerobic digestion of alkaline-pretreated poplar processing residues SEM photos of PPRs. Untreated PPRs, 50 × A-I, 500 × A-II; PPRs pretreated with 3.0% NaOH, 50 × B-I, 500 × B-II.Back to article page