469378.fig.003a
(a)
469378.fig.003b
(b)
Figure 3: Effects of different pretreatment time and wood size on the methane yield of pinewood powder (a) and chips (b). The symbols correspond to 1 h (●), 3 h (◆), and 15 h (■) treatment, and (▲) corresponds to untreated wood. VS stands for volatile solids.