Figure 1 shows the cumulative CH4 produced by three different substrates in a 40 day BMP test. Methane volume released is divided by mass of substrate VS to scale results. According to the curves in Figure 1, it took nearly 40 days for all the CH4 to be produced from the substrates; therefore, the specific methane yield is the cumulative volume of CH4 released at the end of 40 days, divided by the mass of original VS content. Based on these curves, specific methane yield of digested sewage sludge is approximately 0.07 liters CH4/g VS. Specific methane yield of ground peanut hulls is 0.30 liters CH4/g VS, and specific methane yield of cellulose fibers is 0.35 liters CH4/g VS.