Purpose
The twofold aim of this study was to optimize nutrients important for methane yield in substrate mixtures and to assess the effect of the optimized nutrients on methane production.
Method
Augmented simplex lattice design was used on three substrates, i.e., matooke peels (MPs), cassava peels (CPs), and sweet potato peels (SPs) wherein 16 ratio combinations were assessed for their macro- and micronutrient compositions and methane production potential. Experimental data was simulated using canonical polynomial models to determine mixture combinations with optimal nutrients stimulatory to methane yield.
Results
Six optimization solutions with the global optimal having a desirability of 0.93 and a ratio of 0.611:0.375:0.015 were observed to be localized over the design space. Biomethane experiments were in agreement with the optimized mixture ratios as ratios that gave the highest methane yield of 0.3 Nm3CH4/kg VS and above lay in the optimized design region.
Conclusion
Therefore, charts showing optimized regions of different substrate mixtures in terms of their nutrients can be a tool in biogas digester operations.