Substrate Mixture Optimization of Nutrients Needed for Methane Yield

  • Peter TumutegyereizeEmail author
  • Clever Ketlogetswe
  • Jerekias Gandure
  • Noble Banadda
Original Article



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.


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.


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.


Therefore, charts showing optimized regions of different substrate mixtures in terms of their nutrients can be a tool in biogas digester operations.


Substrate mixtures Nutrients Anaerobic digestion Polynomial models Methane 


Funding Information

Support for this research was made possible through a capacity building competitive grant Training the next generation of scientists provided by the Carnegie Cooperation of New York through the Regional Universities Forum for Capacity Building in Agriculture (RUFORUM) and Office of Research and Development (ORD) University of Botswana. Grant number: RU/2015/DFS/INTRA ACP/01

Compliance with Ethical Standards

Conflict of Interest

The authors declare that they have no conflict of interests.


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Copyright information

© The Korean Society for Agricultural Machinery 2019

Authors and Affiliations

  • Peter Tumutegyereize
    • 1
    Email author
  • Clever Ketlogetswe
    • 2
  • Jerekias Gandure
    • 2
  • Noble Banadda
    • 1
  1. 1.Department of Agricultural and Biosystems EngineeringMakerere UniversityKampalaUganda
  2. 2.Department of Mechanical EngineeringUniversity of BotswanaGaboroneBotswana

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