African Journal of
Biotechnology

  • Abbreviation: Afr. J. Biotechnol.
  • Language: English
  • ISSN: 1684-5315
  • DOI: 10.5897/AJB
  • Start Year: 2002
  • Published Articles: 12125

Full Length Research Paper

Enhancement of anaerobic batch digestion of spineless cacti (Opuntia ficus indica) feedstock by aerobic pre-treatment

Hawa Myovela
  • Hawa Myovela
  • Department of Molecular Biology and Biotechnology, Pan African University, Institute of Basic Science, Innovation and Technology, Kenya.
  • Google Scholar
Anthony Manoni Mshandete
  • Anthony Manoni Mshandete
  • Department of Molecular Biology and Biotechnology, College of Natural and Applied Sciences, University of Dares Salaam, Mwalimu J. K. Nyerere Mlimani Campus, Science Complex Building, University Road, Tanzania.
  • Google Scholar
Samuel Imathiu
  • Samuel Imathiu
  • Department of Food Science and Technology, Jomo Kenyatta University of Agriculture and Technology, Kenya.
  • Google Scholar


  •  Received: 14 September 2018
  •  Accepted: 22 November 2018
  •  Published: 02 January 2019

Abstract

One of the best options for African countries to meet rural energy needs is to grow care-free crassulacean acid metabolism plants on a massive scale in waste lands. This can enable bioenergy production without disrupting food supplies and hence sustainable energy supply for the future. Opuntia ficus indica is an ideal plant for arid regimes but has barely been studied as a potential bioenergy source. This study investigated the effect of aerobic pretreatment on methane yield of O. ficus indica biomass. This effect was investigated in batch bioreactors which were exposed to aerobic conditions by varying time from 3 to 72 h before the start of anaerobic digestion. Reducing sugar content and dissolved oxygen levels after pretreatment period was analyzed. Reducing sugar content in bioreactors increased with increase in pretreatment time from 12.22 ±0.69 to 59.08 ± 5.35 g/L in the untreated and 72 h pretreated batches, respectively. Methane yields after pretreatment were observed to range from 0.286 to 0.702 L/kg volatile solids at 9 and 72 h of pre-treatment, respectively. A 9 h pre-treatment of feedstock prior to anaerobic digestion yielded 123% higher methane yield when compared to that without pre-treatment. The findings that there was an  increase in reducing sugar production and methane yield at 9 h of aerobic pre-treatment suggests that there was increased hydrolysis with pretreatment. Hence, short pre-treatment period could be an option to increasing solubilization of cladodes and promoting methane productivity. Therefore, pre-aeration of O. ficus indica, was shown to be an effective method for enhancing both its digestibility and improved methane yield during anaerobic digestion.

 

Key words: Anaerobic digestion, biogas, methane, Opuntia, pretreatment, spineless cacti.