No abstract

The matooke processing industry being set up by the Presidential Initiative on Banana Industrial Development (PIBID), once fully operational will generate much matooke associated waste that requires a sustainable waste handling mechanism. Anaerobic digestion of the peel waste for biogas production would provide a solution to that waste, but information on the pre-treatment of the matooke peel waste is inadequate. Hence, a study of the changes in the physicochemical characteristics of matooke peels under storage and optimization of particle size for biogas production was sought. Peels from five banana cultivars were analysed after one day, four and seven days of storage at ambient conditions. Peels of one cultivar were reduced to 1, 5 and 10 mm particle sizes and the other four cultivar peels were reduced to 1 mm of particle size. Peel storage pre-treatment of utmost four days was found to bring the carbon to nitrogen (C/N) ratio to the optimal range for anaerobic digestion of 10 to 32. C/N ratio was also found to be cultivar-dependent as it was significant at α = 0.05 between the different banana cultivars. A model of methane content depending on particle size was developed. A particle size of 6.73 mm was projected for optimum biogas production, although further validation of this model and optimal particle size is required with a bigger sample.

No abstract

This paper presents the results of batch anaerobic co-digestion of matooke, cassava, and sweet potato peels and vines. These agricultural wastes and others form the biggest portion of household wastes in developing countries. However, they have remained an unexploited resource amidst the ever increasing needs of clean energy and waste disposal challenges. Efforts to use them individually as biogas substrates have been associated with process acidification failure resulting from their fast hydrolysis. The aim of this work was to exploit agricultural wastes is co-digestion among themselves and assess their effect on methane yield and its kinetics, pH and hydraulic retention time (HRT). Sixteen ratios of Matooke peels (MP), cassava peels (CP) and sweet potato peels (SP) were assessed in duplicate. Methane yield and its kinetics, pH and HRT demonstrated dependence on the proportion of substrates in the mixture. Depending on the ratio mixture, HRT increased to 15 days compared to less than 5 days for single substrates, hydrolysis rate constant (k) reduced to a range of 0.1 -0.3 d −1 compared to single substrates whose k-values were above 0.5 d −1 , pH was maintained in the range of 6.38 -6.43 and CH 4 yield increased by 15% -200%. Ratios 2:1:0, 2:0:1, 0:1:2, 1:1:1 and 1:1:4 were consistent all through in terms of model fitting, having a positive synergetic effect on HRT, hydrolysis rate constant, lag phase and methane yield. However, more research is needed in maintaining the pH near the neutral for process stability assurance if household wastes are to be used as standalone substrates for biogas production without being co-substrates with livestock manure.