Anaerobic digestion of pineapple pulp and peel in a plug-flow reactor

The objective of this research was to study the production of biogas by using pineapple pulp and peel, the by-products from fruit processing plants, in a plug-flow reactor (17.5 L total volume). The effects of feed concentration, total solids (TS) and hydraulic retention time (HRT) on degradation of the waste were investigated. The increase of pineapple pulp and peel of 2% (wt/vol) at HRT 7 d to 4% (wt/vol) at HRT 10 d showed increases in biogas production rate, biogas yield and methane yield – from 0.12 v/v-d, 0.26 m3/kg COD removed and 0.11 m3/kg COD removed, with COD removal at 64.1%, to 0.25 v/v-d, 0.43 m3/kg COD removed and 0.14 m3/kg COD removed, with COD removal at 60.41%. The methanogenic fermentation was more active in the middle and final parts of the reactor. The recirculation of fermentation effluent at 40% (vol/vol) of the working volume into the reactor could increase the biogas production rate and biogas yield up to 52% and 12%, respectively. The results showed technological potential for waste treatment of pineapple pulp and peel in a plug-flow reactor.

► Pineapple pulp could be used successfully for biogas production.
► Effect of HRT and total solid on biogas production was studied.
► HRT could be reduced to 10 d with 4% TS with COD removal at 60.41%.
► The recirculation of effluent could improve the biogas yield and COD removal.