Estimation of proximate composition and biogas production from in vitro gas fermentation of sweet potato (Ipomea batatas) and wild cocoyam (Colocasia esculenta) peels

Abstract

The proximate composition in terms of percentage dry matter (DM), crude protein (CP), crude fibre (CF), ether-extract (EE), ash, nitrogen free extract (NFE) and carbohydrate of sweet potato peel (SPP) and wild cocoyam peel (WCP) were determined. Buffered and sieved goat’s rumen liquor was added to 200mg of dried and milled SPP and WCP in 100 ml syringes supplied with C02 under anaerobic condition and incubated for 24 h. Total biogas produced was measured at 3 h intervals till the 24th h when the fermentation was terminated. The inoculum was also incubated separately. All treatments were replicated three times and readings were taken in duplicates. The proximate composition of SPP and WCP were similar except for the higher EE content (12%) of SPP. The SPP and WCP used contained 26.81 and 26.97% DM, 3.06 and 3.83% CP, and 78.94 and 79.17% carbohydrate respectively. Both samples had the same crude fibre (7.00%) content. Total biogas produced from SPP, WCP and the inoculum varied from 13.0, 11.0 and 5.0 ml respectively at the 3rd h through 66.5, 61.5 and 18.0 ml at the 18th h to 77.5, 72.0 and 30.0 ml at the 24th h respectively. The differences in biogas production across the treatments were significant (p 0.05) in the volumes of methane produced from SPP (42.5 ml) and WCP (39.5 ml) which were significantly (p < 0.05) higher than 20.0 ml produced by the inoculum. Fermentation is a cheap method to produce methane gas as fuel for domestic and industrial use, which may sanitize the environment from pollution. The remaining residue can be used as livestock feed.