Nutrient characterisation and bioenergy potential of common Nigerian food wastes

Nigeria is the world's largest producer of yam, cassava, cocoyam/taro, beans/cowpea, egusi/melon seeds and among the largest producers of groundnut/peanut, plantain, corn/maize and ugwu/pumpkin leaves. These food crops generate unavoidable food wastes that can contribute to environmental degradation through unsanctioned waste disposal methods. Such food wastes can be utilised as feedstock for the anaerobic digestion (AD) process to produce renewable energy. In order to determine the suitability of the food wastes as biofuel feedstock, they were experimentally analysed. Their waste content was determined, characterised and used to evaluate their bio-methane potential. The tests were performed using standard proximate analytical methods while the bioenergy potential of the samples was determined using the Baserga model. Results indicated a specific waste index range of 0.2-1.5, with corn having the highest waste proportion. The proximate analysis results of the wastes were within the range of common AD feedstocks such as energy crops and plant by-products. The bio-methane potentials of the samples varied widely with results ranging from 35-460 m³ tonne^-1 on fresh weight and (5.4-6.2) × 10⁵ m³ kg^-1 on volatile solid basis. The methane potential varied between 51% and 58% of produced biogas. The energy potential of the food wastes was 31 TWh yr^-1 which can make a substantial contribution to the bioenergy production of the country and meet up to the energy demand of 4.7 × 10⁷ Nigerian households. Further studies would be required to determine the actual biogas yields of the food wastes.