Anaerobic Digestion of Lime Waste in Batch Assay Digestion for Potential Biogas Recovery

The term" lime" includes a wide variety of materials produced by calcining or burning limestone or dolostone. Lime and products containing lime have been widely employed in landfill covers (caps), wastes, and liners. The accumulation of lime wastes, an environmental hazard on dumpsites, causes economic and environmental problems. Nonetheless, there is a potential to recover biogas from lime wastes due to their high concentration in soluble sugars. The liming of waste is supposed to stop biodegradation and reduce the impacts of landfilling activity. D-Limonene, a chemical compound present in lime peels, is, however, known to negatively affect the anaerobic digestion and conversion of lime waste to biogas. This study is aimed at reducing the effect of DLimonene on biogas production from lime wastes. The study assessed the impact of lime waste pre-treatment and co-digestion with poultry litter on improving biogas recovery. This study further describes the adoption of a biodigestion system for the degradation of organic matter and biogas production. In co-digestion, an equal mass of lime waste was mixed with that of poultry litter. The pre-treatment of lime waste was done using a solid-liquid extraction process to filter out essential oil, containing D-Limonene, from lime wastes. Different samples from untreated, pre-treated, and mixed wastes were digested in laboratory under mesophilic conditions. The results indicate that the pre-treatment process alone increased biogas yield by about 40% while the co-digestion of untreated lime waste with poultry litter did not affect improving biogas yield. The use of these pre-treated samples in co-digestion with other nutrients filled and high energy yielding biomass would provide a better nutrient balanced and microbial diversity. Economic estimation of the biogas production process from lime waste that was carried out indicated lesser cost than the current market price of cooking gas in Nigeria. The findings show that there is economically viable recovery option of biogas from lime waste, which would boost the drive of government towards an alternative source of energy.