Potential Recovery Of Biogas From Citrus Auranttfolia Waste (Lime Waste)

Abstract

Roughly 50% of the fruit mass remains as waste after fresh consumption or processing of citrus fruits. The build-up of these wastes typically signifies an economic and environmental nuisance owing to disposal problems. However, studies have shown that biogas can be recovered as a valuable product from citrus wastes due to its high concentration in soluble sugars, making it a suitable source of cellulosic biomass. DLimonene, the major constituent of essential oil present in citrus peel, is however known to hamper the conversion process of citrus wastes to biogas. To improve biogas production, a study to reduce the effect of D-Limonene was carried out on specific citrus fruit waste (Lime waste) after juice extraction. Co-digestion of lime wastes with other wastes of high organic content and pre-treatment of lime wastes was studied. From the pre-treatment procedure, 42.6 mL of essential oil was recovered from 1 kg pulverized lime waste, indicating an oil yield of 3.8%. The co-digested substrate of treated lime waste and poultry litter gave the best biogas yield of 138.1 mL/g VS after 28 days. Substrates of codigested untreated lime waste and poultry litter, untreated lime waste, and treated lime waste yielded 66.8, 66.9, and 93.2 mL/g VS biogas, respectively. ANOVA showed that the methods employed to reduce D-Limonene concentration in lime waste had no significant effect on biogas generation. Furthermore, an economic estimation of the biogas production process from lime waste revealed that gas can be produced at a rate of ₦574.28/cm3 which is less than the current market price of ₦620.69 for cooking gas in Nigeria. The findings of this research show that there is a viable recovery option of biogas from lime waste, and recommendations of this research can be further explored to develop an economically viable biogas plant process that efficiently utilizes citrus wastes.