Mitigation of greenhouse gases and nutrient losses attributable to wasted fruits and vegetables

Abstract

Given their perishable nature, substantial quantities of fruits and vegetables (FV) are lost along the supply chain due to various reasons including lack of refrigerated transport systems, rough road conditions, and a lack of cold storage facilities. The overall objective of this study was to evaluate the ways of mitigating the impact of Fruit and Vegetable wastes on the environment. A predetermined quantity of FV was sorted at each stage of the supply chain to determine FV wastage as well as to collect samples for nutrient loss analysis. The static chamber method was used to determine emissions of GHGs. Four different mixes of FV waste and cow dung were used to optimize AD. The percentage losses of potato, mango, banana, and tomato from main FV growing districts along the supply chain were 19.8, 27.6, 34.1, and 39.3% respectively. Nutrient loss ranged from 4.31% (potassium) to as high as 20.76% (nitrogen). The total CO2 emissions for the different FV waste treatment methods investigated were 108.0, 87.5, and 61.21 g CO2 kg-1 of FV waste initial FV for BSFL, AC, and AD respectively. Anaerobic digestion, the lowest greenhouse gas emitting technology was then optimized for better utilization of wasted FV. A 50:50 (FVW: cow dung combination) operated at mesophilic temperature yielded the highest biogas value of 1328.4 mL/gVs with a methane content of up to 60.5%. This particular combination also had a nutrient content of N, P, and K of 64.6, 15.3, and 20.3 gkg-1, respectively, recoverable in the digestate. The heavy metal contents of Cu, Zn, Pb, Fe, and Mn of 0.02, 0.05, not detectable, 88.6, and 3.67 gkg-1 were below the range of compost quality guidelines and standards for unrestricted use by international standards. Overall this study established that AD should be utilized to ultimately reduce GHG emissions and nutrient losses while managing wasted FV.