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The urban environment of every city of Pakistan has been degraded because of open dumping and burning of organic wastes along with other wastes. The focus of this study was to evaluate the fruit and vegetable wastes for methane generation through biomethanation process. After collection, various parameters such as alkalinity, volatile fatty acids, pH, lignin content, moisture content, total solids, volatile solids, fixed carbon, and elements (C, H, N, O, S) of waste samples were determined by using standard methodology. Anaerobic biodegradability of fruit and vegetable wastes was observed from 54 to 77% and from 59 to 87% along with their methane generation potential in the range of 258-367 NmL /gmVS and 274-407 NmL/gmVS, respectively. Further, the effect of feedstock to inoculum ratio was studied. The result of that showed that lower methane potential at a higher ratio and vice versa was observed. It was concluded that at a lower feedstock to inoculum ratio, fruit as well as vegetable wastes become more feasible for the biomethanation process. The study recommends that the conversion of fruit and vegetable wastes into methane gas by anaerobic digestion plays a significant role to save urban environment of the country. [ABSTRACT FROM AUTHOR]

Fungal pretreatment is one of the most eco-friendly and less energy consuming method. Abundant species of fungus are accountable for degrading the roots. This study examined the influence of pretreatment of isolated fungal strains for methane production through co-digestion. Three different strains (Aspergillus niger, Aspergillus sojae , and Aspergillus terrerus) were identified from the rice plant roots after isolation. Strains were applied on same rice straw (RS) prior to use in anaerobic digestion at 7 d, 15 d and 30 d, named as group A, B and C respectively. Pretreated and untreated RS mixed with buffalo dung (BD) in a ratio of 30:70. Results indicated that pretreatment with A. terreus was most optimal in group B as compared with A. niger and A. sojae , whereas the methane production of 204.7, 181.3 and 167.6 mL CH 4 g-1VS was observed. While, maximum biodegradability (about 16.6%) was analyzed in the group C respectively. The Gompertz model show best fitted to experimental methane and the process even under biological conditions was statistically analyzed (p < 0.05). Thus, isolated fungus appears as a good potential strategy for increasing methane generation. Image 1 • Isolate fungal strains A. niger, A. sojae and A. terreus are used to pretreat RS before its AcoD. • Fungal decrease of VS and increase methane production as a function of incubation time. • Pretreated with A. terreus at 15th day improved methane by 32.2% in anaerobic digester. • Modified Gompertz model showed the best fit among all fungal strain groups. [ABSTRACT FROM AUTHOR]