Universal Journal of Agricultural Research 5(3): 197-201, 2017 DOI: 10.13189/ujar.2017.050303 http://www.hrpub.org Numerical Study of Anaerobic Digestion Processes and Biogas Generation from Fruit and Vegetable Waste Puteri Kusuma Wardhani ∗ , Masaji Watanabe Graduate School of Environmental and Life Science, Okayama University, Okayama, Japan Copyright c 2017 by authors, all rights reserved. Authors agree that this article remains permanently open access under the terms of the Creative Commons Attribution License 4.0 International License Abstract Batch experiments with fruit and vegetable waste and sludge from biogas plant as the feedstock were conducted in this study. Mathematical models are introduced here to explain the anaerobic processes, and some unknown parameters were determined by solving inverse problems numerically. Numerical results were compared with the experimental outcomes. We conclude that the results only show for situation where there is no inhibition by intermedi- ate compounds such as volatile fatty acids. Keywords Anaerobic Digestion, Kinetics, Inverse Prob- lem, Mathematical Model, Numerical Simulation 1 Introduction Solid wastes generated largely in traditional markets, in- clude fruit and vegetable wastes that are mostly disposed in municipal landfill or dumping sites. Due to their nature and composition, they degrade rather quickly and cause a foul smell. In some fruit and vegetable waste (FVW) and food waste (FW) samples, the volatile solids (VS) content is 80% - 90%, and the water content is 75% - 95%. The high or- ganic and water contents are the main cause of heavy odor and plenty of leachate during the collection, transportation and landfill of municipal solid waste (MSW). Considering the high moisture and organic content, those wastes are treated more effectively in biological treatment such as anaerobic di- gestion than other techniques such as incineration or com- posting [1]. Anaerobic digestion is a biochemical process in which mi- croorganisms breakdown the biodegradable material into bio- gas (methane and carbon dioxide) under the absence of oxy- gen [2]. Those biochemical processes are very complex and difficult to operate into the optimum conditions because nu- merous parameters must be taken into consideration and be controlled [3]. Additionally, some parameters are difficult to estimate due to technical or economic constraints, i.e., the substrate consumption measurement is expensive, needs three hours and to be done off-line [4]. In this respect, math- ematical modeling and computer simulation are a good tool for these purposes. Various mathematical models have been constructed for anaerobic digestion processes. Since the initial dynamic mathematical digester models in the late 1960s by Andrews JF (1968) and Graef SP (1974) [6], additional and more complex models have been developed to account for signif- icant microbial interactions and inhibitions [5]. These mod- els include additional processes with more detailed kinetics with inhibition and various kind of substrates. However, the task of achieving valid kinetic constants is difficult, due to its complex dynamic process that involves several groups of bacteria. The objective of the study reported here is to intro- duce simulations of anaerobic digestion of fruit and vegetable waste, and to determine some unknown parameters from the proposed mathematical models [14]. The simplifying model proposed by P. Sosnowski et al., [9] was applied to this study, in order to obtain a mathematical model simulating the exact conditions. 2 Materials and Methods 2.1 Substrate and Inoculum The FVW as the substrate was collected from the local market, while inoculum was provided from biogas plant lo- cated in Tsuyama, Okayama, Japan. The sample consisted of bananas, potatoes, paprika, apples, broccoli, lettuce, cab- bage, and cucumbers. The samples were prepared into small pieces using blender. The ratio between FVW and inoculum was 50:50, with initial condition of inoculum and substrate concentration was 0.107 g TS/L and 13 g COD/L, respec- tively. 2.2 Batch Digester Setup Batch experiment was carried out using 2 L digester made of glass. The detail of digester setup is showed in Fig.1. The working volume was 1.8 L, inoculated with 0.9 L for each FVW and inoculum, respectively. The temperature was CITE THIS PAPER [1] Puteri Kusuma Wardhani , Masaji Watanabe , "Numerical Study of Anaerobic Digestion Processes and Biogas Generation from Fruit and Vegetable Waste," Universal Journal of Agricultural Research, Vol. 5, No. 3, pp. 197 - 201, 2017. DOI: 10.13189/ujar.2017.050303.