Journal of Energy Bioscience 2024, Vol.15, No.2, 118-131 http://bioscipublisher.com/index.php/jeb 122 4 Pre-treatment Methods to Enhance Biomethane Production 4.1 Physical pre-treatments Physical pre-treatments such as grinding, milling, and thermal treatment are commonly used to enhance the efficiency of anaerobic digestion by increasing the surface area of the substrate and making it more accessible to microbial action. Thermal pre-treatment, in particular, has shown significant promise. For instance, heating food waste at 50℃ for 6-12 hours or at 80℃ for 1.5 hours can increase biomethane production by 44%-46% (Ariunbaatar et al., 2015). Similarly, mechanical treatments like grinding and milling can break down complex organic materials, making them more digestible and thus improving biogas yields (Bong et al., 2018). 4.2 Chemical pre-treatments Chemical pre-treatments involve the use of acids, alkalis, or oxidative agents to break down complex organic materials into simpler compounds that are more easily digested by anaerobic microbes. Acid pre-treatment is particularly effective for lignocellulosic materials, enhancing hydrolysis and subsequent biomethane production (Rawoof et al., 2020). Alkaline treatments, such as the use of NaHCO3, have also been shown to improve methane yields by reducing lignin, cellulose, and hemicellulose content in agricultural waste, thereby increasing the cumulative methane production by 11.2%-29.7% (Figure 2) (Almomani and Bhosale, 2020). Ozonation is another chemical pre-treatment that has been found to enhance biomethane production, although its energy requirements may offset some of the gains (Ariunbaatar et al., 2014). Figure 2 (a) Methane flow rate in the studied reactors under different alkalinity doses, (b) improvement in CMP for all studied reactors under different NaHCO3 doses and (c) maximum MP potential and %ADE under D4 (Adopted from Almomani and Bhosale, 2020)
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