Biogas is a renewable energy source produced through the anaerobic digestion of organic materials such as agricultural residues, manure, sewage, and food waste. This process involves the breakdown of these materials by microorganisms in the absence of oxygen, resulting in the production of a mixture of gases, primarily methane (CH4) and carbon dioxide (CO2), along with trace amounts of other gases like hydrogen sulfide (H2S) and ammonia (NH3). Biogas production from agricultural residues like olive pomace (OLV), cottonseed meal (CTM), and red pepper processing (RPP) waste holds promise for sustainable energy generation and waste management. This study investigates the chemical composition and methane production potential of these residues, emphasizing their protein, fat content, and Acid Detergent Fiber (ADF)/Neutral Detergent Fiber (NDF) ratios. Chemical analyses revealed significant variations among the materials, with cotton waste exhibiting the highest dry matter, organic matter, protein, and fat content, while pepper waste showed the highest ash content, and olive waste had the highest fiber (ADF and NDF) content. Methane production ranged from 0.34 to 0.45 m³ kg-1 of organic dry matter (ODM), with cotton displaying the highest methane yield. Biogas production ranged from 0.61 to 0.78 m³ kg-1 ODM, with cotton again yielding the highest biogas production. Methane content in biogas varied between 54.64% and 57.72%, with cotton also showing the highest methane content. At the end of the study, the dry matter (DM) and organic dry matter (ODM), ash, protein, fat, ADF, and NDF ratios of the materials were determined to be 85.51%-94.09%, 87.91%-92.92%, 7.08%-12.09%, 7.49%-15.93%, 3.76%-8.01%, 52.16%-71.07%, and 34.49%-55.58%, respectively. The materials showed chemical differences. Research highlights include the significant bioenergy potential of olive waste and cottonseed meals, alongside the environmental benefits of utilizing olive pomace for biogas production. Experimental findings reveal varying methane and biogas yields across materials, influenced by their nutrient compositions. The study underscores the viability of integrating these agricultural residues into biogas production systems, contributing to renewable energy initiatives and sustainable agricultural waste management practices.
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