CUNANAN, ROSE ANN O., Department of Resource Engineering and Agricultural Mechanization, College of Engineering and Computer Studies, Pampanga State Agricultural University, Magalang, Pampanga. August 2022, "Evaluation of PSAU Portable Biogas Digester Using Goat Manure as Substrate" Adviser: Engr. Sidney C. Samson This study was conducted to evaluate the performance and economic aspect of the PSAU portable biogas digester in producing biogas using goat manure as substrate. It was conducted at the ALIAS R&DE Center at Pampanga State Agricultural University from March to May 2022. The study utilized 400 L of digested goat manure to initiate microbial growth during anaerobic digestion and loaded another 400 L of goat manure and water mixture with a ratio of 1:1 into the digester. When the produced gas was already flammable, the generated biogas was measured and utilized for actual cooking. in addition, the monitoring period lasted for 35 days. The results of the study showed that the highest and lowest volume of gas produced were 205.76 and 142.57 L, respectively, while the average biogas yield and cumulative biogas yield were 163.60 and 4,744.54 L, respectively. Moreover, the volume of biogas utilized for boiling 1 L of water was 35.62 L and 137.15 L for cooking 651g of rice. The produced biogas can last for 13.33 to 69.85 mins, depending on the volume of gas produced and flame usage. Furthermore, a 35-day retention time was found to be sufficient in batch feeding method given that the substrate used was purely animal manure and was subjected in the mesophilic temperature range (25°C - 45°C). In addition, economic analysis revealed that the investment on the portable digester has a payback period of 1.49 years. Based from the results of this study, it was concluded that the PSAU portable biogas digester was capable in producing biogas using goat manure as substrate and can accommodate the daily fuel requirement of 1-2 persons for cooking. Consequently, the capital invested in purchasing a portable biogas digester was considered economicallyviable.