Every day 493 tonnes of waste containing 67% of organic material is generated in the city of El Alto in Bolivia. The majority of the waste is disposed to a landfill that is expected to reach its maximum capacity by 2015. Therefore, new waste treatment methods need to be explored. The high content of organic material in waste makes biogas technologies a potential solution for waste treatment in El Alto. These technologies can generate a renewable energy source and organic fertilizer that can provide several benefits to the city. The objective of this study is to investigate the techno-economic feasibility of a small-scale biogas plant for treating organic market waste in the city of El Alto. To this end, a multi-criteria analysis was performed to identify a suitable technology. The garage-shaped digester was selected as the most appropriate technology for the conditions of El Alto. By implementing this technology, 1.8 GWh of electricity and 2,340 tonnes of organic fertilizer can be produced annually. Furthermore, an economic analysis of two scenarios was conducted. The Net Present Value (NPV), Internal Rate of Return, Payback time, Levelized Cost of Electricity (LCOE) and sensitivity analysis were evaluated. The biogas plant resulted economically viable in both cases. However, the LCOE estimated (0.17-0.26 USD/kWh) were very high in comparison to the LCOE from natural gas in Bolivia (0.026 USD/kWh). Regarding the sensitivity analysis, several parameters were evaluated from which the compost price was the most influential on changing the NPV. The study also included the estimation of the emission savings. A total of 900 tonnes of CO2/year could be avoided for producing electricity from biogas. Moreover, social benefits could also be generated such as new job opportunities. The use of a small-scale biogas plant for treating organic market waste in the city of El Alto is a cost-effective option. Though, it is fundamental that the government support the waste-to-biogas technologies by introducing economic mechanisms and promoting awareness to ensure the markets for both, biogas and organic fertilizer.

The study evaluates sustainability aspects of small scale biogas production in Yogyakarta Province of Indonesia. Growing number of livestock (i.e. cows, sheep, chicken, pigs, and other domestic animals) in the region brings opportunity to produce biogas from livestock manure, leading to improve energy security especially in household, while contributing to renewable energy target which is 31% from Total Primary Energy Demand (TPES) in all sectors by 2050. Biogas potential from cattle, horse, buffalo, pig, sheep, goat, chicken and duck which own by household in all regencies within the province of Yogyakarta (i.e. Bantul, Gunung Kidul, Kulon Progo, Sleman, and City of Yogyakarta) are calculated. Biogas digesters types and options for biogas utilization are evaluated by set of indicators in terms of technical, economic and environmental dimensions. Performance of the four types of digesters (i.e. fixed dome, floating drum, polyethylene tubular and concrete tubular digester) are examined based on the dimensions. For digester assessment, the dimensions are divided into several indicators, such as the lifetime, process efficiency, capital cost, operation and maintenance cost, feed-to-water ratio. The assessment would ensure that installation of biogas have optimum technical performance, attractive investment for the owner, and does not exploit too much natural resources. Equal weighted sum method is used to compare the digesters performance. The second assessment is to evaluate options for off-grid electricity use and cooking based on several indicators which are levelized cost of energy (LCOE), Net Present Value (NPV), Internal Rate of Return (IRR), Benefit-to-Cost Ratio (BCR), Payback period and emissions saving. The production of biofertilizer, which is not part of the current system, is taken into account for additional income for biodigester’s user. The study estimates 1,211.35 TJ/year of biogas energy can be produced from livestock manure or equals to 44.72% of the total energy consumption in the household sector in Yogyakarta province in 2013. Gunung Kidul Regency has the most potential biogas from livestock, followed by Kulon Progo, Sleman, Bantul, then City of Yogyakarta. Utilization of biogas for household cooking could reduce greenhouse gas emissions in the province up to 1,260.66 MtCO2e per year while biogas for electricity reduce 1,562.144 3   MtCO2e annually. The fixed dome digester obtains the highest score in the most of indicators assessed. For biogas utilization, biogas for cooking shows better performance in economic and environmental aspects. Biogas for cooking requires lower capital cost (US$ 850 less) and get higher NPV (US$ 2,000 more) than biogas for electricity. Yet, biogas for electricity save 301.48 MtCO2e more GHG emission than biogas for cooking. From digester and biogas utilization assessments, household biogas in Yogyakarta has been used the sustainable option for digester, which is fixed dome digester, and biogas utilization, which is biogas for cooking. Furthermore, sensitivity analysis is done to know parameters that affect NPV for biogas for cooking and biogas for electricity. Biogas yields, fertilizer price, and LPG price are shown as the top three parameters that affect NPV for biogas for cooking utilization. While for biogas for electricity, the affecting parameter are electricity price, biogas yields, fertilizer price, and generator efficiency. From the sensitivity analysis, several recommendations were developed to maximize the current project. The recommendations are improvement of biogas stove efficiency, recommendation for biogas installation system, creating market demand for biogas by diminishing LPG subsidy, suggestion for progress monitoring and institutional recommendation for the program. Ministry of Energy and Mineral Resource done several monitoring to check whether the digester is still operating. However, there is no follow-up action for digester that is not operating anymore. On the other hand, Yayasan Rumah Energi (YRE), the main provider of biogas installation and service in Yogyakarta Province, conduct annual user survey. This survey focuses on satisfaction level of digester’s user after installation. Investigation regarding the impact of biogas project, such as energy shift from LPG to biogas and digestate utilization, is missing. Besides biogas for cooking, there are opportunity to develop biogas for electricity since several regencies in Yogyakarta does not have 100% electrification ratio, such as Gunung Kidul (82%) and City of Yogyakarta (69%). Due to available biogas potential, development of biogas for electricity in Gunung Kidul is more promising than in City of Yogyakarta. Additionally, research of biogas in Indonesia should be integrated with industries and private sector. For instance, by mass production of low cost generator which had been developed by Indonesian Institute for Sciences (LIPI) and by developing mini grid installation for biogas.