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.

The rural areas in the Gaza Strip suffer from the problem of sanitation and organic waste as well as electricity and cooking fuel. In this thesis, the biogas plant was designed to solve those problems based on the fixed dome plant design as shown in Figure 3 and4. Therefore, the efficiency and selectivity was good for biogas plant which is easy for the local people disposal of organic waste and wastewater as well as self-sufficiency of biogas for cooking and electricity for the family. The sediments from the biogas plant are also used as fertilizers in agriculture. Thus it is possible to know the amount of biogas production, the cost of biogas, the amount of fertilizer, the cost of fertilizers and the amount of disposal of organic waste and wastewater. The calculation shows that the size of digester which is equal to 12 cubic meters as shown in figure 4.The construction is cost of $ 930 as shown in Table 2. Through the results will be disposed of organic waste, wastewater and manure are about 48 kilograms per day for the family. The Biogas is produced 0.5 tons of biogas is estimated about $ 100 in rural areas in the Gaza Strip. It is also produced fertilizers equivalent of $ 113 per month. So the results and calculations are clear that the rural family is self-sufficient of biogas, the dispose of organic waste and wastewater and agricultural growth by the fertilizers from the biogas plant.