Review of Energy Efficiency of the Gas Production Technologies From Gas Hydrate-Bearing Sediments

Even in the carbon-neutral age, natural gas will be valuable as environment-friendly fuel that can fulfill the gap between the energy demand and supply from the renewable energies. Marine gas hydrates are a potential natural gas source, but gas production from deposits requires additional heat input owing to the endothermic nature of their dissociation. The amount of fuel needed to produce a unit of energy is important to evaluate energy from economic and environmental perspectives. Using the depressurization method, the value of the energy return on investment or invested (EROI) can be increased to more than 100 for the dissociation process and to approximately 10 or more for the project life cycle that is comparable to liquefied natural gas (LNG) import. Gas transportation through an offshore pipeline from the offshore production facility can give higher EROI than floating LNG; however, the latter has an advantage of market accessibility. If the energy conversion from methane to hydrogen or ammonia at the offshore facility and carbon capture and storage (CCS) can be done at the production site, problems of carbon dioxide emission and market accessibility can be solved, and energy consumption for energy conversion and CCS should be counted to estimate the value of the hydrate resources.

Assessing Global Long-Term EROI of Gas: A Net-Energy Perspective on the Energy Transition

Natural gas is expected to play an important role in the coming low-carbon energy transition. However, conventional gas resources are gradually being replaced by unconventional ones and a question remains: to what extent is net-energy production impacted by the use of lower-quality energy sources? This aspect of the energy transition was only partially explored in previous discussions. To fill this gap, this paper incorporates standard energy-return-on-investment (EROI) estimates and dynamic functions into the GlobalShift bottom-up model at a global level. We find that the energy necessary to produce gas (including direct and indirect energy and material costs) corresponds to 6.7% of the gross energy produced at present, and is growing at an exponential rate: by 2050, it will reach 23.7%. Our results highlight the necessity of viewing the energy transition through the net-energy prism and call for a greater number of EROI studies.

An Explanation of Energy Return on Investment From an Entropy Perspective

Low-carbon energy transformation is a major trend in world energy development, and measures to mitigate carbon emissions can vary substantially in terms of the energy they require. A common method of evaluating energy use in energy resource exploitation is energy return on investment (EROI). One of the criticisms of EROI concerns uncertainty regarding the input and output factors for the calculation. To make the issue clear, we interpret EROI in terms of entropy, which is the most basic concept in physics. We consider an energy resource exploitation system to be a kind of dissipative structure and construct a basic entropy analysis framework for an energy resource exploitation system. We then derive the relationship between EROI and entropy change. The theory of EROI is consistent with the basic requirement for a dissipative structure, which is that the total entropy change must be negative. EROI is a method of using entropy theory to evaluate energy resource exploitation. It is inappropriate and unnecessary to quantify all factors as energy units as the input and output factors are multidimensional while energy is a one-dimensional standard. Future development of the EROI method should be guided by entropy theory. A series of EROI related indicators will increase its application and policy significance.

Assessment of Indonesia’s Future Renewable energy Plan: A Meta-Analysis of Biofuel Energy Return on Investment (EROI)

In early 2020, Indonesia implemented the biodiesel 30 (B30) program as an initiative to reduce Indonesia’s dependency on fossil fuels and to protect Indonesia’s palm oil market. However, palm oil has received international criticism due to its association with harmful environmental externalities. This paper analysed whether an investment in palm oil-based biofuel (POBB) provides Indonesia with the ability to achieve its environmental and financial goals. In this research, we performed a meta-analysis on biofuel energy return on investment (EROI) by examining 44 biofuel projects using ten types of biofuel feedstocks from 13 countries between 1995 and 2016. Results showed an average EROI of 3.92 and 3.22 for POBB and other biomass-based biofuels (OBBB), respectively. This shows that if only energy inputs and outputs are considered, biofuels provide a positive energy return. However, biofuels, including those from palm oil, produce externalities especially during land preparation and land restoration. We also compared these EROI biofuel results with other renewable energy sources and further analysed the implications for renewable energies to meet society’s energy demands in the future. Results showed that biofuel gives the lowest EROI compared to other renewable energy sources. Its EROI of 3.92, while positive, has been categorised as “not feasible for development”. If Indonesia plans to continue with its biofuel program, some major improvements will be necessary.

Edible Energy Production and Energy Return on Investment—Long-Term Analysis of Global Changes

The projected increase in the world’s population requires an increase in the production of edible energy that would meet the associated increased demand for food. However, food production is strongly dependent on the use of energy, mainly from fossil fuels, the extraction of which requires increasing input due to the depletion of the most easily accessible deposits. According to numerous estimations, the world’s energy production will be dependent on fossil fuels at least to 2050. Therefore, it is vital to increase the energy efficiency of production, including food production. One method to measure energy efficiency is the energy return on investment (EROI), which is the ratio of the amount of energy produced to the amount of energy consumed in the production process. The literature lacks comparable EROI calculations concerning global food production and the existing studies only include crop production. The aim of this study was to calculate the EROI of edible crop and animal production in the long term worldwide and to indicate the relationships resulting from its changes. The research takes into account edible crop and animal production in agriculture and the direct consumption of fossil fuels and electricity. The analysis showed that although the most underdeveloped regions have the highest EROI, the production of edible energy there is usually insufficient to meet the food needs of the population. On the other hand, the lowest EROI was observed in highly developed regions, where production ensures food self-sufficiency. However, the changes that have taken place in Europe since the 1990s indicate an opportunity to simultaneously reduce the direct use of energy in agriculture and increase the production of edible energy, thus improving the EROI.