Analysis of the Energy Balance of Shale Gas Development

Sustainable development index of shale gas exploitation in China, the UK, and the US

While shale gas could complement the world's natural gas supply, its environmental tradeoffs and sustainability potential should be cautiously assessed before using it to satisfy future energy needs. Shale gas development in China is still in its infancy but has been progressing by the Central Government at a fast pace nowadays. Advanced experience from North America would greatly benefit sustainable design and decision-making for energy development in China. However, the lack of consistency concerning internal and external parameters among previous investigations does not allow an integrated impact comparison among shale gas-rich countries. Herein, we applied a meta-analysis to harmonize environmental tradeoff data through a comprehensive literature review. Greenhouse gas emission, water consumption, and energy demand were selected as environmental tradeoff indicators during shale gas production. Data harmonization suggested that environmental tradeoffs ranged from 5.6 to 37.4 g CO₂-eq, 11.0-119.7 mL water, and 0.027-0.127 MJ energy to produce 1 MJ shale gas worldwide. Furthermore, sustainable development indexes (SDIs) for shale gas exploitation in China were analyzed and compared to the United States and the United Kingdom by considering environment, economy, and social demand through an analytic hierarchy process. The United States and China elicit higher SDIs than the United Kingdom, indicating higher feasibility for shale gas exploitation. Although China has relatively low scores in the environmental aspect, large reservoirs and high future market demand make Chinese shale gas favorable in the social demand aspect. Region-specific SDI characteristics identified among representative countries could improve the sustainability potential of regional development and global energy supply.

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.

Analysis of Point-of-Use Energy Return on Investment and Net Energy Yields from China’s Conventional Fossil Fuels

There is a strong correlation between net energy yield (NEY) and energy return on investment (EROI). Although a few studies have researched the EROI at the extraction level in China, none have calculated the EROI at the point of use (EROIPOU). EROIPOU includes the entire energy conversion chain from extraction to point of use. To more comprehensively measure changes in the EROIPOU for China’s conventional fossil fuels, a “bottom-up” model to calculate EROIPOU was improved by extending the conventional calculation boundary from the wellhead to the point of use. To predict trends in the EROIPOU of fossil fuels in China, a dynamic function of the EROI was then used to projections future EROIPOU in this study. Results of this paper show that the EROIPOU of both coal (range of value: 14:1–9.2:1), oil (range of value: 8:1–3.5:1) and natural gas (range of value: 6.5:1–3.5:1) display downward trends during the next 15 years. Based on the results, the trends in the EROIPOU of China’s conventional fossil fuels will rapidly decrease in the future indicating that it is more difficult to obtain NEY from China’s conventional fossil fuels.