Outlook for the coal industry and new coal production technologies

Historically, energy resources have evolved from high carbon to lower carbon fuels (from coal to oil to natural gas), then to non-carbon (hydroelectric, geothermal, wind power and solar). This dynamic process has reflected the evolution of human civilization and industrialization. As one of the most useful and classical energy resources, what is the outlook for the coal industry in the future? What factors will have a great impact on the outlook? Can new technologies in coal production make the coal industry cleaner and more competitive and increase its demand in the world market? How effective are CO2 capture technologies for coal power plants? This editorial work attempts to provide insights into these issues.1. The future outlook for the coal industryLimiting global warming to 2 ◦C versus pre-industrial levels would imply reducing carbon dioxide (CO2) emissions by 80% of the 1990 level by 2050 and a net-zero emission by the end of this century. To make this happen requires a fast transition of traditional fossil fuels to renewable energy such as wind and solar. In this framework, coal demand is expected to decline by about 8% by 2030 compared to the pre-crisis level in 2019. Advanced economies will cut their demand by 45% compared to 2019. China is still the largest consumer and producer, and the coal usage in China is expected to rebound in the near term and achieve its peak around 2025 followed by a gradual decline after 2025. In the Asia Pacific area, India, Indonesia and Southeast Asian countries will increase their coal demand for power and industrial usage in the next decade (IEA, 2020). By 2030 the global coal demand is projected to decrease by about 400 million tonnes of coal equivalent compared to 2019.2. The impact of major factors on the outlookEnvironmental concerns to reduce CO2 emissions from coal-fired plants, declining coal usage in the power sector due to renewables expansion and a cheap natural gas price, and policies that phase out coal to achieve carbon neutralities are the three major factors leading to the coal market downturn. The power sector accounts for nearly 65% of coal demand. By 2030, advanced economies will consume 50% less coal compared to their level in 2019 mainly due to policy-driven requirements. The increasing supply of renewables and natural gas has diversified the power generation sources, and significantly reduced the coal usage in this sector. Coal is the largest source of CO2 emissions and will be responsible for approximately 38% of the global CO2 emissions from 2020 to 2030. The policy-driven changes are significantly affecting coal usage worldwide (IEA, 2020; IMF, 2020).3. Development of new technologies in the coal industryPotential technologies are emerging in the coal industry, such as hydraulic fracturing to improve the coalbed methane production; the CO2 capture, utilization and sequestration (CCUS) to reduce CO2 emissions from coal combustion; the coal-to-liquid and coal-to-gas fuel conversion technologies to improve the fuel efficiency and reduce the CO2 emissions; internet of things, big data analytics, artificial intelligence, and automation to reduce operational costs and improve safety concerns and production efficiency in coal operations; and, underground coal gasification (UCG) to recover unminable coal. Particularly, UCG has been attempted for over a century, and has not yet achieved a commercial-scale development. Successful development and utilization of this technology would make the coal industry more competitive and increase its demand in the world market. A UCG operation consists of a series of injection and production wells drilled into a coal seam; the coal is ignited after certain air and/or oxygen is injected. Chemical reactions convert the coal to syngas by pyrolysis, combustion and gasification reactions in a manner similar to those processes in a surface gasifier. The produced syngas is a mixture of mainly carbon monoxide and hydrogen, which can be used as fuel for power generation and feedstock for various chemical products (i.e., hydrogen and ammonia) (Nourozieh et al., 2010; Seifi et al., 2015). The carbon captured during syngas utilization can be used for enhanced oil recovery.Emissions from syngas combustion are generally cleaner and less greenhouse gas emissions than coal-fired facilities. The UCG process is less costly than conventional surficial coal gasification because no coal mining, processing and transport are required, and no ash and slag removal or disposal is necessary. The environmental impact of UCG is relatively low compared to surficial gasification, as major disturbances in landscape and surface disposal of ash and coal tailings are not required. A properly designed UCG site will recognize and address potential groundwater pollution and subsidence issues; tests related to the cap rock integrity and highly cemented wells should be performed to avoid these issues. UCG can have obvious advantages compared with other in situ coal applications, including mining, coalbed methane exploration and development; the cavities after UCG can be used as CO2 storage (Jiang et al., 2019).4. CO2 capture technologies for coal power plantsFive main types of CO2 capture technologies from flue gas are proven. The average capture efficiency is from 80% to 90%. Cryogenic separation can provide the highest capture efficiency up to 99.99%. The CO2 capture step represents 70-80% of the overall CO2 capture and sequestration costs. Economic analysis shows that US $70-100 are needed to capture one tonne CO2 from flue gas (the average CO2 concentration is about 3-14$300 to $1,500 to capture CO2 directly from air (Brandl et al., 2021). It would be possible to commercialize the capture efficiency beyond 90%. However, operators are not able to make benefits under the current policies because of the high associated  capital and operational costs. The capture approaches include post-combustion, pre-combustion, oxyfuel combustion, chemical looping combustion and from air. The post-combustion technology is a mature technology, and has been widely applied. Future CO2 capture technologies are likely to focus on hybrid capture technologies, such as integrated CO2 capture and conversion. The coal use in the power sector surpassed 10 Gt CO2 emissions globally in 2018, and a successful application of carbon capture technologies can help the world reduce up to 8-10 Gt CO2 emissions annually. CCUS has received much research attention over the past two decades.Cited as: Ma, H., Chen, S., Xue, D., Chen, Y., Chen, Z. Outlook for the coal industry and new coal production technologies. Advances in Geo-Energy Research, 2021, 5(2): 119-120, doi: 10.46690/ager.2021.02.0

Sharing tableware reduces waste generation, emissions and water consumption in China’s takeaway packaging waste dilemma

China has a rapidly growing online food delivery and takeaway market, serving 406 million customers with 10.0 billion orders and generating 323kilotonnes of tableware and packaging waste in 2018. Here we use a top-down approach with city-level takeaway order data to explore the packaging waste and life-cycle environmental impacts of the takeaway industry in China. The ten most wasteful cities, with just 7% of the population, in terms of per capita waste generation, were responsible for 30% of the country's takeaway waste, 27-34% of the country's pollutant emissions and 30% of the country's water consumption. We defined one paper substitution and two sharing tableware scenarios to simulate the environmental mitigation potentials. The results of the scenario simulations show that sharing tableware could reduce waste generation by up to 92%, and environmental emissions and water consumption by more than two-thirds. Such a mechanism provides a potential solution to address the food packaging waste dilemma and a new strategy for promoting sustainable and zero-waste lifestyles. The online food delivery and takeaway market is growing in China, serving 406 million customers with 10.0 billion orders in 2018. Here, data from an online food delivery platform, life-cycle environmental impacts of packaging and tableware waste generated across 353 cities in China, and scenarios for paper alternatives and tableware sharing are presented

Modelling underground coal gasification: What to start with

Underground coal gasification (UCG) is widely regarded as a clean coal technology that holds enormous potential to decarbonize the world's coal industry. It converts coal underground into combustible syngas through a set of complex physiochemical events. Experimental and numerical efforts over the past century have contributed to the development of UCG around the world; however, tapping the world's deep-situated coal resources with UCG requires substantial contributions from numerous high-quality researchers. To facilitate effective engagement, this paper will provide a background on where to start if one wishes to undertake UCG modelling. First, a brief description of the fundamental phenomena involved in UCG is given. Then, a succinct introduction of the widely used modelling software is rendered, followed by a description of UCG studies to provide insight how to tune the various software packages for modelling UCG and where their strengths lie. This paper shall serve as guidance to new UCG modellers

Comparison of staged-stent and stent-assisted coiling technique for ruptured saccular wide-necked intracranial aneurysms: Safety and efficacy based on a propensity score-matched cohort study

BackgroundApplication of stent-assisted coiling and FD in acute phase of ruptured wide-necked aneurysms is relatively contraindicated due to the potential risk of ischemic and hemorrhagic complications. Scheduled stenting after initial coiling has emerged as an alternative paradigm for ruptured wide-necked aneurysms. The objective of this study is to evaluate the safety and efficacy of a strategy of staged stent-assisted coiling in acutely ruptured saccular wide-necked intracranial aneurysms compared with conventional early stent-assisted coiling strategy via propensity score matching in a high-volume center.MethodsA retrospective review of patients with acutely ruptured saccular wide-necked intracranial aneurysms who underwent staged stent-assisted coiling or conventional stent-assisted coiling from November 2014 to November 2019 was performed. Perioperative procedure-related complications and clinical and angiographic follow-up outcomes were compared.ResultsA total of 69 patients with staged stent-assisted coiling and 138 patients with conventional stent-assisted coiling were enrolled after 1:2 propensity score matching. The median interval time between previous coiling and later stenting was 4.0 weeks (range 3.5–7.5 weeks). No rebleeding occurred during the intervals. The rate of immediate complete occlusion was lower with initial coiling before scheduled stenting than with conventional stent-assisted coiling (21.7 vs. 60.9%), whereas comparable results were observed at follow-up (82.5 vs. 72.9%; p = 0.357). The clinical follow-up outcomes, overall procedure-related complications and procedure-related mortality between the two groups demonstrated no significant differences (P = 0.232, P = 0.089, P = 0.537, respectively). Multivariate analysis showed that modified Fisher grades (OR = 2.120, P = 0.041) were independent predictors for overall procedure-related complications and no significant predictors for hemorrhagic and ischemic complications.ConclusionsStaged stent-assisted coiling is a safe and effective treatment strategy for acutely ruptured saccular wide-necked intracranial aneurysms, with comparable complete occlusion rates, recurrence rates at follow-up and overall procedure-related complication rates compared with conventional stent-assisted coiling strategy. Staged stent-assisted coiling could be an alternative treatment option for selected ruptured intracranial aneurysms in the future