Oil shale, a significant fossil energy source, has garnered global attention due to its huge reserves and potential as an alternative to conventional petroleum. This minireview evaluates the comprehensive utilization of oil shale, focusing on its entire lifecycle, from extraction to energy production, treatment of abandoned mines, and subsequent utilization to gain more economic and environmental benefits. In addition, the minireview underscores the necessity of green and high-value utilization of oil shale and its by-products (i.e., semi-coke and ash) to mitigate environmental pollution. To promote comprehensive utilization of oil shale and its by-products, we summarize current knowledge extending beyond traditional energy applications to encompass construction materials, environmental functional materials, and other high-value products. Strategies such as circulating fluidized bed combustion, in situ conversion, and co-combustion and co-pyrolysis with biomass are introduced for efficient resource use. The treatment of abandoned oil shale mines for energy storage and the recovery of trace and rare earth elements are also addressed. The minireview concludes with recommendations for improving testing strategies, assessing environmental impacts, and exploring new applications to ensure green and sustainable development in the oil shale industry.

In Estonian oil shale power plants, ash is transported to disposal sites using a wet transport method. Due to regional climatic conditions, where annual precipitation exceeds evaporation, part of the recirculated ash transport water has to be periodically discharged into natural surface waters. This discharge practice raises concerns about the potential environmental impact of the discharged water. This paper investigates the leaching behavior of several trace elements from oil shale ash, demolition wood ash, and their mixtures, with a focus on chromium. In particular, the occurrence, mobility, and oxidation state of chromium in the leachate are considered using the example of the mentioned ashes. The possible effect of ash content, influenced by fuel type and the liquid-to-solid (L/S) ratio, on trace element concentrations in the discharged water was studied. In leaching tests with 100% oil shale ash, the chromium concentration in the circulating water increases only slightly when circulating water from the oil shale ash field is used as the leaching medium. On the one hand, the amount of chromium and other trace elements leached from oil shale ash depends on the L/S ratio. At the same time, it is known from the literature that oil shale ash is also capable of binding chromium. The release and concentration of chromium in the leachate increase significantly as the proportion of waste wood ash rises, compared to tests using 100% oil shale ash. Consequently, the concentration of chromium in surface water, depending on the specific ratio of oil shale to waste wood used in co-combustion, can easily exceed the nationally permitted limit value.

This study introduces a novel visual online observation technique for identifying the critical temperature for oil generation. It also examines the hydrocarbon generation properties of Maoming oil shale when subjected to supercritical water. Findings indicate that the critical temperature for Maoming oil shale in supercritical water ranges from 262 to 292 °C, and the visualization reactor facilitates the investigation of this critical temperature. The organic carbon conversion rate for Maoming oil shale can exceed 25.4% within a limited reaction time of one hour. Increasing the water-shale mass ratio enhances the overall conversion of organic carbon in the oil shale and boosts oil production, although it does not significantly improve gas production. Additionally, a higher water-shale mass ratio can decrease the heavy oil fraction in the oil and enhance the selectivity for hydrogen and methane in the gas produced.

A top-fired heating furnace is a type of heating equipment for the heat carrier used in the dry retorting process of oil shale. This study explores the energy consumption and pollutant emissions of such furnaces, focusing on the influence of the excess air coefficient and air staging ratio on the NO emission characteristics of the combustion chamber outlet, using the numerical simulation method. The research shows that with the increase of the excess air coefficient α, the combustion chamber temperature and the NO emission value of the combustion chamber outlet first increase and then decrease, reaching a peak at α = 1.05. The combustion chamber temperature directly affects the NO emission value, showing the change law of thermodynamic NO with temperature. When the air is staged, the factors affecting the NO emission value are more complicated, and the amount of NO generation is not only affected by the uniformity of combustion temperature but also by the mixing characteristics. When the proportion of secondary air is 30%, the mixing fraction distribution is the most uniform, the mixing effect of fuel gas and air is the best, and the NO emission value at the combustion chamber outlet is the lowest.

A co-pyrolysis of woodchips and oil shale was conducted in a continuous reactor at 520 °C in a CO2 atmosphere. Experimental product yields were derived and an analysis of the liquid products was conducted, using gas chromatography, infrared spectroscopy, and physicochemical analysis. A maximum yield of liquids and gases was obtained as the share of biomass increased (43.9 and 35.1 wt%, respectively). Product characterization confirmed additive behavior in co-pyrolysis. The liquid products from co-pyrolysis blends exhibited fewer oxygenated compounds, derived from biomass, and fewer aromatic compounds, derived from oil shale. Co-pyrolysis liquids contained abundant aliphatic hydrocarbons (C6 to C11).

Continental shale oil resource is an important alternative source for increasing and stabilizing China’s crude oil production. China has abundant continental shale oil resources. The opinions of researchers are divided over the classification of shale oil resources in China, resource evaluation methods and criteria, and resource potential prediction. Considering this fact, the authors of this article first summarized and analyzed the exploration progresses made in the typical shale oil exploration areas in China and the geological insights gained through exploration activities. Then, based on the current shale oil research status and actual oil production conditions in China, shale oil resources were classified into three types: interlayer shale oil, pure shale oil, and in-situ converted shale oil. Furthermore, the corresponding resource evaluation methods and quantitative models were proposed, the key parameters and their lower limits were determined and the resources of the three major types of shale oil in the shale formations in China’s major basins were evaluated using a set of unified evaluation criteria. The in-place resources of pure shale oil, interlayer shale oil and in-situ converted shale oil are 145.4 × 108 t, 95.1 × 108 t and 708.2 × 108 t, respectively, and the recoverable resources are respectively 9.4 × 108 t, 7.1 × 108 t and 460.3 × 108 t. The research results can provide guidance for the evaluation of shale oil resources in China and the exploration planning for such resources and serve as valuable references for international peers to understand China’s current status of research and development potential of shale oil.

In this paper, the catalytic pyrolysis of Jimsar oil shale was studied using CoCl2·6H2O as a catalyst. The thermogravimetric analysis (TGA) was carried out on oil shale samples with the catalyst added. The kinetic analysis of the pyrolysis reaction of each sample was performed using the main curve method and several model-free methods. The results showed that CoCl2·6H2O could not only reduce the average activation energy of oil shale pyrolysis from 216 kJ/mol to 163 kJ/mol, but also decrease the pyrolysis temperature by about 100 °C.

In the present work, Moroccon Tarfaya oil shale was treated by acids and different solvents under supercritical conditions, successively. Experimental results showed clearly that residual mineral matter had a significant effect on the yield and composition of the resulting organic fraction. Indeed, theoil yields obtained from some samples, 43% and 56%, respectively, were much higher than that from the sub-layer, 18%. In addition, the yield of recuperation and quality of extracted oils were largely dependent on the nature of solvents (toluene, water, shale oil). Thus, phenol was shown to be a very efficient modifier for the supercritical extraction of organic matter from Tarfaya oil shale with toluene, affording a good yield of recovery and a suitable maturation of organic matter. The pitches prepared by mixing phenol and toluene contained more aromatics and had a high char yield (46%) at 950 °C compared to those obtained by extraction with supercritical toluene alone.

Despite the fact that the shale oil industry in Estonia is a century old, there is still too little data about the thermodynamic and transport properties of the fuel. Information about these properties is important in producing and handling the fuel and in environmental and safety analyses. The current article addresses this problem by presenting experimental viscosity data for the lighter portion of kukersite shale oil, often called shale gasoline. The data is for 23 narrow boiling fractions, and also shows the change in viscosity for portions of the gasoline with different average boiling points. Viscosities were measured over a range of temperatures, and equations were fit to the data to describe the temperature dependence of the viscosity. Correlations are also presented which can be used for predicting the viscosity of kukersite shale gasoline if its density at 20 °C is known.

Cadmium (Cd) is the most highly toxic heavy metal even at a trace level. In this study, the oil shale ash treated material was used as an adsorbent to remove cadmium and lead (Pb) metals/ions from aqueous solutions. The absorbent treated oil shale material was characterized prior to experimental work using X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The effects of multiple factors on percent metal removal, including contact time, initial ions concentration and pH, are investigated. Results show that the adsorption capacities of Pb and Cd are 29.15 and 23.81 mgg–1, whereas removal efficiencies are 56% and 48% in 10 minutes, respectively. Removal efficiency and time of equilibrium are affected by the metal atomic weight (Pb 207.2 u and Cd 112.4 u) and pH values. The equilibrium isotherms were analyzed using Freundlich and Langmuir isotherm models and described by the Freundlich isotherm model indicating a heterogeneous surface of the adsorbent. The calculated Langmuir adsorption constant and maximum adsorption capacity of adsorbent, KL and qmax, are 1.313*10–2 and 25.25, respectively. The Freundlich adsorption constant KF and the characteristic constant of the Freundlich isotherm n are 0.5234 and 1.39, respectively.