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Parties to the 2015 Paris Agreement pledged to limit global warming to well below 2 °C and to pursue efforts to limit the temperature increase to 1.5 °C relative to pre-industrial times 1 . However, fossil fuels continue to dominate the global energy system and a sharp decline in their use must be realized to keep the temperature increase below 1.5 °C (refs. 2 , 3 , 4 , 5 , 6 – 7 ). Here we use a global energy systems model 8 to assess the amount of fossil fuels that would need to be left in the ground, regionally and globally, to allow for a 50 per cent probability of limiting warming to 1.5 °C. By 2050, we find that nearly 60 per cent of oil and fossil methane gas, and 90 per cent of coal must remain unextracted to keep within a 1.5 °C carbon budget. This is a large increase in the unextractable estimates for a 2 °C carbon budget 9 , particularly for oil, for which an additional 25 per cent of reserves must remain unextracted. Furthermore, we estimate that oil and gas production must decline globally by 3 per cent each year until 2050. This implies that most regions must reach peak production now or during the next decade, rendering many operational and planned fossil fuel projects unviable. We probably present an underestimate of the production changes required, because a greater than 50 per cent probability of limiting warming to 1.5 °C requires more carbon to stay in the ground and because of uncertainties around the timely deployment of negative emission technologies at scale. A global energy system model finds that planned fossil fuel extraction is inconsistent with limiting global warming to 1.5 °C, because the majority of fossil fuel reserves must stay in the ground.

The issue of air pollution caused by ship emissions is becoming prominent with the increasing global shipping activities. China has carried out fuel oil policies in three stages in the past few years to meet the requirements of the global low sulfur regulation by the International Maritime Organization (IMO). However, the impacts of staged policies on air quality in China are not sufficiently understood. This study firstly updated the ship emission inventory including PM.sub.2.5 components based on field and on-board measurements under the staged fuel oil policies. Then, the impacts of ship emissions on PM.sub.2.5 and its gas precursors and primary and secondary components in China from 2017 to 2021 were revealed by using the Weather Research and Forecasting (WRF) model and the Community Multiscale Air Quality (CMAQ) model. In the model domain, the 99th percentile of the shipping-related PM.sub.2.5 concentrations was reduced by 19.5 % and then by 35.6 % due to the policy shifts. Ship emissions increased the PM.sub.2.5 concentrations up to 3.8 µg m.sup.-3 in 2017 and 2.6 µg m.sup.-3 in 2021. The areas with high concentration levels widely distributed over offshore waters in 2017 and shrunk to some parts of China's coast in 2021. The contributions of ship emissions to the PM.sub.2.5 concentrations over China's main port cities ranged from 3.0 % to 17.4 % in 2017 and 2.5 % to 10.3 % in 2021. In these cities, the change rates of the concentrations of PM.sub.2.5, SO42-, NO3-, NH4+, carbonaceous aerosols, V, and Ni related to ship emissions from 2017 to 2021 were -32.7 %, -74.0 %, +11.0 %, -27.5 %, -76.9 %, -90.3 %, and -38.4 %, respectively. NO3- constituted 54.6 % of the shipping-related PM.sub.2.5 in 2021. Our findings suggest that it is important to consider both transport pathways and secondary aerosol formation mechanisms to combat the PM.sub.2.5 pollution caused by shipping in different regions.

Analysis of the very-low-sulfur fuel oil (VLSFO) and ultra-low-sulfur fuel oil (ULSFO) bunkered in key ports in Asia, the Middle East, North America, Western Europe, and Russia is presented. The characteristics of said fuels, including density, sulfur content, kinematic viscosity, aluminum and silicon content, vanadium and nickel content, as well as pour point are investigated. Furthermore, the main trends and correlations are also discussed. Based on the graphical and mathematical analysis of the properties, the composition of the fuels is predicted. The key fuel components in Asian ports, the most important of which is Singapore, are hydrodesulfurized atmospheric residues (AR) (50–70%) and catalytic cracker heavy cycle oil (HCO) (15–35%) with the addition of other components, which is explained by the presence of a number of large oil refining centers in the area. In the Middle East ports, the most used VLSFO compositions are based on available resources of low-sulfur components, namely hydrodesulfurized AR, the production facilities of which were recently built in the region. In European ports, due to the relatively low sulfur content in processed oils, straight-run AR is widely used as a component of low-sulfur marine fuels. In addition, fuels in Western European ports contain on average significantly more hydrotreated vacuum gas oil (21%) than in the rest of the world (4–5%). Finally, a mixture of hydrotreated (80–90%) and straight-run fuel oil (10–15%) with a sulfur content of no more than 2.0–2.5% is used as the base low-sulfur component of marine fuels in the ports of Singapore and the Middle East.

Residual oils, high viscosity and large sulfur content petroleum products from the refining process of crude oil, are receiving increasing interest in pre-combustion carbon capture applications. Gasification is a promising technology to convert such complicated hydrocarbons into syngas. Pyrolysis and combustion are very important stages in the gasification process, and therefore a better understanding of these processes leads to higher efficiency and better development of such applications. In this work, pyrolysis and combustion of heavy fuel oil (HFO) and vacuum residual oil (VRO) were studied in a thermogravimetric analyzer (TGA). The HFO studied in this work is a blend of VRO and diesel, which provides insight into the performance of residual oils/diesel blends. The TGA experiments were conducted using nitrogen and mixtures of oxygen and nitrogen for pyrolysis and combustion studies, respectively, at different heating rates (5–20 °C min −1 ). The oxygen concentration was varied from 0 to 71.4% vol. to replicate oxygen concentration in applications ranging from pyrolysis (0% O 2 ) to combustion (21% O 2 ) and gasification (high O 2 %). The TGA experiments covered a temperature range from ambient to 1200 °C. The results show that pyrolysis is slightly slower than combustion at low temperatures for both oils. However, pyrolysis is significantly faster at high temperatures. The combustion of both oils resulted in minimal residue, while the residue remaining in the pyrolysis is 10–19%. The TGA was coupled with Fourier transform infrared spectroscopy (FTIR) to monitor the evolved volatiles from the pyrolysis and combustion processes. The results show more aromatics evolved from VRO than HFO. Apparent kinetic parameters were calculated using three model-free methods and a model-based method (Coats and Redfern).

The production of green fuel oil is of the utmost importance for maintaining a healthy life and environment in the current world. Effective and complete removal of sulfur refractory compounds (such as 4,6-dimethyldibenzothiophene and other alkyl-substituted thiophene derivatives) from fuel oil is essential to meet the new requirements of sulfur standards. Several techniques have been proposed for desulfurization of fuel oil, such as hydrodesulfurization (HDS), selective adsorption, extractive distillation, biodesulfurization, and oxidative desulfurization (ODS). The removal of sulfur by the HDS process requires higher investment costs, high reaction temperature (up to 400 °C), and high pressure (up to 100 atm) reactors. On the other hand, studies have shown that the ODS process is remarkably successful in the removal of sulfur under mild reaction conditions. This review article presents a comparative analysis of various existing catalytic oxidation techniques: acetic acid/formic acid catalytic oxidation, heteropolyacid (HPA) catalytic oxidation, ionic liquid catalytic oxidation, molecular sieve catalytic oxidation, polyoxometalates catalytic oxidation, titanium catalytic oxidation, and ultrasound-assisted oxidation systems, as well as discusses research gaps, and proposes important recommendations for future challenges.

Waste plastics are non‐degradable constituents that can stay in the environment for centuries. Their large land space consumption is unsafe to humans and animals. Concomitantly, the continuous engineering of plastics, which causes depletion of petroleum, poses another problem since they are petroleum‐based materials. Therefore, energy recovering trough pyrolysis is an innovative and sustainable solution since it can be practiced without liberating toxic gases into the atmosphere. The most commonly used plastics, such as HDPE, LDPE (high‐ and low‐density polyethylene), PP (polypropylene), PS (polystyrene), and, to some extent, PC (polycarbonate), PVC (polyvinyl chloride), and PET (polyethylene terephthalate), are used for fuel oil recovery through this process. The oils which are generated from the wastes showed caloric values almost comparable with conventional fuels. The main aim of the present review is to highlight and summarize the trends of thermal and catalytic pyrolysis of waste plastic into valuable fuel products through manipulating the operational parameters that influence the quality or quantity of the recovered results. The properties and product distribution of the pyrolytic fuels and the depolymerization reaction mechanisms of each plastic and their byproduct composition are also discussed. Recent trends in thermal and catalytic pyrolysis for obtaining valuable fuel products from plastic waste are discussed and highlighted. Several factors that influence the pyrolysis process are briefly discussed. Moreover, the depolymerization mechanism and the nature and pyrolysis product distribution are summarized along with their corresponding by‐products.

By using our newly defined measure, we detect and quantify asymmetries in the volatility spillovers of petroleum commodities: crude oil, gasoline, and heating oil. The increase in volatility spillovers after 2001 correlates with the progressive financialization of the commodities. Further, increasing spillovers from volatility among petroleum commodities substantially change their pattern after 2008 (the financial crisis and advent of tight oil production). After 2008, asymmetries in spillovers markedly declined in terms of total as well as directional spillovers. In terms of asymmetries we also show that overall volatility spillovers due to negative (price) returns materialize to a greater degree than volatility spillovers due to positive returns. An analysis of directional spillovers reveals that no petroleum commodity dominates other commodities in terms of general spillover transmission.

The transformation of waste plastics into fuels via energy-efficient and low-cost pyrolysis could incentivize better waste plastic management. Here, we report pressure-induced phase transitions in polyethylene, which continue to heat up without additional heat sources, prompting the thermal cracking of plastics into premium fuel products. When the nitrogen initial pressure is increased from 2 to 21 bar, a monotonically increasing peak temperature is observed (from 428.1 °C to 476.7 °C). At 21 bar pressure under different atmosphere conditions, the temperature change driven by high-pressure helium is lower than that driven by nitrogen or argon, indicating that phase transition is related to the interaction between long-chain hydrocarbons and intercalated high-pressure medium layers. In view of the high cost of high-pressure inert gases, the promotion or inhibition effect of low-boiling hydrocarbons (transitioning into the gaseous state with increasing temperature) on phase transition is explored, and a series of light components are used as phase transition initiators to replace high-pressure inert gases to experiment. The reason that the quantitative conversion of polyethylene to high-quality fuel products is realized through the addition of 1-hexene at a set temperature of 340 °C and the initial atmospheric pressure. This discovery provides a method for recycling plastics by low energy pyrolysis. In addition, we envisage recovering some of the light components after plastic pyrolysis as phase change initiators for the next batch of the process. This method is able to reduce the cost of light hydrocarbons or high-pressure gas insertion, reduce heat input, and improve material and energy utilization.

The widespread utilization of low-sulfur fuels in compliance with global sulfur limit regulations has significantly mitigated the emissions of sulfur dioxide (SO2) and particulate matter (PM) on ships. However, significant uncertainties still persist regarding the impact on intermediate-volatility/semi-volatile organic compounds (I/SVOCs). Therefore, onboard tests of I/SVOCs from three ocean-going vessels (OGVs) and four inland cargo ships (ICSs) with low-sulfur fuels (<0.50 % m/m) in China were carried out in this study. Results showed that the emission factors of total I/SVOCs were 881 ± 487, 1181 ± 421, and 1834 ± 667 mg per kg fuel for OGVs with heavy fuel oil (HFO), marine gas oil (MGO), and ICSs with no. 0 diesel, respectively. The transition from low-sulfur-content (<0.50 % m/m) to ultra-low-sulfur-content (<0.10 % m/m) fuels had evidently enhanced the emission factor of I/SVOCs, with unignorable contributions from particle-phase I/SVOCs, thereby further amplifying the secondary organic aerosol formation potential (SOAFP). Fuel type, engine type, and operating conditions comprehensively influenced the emission factor level, compositions, and volatility distribution of I/SVOCs. Notably, a substantial proportion of fatty acids had been identified in ship exhausts, necessitating heightened attention. Furthermore, organic diagnostic markers of hopanes, in conjunction with the C18:0-to-C14:0 acid ratio, could be considered potential markers for HFO exhausts. The findings suggest that there is a need to optimize the implementation of a global policy on ultra-low-sulfur oil in the near future.