Improving energy efficiency is considered to be important and cost-effective strategies to reduce greenhouse gas emissions, which is crucial in the face of global climate change. This study hypothesizes that there are significant differences in the impact of energy efficiency on economic and energy systems. Using quantile regression method, the impact of economic and energy characteristics on energy-related greenhouse gas emissions in 120 countries over the period 2010–2020 is investigated. Detailed analyses are conducted by dividing the countries into 12 groups based on gross national income per capita (Atlas method) and the share of resource rents in gross domestic product. A macro-level system of indicators for assessing energy efficiency is proposed, which can be linked to the economic and energy characteristics of the systems: National Energy Efficiency, Energy Intensity Ratio, Primary Energy Production Efficiency, Industrial Sector Energy Efficiency, Share of Low Carbon Energy, Population Energy Efficiency. The findings show that (1) global energy efficiency has remained largely unchanged over the decade; (2) there are differences in energy efficiency between fossil fuel producing and non-fossil fuel producing countries; (3) the factors that have an inverse effect on emissions in fossil fuels dependent countries include industrial energy efficiency and population energy efficiency, which are far from exhausting their potential; (4) despite the recognized importance of energy efficiency, its impact on reducing greenhouse gas emissions globally has been unnoticeable. The study highlights that Sustainable Development Goals 7 and 13 on energy affordability and emission reductions are conflicting and require harmonization of mechanisms to achieve them, such as balancing climate change mitigation investments, identifying the potential for energy efficiency improvements across economy or improving energy saving practices. The overall conclusion suggests that there is an urgent need to review current decarbonization and energy efficiency initiatives, given the lack of significant global progress in reducing greenhouse gas emissions or improving energy efficiency between 2010 and 2020.

The causes of failure of the bucket teeth of the excavator during excavations in rocks are analyzed in the article. It is shown that the most typical cause of failure of bucket teeth is wear of teeth. The wear with soft rocks (less than 1100 HV) which hardness is lower than the hardness of steel in the cold-work hardened state, a preliminary cold-work hardening can essentially (up to 10 times) increase the material wear resistance. The wear with rocks, having greater hardness with hardness of ~1250 HV, the cold-work hardening do not lead to increase of the Hadfield steel wear resistance.

The necessary condition for the operation of crushers in the production of crushed granite is feeding of the crushers with granite fragments of a certain size. At the same time, granite fragmentation after blasting does not always meet the required size for the crushers and needs additional destruction by blasting or disintegration directly on site. Hydraulic breakers are most often used in disintegration of oversizes. For example, in quarries in Vietnam, JCB HM380 hydraulic breakers with a fracture energy of up to 2.5 kJ are widely used. The working tools of the hydraulic breakers are steel picks of various diameters and shapes. The operation of this tool is accompanied by its intensive wear due to the impact-abrasive action of rocks; the pointed part of the tool gets gradually blunted, which affects the rate of penetration of the pick in rock. In this regard, it is relevant to determine the influence exerted by the degree of wear of the pick on the performance of the hydraulic breaker, and to find out whether replacement or re-sharpening of the pick is expedient. In this paper, based on the previously determined crack propagation velocity in granite and the impact time, the length of the fracture is calculated. The dimensions of a crack in a granite block are calculated depending on the degree of blunting of the pick at a certain number of blows per cycle. At the same time, the limiting value of a crack that causes chipping of a piece from rock mass was considered as the fracture length to free surface at different degrees of pick blunting. Based on these calculations, the average productivity and energy input of disintegration process were determined. It is shown that for a tool with a completely worn tip, the decrease in the productivity and the increase in the energy input of fracture reach two times compared with a sharpened pick. In this regard, from the point of view of increasing the hydraulic breaker capacity, it is advisable to replace or re-sharpen the pick after complete wear of its tip.