Decreasing methane emissions from China's coal mining with rebounded coal production

China is the world’s largest anthropogenic methane (CH4) emitter, with coal mine methane (CMM) as one of the main contributors. However, previous studies have not reach consensus on the magnitude and trend of China’s CMM emissions since 2010. Through distribution fitting and Monte Carlo methods, dynamic emission factors (EFs) of CMM at the province-level were derived with high confidence; along with the updated data on surface mining, abandoned coal mines, and methane utilization, we revealed that China’s annual CMM emissions were estimated at 20.11 Tg between 2010 and 2019 with a decline of 0.93 Tg yr-1. Although coal production was revived in 2017, we found that the growing trend of China’s CMM emissions since 2012 were curbed by the previously-overlooked factors including the growth of CMM utilization and coal production from surface mining, and decrease of emission factors driven by the closure of high CH4-content coal mines and a regional production shift to lower-emission areas.

Comparative study of methane oxidation within various biofilter media

A considerable fraction of the methane gas generated by landfills can be oxidized by the landfill cover. In this study, the use of disposable sawdust material to utilize and reduce methane gas from the landfill gas (LFG) was demonstrated. Three laboratory scale bioreactors were constructed to reflect the performance of sawdust with respect to the compost and sand (control media). Patterns of methane (CH₄) oxidation were evaluated through the degree of methane oxidation in correlation to the bacterial development in all three media. Later, the use of nutrients during the respiration of the bacteria was interpreted through the analysis of chemical oxygen demand (COD), biochemical oxygen demand (BOD), and biomass growth variations. The overall methane oxidation efficiency in the sawdust medium was 60% with a biomass content of 238 g/m³, whereas the compost medium had 86% methane oxidation efficiency with a 539 g/m³ biomass content. Furthermore, the COS and BOD removal were 2555 mg/L and 332 mg/L from the compost, and 1984 mg/L and 156 mg/L from the sawdust respectively. The overall results of this study indicated that the sawdust material can be used as a biofilter media for methane utilization from the landfill. The oxidation capacity of sawdust could be accelerated by adding necessary nutrients to this media before implementation. Moreover, the oxidation rate variance between compost and sawdust may be eliminated over time due to nutrient exhaustion in the compost media, and/or production of usable carbon with decomposition of the sawdust media.

Comparative study of methane oxidation within various biofilter media

A considerable fraction of the methane gas generated by landfills can be oxidized by the landfill cover. In this study, the use of disposable sawdust material to utilize and reduce methane gas from the landfill gas (LFG) was demonstrated. Three laboratory scale bioreactors were constructed to reflect the performance of sawdust with respect to the compost and sand (control media). Patterns of methane (CH₄) oxidation were evaluated through the degree of methane oxidation in correlation to the bacterial development in all three media. Later, the use of nutrients during the respiration of the bacteria was interpreted through the analysis of chemical oxygen demand (COD), biochemical oxygen demand (BOD), and biomass growth variations. The overall methane oxidation efficiency in the sawdust medium was 60% with a biomass content of 238 g/m³, whereas the compost medium had 86% methane oxidation efficiency with a 539 g/m³ biomass content. Furthermore, the COS and BOD removal were 2555 mg/L and 332 mg/L from the compost, and 1984 mg/L and 156 mg/L from the sawdust respectively. The overall results of this study indicated that the sawdust material can be used as a biofilter media for methane utilization from the landfill. The oxidation capacity of sawdust could be accelerated by adding necessary nutrients to this media before implementation. Moreover, the oxidation rate variance between compost and sawdust may be eliminated over time due to nutrient exhaustion in the compost media, and/or production of usable carbon with decomposition of the sawdust media.

Methane utilization as a resource-saving method inthe coal industry

Risks of partial or total loss of ecosystems and species due to climate change are currently increasing. Russia is the world’s fourth largest emitter of greenhouse gases, which have a detrimental effect on ecosystems. The fuel and energy complex is the largest emitter of greenhouse gases; in this regard, it is precisely the reduction of greenhouse gas emissions in this area has the utmost significance.In addition, methane as one of the greenhouse gases is harmful not only for the ecosystem but also for industrial safety, and this is also a sphere of state regulation.Since methane, based on its forecast volumes, may well be mined as an independent mineral product, it is necessary to develop a rational method for its use, since today everything that is mined is emitted into the atmosphere.The report analyzes how coal mining companies are currently using coal-seam methane. The volumes of methane in coal seams in the Russian Federation and in coal basins are analyzed. The world experience in the extraction of coalbed methane as a separate mineral product is investigated. A project is proposed for the rational use of methane as a separate mineral product.The main purpose of the article is to show that resource-saving measures for the use of methane can have not only environmental but also economic effect.A financial model of the project is proposed, which allowed to prove the economic efficiency of the project for the use of methane as a fuel. The article is based on the case method, the method for constructing financial models, the method for assessing risks, the method for analyzing information, etc.

Functional metagenomics of bark microbial communities from avocado trees (Persea americana Mill.) reveals potential for bacterial primary productivity

SummaryBark microbial communities are poorly understood, and information on the metabolic capacities of their inhabitants is lacking. Bark microbial communities share part of their taxonomic composition with soil, but the functional differences and similarities are unknown. By comparing bark microbial communities of avocado trees (Persea americana, Mill.) with rhizospheric soil, functional processes relevant to the bark environment were identified. DNA from bark and soil communities was extracted from the same trees, and shotgun metagenomics sequencing was performed using nextSeq technology. Genes were identified by BLAST methods, and functional annotation was performed with KEGG databases as a reference. Bacterial oxygenic and anoxygenic photosynthesis genes were highly abundant in bark as compared to soil. Furthermore, increased presence of nitrogenase genes suggests a potential for nitrogen fixation. Genes for methanol utilization were abundant in bark, but no evidence of methane utilization potential was observed. Bark microbial communities have the genetic information for potential primary productivity, which might contribute to microbial growth independent of plant-derived carbon substrates.

Dioxygen dissociation over man-made system at room temperature to form the active α-oxygen for methane oxidation

Activation of dioxygen attracts enormous attention due to its potential for utilization of methane and applications in other selective oxidation reactions. We report a cleavage of dioxygen at room temperature over distant binuclear Fe(II) species stabilized in an aluminosilicate matrix. A pair of formed distant α-oxygen species [i.e., (Fe(IV)═O)2+] exhibits unique oxidation properties reflected in an outstanding activity in the oxidation of methane to methanol at room temperature. Designing a man-made system that mimicks the enzyme functionality in the dioxygen activation using both a different mechanism and structure of the active site represents a breakthrough in catalysis. Our system has an enormous practical importance as a potential industrial catalyst for methane utilization because (i) the Fe(II)/Fe(IV) cycle is reversible, (ii) the active Fe centers are stable under the reaction conditions, and (iii) methanol can be released to gas phase without the necessity of water or water-organic medium extraction.