Quality assessment of biomass pellets available on the market; example from Poland

This study evaluates the quality of 30 biomass pellets sold for residential use in Poland. It provides data on their physical, chemical, and petrographic properties and compares them to existing standards and the information provided by the fuel producers. The results reveal considerable variations in the quality of the pellets and show that some of the purchased samples are not within the DINplus and/or ENplus certification thresholds. Among all 30 purchased samples, only one passes the quality thresholds set by the PL-US BIO, a newly established quality certification in Poland that combines quality assessment following DINplus with optical microscopy analysis. The primary issues causing a decrease in pellet quality include elevated ash and fines content, compromised mechanical durability, too low ash melting temperature, and additions of undesired additions like bark, inorganic matter, and petroleum products. Our research highlights the need for improved fuel quality control measures, and transparent and accurate product labeling, as well as the need for a comprehensive and publicly available national database of solid biomass fuel producers and fuels sold. These are essential steps toward increasing customers' awareness and trust, encouraging them to embrace biomass fuels as reliable and sustainable sources of energy.

Environmental implications of the quality of charcoal briquettes and lump charcoal used for grilling

Numerous studies have been conducted to assess air pollution and human health risks arising from exposure to outdoor cooking, but limited standards have been implemented around the world to assure fuel quality. While charcoal briquettes and lumps are a popular fuel choice for grilling, almost no data specifying their properties are available to consumers. Because the properties of fuels affect the flue gases, it is critical to understand how the quality of grilling briquettes and lumps translates not only into the quality of the grilled food, but, even more importantly, how their emissions impact human safety and the environment. The main purpose of this study is to investigate the impacts of the quality of charcoal briquettes and lumps on potentially harmful emissions during grilling. To analyze their quality, we used reflected light microscopy to identify a range of contaminants, including biomass, mineral matter, coal, coke, metal, rust, plastics, glues, and synthetic resins, in 74 commercially available products made in Poland, the United States of America, Ukraine, Germany, Belarus, the Czech Republic, and the Republic of South Africa. Our data show that majority of the products analyzed do not meet the existing quality standard EN 1860-2:2005 (E) of less than 1% contaminants, some of these products contain up to 26.6% of impurities. The amount of contaminants correlates with particulate matter, as well as CO and CO₂. The contribution of biomass is especially significant because it can be used to predict harmful particulate matter emissions during grilling. The relationship between the composition of charcoal briquettes and lump charcoal and their emissions is particularly strong during the first 15 to 20 min after ignition (when emissions are the highest), therefore, this initial stage is especially unsafe to consumers, and staying away from the grill during this time is recommended.

Natural geological seepage of hydrocarbon gas in the Appalachian Basin and Midwest USA in relation to shale tectonic fracturing and past industrial hydrocarbon production

Geological hydrocarbon gas seepage is a major global source of atmospheric methane, ethane and propane as greenhouse gases and photochemical pollutants. Natural gas seepage is generally related to faults and associated fracture intensification domains that provide conduits for natural gas from reservoir rocks to migrate upward and enter the atmosphere. In this study, we compare the case of intense gas seepage stemming directly from source rocks, mostly organic-rich fractured black shales in western New York State (NYS) versus areas with rare seepage in the more southern regions of the Appalachian Basin and the Midwest USA. In addition to thermogenic methane, western NYS shale gas seeps emit ethane and propane with C₂₊₃ gas concentrations reaching up to 35 vol%. Fractures in NYS developed, reactivated and maintained permeability for gas as a result of Quaternary glaciation and post-glacial basin uplift. In contrast, the Appalachian regions farther south and the southern Midwest regions experienced less glacial loading and unloading than in NYS, resulting in less recent natural fracturing, as witnessed by the rarity of seepage on surface outcrops and in caves overlying gas-bearing shales and coals. The historical literature suggests that early western NYS drilling and production of oil and gas diminished shale gas pressure and resulted in declining gas seepage rates. Our survey documented 12 active western NYS natural gas seeps, whereas >32 seeps have been reported or documented since the 17th century. Preliminary tests showed that SCIAMACHY satellite data did not detect atmospheric methane anomalies over western NYS seeps.

Microbial contributions to subterranean methane sinks

Sources and sinks of methane (CH₄ ) are critical for understanding global biogeochemical cycles and their role in climate change. A growing number of studies have reported that CH₄ concentrations in cave ecosystems are depleted, leading to the notion that these subterranean environments may act as sinks for atmospheric CH₄ . Recently, it was hypothesized that this CH₄ depletion may be caused by radiolysis, an abiotic process whereby CH₄ is oxidized via interactions with ionizing radiation derived from radioactive decay. An alternate explanation is that the depletion of CH₄ concentrations in caves could be due to biological processes, specifically oxidation by methanotrophic bacteria. We theoretically explored the radiolysis hypothesis and conclude that it is a kinetically constrained process that is unlikely to lead to the rapid loss of CH₄ in subterranean environments. We present results from a controlled laboratory experiment to support this claim. We then tested the microbial oxidation hypothesis with a set of mesocosm experiments that were conducted in two Vietnamese caves. Our results reveal that methanotrophic bacteria associated with cave rocks consume CH₄ at a rate of 1.3-2.7 mg CH₄  · m^-2  · d^-1 . These CH₄ oxidation rates equal or exceed what has been reported in other habitats, including agricultural systems, grasslands, deciduous forests, and Arctic tundra. Together, our results suggest that depleted concentrations of CH₄ in caves are most likely due to microbial activity, not radiolysis as has been recently claimed. Microbial methanotrophy has the potential to oxidize CH₄ not only in caves, but also in smaller-size open subterranean spaces, such as cracks, fissures, and other pores that are connected to and rapidly exchange with the atmosphere. Future studies are needed to understand how subterranean CH₄ oxidation scales up to affect local, regional, and global CH₄ cycling.