Environmental life-cycle assessment of waste-coal pellets production

Industrial decarbonization is crucial to keeping the global mean temperature <1.5°C above pre-industrial levels. Although unabated coal use needs to be phased out, coal is still expected to remain an important source of energy in power and energy-intensive industries until the 2030s. Decades of coal exploration, mining and processing have resulted in ~30 billion tonnes of waste-coal tailings being stored in coal impoundments, posing environmental risks. This study presents an environmental life-cycle assessment of a coal-processing technology to produce coal pellets from the waste coal stored in impoundments. It has been shown that the waste-coal pellets would result in the cradle-to-gate global warming of 1.68–3.50 kgCO2,eq/GJch, depending on the source of electricity used to drive the process. In contrast, the corresponding figure for the supply of conventional coal in the US was estimated to be 12.76 kgCO2,eq/GJch. Such a reduction in the global-warming impact confirms that waste-coal pellets can be a viable source of energy that will reduce the environmental impact of the power and energy-intensive industries in the short term. A considered case study showed that complete substitution of conventional coal with the waste-coal pellets in a steelmaking plant would reduce the greenhouse-gas emissions from 2649.80 to 2439.50 kgCO2,eq/tsteel. This, in turn, would reduce the life-cycle greenhouse-gas emissions of wind-turbine manufacturing by ≤8.6%. Overall, this study reveals that the use of waste-coal pellets can bring a meaningful reduction in industrial greenhouse-gas emissions, even before these processes are fully decarbonized.

Bio-Adsorbent Derived from Sewage Sludge Blended with Waste Coal for Nitrate and Methyl Red Removal: Synthesis, Oxidation, Performance and Environmental Consideration

Low-cost bio-adsorbents were synthesized using two types of sewage sludge: D, which was obtained during the dissolved air flotation stage, and S, which was a mixture of primary and secondary sludge from the digestion and dewatering stages. The sewage sludge was mixed with waste coal before being activated with Potassium Hydroxide (KOH) and oxidized with ammonium persulfate (APS). The nitrate and methyl red removal capacities of the synthesized bio-adsorbents were evaluated and compared to those of industrial activated charcoal. The oxidation surface area of bio-adsorbents derived from sludge S shrank by six fold after modification, while those derived from D only varied narrowly from 312,72 m2/g to 282,22 m2/g, but surface modification had no effect on inorganic composition in either case. The adsorption of nitrate and methyl red (MR) was performed in batch mode, and the removal processes followed the pseudo second order kinetic model and the Langmuir isotherm fairly well. The adsorption capacities of nitrate and MR were higher at pH=2 and pH=4, respectively. The total nitrate Langmuir adsorption potential was DC-5-750 (26,735 mg/g) > commercial activated carbon (Com-AC) (20,61 mg/g) > DC-55-750M1 (17,06 mg/g), and for MR, Com-AC (196,07 mg/g) > DC-5-750M2 (175 mg/g).Statement of Novelty: This paper examines how the chemical structure of activated carbon derived from sewage sludge and blended with waste coal is altered during the chemical activation process to provide the optimal porous surface for nitrate and methyl red adsorptive remediation. The formation of carboxylic sites or the transformation of oxygen sites to carboxylic sites is the aim of the oxidation process of activated carbon in general. Ammonium peroxydisulfate was chosen because of its ability to oxidize the surface without significantly altering the porous structure and increase surface acidity by increasing carboxylic group presence. There are no studies that we are aware of that use ammonium peroxydisulfate to oxidize activated carbon from sewage sludge blended with waste coal

Impacts of Syngas Composition on Anaerobic Fermentation

Energy consumption places growing demands on modern lifestyles, which have direct impacts on the world’s natural environment. To attain the levels of sustainability required to avoid further consequences of changes in the climate, alternatives for sustainable production not only of energy but also materials and chemicals must be pursued. In this respect, syngas fermentation has recently attracted much attention, particularly from industries responsible for high levels of greenhouse gas emissions. Syngas can be obtained by thermochemical conversion of biomass, animal waste, coal, municipal solid wastes and other carbonaceous materials, and its composition depends on biomass properties and gasification conditions. It is defined as a gaseous mixture of CO and H2 but, depending on those parameters, it can also contain CO2, CH4 and secondary components, such as tar, oxygen and nitrogenous compounds. Even so, raw syngas can be used by anaerobic bacteria to produce biofuels (ethanol, butanol, etc.) and biochemicals (acetic acid, butyric acid, etc.). This review updates recent work on the influence of biomass properties and gasification parameters on syngas composition and details the influence of these secondary components and CO/H2 molar ratio on microbial metabolism and product formation. Moreover, the main challenges, opportunities and current developments in syngas fermentation are highlighted in this review.