This study was a preliminary investigation of solid recovered fuel production from spent coffee grounds using the hydrothermal carbonization (HTC) technique. The spent coffee grounds (SCGs) were subjected to HTC at 170 to 250 °C. The biochar was characterized by proximate analysis, ultimate analysis, capillary suction time, time to filter, suspended solids, and particle size distribution. The biochar yields decreased with increasing HTC temperature and time. However, the higher heating value (HHV) of biochar increased with the HTC temperature and time. The H/C slop relative to the O/C atomic rate of spent coffee grounds was 0.10 with low decarboxylation selectivity. Considering the HHV of biochar and dehydration capacity depend on ratio of H/C vs. O/C, the optimum reaction temperature of HTC was 200 °C, and the biochar from SCGs is an attractive biochar.

Since coastal wetlands have been severely degraded and polluted by human activities, they have increasingly become a significant source of greenhouse gases (GHGs), so understanding the characteristics of their emissions is critical for devising future climate change mitigation strategies. This study modified a model based on carbon balance to forecast carbon stored and CO₂, CH₄ emissions in four types of typical tidal flats—Phragmites australis (PA), Spartina alterniflora (SA), Suaeda japonica (SJ), and Bare Tidal Flat (BTF) in Korea’s Ganghwa province from 2017 to 2047. The model was built using biomass data from salt plant species collected in different locations. The results indicate that the total annual simulated flow of CH₄ increased over time in all four areas, most notably in SA, while CO₂ remained relatively stable. The mean CO₂ and CH₄ fluxes in the four types of representative tidal flats were in the range of 0.03 to 19.1 mg m⁻² d⁻¹ and 0.007 to 5.23 mg m⁻² d⁻¹, respectively, across all seasons. Besides, the results indicate that the amount of carbon accumulated in the top soil increases linearly over time in nearly all areas studied, ranging from 0.01 to 0.13 (kgC m⁻² yr⁻¹). In general, the study provides a model for Korean tidal flats that incorporates carbon storage and GHG emissions in the intertidal zone in order to develop potential GHG reduction scenarios.

Recently, incinerators have been shifted to underground complexes because of concerns regarding environmental pollution and declining land prices. In Korea, an underground waste incinerator has been built for the first time, with additional construction being expected in the near future. Therefore, a perception survey was conducted to acquire responses from South Korean experts regarding the impact of underground complex incinerators. The Q-methodology was used in the survey to examine various viewpoints. Academicians showed concerns regarding environmental effects of ground incinerators, and environmental and economic effects of underground complex incinerators; conversely, industrialists were concerned about civil complaints and administrative processing, indicating that the academicians were more concerned about scientific issues, whereas the industrialists were more concerned about democratic issues. Furthermore, both groups expressed concerns regarding land value and civil complaints of ground incinerators, safety issues and resultant social distrust of underground incinerators. The findings suggest that, to address the safety issues involving underground incinerator construction, governance by local experts is required for a holistic evaluation of environmental issues and economic feasibility of underground incinerators. To establish a link between science and democracy, measures for transparently sharing information are necessary.

Although operators periodically measure the sludge volume index (SVI) to stabilize the bioreactor and solid–liquid separation during the wastewater treatment process, there is a problem of inconsistency attributed to the subjective judgment of the operator. This study aims to investigate the possibility of securing objective data by employing CdS (cadmium–sulfur) photoresistors for SVI measurements. The sedimentation velocity of settling sludge was measured using LED (Light Emitting Diode) lights at the same level as the installed CdS photoresistors. As a result of the experiment, the settling velocity of sludge in the CdS photoresistors’ installation position H1 to H8 (non-flocculent settling), H9 to H12 (discrete flocculent settling) and H13 to H18 (zone settling and compressive settling), was 0.594 mm/s, 0.180 mm/s and 0.056 mm/s, respectively. Through this study, it was confirmed that measuring sludge sedimentation using the CdS photoresistors is possible. If the measurement of solid matter in sludge using several sludge sedimentation measurements is enabled in the future, it will be possible to develop calculation algorithms to measure the SVI.