Can the biological stage of a mechanical-biological treatment plant that is designed for mixed municipal solid waste be successfully utilized for effective composting of selectively collected biowaste?

Detecting and sourcing GHGs and atmospheric trace gases in a municipal waste treatment plant using coupled chemistry and isotope compositions

Landfill operations and waste processing facilities are important and highly heterogeneous sources of both greenhouse gases (GHGs) and non-GHG air pollutants in the atmosphere. This arises the need for detailed apportionment of waste sources in order to locate and subsequently reduce emissions from landfills. Here, a time series of in situ measurements of atmospheric trace gases and spatial allocation of specific emission source types under different processing phases and environmental conditions were conducted in and in the surroundings of a Municipal Solid Waste Treatment Plant (MSWTP) in south-western Poland. Results revealed that several individual GHG sources dominated across the waste processing facility and that GHGs concentrations displayed spatial seasonality. An increase in the ground-level CH4 concentrations, from ∼ 30.3 to 56.3 ppmv, was observed close (∼5 - 10 m) to the major emission sources within the MSWTP. While hotspot areas generally yielded elevated CH4 concentrations near the soil surface, these were relatively low (2.4 to 8.9 ppmv) along the facility's fence line. The study of the corresponding δ13C delineated the extent of dispersion plumes downwind emission hotspots, characterized by a 13C depletion (around 4.0 ‰) in the atmospheric CH4 and CO2. For CH4, emissions were isotopically discriminated between the extraction wells at active quarters/cells (δ13C = -58.3 ± 1.1 ‰) and biogas produced in the biological waste treatment installation (δ13C = -62.7 ± 0.7 ‰). Most of the trace compounds (non-methane hydrocarbons, halocarbons, oxygen-bearing organic gases, ketones, nitrogenous and sulphurous gases, and other admixture compounds) detected at the ground surface were linked to the CH4- and CO2-rich spots. Despite the relatively high variability in the concentrations of organic and inorganic compounds observed at the MSWTP active zones, our results suggest that they do not have a meaningful impact on the surrounding air quality.

Evaluation of the biodegradability of hazardous industrial solid waste: Study of key parameters

The biological stability of solid waste is one of the main problems related to the environmental impact of landfills and their long-term emission potential. Current European legislation (European Landfill Directive, EC/99/31) introduced the need to reduce biodegradable organic compounds deposited in landfills; however, it set neither official parameters nor methods to define the stability of such a waste. In Spain, biodegradability is generally evaluated using the biological oxygen demand/chemical oxygen demand (BOD5/COD) ratio, measuring it on the leachate, thus not considering the non-soluble fraction and therefore creating false negatives. To solve this problem, the biodegradability of hazardous industrial waste has been determined by measuring its respirometric activity (AT4). Our results show that the measure of the AT4 is independent of the enrichment with a microbial inoculum, and a sample size no higher than 20 g could be a reasonable value for a sensitive biodegradability determination. The highest respirometric index is obtained in waste with pH values between 6.5 and 10.5. Furthermore, respirometric biodegradability values are independent of traditional parameters of organic matter characterization such as BOD5/COD ratio, volatile content, and total and dissolved organic carbon. Consequently, the AT4 parameter provides new information on the composition and stability of organic matter in hazardous industrial waste. Its incorporation into pre-disposal waste characterization protocols allows to identify waste that exceeds recommended biodegradability thresholds. This approach ensures that only waste meeting specified biodegradability standards is deposited, avoiding landfill emissions and related environmental impacts, and thereby improving the overall effectiveness and sustainability of waste management practices.

A systematic review of coastal zone integrated waste management for sustainability strategies

Coastal areas stand out because of their rich biodiversity and high tourist potential due to their privileged geographical position. However, one of the main problems in these areas is the generation of waste and its management, which must consider technical and sustainable criteria. This work aims to conduct a systematic review of the scientific literature on integrated solid waste management (ISWM) by considering scientific publications on the scientific basis for the proposal of sustainability strategies in the context of use and efficiency. The overall method comprises i) Search strategy, merging and processing of the databases (Scopus and Web of Science); ii) Evolution of coastal zone waste management; iii) Systematic reviews on coastal landfills and ISWM in the context of the circular economy; and iv) Quantitative synthesis in integrated waste management. The results show 282 studies focused on coastal landfills and 59 papers on ISWM with the application of circular economy criteria. Systematic reviews allowed for the definition of criteria for the selection of favorable sites, such as i) sites far from the coastline, ii) impermeable soils at their base to avoid contamination of aquifers, iii) use of remote sensing and geographic information system tools for continuous monitoring, iv) mitigation of possible contamination of ecosystems, v) planning the possibility of restoration (reforestation) and protection of the environment. In coastal zones, it is necessary to apply the ISWM approach to avoid landfill flooding and protect the marine environment, reducing rubbish and waste on beaches and oceans. Therefore, applying the circular economy in ISWM is critical to sustainability in coastal environments, with the planet's natural processes and variations due to climate change.

The effect of biological methods for MSW treatment on the physicochemical, microbiological and phytotoxic properties of used biofilter bed media

Biofilters are commonly used in municipal solid waste treatment (MSW) facilities to remove odors and pollutants from process gases. However, the effectiveness of biofilter bed media decreases over time, necessitating periodic replacement. The type of the treatment process may affect the lifespan of the bed and the way it should be utilized after replacement. This study aimed to analyze the physical, chemical, calorific, microbiological, and phytotoxic parameters of bed media in biofilters operated at an industrial scale in MSW treatment plants. The experiments included three full cycles of biofiltering gases from biodrying, composting, and aerobic biostabilization in two variations. Physicochemical properties (moisture, organic matter, carbon, nitrogen, sulfur, heavy metal contents), respiration activity (AT4), phytotoxicity, and microorganism abundance were determined for initial materials and samples from two biofilter layers collected after each cycle. Results revealed a substantial reduction in AT4 (by 63%-87% compared to initial material), significant moisture content increase in the bottom layers (by 61% or more, depending on the process), and a considerable decrease in microorganism abundance. Biofilter bed media from biodrying and composting exhibited low environmental risk (low heavy metal concentrations, negligible phytotoxicity, and microbiological stability). However, bed packings from aerobic biostabilization processes showed significant inhibition of indicator plants and incomplete sanitization (presence of pathogens like E. coli and Salmonella spp.). Therefore, these bed packings can be utilized for energy recovery, such as incineration after drying. This research provides significant insights into the effectiveness and safety of biofilter bed media in MSW treatment plants.

Efficiency of biological and mechanical-biological treatment plants for MSW: The case of Spain

Biological and mechanical biological treatment plants combine mechanical and biological treatments to recover the greatest possible amount of materials from municipal solid waste (MSW) and biostabilize the organic fraction to be landfilled or applied in land. These plants handle a high percentage of the MSW generated in Europe. This work presents an exhaustive analysis of the existing plants in Spain which evaluates their typology as well as their performance. In Spain, 137 plants, which receive 13 Mt/year of waste, provide the country with total coverage. Twenty-two types of plants have been identified and grouped into six categories. There are four categories that receive mixed MSW: 1) sorting plants; 2) recovery and composting plants; 3) biodrying and recovery plants; and 4) recovery, biomethanation and composting plants and two that receive separately collected biowaste: 5) composting plants, and 6) biomethanation and composting plants. In plants that receive mixed waste, around 5% of the total input is recovered as recyclable materials (662,182 t/year), of which 29% corresponds to plastics, 27% to metals, and 27% to paper and cardboard. In addition, biostabilized material and/or biogas, and rejects (45-77% of the input) are obtained. In the biowaste plants, high-quality compost (more than 105,000 t/year), a higher biogas yield (43.60 Nm3/t·year) and a lower proportion of rejects (around 29%) are obtained.