The Influence of Waste Composition on Landfill Gas Generation in a Pilot-Scale Lysimeter

Prediction of landfill gases concentration based on Grey Wolf Optimization - Support Vector Regression during landfill excavation process

In some areas, there is a phenomenon that the landfill is full or even over-capacity with the extension of the service period. With the aging and damage of the protective facilities, this phenomenon may have a more serious impact on the surrounding environment. It is necessary to excavate and transport the waste beyond the part to control it. This process will inevitably produce many landfill gas emissions, which will pollute the air. Therefore, it is necessary to predict and control the landfill gas. This study utilizes the Grey Wolf Optimization (GWO) algorithm to optimize Support Vector Regression (SVR). It establishes prediction models for various LFG concentrations based on previous LFG concentration data and real-time environmental monitoring data. The models are compared with traditional Support Vector Regression and Random Forest (RF) algorithms, predicting the concentrations of odor, ammonia, hydrogen sulfide, methane, and nitrogen oxides. The results indicate that GWO-SVR demonstrates more stable and accurate predictions across various LFG, with the coefficient of determination R2 approximately 10% higher than that of SVR and RF, and most other error metrics significantly lower. In contrast, SVR and RF show substantial errors in predicting odor, hydrogen sulfide, and nitrogen oxides. Thus, the GWO-SVR algorithm substantially improves the performance in predicting LFG concentrations, meeting the needs of on-site management.

Reprocessed construction and demolition waste as an adsorbent: An appraisal

Construction and Demolition (C&D) waste is solid wastes generated from the construction, demolition, and renovation activities that constitute almost 30-40 % of globally generated solid wastes. Improper disposal and management of these materials can cause negative impacts on the environment, economy, and human health. Most research on C&D waste is limited to reduction, recycling, and reuse of the wastes. However, there is no systematic review dedicated entirely to the applicability of C&D wastes as adsorbent for waste management. This review presents the utilization of C&D wastes-based adsorbents for removing contaminants from environmental matrices covering triple edge benefits in the viewpoints of waste treatment, solid waste management, and disposal. The properties, the capability of C&D waste adsorbents on contaminant removal, and the influence of various factors on the adsorptive removal is detailed. Further, the mechanisms involved in contaminant removal by C&D waste are summarized. The review revealed that, chemisorption is the prominent mechanism of contaminant removal by most C&D wastes. Among the three types of C&D waste reviewed; concrete-based adsorbents were the most efficient for contaminant removal. Limited studies are avaiable in the literature on binary and multiple contaminant systems, reusability studies, and high dependence on solution pH, therefore further studies are warrated. As C&D waste contain trace concentration of heavy metals and contaminants, its leaching potential at different pH levels and adsorbate concentration need to be conducted, which has been hitherto neglected. Finally, the approaches, obstacles, and potential solutions to build an industrially and economically efficient C&D adsorbent are discussed.

Waste to energy: a decision-making process for technology selection through characterization of waste, considering energy and emission in the city of Ahmedabad, India

Municipal solid waste (MSW) disposal has become major issue for the city of Ahmedabad, India. Development, concentrated population and economic growth have led to a substantial increase of MSW generation. Therefore, the objective of the study was to characterize MSW for selection of waste processing technology. To provide a solution for sustainable processing and for safe disposal of fresh MSW, Abellon Clean Energy Ltd joined forces with Ahmedabad Municipal Corporation (AMC) under Public-Private Partnership (PPP) to establish a 14.9MW advanced controlled combustion-based waste to energy (WTE) generation facility to process and dispose 1000 tons/day of fresh MSW. For waste characterization, samples (n=201) were collected from the Pirana waste dumping site using quadrate sampling method. A yearly weighted average Low Heating Value (LHV) of 9.85/kg and ash content 25.12% for unsegregated MSW makes controlled combustion with electricity generation an eligible technology. After combustion, the waste volume is reduced by 75%. The 14.9MW WTE facility replaces 417 t coal/day, reducing greenhouse gas (GHG) emissions of 300.38 tCO₂eq/day through coal replacement, while avoiding 735.24 t CO₂eq/day on account of landfill emissions from MSW dumping. Waste to energy is the fastest solution to reduce waste volume by generating electricity through reduction of GHG.

Physical process to sort construction and demolition waste (C&DW) fines components using process water

Modern societies are generating considerable volume of Construction and Demolition Wastes (C&DW) annually. Most recycling facilities offers viable sorting and recycling options for the coarser particles of the different materials found in those wastes. However, usual dry mechanical sorting and human sorting are not efficient on C&DW fines particles (C&DF, <10 mm) representing the third of the C&DW produced and being composed of similar materials. Recent environmental issues related to the landfilling of C&DF have pointed out the need to develop innovative alternative and adapted recycling paths for the C&DF. This study presents an efficient sorting process train based on physical separation steps used in the mining and the soil treatment industries. The use and recirculation of process water allowed to segregate and concentrate the gypsum from the 2-12 mm C&DF into a specific fraction (55-65% gypsum content) representing 40% of the total mass. Other constituents were sorted based on their relative density, size and shapes; thanks to hydraulic classification and physical sorting forming four more fractions with high recycling potential: coarse aggregates (15%), fine aggregates (9.4%), organic and inorganic fibers (10.8%) and light organic compounds (24.8%). The process has been designed to be integrated in existing sorting facilities and the process costs were evaluated to 38 CAN$/t.

Chemical and olfactive impacts of organic matters on odor emission patterns from the simulated construction and demolition waste landfills

The explosive increase of construction and demolition waste (CDW) caused the insufficient source separation and emergency disposal at domestic waste landfills in many developing countries. Some organic fractions were introduced to the CDW landfill process and resulted in serious odor pollution. To comprehensively explore the impacts of organic matters on odor emission patterns, five CDW landfills (OIL), with organic matters/ inert CDW components (O/I) from 5% to 30%, and the control group only with inert components (IL) or organics (OL) were simulated at the laboratory. The chemical and olfactive characters of odors were evaluated using the emission rate of 94 odorants content (ER_total), theory odor concentration (TOC_total), and e-nose concentration (ER_ENC), and their correlations with waste properties were also analyzed. It was found that the main contributors to ER_total (IL: 93.0% NH₃; OIL: 41.6% sulfides, 31.0% NH₃, 25.9% oxygenated compounds) and TOC_total (IL: 64.1% CH₃SH, 28.2% NH₃; OIL: 71.7% CH₃SH, 24.8% H₂S) changed significantly. With the rise of O/I, ER_total, TOC_total, and ER_ENC increased by 10.9, 20.6, and 2.1 times, respectively. And the organics content in CDW should be less than 10% (i.e., DOC<101.3 mg/L). The good regressions between waste properties (DOC, DN, pH) and ER_ENC- (r=0.86, 0.86, -0.88, p<0.05), TOC_total- (r=0.82, 0.79, -0.82, p<0.05) implied that the carbon sources and acidic substances relating to organics degradation might result in that increase. Besides, the correlation analysis results (ER_ENC-vs.TOC_total-, r=0.96, p<0.01; vs.ER_total-, r=0.86, p<0.05) indicated that e-nose perhaps was a reliable odor continuous monitoring tool for CDW landfills.

A Review of Lysimeter Experiments Carried Out on Municipal Landfill Waste

The groundwater risk assessment in the vicinity of landfill sites requires, among others, representative monitoring and testing for pollutants leaching from the waste. Lysimeter studies can serve as an example of dynamic leaching tests. However, due to the bacteriological composition of the municipal waste, they are rarely carried out. These tests allow for the proper design of the landfill protection system against migration of pollutants into the ground, assessment of bacteriological, biochemical and chemical risk for the groundwater, determination of the water balance of leachate as well as examination of the course of processes taking place in the waste landfill with a diversified access to oxygen. This paper addresses the issue of performing lysimeter studies on a sample of municipal waste in various scientific centers. It analyzes the size of lysimeters, their construction, the method of water supply, the duration of the experiment, the scope of research, and the purpose of lysimeter studies.