Turning waste management into a carbon neutral activity: Practical demonstration in a medium-sized European city

Municipal solid waste management instruments that influence the use of the refuse as fuel in developing countries: A critical review

Landfills are the destination of most of the refuse generated whereas composting, material recycling, and Waste-to-Energy (WtE) technologies are not commonly employed in developing countries. However, the destination for energy purposes could be supplied with this refuse, improving the viability of energy use. Thus, this article raises some questions to identify aspects that could encourage its use as refuse-derived fuel (RDF) in these countries. Among them, does environmental education affect the municipal solid waste (MSW) source separation with emphasis on a destination? Can selective collection and extended producer responsibility (EPR) affect the MSW for energy recovery? Is there competition between the recycling market and the energy market for RDF? A systematic review of the literature was conducted to gather data and provide answers to such questions. This enabled to observe that EPR, selective collect expansion and source separation influence the quantity and quality of waste sent for energy use. Both internal and external factors impact on source separation. Additionally, there is evidence to support that despite several studies showing their technical, economic, environmental and social viability, the methods of energy usage of the refuse still need to improve their deployment in developing countries. In addition to identifying the main research gaps to be filled in future studies, the article also identified the instruments of MSW management that are to be applied in developing countries to divert recyclable and organic waste from landfill.

Life-cycle economic and environmental impacts of municipal solid waste reverse logistics in residential areas

The economic and environmental impacts of the reverse logistics (RL) process (including drop-off, collection and transportation [C&T]) of the waste disposal chain are becoming increasingly prominent with the increasing generation of municipal solid waste (MSW) and promotion of MSW classification. Quantitative evaluation of this process from economic and environmental perspectives is of great significance for MSW management. This study focused on the financial capital, materials, and energy consumption in the RL process in Xi an City, China. Based on field investigation, the magnitude of pollutant emissions from MSW C&T vehicles over their life cycle was predicted using the GREET software and total RL life-cycle cost and life-cycle assessment were analyzed. The results showed that the finical costs of RL were $46.35-$49.03 per ton of food waste and $62.52-$88.84 per ton of residual waste; the environmental impacts caused by the RL process accounted for 79.24%-96.00% and 20.87%-68.55% of the entire food waste and residual waste management chains, respectively. Labor costs were the biggest financial expenditure and the fuel cycle of C&T vehicles caused the majority of the environmental impacts. Source-separated waste management scenarios represented more environmental benefits but poorer economic positions. In the future, improving MSW source-separation accuracy, replacing diesel C&T vehicles with electric ones, and optimizing the RL system could reduce the environmental and economic impacts of the entire waste management system.

Life cycle assessment of end-of-life options for cellulose-based bioplastics when introduced into a municipal solid waste management system

The partial degradation of cellulose-based bioplastics in industrial treatment of organic fraction of Municipal Solid Waste (MSW) opened to the investigation of further disposal routes for bioplastics in the waste management system. For this purpose, the environmental footprint of three MSW management scenarios differing only for the bioplastics final destination (organic, plastic or mixed waste streams) was assessed through a Life Cycle Assessment (LCA) approach. Results revealed how the treatment of bioplastics with organic waste achieved the worst environmental performance (5.8 kg CO₂ eq/FU) for most impact categories. On the other hand, treatment with plastics and mixed waste achieved negative impact values (that mean avoided GHG emissions) of -9.8 and -7.7 kg CO₂ eq/FU respectively, showing comparable benefits from these scenarios. The key reason was the lower quality of compost obtained from the organic treatment route, which reduced the environmental credits achieved by the energy recovery during anaerobic digestion.

Urban Intelligence for Carbon Neutral Cities: Creating Synergy among Data, Analytics, and Climate Actions

Cities are critical research subjects in carbon neutrality, considering they produce more than 70% of greenhouse gas emissions and their crucial role in taking climate actions. The pathway towards a greener society requires consensus, intelligence, and actions among global cities as a network of carbon neutral cities (CNC). Considering cities as complex system-of-systems, synergy among various sub-systems can create co-benefits through the progress towards carbon neutrality. Large volume, velocity, and variety of urban data provide new opportunities for quantifying, analyzing, and visualizing environmental–social–technical dynamics in urban systems. Rich data resources, advanced analytics, and climate actions collectively enable urban intelligence by leveraging data from heterogeneous sources with different spatial granularity and temporal frequency. Such intelligence can promote synergy across sub-systems and domains to support more responsive, precise, proactive planning, policy, and managerial actions. With a discussion on future innovation in urban intelligence for CNC, this paper presents conclusions on how urban intelligence can promote a smarter and greener society.

Assessing Urban Metabolism through MSW Carbon Footprint and Conceptualizing Municipal-Industrial Symbiosis—The Case of Zaragoza City, Spain

This paper proposes a holistic vision of the urban metabolism (UM), viewing the city as a subsystem within an industrial ecosystem (IE) in which municipal-industrial symbiosis is essential to achieve sustainability goals. For this purpose, the metabolism of a large Spanish city, Zaragoza, was studied by analyzing the main fractions of its MSW. A methodology based on carbon footprint (CF) was developed to analyze the environmental impact—in terms of CO2—of the influence of households’ behavior, the City Council’s strategies, and the main MSW fractions. Zaragoza’s IE represents a footprint of 931,250 CO2 tons for the fractions studied, of which 438,000 CO2 tons are due to organic fraction, 180,371 to plastics and 154,607 to paper and cardboard, which are the three most significant contributors. If households selectively separated 100% of their waste, the footprint would drop to 648,660 tons of CO2. Furthermore, monetary savings were quantified through the CO2 emissions price. The proposed methodology accounts for the CF of the whole IE, not just the city. Moreover, it enables the creation of Sankey diagrams to visualize the distribution of emissions of each subsystem, highlighting the importance of cooperation between the city and its recycling industries to reduce its CF.

Sustainable municipal waste management strategies through life cycle assessment method: A review

Increasing amounts of municipal solid waste (MSW) has gained widely concern on reduction, utilization and minimizing environmental impacts associated with waste management. Life cycle assessment (LCA) has been used to evaluate total environmental impact of municipal waste management (MSWM) options in strategy-planning and decision-making process. The exiting LCA studies have covered a large range of detailed focus from waste treatment technology to applied modelling methods in LCA of MSWM, yet an important concern for stakeholders, the relationship between practical management strategies and their LCA results, has not been comprehensively summarized. This paper reviews recent LCA studies focusing on MSWM system in 45 cases from both developing and developed regions to promote evolution of the MSWM system through modification of waste management strategies. Selected literatures conducted LCA with system boundary covering the whole MSWM system rather than single treatment process or specific type of waste. This review has explored distribution and evolution of LCA studies in waste management field and summarized critical parameters (system boundary, functional unit, assessment approach and data uncertainty) for conducting LCA of MSWM system. Comparison results from 45 worldwide cases indicated 33%-154% environmental benefit in Global warming potential (GWP) impact with implement of integrated solid waste management system to replace single landfill, incineration, or open dumping treatment. Key issues with upgrading of MSWM system have been highlighted to raise concern, i.e., the importance of targeted management strategy on organic and recyclable waste, the growing contribution of waste collection and transportation to the total environmental impact, as well as promoting multi-impacts assessment for MSWM system to achieve environmentally effective, economically affordable, and socially acceptable. Rather than focus on technical factors, results from this study indicated the key influences from understanding local limitation, environmental concern, management chain and comprehensive impact, providing useful strategies on improving MSWM with generalization results of LCA studies.

A structured methodology to understand municipal waste generation at local level with minimized effort: development and case study

Understanding municipal solid waste (MSW) generation is a key requirement for designing and optimizing MSW collection services. The present contribution proposes a statistical methodology to identify MSW generation patterns from MSW collection records. The methodology aims at finding statistically distinct household waste generation patterns within the days of the week and within months (seasonal variation). It is based on standard statistical methods (ANOVA complemented by non-parametric tests and cluster analysis). The methodology was applied to a Portuguese neighbourhood to assist in the definition of a waste sampling campaign to support the implementation of a pilot PAYT. The results showed the existence of groups with statistically distinct MSW generation patterns both at the weekly and monthly time scales. Three clusters of days of the week, with high, medium and low generation, and two clusters of months, with high and low generation, were identified. These results allowed to design and implement a customized field waste sampling campaign to estimate the MSW generated at the study site with minimal field work. Instead of implementing a homogeneous sampling campaign (equal number of samples for every day of the week and for every month), the samples were collected from the days and months that showed statistically distinct MSW generation pattern. The systematic procedure can be easily adapted to any given location, thus being a useful tool that combines statistical analysis with field collected data.

Potential utilization of waste nitrogen fertilizer from a fertilizer industry using marine microalgae

This study investigated the feasibility of microalgal biomass production using waste nitrogen fertilizers (WNFs) generated by the Qatar Fertiliser Company (QAFCO). From the plant, three types of WNFs (WNF1, WNF2, and WNF3) were collected; WNF1 and WNF2 had high solubility (e.g., 1000 g/L) whereas WNF3 had low solubility (65 g/L). For a lower dosage (i.e., 100 mg N/L) of these WNFs, >98% of nitrogen was soluble in water for WNF1 and WNF2; however, 52 mg N/L was soluble for WNF3. Nitrogen content in these wastes was 44, 43, and 39% for WNF1, WNF2, and WNF3, respectively. As these WNFs were used as the sole nitrogen source to grow Tetraselmis sp., Picochlorum sp., and Synechococcus sp., Tetraselmis sp. could utilize all the three WNFs more efficiently than other two strains. The biomass yield of Tetraselmis sp. in a 100,000 L raceway pond was 0.58 g/L and 0.67 g/L for mixed WNFs (all WNF in equal ratio) and urea, respectively. The metabolite profiles of Tetraselmis sp. biomass grown using mixed WNFs were very similar to the biomass obtained from urea-added culture - suggesting that WNFs produced Tetraselmis sp. biomass could be used as animal feed ingredients. Life cycle impact assessment (LCIA) was conducted for six potential scenarios, using the data from the outdoor cultivation. The production of Tetraselmis sp. biomass in QAFCO premises using its WNFs, flue gas, and waste heat could not only eliminate the consequences of landfilling WNFs but also would improve the energy, cost, and environmental burdens of microalgal biomass production.