This work presents the enforcement performance of recent Haulien County, Taiwan municipal solid waste (MSW) recycling management programs. These programs include: Mandatory Refuse Sorting and Recycling, Diverse Bulk Waste Reuse, Pay-as-you-Discharge, Total Food Waste Recycling, Restricted Use on Plastic Shopping Bags & Plastic Tableware, Recycling Fund Management, and Ash Reuse. These programs provide incentives to reduce the MSW quantity growth rate. It was found that the recycled material fraction of MSW generated in 2001 was from 6.8%, but was 32.4% in 2010 and will increase stably by 2-5% yearly in the near future. Survey data for the last few years show that only 2.68% (based on total MSW generated) of food waste was collected in 2001. However, food waste was up to 9.7 % in 2010 after the Total Food Waste Recycling program was implemented. The reutilization rate of bottom ash was 20% in 2005 and up to 65% in 2010 owing to Ash Reuse Program enforcement. A quantified index, the Total Recycle Index, was proposed to evaluate MSW management program performance. The demonstrated county will move toward a zero waste society in 2015 if the Total Recycle Index approaches 1.00. Exact management with available programs can lead to slow-growing waste volume and recovery of all MSW.
This study explores the influence of the chemical composition (SiO(2), CaO, Fe(2)O(3), and Al(2)O(3)) of incinerator bottom ash on its friction angle. Direct shear tests were performed to measure the strength of bottom ash with two distinctly different compositions. Then, an empirical equation was regressed to determine the correlation between each composition and the friction angle. The experimental results showed that the main constituent material of the incinerator bottom ash from general municipal wastes is SiO(2), and the friction angle is 48.04°-52.66°. The bottom ash from incineration plants treating both municipal wastes and general industrial wastes has a high content of iron-aluminum oxides, and its friction angle is 44.60°-52.52°. According to the multivariate regression analysis result, the friction angle of bottom ash of any composition is influenced mainly by the Fe(2)O(3) and Al(2)O(3) contents. This study used the friction angle of the bottom ash from four different incineration plants to validate the empirical equation, and found that the error between actual friction angles and the predicted values was -1.36% to 5.34%. Therefore, the regressed empirical equation in this study can be employed in engineering applications to preliminarily identify the backfill quality of incinerator bottom ash.
A sensor unit was placed online in the particle stream produced by an eddy current separator (ECS) to investigate its functionality in non-ferrous metals recovery. The targeted feed was the 1-6mm size fraction bottom ash from a municipal waste incinerator. The sensor unit was attached to the ECS splitter, where it counted in real-time metal and mineral particles and accurately measured the grade of the stream in the metals product. Influence of segregation (e.g. due to particle size or density) on the metals concentrate were detected and studied using the sensor data collected at different splitter distances. Tests were performed in the laboratory and in a bottom ash processing plant with two different types of ECS and two sources of bottom ash with different moisture content. The measured metal grades matched the manual analyses with errors 0%, 1.5% and 3.1% for moist, dry and very wet feed, respectively. For very wet feed the ECS metals recovery dropped, which was observed from the strongly reduced particle counts and the large changes in cumulative particle properties. The measured sample proved representative for the whole metals concentrate if it is collected at a representative position within the metals particle trajectory fan produced by the ECS. ECS-performance proved sensitively dependent on splitter distance, since a 10mm shift may result in 10% change in metal recovery and 18% change in grade. The main functionalities of the sensor unit are determined as online quality control and facilitation of automatic control over the ECS splitter distance. These functionalities translate in significant improvements in ECS metals recovery which in turn is linked to economic benefits, increased recycling rate of scrap metals and a further reduction of the ecological drawbacks of incinerator bottom ash.
The objective of this study is to discuss the role of networks formed of waste-picker cooperatives in ameliorating problems of final disposal of solid waste in the city of Rio de Janeiro, since the city’s main landfill will soon have to close because of exhausted capacity. However, it is estimated that in the city of Rio de Janeiro there are around five thousand waste-pickers working in poor conditions, with lack of physical infrastructure and training, but contributing significantly by diverting solid waste from landfills. According to the Sustainable Development Indicators (IBGE, 2010a,b) in Brazil, recycling rates hover between 45% and 55%. In the municipality of Rio de Janeiro, only 1% of the waste produced is collected selectively by the government (COMLURB, 2010), demonstrating that recycling is mainly performed by waste-pickers. Furthermore, since the recycling market is an oligopsony that requires economies of scale to negotiate directly with industries, the idea of working in networks of cooperatives meets the demands for joint marketing of recyclable materials. Thus, this work presents a method for creating and structuring a network of recycling cooperatives, with prior training for working in networks, so that the expected synergies and joint efforts can lead to concrete results. We intend to demonstrate that it is first essential to strengthen the waste-pickers' cooperatives in terms of infrastructure, governance and training so that solid waste management can be environmentally, socially and economically sustainable in the city of Rio de Janeiro.
The economic and environmental impact of several waste-to-energy (WtE) schemes to produce electricity from municipal solid waste (MSW) refuse is evaluated and compared with landfill disposal. Both incineration and gasification alternatives are considered. The gasification option includes three different configurations: (1) a fluidized bed gasifier (FBG) with internal combustion engine (ICE), (2) a FBG with organic Rankine cycle (ORC) and (3) a grate gasifier with steam Rankine cycle (SRC). The study is primarily applied to regions where the management system is based on Mechanical Biological Treatment (MBT) plants, generating a large share of refuse (>70%), which is currently landfilled. The specific case of Andalusia, a region in the south of Spain with 23 MBT plants distributed over a region of 87.000 km2, where about 80% of municipal solid waste (MSW) is currently landfilled, is taken as main reference; thereafter, the study is further extended to preliminary assess other regions of some European landfill-dominated countries with similar characteristics. The results show that both incineration and gasification improve landfill disposal, contributing favorably to greenhouse gas (GHG) reduction and fulfilling EU environmental regulations, although the three gasification options analyzed yield lower GHG emissions than incineration. In addition, gasification enables better integration of WtE into existing MBT plants, especially in the particular case of Andalusia, where MBT plants are widespread on the region, making it a more promising option than incineration, which is mainly based on large centralized plants, and less socially accepted. From the options analyzed, the WtE scheme based on FBG with ICE gives the highest profitability for a given gate fee, due to much higher electrical efficiency. However, FBG with ORC seems to be a better option in the short-term for landfill-dominated countries, due to its higher technical reliability and the low gate fee currently available in these countries.
Cities are a key system in anthropogenic phosphorus (P) cycling because they concentrate both P demand and waste production. Urban agriculture (UA) has been proposed as a means to improve P management by recycling cities' P-rich waste back into local food production. However, we have a limited understanding of the role UA currently plays in the P cycle of cities or its potential to recycle local P waste. Using existing data combined with surveys of local UA practitioners, we quantified the role of UA in the P cycle of Montreal, Canada to explore the potential for UA to recycle local P waste. We also used existing data to complete a substance flow analysis of P flows in the overall food system of Montreal. In 2012, Montreal imported 3.5 Gg of P in food, of which 2.63 Gg ultimately accumulated in landfills, 0.36 Gg were discharged to local waters, and only 0.09 Gg were recycled through composting. We found that UA is only a small sub-system in the overall P cycle of the city, contributing just 0.44% of the P consumed as food in the city. However, within the UA system, the rate of recycling is high: 73% of inputs applied to soil were from recycled sources. While a Quebec mandate to recycle 100% of all organic waste by 2020 might increase the role of UA in P recycling, the area of land in UA is too small to accommodate all P waste produced on the island. UA may, however, be a valuable pathway to improve urban P sustainability by acting as an activity that changes residents' relationship to, and understanding of, the food system and increases their acceptance of composting.
The intentional use of mercury (Hg) in products and processes (‘commercial Hg’) has contributed a large and previously unquantified anthropogenic source of Hg to the global environment over the industrial era, with major implications for Hg accumulation in environmental reservoirs. We present a global inventory of commercial Hg uses and releases to the atmosphere, water, soil, and landfills from 1850 to 2010. Previous inventories of anthropogenic Hg releases have focused almost exclusively on atmospheric emissions from ‘by-product’ sectors (e.g., fossil fuel combustion). Cumulative anthropogenic atmospheric Hg emissions since 1850 have recently been estimated at 215 Gg (only including commercial Hg releases from chlor-alkali production, waste incineration, and mining). We find that other commercial Hg uses and non-atmospheric releases from chlor-alkali and mining result in an additional 540 Gg Hg released to the global environment since 1850 (air: 20%, water: 30%, soil: 30%, landfills: 20%). Some of this release has been sequestered in landfills and benthic sediments, but 310 Gg actively cycles among geochemical reservoirs and contributes to elevated present-day environmental Hg concentrations. Commercial Hg use peaked in 1970 and has declined sharply since. We use our inventory of historical environmental releases to force a global biogeochemical model that includes new estimates of the global burial in ocean margin sediments. Accounting for commercial Hg releases improves model consistency with observed atmospheric concentrations and associated historical trends.
Environmental policies in the European Union focus on the prevention of hazardous waste and aim to mitigate its impact on human health and ecosystems. However, progress is promoting a shift in perspective from environmental impacts to resource recovery. Municipal solid waste incineration (MSWI) has been increasing in developed countries, thus the amount of air pollution control residues (APCr) and fly ashes (FA) have followed the same upward trend. APCr from MSWI is classified as hazardous waste in the List of Waste (LoW) and as an absolute entry (19 01 07*), but FA may be classified as a mirror entry (19 0 13*/19 01 14). These properties arise mainly from their content in soluble salts, potentially toxic metals, trace organic pollutants and high pH in contact with water. Since these residues have been mostly disposed of in underground and landfills, other possibilities must be investigated to recover secondary raw materials and products. According to the literature, four additional routes of recovery have been found: detoxification (e.g. washing), product manufacturing (e.g. ceramic products and cement), practical applications (e.g. CO2 sequestration) and recovery of materials (e.g. Zn and salts). This work aims to identify the best available technologies for material recovery in order to avoid landfill solutions. Within this scope, six case studies are presented and discussed: recycling in lightweight aggregates, glass-ceramics, cement, recovery of zinc, rare metals and salts. Finally, future perspectives are provided to advance understanding of this anthropogenic waste as a source of resources, yet tied to safeguards for the environment.
Raw materials were co-sintered with municipal solid waste incineration (MSWI) fly ash through iron ore sintering to promote the safe treatment and utilization of MSWI fly ash. To assess the feasibility of this co-sintering method, in this study, the effects of the addition of MSWI fly ash on the formation and emission of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) were estimated via iron ore sintering pot experiments. During co-sintering, most of the PCDD/Fs in the added MSWI fly ash were decomposed and transformed into PCDD/Fs associated with iron sintering, and the concentrations of lower- and mid-chlorinated congeners increased. As there was a sufficient chlorine source and the sintering bed permeability was decreased by the addition of MSWI fly ash, the PCDD/F concentration in the exhaust gas increased. The mass emission of PCDD/Fs decreased; however, the emission of toxic PCDD/Fs increased beyond the total emissions from the independent MSW incineration and iron ore sintering processes due to the transformation of PCDD/F congeners. The co-sintering may be an important solution after technological improvements in the flue gas cleaning system and PCDD/F formation inhibition procedures.
In Europe over 5.25 billion tonnes of waste has been landfilled between 1995 and 2015. Among this large amount of waste, plastic represents typically 5-25 wt% which is significant and has the potential to be recycled and reintroduced into the circular economy. To date there is still however little information available of the opportunities and challenges in recovering plastics from landfill sites. In this review, the impacts of landfill chemistry on the degradation and/or contamination of excavated plastic waste are analysed. The feasibility of using excavated plastic waste as feedstock for upcycling to valuable chemicals or liquid fuels through thermochemical conversion is also critically discussed. The limited degradation that is experienced by many plastics in landfills (>20 years) which guarantee that large amount is still available is largely due to thermooxidative degradation and the anaerobic conditions. However, excavated plastic waste cannot be conventionally recycled due to high level of ash, impurities and heavy metals. Recent studies demonstrated that pyrolysis offers a cost effective alternative option to conventional recycling. The produced pyrolysis oil is expected to have similar characteristics to petroleum diesel oil. The production of valuable product from excavated plastic waste will also increase the feasibility of enhanced landfill mining projects. However, further studies are needed to investigate the uncertainties about the contamination level and degradation of excavated plastic waste and address their viability for being processed through pyrolysis.