Effective waste management is a major challenge for Small Island Developing States (SIDS) like Maldives due to limited land availability. Maldives exemplifies these issues as one of the most geographically dispersed c...Effective waste management is a major challenge for Small Island Developing States (SIDS) like Maldives due to limited land availability. Maldives exemplifies these issues as one of the most geographically dispersed countries, with a population unevenly distributed across numerous islands varying greatly in size and population density. This study provides an in-depth analysis of the unique waste management practices across different regions of Maldives in relation to its natural and socioeconomic context. Data shows Maldives has one of the highest population density and per capita waste generation among SIDS, despite its small land area and medium GDP per capita. Large disparities exist between the densely populated capital Male’ with only 5.8 km2 area generating 63% of waste and the ~194 scattered outer islands with ad hoc waste management practices. Given Male’s dense population and high calorific waste, incineration could generate up to ~30 GW/a energy and even increase Maldives’ renewable energy supply by 200%. In contrast, decentralized anaerobic digestion presents an optimal solution for outer islands to reduce waste volume while providing over 40%–100% energy supply for daily cooking in local families. This timely study delivers valuable insights into designing context-specific waste-to-energy systems and integrated waste policies tailored to Maldives’ distinct regions. The framework presented can also guide other SIDS facing similar challenges as Maldives in establishing sustainable, ecologically sound waste management strategies.展开更多
Under optimal process conditions,pyrolysis of polyolefins can yield ca.90 wt%of liquid product,i.e.,combination of light oil fraction and heavier wax.In this work,the experimental findings reported in a selected group...Under optimal process conditions,pyrolysis of polyolefins can yield ca.90 wt%of liquid product,i.e.,combination of light oil fraction and heavier wax.In this work,the experimental findings reported in a selected group of publications concerning the non-catalytic pyrolysis of polyolefins were collected,reviewed,and compared with the ones obtained in a continuously operated bench-scale pyrolysis reactor.Optimized process parameters were used for the pyrolysis of waste and virgin counterparts of high-density polyethylene,low-density polyethylene,polypropylene and a defined mixture of those(i.e.,25:25:50 wt%,respectively).To mitigate temperature drops and enhance heat transfer,an increased feed intake is employed to create a hot melt plastic pool.With 1.5 g·min^(-1) feed intake,1.1 L·min^(-1) nitrogen flow rate,and a moderate pyrolysis temperature of 450℃,the formation of light hydrocarbons was favored,while wax formation was limited for polypropylene-rich mixtures.Pyrolysis of virgin plastics yielded more liquid(maximum 73.3 wt%)than that of waste plastics(maximum 66 wt%).Blending polyethylenes with polypropylene favored the production of liquids and increased the formation of gasoline-range hydrocarbons.Gas products were mainly composed of C3 hydrocarbons,and no hydrogen production was detected due to moderate pyrolysis temperature.展开更多
Waste is a valuable secondary carbon resource.In the linear economy,it is predominantly landfilled or incinerated.These disposal routes not only lead to diverse climate,environmental and societal problems;they also re...Waste is a valuable secondary carbon resource.In the linear economy,it is predominantly landfilled or incinerated.These disposal routes not only lead to diverse climate,environmental and societal problems;they also represent a loss of carbon resources.In a circular carbon economy,waste is used as a secondary carbon feedstock to replace fossil resources for production.This contributes to environmental protection and resource conservation.It furthermore increases a nation’s independence from imported fossil energy sources.China is at the start of its transition from a linear to circular carbon economy.It can thus draw on waste management experiences of other economies and assess the opportunities for transference to support its development of‘zero waste cities’.This paper has three main focuses.First is an assessment of drivers for China’s zero waste cities initiative and the approaches that have been implemented to combat its growing waste crisis.Second is a sharing of Germany’s experience-a forerunner in the implementation of the waste hierarchy(reduce-reuse-recycle-recover-landfill)with extensive experience in circular carbon technologies-in sustainable waste management.Last is an identification of transference opportunities for China’s zero waste cities.Specific transference opportunities identified range from measures to promote waste prevention,waste separation and waste reduction,generating additional value via mechanical recycling,implementing chemical recycling as a recycling option before energy recovery to extending energy recovery opportunities.展开更多
Landfill gas(LFG)generation is commonly modeled by using a first-order model.Methane generation potential(L0)and methane generation rate constant(k)are two key parameters in the first-order model.Coal-ash based defaul...Landfill gas(LFG)generation is commonly modeled by using a first-order model.Methane generation potential(L0)and methane generation rate constant(k)are two key parameters in the first-order model.Coal-ash based default values or roughly analyzed values often used in China may not be appropriate for accurately estimating of LFG generation.In this study,seven groups of parameters were evaluated by comparing the theoretical predictions with real measurements from five Chinese landfills.The optimal approach for calculating L0 is the use of site-specific waste composition and the default values of degradable organic carbon(DOC)reported by the Chinese industry standard(CJJ133-2009),and the matching k can be adjusted by fitting and regression.The optimized average values were L0=67 m3 Mg−1,k=0.06 per year for landfills in Beijing and Zhengzhou in cold–dry regions,L0=69 m3 Mg−1,k=0.16 per year for landfill in Shanghai in cold–wet region,and L0=64 m3 Mg−1,k=0.21 per year for landfills in Guangzhou and Shenzhen in hot–wet regions.Monte Carlo analysis showed that the uncertainty of LFG generation at closure year varied in−22.5%to 20.5%,−17.1%to 17.1%and−28.2%to 34.7%for three climatic regions,respectively.The k value is the key influencing factor,with a 95.6%contribution ratio in the hot–wet region landfill.The results provide references for future better waste management.展开更多
Municipal solid waste(MSW)generation and characterization are the basic inputs for waste handling and treatment systems design.In present research,we performed waste characterization investigations in Visakhapatnam(In...Municipal solid waste(MSW)generation and characterization are the basic inputs for waste handling and treatment systems design.In present research,we performed waste characterization investigations in Visakhapatnam(India),using a waste characterization methodology by integrating two standard sampling and characterization approaches.The characterization methodology was designed by combining seasonal variations,source,and socio-economic stratifications.Source-based sampling was performed at household(s),dumpster(s),transfer station,and landfill.Socio-economic-based sampling was performed based on the zone classification of the city.Three sampling campaigns were conducted to identify the waste composition based on seasonal variations.Studies aimed to perform stratified characterization of waste and assess chemical characteristics of the mixed waste fractions to evaluate waste-to-energy potential.Results indicate that the amount of MSW generated in the city is 1250±100 tons/day,with a generation rate of 0.65 kg/capita/day.Based on source stratification,organic matter(45.5%±6.5%)is a major component followed by inert waste.The paper,plastic,and textile components amount to 25%of overall waste.From seasonal studies,organic matter was higher in pre-monsoon(42%)compared to winter(39%).The moisture content of MSW varied between 30%and 35%and volatile solids between 39%and 43%.The calorific value was determined to be between 5680-7110 kJ/kg.Outlined the limitations and potential errors associated with sampling and waste characterization.Biochemical and thermal conversion treatment alternatives for processing,treatment,and handling were discussed.The findings of this research would assist regulatory bodies and city councils to formulate policy directives on waste sampling,characterization,segregation,education,and awareness campaigns.展开更多
文摘Effective waste management is a major challenge for Small Island Developing States (SIDS) like Maldives due to limited land availability. Maldives exemplifies these issues as one of the most geographically dispersed countries, with a population unevenly distributed across numerous islands varying greatly in size and population density. This study provides an in-depth analysis of the unique waste management practices across different regions of Maldives in relation to its natural and socioeconomic context. Data shows Maldives has one of the highest population density and per capita waste generation among SIDS, despite its small land area and medium GDP per capita. Large disparities exist between the densely populated capital Male’ with only 5.8 km2 area generating 63% of waste and the ~194 scattered outer islands with ad hoc waste management practices. Given Male’s dense population and high calorific waste, incineration could generate up to ~30 GW/a energy and even increase Maldives’ renewable energy supply by 200%. In contrast, decentralized anaerobic digestion presents an optimal solution for outer islands to reduce waste volume while providing over 40%–100% energy supply for daily cooking in local families. This timely study delivers valuable insights into designing context-specific waste-to-energy systems and integrated waste policies tailored to Maldives’ distinct regions. The framework presented can also guide other SIDS facing similar challenges as Maldives in establishing sustainable, ecologically sound waste management strategies.
基金supported by an Institutional Links (Grant No.527641843)under the Türkiye partnershipfunded by the UK Department for Business,Energy and Industrial Strategy together with the Scientific and Technological Research Council of Türkiye (TÜBİTAK,Project No.119N302)and delivered by the British Council.
文摘Under optimal process conditions,pyrolysis of polyolefins can yield ca.90 wt%of liquid product,i.e.,combination of light oil fraction and heavier wax.In this work,the experimental findings reported in a selected group of publications concerning the non-catalytic pyrolysis of polyolefins were collected,reviewed,and compared with the ones obtained in a continuously operated bench-scale pyrolysis reactor.Optimized process parameters were used for the pyrolysis of waste and virgin counterparts of high-density polyethylene,low-density polyethylene,polypropylene and a defined mixture of those(i.e.,25:25:50 wt%,respectively).To mitigate temperature drops and enhance heat transfer,an increased feed intake is employed to create a hot melt plastic pool.With 1.5 g·min^(-1) feed intake,1.1 L·min^(-1) nitrogen flow rate,and a moderate pyrolysis temperature of 450℃,the formation of light hydrocarbons was favored,while wax formation was limited for polypropylene-rich mixtures.Pyrolysis of virgin plastics yielded more liquid(maximum 73.3 wt%)than that of waste plastics(maximum 66 wt%).Blending polyethylenes with polypropylene favored the production of liquids and increased the formation of gasoline-range hydrocarbons.Gas products were mainly composed of C3 hydrocarbons,and no hydrogen production was detected due to moderate pyrolysis temperature.
基金This research is supported by the German Federal Ministry of Education and Research(BMBF)through the research project grant no.01LN1713A to the research group Global Change:STEEP-CarbonTransAny opinions,findings,conclusions and recommendations in the document are those of the authors and do not necessarily reflect the view of the BMBFThe authors also give thanks for the feedback from the Institute of Coal Chemistry,Chinese Academy of Sciences(ICC CAS),in particular the project team from‘Zero Waste Cities:International Best Practices and Current Waste Situation in Shanxi Province’under the Shanxi International Cooperation Program(Project No:201903D421086).
文摘Waste is a valuable secondary carbon resource.In the linear economy,it is predominantly landfilled or incinerated.These disposal routes not only lead to diverse climate,environmental and societal problems;they also represent a loss of carbon resources.In a circular carbon economy,waste is used as a secondary carbon feedstock to replace fossil resources for production.This contributes to environmental protection and resource conservation.It furthermore increases a nation’s independence from imported fossil energy sources.China is at the start of its transition from a linear to circular carbon economy.It can thus draw on waste management experiences of other economies and assess the opportunities for transference to support its development of‘zero waste cities’.This paper has three main focuses.First is an assessment of drivers for China’s zero waste cities initiative and the approaches that have been implemented to combat its growing waste crisis.Second is a sharing of Germany’s experience-a forerunner in the implementation of the waste hierarchy(reduce-reuse-recycle-recover-landfill)with extensive experience in circular carbon technologies-in sustainable waste management.Last is an identification of transference opportunities for China’s zero waste cities.Specific transference opportunities identified range from measures to promote waste prevention,waste separation and waste reduction,generating additional value via mechanical recycling,implementing chemical recycling as a recycling option before energy recovery to extending energy recovery opportunities.
基金supported by the cooperation project of Henan Collaborative Innovation Center for Environmental Pollution Control and Ecological Restoration and Zhengzhou Municipal Solid Waste Comprehensive Treatment Center,Zhengzhou City Administration Bureau.
文摘Landfill gas(LFG)generation is commonly modeled by using a first-order model.Methane generation potential(L0)and methane generation rate constant(k)are two key parameters in the first-order model.Coal-ash based default values or roughly analyzed values often used in China may not be appropriate for accurately estimating of LFG generation.In this study,seven groups of parameters were evaluated by comparing the theoretical predictions with real measurements from five Chinese landfills.The optimal approach for calculating L0 is the use of site-specific waste composition and the default values of degradable organic carbon(DOC)reported by the Chinese industry standard(CJJ133-2009),and the matching k can be adjusted by fitting and regression.The optimized average values were L0=67 m3 Mg−1,k=0.06 per year for landfills in Beijing and Zhengzhou in cold–dry regions,L0=69 m3 Mg−1,k=0.16 per year for landfill in Shanghai in cold–wet region,and L0=64 m3 Mg−1,k=0.21 per year for landfills in Guangzhou and Shenzhen in hot–wet regions.Monte Carlo analysis showed that the uncertainty of LFG generation at closure year varied in−22.5%to 20.5%,−17.1%to 17.1%and−28.2%to 34.7%for three climatic regions,respectively.The k value is the key influencing factor,with a 95.6%contribution ratio in the hot–wet region landfill.The results provide references for future better waste management.
基金The project was financially supported(Code:SRIC/TOUR/AIR/17-18/3)by the Sponsored Research and Industrial Consultancy(SRIC),IIT Kharagpur,India for performing the field studies at Visakhapatnam.
文摘Municipal solid waste(MSW)generation and characterization are the basic inputs for waste handling and treatment systems design.In present research,we performed waste characterization investigations in Visakhapatnam(India),using a waste characterization methodology by integrating two standard sampling and characterization approaches.The characterization methodology was designed by combining seasonal variations,source,and socio-economic stratifications.Source-based sampling was performed at household(s),dumpster(s),transfer station,and landfill.Socio-economic-based sampling was performed based on the zone classification of the city.Three sampling campaigns were conducted to identify the waste composition based on seasonal variations.Studies aimed to perform stratified characterization of waste and assess chemical characteristics of the mixed waste fractions to evaluate waste-to-energy potential.Results indicate that the amount of MSW generated in the city is 1250±100 tons/day,with a generation rate of 0.65 kg/capita/day.Based on source stratification,organic matter(45.5%±6.5%)is a major component followed by inert waste.The paper,plastic,and textile components amount to 25%of overall waste.From seasonal studies,organic matter was higher in pre-monsoon(42%)compared to winter(39%).The moisture content of MSW varied between 30%and 35%and volatile solids between 39%and 43%.The calorific value was determined to be between 5680-7110 kJ/kg.Outlined the limitations and potential errors associated with sampling and waste characterization.Biochemical and thermal conversion treatment alternatives for processing,treatment,and handling were discussed.The findings of this research would assist regulatory bodies and city councils to formulate policy directives on waste sampling,characterization,segregation,education,and awareness campaigns.
