UiO-66 series metal-organic framework materials(MOFs)are typical porous materials assembled by Zr^(4+) with a large mass-to-nucleus ratio and terephthalic acid ligands,which form tetrahedral and octahedral cages arran...UiO-66 series metal-organic framework materials(MOFs)are typical porous materials assembled by Zr^(4+) with a large mass-to-nucleus ratio and terephthalic acid ligands,which form tetrahedral and octahedral cages arranged in a periodic triangular window pattern.Due to the strong interaction between Zr and O,UiO-66 series MOFs exhibit high thermal stability,structural stability,and chemical stability.This article mainly reviews the applications of UiO-66 and its composites in adsorption,photocatalysis,and resource utilization,while exploring the harm of pollutants to human health and the environment.In the first part,the differences in adsorption and removal mechanisms of liquid organic pollutants,heavy metals,and volatile organic compounds(VOCs)are investigated.The results show that organic pollutants are mainly removed by physical adsorption,electrostatic interactions,hydrogen bonding,andπ-πinteractions,while heavy metals are mainly removed by chemical adsorption,electrostatic interactions,reduction,and chelation.VOCs are mainly removed by the pore volume and pore size structure of the material.Heterojunction catalysis can achieve non-toxic treatment of pollutants,and this study mainly focuses on UiO-based composite materials constructed by strategies such as semiconductor composites,ion doping,and metal/dye encapsulation.In the second part,the synergistic effect between the components of UiO-based composite materials promotes the oriented and rapid separation and transfer of earriers at the material interface,thereby promoting the generation of active species such as h^(+),·O_(2)^(-) and·OH,and achieving rapid degradation of pollutants and detoxification of heavy metals.In the third part,heterojunctions can realize the resource utilization of pollutants in water and air,producing energy-type substances such as hydrogen and methanol while solving environmental problems.In addition,this article also summarizes the harm of common typical pollutants to the environment and human health.Finally,the development prospects and unresolved problems of UiO-66-based materials in water remediation,gas purification,and environmental resource utilization are reviewed.展开更多
One of the major problems of agricultural soils in the tropical regions of the Pacific is the low organic matter content.Because of the hot and humid environment,the soil organic matter(SOM)is minimal due to rapid dec...One of the major problems of agricultural soils in the tropical regions of the Pacific is the low organic matter content.Because of the hot and humid environment,the soil organic matter(SOM)is minimal due to rapid decomposition.Composted organic material is being applied on agricultural fields as an amendment to provide nutrients and enhance the organic matter content for improving the physical and chemical properties of the cultivated soils.In addition land application of composted material as a fertilizer source effectively disposes of wastes that otherwise are buried in landfills.In our soil program at the University of Guam,we are evaluating the use of organic material as an alternative to synthetic fertilizers.Its goal is to develop management strategies and use available resources for improving crop production while conserving resources and preserving environmental quality.Our case study project is designed to improve soil fertility status by using composted organic wastes and assessing how the nitrogen and other essential nutrients contribute to long-term soil fertility and crop productivity without application of synthetic fertilizers.In our pilot project,compost is produced from wood chips,grinded typhoon debris mixed with animal manure,fish feed,shredded paper and other organic wastes.Mature compost is then applied on the field at the rates of 0,5,10 and 20 t/ha as a soil amendment on the eroded cobbly soils of southern Guam.Corn is planted and monitored for growth performance and yield.The effect of land application of composted material on the SOM content and overall soil quality indices are being evaluated in this pilot study.展开更多
Sludge,the massive by-product of the sewage system,became a major challenge for the wastewater treatment industry.Yet,conventional methods often face challenges like low efficiency,high energy consumption,and environm...Sludge,the massive by-product of the sewage system,became a major challenge for the wastewater treatment industry.Yet,conventional methods often face challenges like low efficiency,high energy consumption,and environmental pollution.Especially,the improper treatment and disposal of toxic sludge generated from different industrial processes or specific wastewater treatment operations exerted significant pressure and threat to hydrosphere,pedosphere,atmosphere and even biosphere.展开更多
Food waste(FW)constitutes a significant portion of municipal solid waste(MSW)and represents an underutilized resource with substantial potential for energy generation.The effective management and recycling of FW are c...Food waste(FW)constitutes a significant portion of municipal solid waste(MSW)and represents an underutilized resource with substantial potential for energy generation.The effective management and recycling of FW are crucial for mitigating environmental issues and minimizing associated health risks.This comprehensive review provides an in-depth overview of current technological applications for converting FW into energy with the dual goals of reducing environmental impact and maximizing resource utilization.It covers various aspects,including pretreatment methods,biological technologies(e.g.,anaerobic digestion and fermentation),and thermal technologies(e.g.,incineration,pyrolysis,gasification,and hydrothermal carbonization).The analysis includes the scope,advantages and disadvantages of these techniques.Landfilling,composting,and incineration are widely considered the most prevalent methods of FW disposal and have substantial negative impacts on the environment.Advanced technologies such as anaerobic fermentation offer environmental benefits and are suitable for scaling up,reducing greenhouse gas emissions,and producing renewable energy such as biogas,thus reducing carbon emissions.The promotion and adoption of advanced technologies like anaerobic fermentation can contribute to more sustainable FW management practices,reduce environmental impacts,and support the transition to a circular economy.Additionally,this article presents successful case studies,emphasizing the importance of technological integration in FW treatment.Furthermore,this article outlines future directions for FW treatment,including advancements in biological treatment technologies,decentralized treatment systems,and the adoption of digital and data-driven FW management systems.These emerging trends aim to promote sustainable,resource-efficient,and environmentally responsible FW management practices.展开更多
The aim of this study is to investigate the anaerobic treatability and generation of potential valuable by-products of agro-food industry wastewaters where bulgur production is carried out.Among the agro-food products...The aim of this study is to investigate the anaerobic treatability and generation of potential valuable by-products of agro-food industry wastewaters where bulgur production is carried out.Among the agro-food products,bulgur which is a wheat product(Triticum spp.)and rich in fibers,is one of the ancient foods of Anatolia.The most critical issue in bulgur production is high energy and water consumption for cooking where wheat starch gelatinizes and results in a considerable amount of high strength wastewater.In the raw bulgur wastewater sample,81% of total chemical oxygen demand(tCOD)was in soluble form which was readily fermentable and acidic by nature.Batch anaerobic study results indicated almost complete tCOD removal(99%)which decreased from 7820 to 100 mg/L.The cumulative methane yield was determined as 275 mL/g tCOD_(fed).Hence,for such industrial wastewaters with high level of organic pollution,anaerobic biotechnology stands out as one of the most effective treatment options.Fermented bulgur wastewater was also tested for the production of polyhydroxyalkanoates(PHAs).It was determined that 37% of the tCOD could be recovered as PHAs without hindering the biogas generation.In this context,it was shown that PHAs and biogas production could be simultaneously achievable with a smart organic carbon utilization strategy which will also contribute to reduce energy requirement and carbon footprint of the industrial bulgur production process as well as create environmentally friendly solutions through resource recovery.展开更多
The acid leaching residue(ALR)of ionic rare earth(IRE)concentrates containing radioactive elements such as thorium(Th)is classified as low-level radioactive waste.ALR holds valuable strategic resources such as rare ea...The acid leaching residue(ALR)of ionic rare earth(IRE)concentrates containing radioactive elements such as thorium(Th)is classified as low-level radioactive waste.ALR holds valuable strategic resources such as rare earth and Th,while improper long-term heaping storage of ALR poses a substantial environmental risk.This paper proposes a comprehensive process involving low-temperature roasting,hydrochloric acid leaching,single extractant enrichment,and stepwise stripping to recover rare earth elements and thorium from ALR.The achieved leaching efficiencies are 80.11%of LnY,99.43%of Sc(Ⅲ),and 98.67%of Th(Ⅳ)after the carbonization of the organic phase in the ALR through low-temperature roasting.Despite large amounts of acid and impurities present in the leachate,2-ethylhexyl phosphonic acid mono 2-ethylhexyl ester(HEHEHP)still exhibits nearly 100%extraction efficiency for Sc(Ⅲ)and Th(Ⅳ).The effective separation of LnY,Th(Ⅳ),and Sc(Ⅲ)was achieved by implementing fractional extraction enrichment of Th(Ⅳ)and Sc(Ⅲ),followed by Th(Ⅳ)removal through H_(2)SO_(4)and Sc(Ⅲ)removal via NaOH from the loaded organic phase.This scheme successfully achieves a recovery of RE and Th and offers a viable solution for the safe disposal of ALR.展开更多
Beyond energy efficiency,there are now urgent challenges around the supply of resources,materials,food and water.After debating energy-efficiency for the last decade,the focus has shifted to include resource and mater...Beyond energy efficiency,there are now urgent challenges around the supply of resources,materials,food and water.After debating energy-efficiency for the last decade,the focus has shifted to include resource and material-efficiency.In this context,urban farming has emerged as a valid urban design strategy in Europe,where food is produced and consumed locally within city boundaries,turning disused sites into productive urban landscapes and community gardens.Agricultural activities allow for effective composting of organic waste,returning nutrients to the soil and improving biodiversity in the urban environment.Urban farming will help to feed the 9 billion by 2050(predicted population growth,UN-Habitat forecast 2009).This paper reports on best practice of urban design principles in regard to materials flow,material recovery,adaptive re-use of building elements and components(‘design for disassembly’;prefabrication of modular building components),and other relevant strategies to implement zero waste by avoiding waste creation,reducing harmful consumption and changing behaviour.The paper touches on two important issues in regard to the rapid depletion of the world’s natural resources:the construction sector and the education of architects and designers.The construction sector:Prefabricated multi-story timber buildings for inner-city living can set new benchmarks for minimizing construction wastage and for sustainable on-site assembly.Today,the construction and demolition(C&D)sector is one of the main producers of waste;it does not engage enough with waste minimization,waste avoidance and recycling.Education and research:It’s still unclear how best to introduce a holistic understanding of these challenges and to better teach practical and affordable solutions to architects,urban designers,industrial designers,and so on.One of the findings of this paper is that embedding‘zero-waste’requires strong industry leadership,new policies and effective education curricula,as well as raising awareness(education)and refocusing research agendas to bring about attitudinal change and the reduction of wasteful consumption.展开更多
The nano-MOF-303 synthesized by microwave method exhibited efficient adsorption capacity(232 mg/g)toward Ag^(+),in which the adsorption behaviors were fitted by the pseudo-second-order kinetic and the Freundlich isoth...The nano-MOF-303 synthesized by microwave method exhibited efficient adsorption capacity(232 mg/g)toward Ag^(+),in which the adsorption behaviors were fitted by the pseudo-second-order kinetic and the Freundlich isotherm model.The outstanding Ag^(+)sorption ability of nano-MOF-303 could be contributed to electrostatic interactions,weak coordination interaction of Ag-N,and Ag Cl precipitates originating from the stored Cl^(-)in nano-MOF-303.Besides the adsorbent regeneration,the formed Ag/Ag Cl onto nano-MOF-303 could produce Ag/Ag Cl/MOF-303 as a photocatalyst for sulfamethoxazole degradation under visible light.In this work,both the adsorption and photocatalysis mechanisms were clarified,which might provide insight to develop more effective adsorbents for mining the critical resource from the wastewater.展开更多
Red mud is a byproduct of alumina refining of bauxite ores,and is a significant source for extracting scandium.However,a large amount of iron in red mud makes it difficult to recover scandium because Fe(III) and Sc(Ⅲ...Red mud is a byproduct of alumina refining of bauxite ores,and is a significant source for extracting scandium.However,a large amount of iron in red mud makes it difficult to recover scandium because Fe(III) and Sc(Ⅲ) have similar physicochemical properties.In this study,a new method was developed for selective separation of iron and scandium in acid leachate of red mud using D201 resin.Theoretical calculations indicate that the ferric species mainly exists as FeCl3 or FeCl4-at chloride concentration above 6.65 mol/L,while scandium still exists as SCl2+,making it possible to selectively separate iron fro m scandium through anion resin adso rption.The factors affecting the adso rption of iron and scandium such as chloride conce ntratio n,resin dosage,adso rption time,and temperature were evaluated in batch experiments,The Langmuir model was successfully applied to both iron and scandium adsorption,and the maximum adsorption capacities of iron and scandium are 147.06 and 0.95 mg/g,respectively,indicating a significant difference between iron and scandium.Raman analysis further demonstrates that the iron is adsorbed onto D201 resin as FeCl4 anion.展开更多
A vacuum membrane distillation(VMD)process with permeate fractional condensation on membrane downstream has been developed for simultaneous recovery of phosphorus and nitrogen from liquid digestate.The polytetrafluoro...A vacuum membrane distillation(VMD)process with permeate fractional condensation on membrane downstream has been developed for simultaneous recovery of phosphorus and nitrogen from liquid digestate.The polytetrafluoroethylene(PTFE)membrane flux could reach 6000 g·m-2·h-1 with the rejection efficiency of total phosphorus(TP)over 0.99,under the condition of flowrate being 120 L·h-1 and temperature being 40°C.Membrane fouling occurred with a film of organics and microorganism deposited on the surface of the membrane.Membrane flux could be reversed after the membrane was rinsed by water.Higher feed temperature and flowrate could improve the membrane flux,while hardly affect the rejection efficiency of total phosphorus.The concentration of TP could reach 1600 mg·L-1 after membrane distillation,which is about 5 times of that in initial liquid digestate.On the downstream of the membrane,some of the permeate vapor was condensed under the vacuum condition and most of water was collected here.The remaining vapor enriched with total nitrogen(TN)was compressed and pumped to the atmospheric condition to condense.The TN concentration in atmospheric condensate was as high as 7000 mg·L-1 with the process separation factor for ammonia being enhanced to 114.展开更多
Based on the principle of bacterial leaching and bacterial metallurgy,a novel technology for the detoxification of chromium-containing slag by Achromobacter sp.CH-1 and chromium recovery was proposed.Strain CH-1 cell ...Based on the principle of bacterial leaching and bacterial metallurgy,a novel technology for the detoxification of chromium-containing slag by Achromobacter sp.CH-1 and chromium recovery was proposed.Strain CH-1 cell morphology before and after Cr(Ⅵ) reduction was observed with a scanning electron microscope(SEM),and the reduction product is found to adhere to terminals of CH-1 cells.Energy-dispersive X-ray(EDX) and electron paramagnetic resonance(EPR) analyses reveal that the main component of the reduction product is Cr(Ⅲ).Furthermore,small and large-scale demonstration projects reveal that Achromobacter sp.can be used to detoxify chromium-containing slag and to selectively recover chromium by using this novel technique.Chromium recovery rate increases with decreasing particle sizes of chromium-containing slag and slagheap height.Chromium recovery rates in 10 t/batch and 20 t/batch of on-site demonstration projects for chromium-containing slag detoxification are more than 90%.展开更多
Ecological compensation is widely considered a policy that encourages farmers to recycle livestock and poultry waste for economic and ecological benefits.Therefore,based on field data from 30 counties(districts)in six...Ecological compensation is widely considered a policy that encourages farmers to recycle livestock and poultry waste for economic and ecological benefits.Therefore,based on field data from 30 counties(districts)in six cities of Shandong Province,China,this study systematically analyzes farmers'willingness to accept compensation for livestock and poultry waste resource utilization as well as its determinants.It does so using the UTAUT theoretical analysis framework,as well as the contingent valuation method and Heckman two-stage selection model.The results show that,first,72.4%of the farmers in the sample are willing to accept a certain amount of compensation—the expected value of which is RMB 98.02 per month per household—as an incentive to utilize livestock waste.Second,the key determinants of farmers'willingness to accept compensation are marital status,family annual income,concurrent business,farming scale,economic performance expectation,social performance expectation,knowledge reserve,public relations,and technical convenience.Finally,the factors that affect farmers’willingness in terms of the compensation amount are gender,age,family annual income,social performance expectation,subjective norms,and public relations.Therefore,to promote the recycling of livestock and poultry waste,this study proposes policies that promote education and technology popularization in relation to livestock and poultry waste resource utilization,provide subsidies for waste recycling,and strengthen government control and social supervision over the non-standard disposal of such waste.展开更多
Recovery of Ni-Cd batteries was studied by a self-designed vacuum-aided recovering system under laboratory conditions. The fundamental research on a process of disassembling and recovering selected materials from Ni-C...Recovery of Ni-Cd batteries was studied by a self-designed vacuum-aided recovering system under laboratory conditions. The fundamental research on a process of disassembling and recovering selected materials from Ni-Cd batterieswas conducted. The impacts of temperature, pressure and time were studied respectively. The mechanism of vacuum thermal recovering was also discussed. The results show that: Ni-Cd batteries can be recovered effectively byvacuum-aided recovering system at 573~1173 K. At constant pressure, the increase of temperature can improve theseparating efficiency of cadmium. When the temperature is 1173 K, the cadmium can evaporate completely fromthe residue during 3 h at 10 Pa. The reduction of pressure in the certain range is effective to separate cadmium byvacuum distillation. Distillation time is a very important factor affecting separation of cadmium.展开更多
Wastewater treatment significantly contributes to greenhouse gas emissions,which are further exacerbated by the environmental impact of external chemical additions.In response,microbial electrochemical wastewater refi...Wastewater treatment significantly contributes to greenhouse gas emissions,which are further exacerbated by the environmental impact of external chemical additions.In response,microbial electrochemical wastewater refining has gained prominence at the interdisciplinary frontier of wastewater resource recovery and green bio-manufacturing.Significant progress has been made in utilizing active electrodes to stimulate CO_(2) fixation rates,applying“binary electron donors”to produce high-value-added chemicals,and developing novel processes and equipment.This review explores various aspects of microbial electrochemical wastewater refining,including microbial electrochemical monitoring of water quality,chemical synthesis from diverse carbon sources,and the deployment of pilot-scale systems for generating electricity,hydrogen,and methane,as well as for in-situ remediation.Additionally,it discusses the challenges and future directions,highlighting the importance of understanding mechanisms,advancing electrocatalyst and microbial engineering,and innovating hybrid processes.In conclusion,the widespread adoption of microbial electrochemical wastewater refining is emphasized for resource recovery and sustainable chemical production,ultimately reducing environmental impact.展开更多
Firstly, the water-quality characteristics of intestinal lavage wastewater and enzymolysis wastewater from the typical heparin sodium pro- ductive process were analyzed, and then the segregation treatment was applied ...Firstly, the water-quality characteristics of intestinal lavage wastewater and enzymolysis wastewater from the typical heparin sodium pro- ductive process were analyzed, and then the segregation treatment was applied in the treatment of enteric coating and heparin sodium manufacturing wastewater. Finally, the treatment of the two kinds of wastewater by different methods were discussed. The results showed that, COD of enzymolysis wastewater treated by centrifugation-coagulation-Fenton reagent oxidation-adsorption process was lower than 100 mg/L, while intestinal lavage wastewater treated by coagulation-ASBR-SBR process could meet the first standard of Comprehensive Discharge Standard of Sewage （GB8978-1996） after one month of continuous operation.展开更多
At present, in the process of rural environmental treatment, the garbage problem has become the main problem that currently affects the rural environmental pollution. In view of this problem, the relevant departments ...At present, in the process of rural environmental treatment, the garbage problem has become the main problem that currently affects the rural environmental pollution. In view of this problem, the relevant departments should adopt effective solutions to classify the rural solid garbage, and at the same time, recycle the valuable garbage for secondary treatment. At present, the garbage in the rural areas of China mainly comes from domestic garbage, livestock breeding waste, agricultural straw and other solid wastes. Aiming at the problems existing in the treatment process of the above pollutants, in-depth research and discussion are carried out to obtain valuable recyclable remediation plan.展开更多
Based on field research data on farmers in 30 counties(districts)of six cities in Shandong Province,this study systematically examines the methods of disposal of livestock and poultry waste and the factors that influe...Based on field research data on farmers in 30 counties(districts)of six cities in Shandong Province,this study systematically examines the methods of disposal of livestock and poultry waste and the factors that influence them,that is,the determinants of farmers’waste disposal behaviors,using the UTAUT theoretical framework and a disordered multi-class logit model.The results show that,first,economic performance expectancy,subjective norms,farming population,and poultry and livestock breeding numbers have significant effects on the four waste recycling methods considered:direct return,compost fermentation,biogas fermentation,and fresh-packed sale.Second,annual family income has a positive effect on the direct return method.Third,compost fermentation is positively affected by farmers'knowledge,distance from sources of water,and farming scale,and negatively affected by gender and marital status.Fourth,biogas fermentation is negatively affected by the age of farmers and positively affected by the farming income ratio and environmental convenience.Finally,the most important factors affecting the four methods are subjective norms,farming scale,economic performance expectancy,and farming population.Therefore,this study proposes that policies to promote resource utilization of livestock and poultry waste must prioritize raising awareness among the farmers of the advantages of resource disposal of waste;provide reasonable subsidies for waste recycling and enhance policy applicability,pertinence,and motivation;strengthen the promotion of waste recycling technology and improve the practicality of lectures or training content;and improve relevant laws and regulations and enhance authority and usability.展开更多
Industries such as non-ferrous metal smelting discharge billions of gallons of highly toxic heavy metal wastewater(HMW)worldwide annually,posing a severe challenge to conventional wastewater treatment plants and harmi...Industries such as non-ferrous metal smelting discharge billions of gallons of highly toxic heavy metal wastewater(HMW)worldwide annually,posing a severe challenge to conventional wastewater treatment plants and harming the environment.HMW is traditionally treated via chemical precipitation using lime,caustic,or sulfide,but the effluents do not meet the increasingly stringent discharge standards.This issue has spurred an increase in research and the development of innovative treatment technologies,among which those using nanoparticles receive particular interest.Among such initiatives,treatment using nanoscale zero-valent iron(nZVI)is one of the best developed.While nZVI is already well known for its site-remediation use,this perspective highlights its application in HMW treatment with metal recovery.We demonstrate several advantages of nZVI in this wastewater application,including its multifunctionality in sequestrating a wide array of metal(loid)s(>30 species);its capability to capture and enrich metal(loid)s at low concentrations(with a removal capacity reaching 500 mg·g^(-1)nZVI);and its operational convenience due to its unique hydrodynamics.All these advantages are attributable to nZVI’s diminutive nanoparticle size and/or its unique iron chemistry.We also present the first engineering practice of this application,which has treated millions of cubic meters of HMW and recovered tons of valuable metals(e.g.,Cu and Au).It is concluded that nZVI is a potent reagent for treating HMW and that nZVI technology provides an eco-solution to this toxic waste.展开更多
The composition of paper cups creates a challenge for the recycling industry,as the paperboard–plastic film composite is hard to separate.Therefore,paper cups are sent to landfills or waste incinerators.This study ex...The composition of paper cups creates a challenge for the recycling industry,as the paperboard–plastic film composite is hard to separate.Therefore,paper cups are sent to landfills or waste incinerators.This study explores the combined use of red worms(Eisenia fetida)and Greater wax moth(Galleria mellonella)in the biodegradation of paper cups.The study investigates the conditions and combinations that promote using Eisenia fetida and Galleria mellonella for degrading paper cups.The study considered the influence of environmental temperature,the presence of food waste,varying the number of Eisenia fetida worms,and the presence of a Galleria mellonella growth-slowing agent on the degradation process.To achieve the study objectives,the study followed a quantitative approach.The study monitored the degradation of paper cup cuts that were placed in jars containing different combinations of Eisenia fetida worms,Galleria mellonella larvae,food waste,bedding material,and Galleria mellonella growth-slowing agents.The study found that the best operating temperature is 30oC.The study found that using food waste improves the performance of Eisenia fetida worms and Galleria mellonella larvae significantly.The study found that adding a Galleria mellonella growth-slowing agent slightly enhances the degradation of the paper cup.Finally,a numerical model was obtained to simulate the paper cup degradation efficiency.展开更多
Given the conditions of residual coal from the boundary of a flat dipping open-pit mine,which uses strip areas mining and inner dumping with slope-covering,we propose an open-pit and underground integrated mining tech...Given the conditions of residual coal from the boundary of a flat dipping open-pit mine,which uses strip areas mining and inner dumping with slope-covering,we propose an open-pit and underground integrated mining technology for residual coal of end slopes.In the proposal a conveyance road and ventilation conveyance near the slope are built,corresponding to the pit mining area and the surface coal mine dump,as well as an interval haulage tunnel and air-inlet tunnel.The outcome shows that such mining method may reduce the effect to slope stability from underground mining,it does not affect the dumping advance and has a high recovery rate of residual coal resources.The working face is timbered by single hydraulic props,transported by a scraper conveyor and supported by coal walls.This method of mining is one of layered top coal caving,with high resource recovery,low production cost where positive economic benefit can be realized.展开更多
基金financially supported by the National Natural Science Foundation of China(No.22206080)Zhongyuan Yingcai Jihua(No.ZYYCYU202012183)+11 种基金Henan Key Scientific Research Projects(No.23B610004)Henan Postdoctoral Foundation(No.202003027)the Natural Science Youth Fund of Henan Province(Nos.202300410034 and 232300420336)the Natural Science Foundation of Jiangsu(No.SBK2022041070)the Science and Technology Project of Henan Province(No.232102321050)the International Science and Technology Cooperation Projects of Henan Province(No.232102521009)the Young Teacher Foundation of Henan University of Urban Construction(No.YCJQNGGJS202306)China Postdoctoral Science Foundation(No.2021M701099)the Academic Leader of Henan Institute of Urban Construction(No.YCJXSJSDTR202204)the Science and Technology Major Special of Pingdingshan(No.2021ZD03)the Key University Scientific Research Project of Henan Province(No.22A610007)the Doctoral Research Start-up Project of Henan University of Urban Construction(No.990/K-Q2022016)。
文摘UiO-66 series metal-organic framework materials(MOFs)are typical porous materials assembled by Zr^(4+) with a large mass-to-nucleus ratio and terephthalic acid ligands,which form tetrahedral and octahedral cages arranged in a periodic triangular window pattern.Due to the strong interaction between Zr and O,UiO-66 series MOFs exhibit high thermal stability,structural stability,and chemical stability.This article mainly reviews the applications of UiO-66 and its composites in adsorption,photocatalysis,and resource utilization,while exploring the harm of pollutants to human health and the environment.In the first part,the differences in adsorption and removal mechanisms of liquid organic pollutants,heavy metals,and volatile organic compounds(VOCs)are investigated.The results show that organic pollutants are mainly removed by physical adsorption,electrostatic interactions,hydrogen bonding,andπ-πinteractions,while heavy metals are mainly removed by chemical adsorption,electrostatic interactions,reduction,and chelation.VOCs are mainly removed by the pore volume and pore size structure of the material.Heterojunction catalysis can achieve non-toxic treatment of pollutants,and this study mainly focuses on UiO-based composite materials constructed by strategies such as semiconductor composites,ion doping,and metal/dye encapsulation.In the second part,the synergistic effect between the components of UiO-based composite materials promotes the oriented and rapid separation and transfer of earriers at the material interface,thereby promoting the generation of active species such as h^(+),·O_(2)^(-) and·OH,and achieving rapid degradation of pollutants and detoxification of heavy metals.In the third part,heterojunctions can realize the resource utilization of pollutants in water and air,producing energy-type substances such as hydrogen and methanol while solving environmental problems.In addition,this article also summarizes the harm of common typical pollutants to the environment and human health.Finally,the development prospects and unresolved problems of UiO-66-based materials in water remediation,gas purification,and environmental resource utilization are reviewed.
文摘One of the major problems of agricultural soils in the tropical regions of the Pacific is the low organic matter content.Because of the hot and humid environment,the soil organic matter(SOM)is minimal due to rapid decomposition.Composted organic material is being applied on agricultural fields as an amendment to provide nutrients and enhance the organic matter content for improving the physical and chemical properties of the cultivated soils.In addition land application of composted material as a fertilizer source effectively disposes of wastes that otherwise are buried in landfills.In our soil program at the University of Guam,we are evaluating the use of organic material as an alternative to synthetic fertilizers.Its goal is to develop management strategies and use available resources for improving crop production while conserving resources and preserving environmental quality.Our case study project is designed to improve soil fertility status by using composted organic wastes and assessing how the nitrogen and other essential nutrients contribute to long-term soil fertility and crop productivity without application of synthetic fertilizers.In our pilot project,compost is produced from wood chips,grinded typhoon debris mixed with animal manure,fish feed,shredded paper and other organic wastes.Mature compost is then applied on the field at the rates of 0,5,10 and 20 t/ha as a soil amendment on the eroded cobbly soils of southern Guam.Corn is planted and monitored for growth performance and yield.The effect of land application of composted material on the SOM content and overall soil quality indices are being evaluated in this pilot study.
基金supported by National Natural Science Foundation of China(Nos.52370025,22176012)BUCEA Post Graduate Innovation Project(No.PG2024086)。
文摘Sludge,the massive by-product of the sewage system,became a major challenge for the wastewater treatment industry.Yet,conventional methods often face challenges like low efficiency,high energy consumption,and environmental pollution.Especially,the improper treatment and disposal of toxic sludge generated from different industrial processes or specific wastewater treatment operations exerted significant pressure and threat to hydrosphere,pedosphere,atmosphere and even biosphere.
基金supported by the Agricultural Technology Collaboration Project of the Zhejiang Department of Agriculture and Rural Affairs(No.2022SNJF079)the Kecheng District Citrus Industry Technology Research Project.
文摘Food waste(FW)constitutes a significant portion of municipal solid waste(MSW)and represents an underutilized resource with substantial potential for energy generation.The effective management and recycling of FW are crucial for mitigating environmental issues and minimizing associated health risks.This comprehensive review provides an in-depth overview of current technological applications for converting FW into energy with the dual goals of reducing environmental impact and maximizing resource utilization.It covers various aspects,including pretreatment methods,biological technologies(e.g.,anaerobic digestion and fermentation),and thermal technologies(e.g.,incineration,pyrolysis,gasification,and hydrothermal carbonization).The analysis includes the scope,advantages and disadvantages of these techniques.Landfilling,composting,and incineration are widely considered the most prevalent methods of FW disposal and have substantial negative impacts on the environment.Advanced technologies such as anaerobic fermentation offer environmental benefits and are suitable for scaling up,reducing greenhouse gas emissions,and producing renewable energy such as biogas,thus reducing carbon emissions.The promotion and adoption of advanced technologies like anaerobic fermentation can contribute to more sustainable FW management practices,reduce environmental impacts,and support the transition to a circular economy.Additionally,this article presents successful case studies,emphasizing the importance of technological integration in FW treatment.Furthermore,this article outlines future directions for FW treatment,including advancements in biological treatment technologies,decentralized treatment systems,and the adoption of digital and data-driven FW management systems.These emerging trends aim to promote sustainable,resource-efficient,and environmentally responsible FW management practices.
基金the Department of Scientific Research Projects of ITU(No.44477)for their financial support,Res.
文摘The aim of this study is to investigate the anaerobic treatability and generation of potential valuable by-products of agro-food industry wastewaters where bulgur production is carried out.Among the agro-food products,bulgur which is a wheat product(Triticum spp.)and rich in fibers,is one of the ancient foods of Anatolia.The most critical issue in bulgur production is high energy and water consumption for cooking where wheat starch gelatinizes and results in a considerable amount of high strength wastewater.In the raw bulgur wastewater sample,81% of total chemical oxygen demand(tCOD)was in soluble form which was readily fermentable and acidic by nature.Batch anaerobic study results indicated almost complete tCOD removal(99%)which decreased from 7820 to 100 mg/L.The cumulative methane yield was determined as 275 mL/g tCOD_(fed).Hence,for such industrial wastewaters with high level of organic pollution,anaerobic biotechnology stands out as one of the most effective treatment options.Fermented bulgur wastewater was also tested for the production of polyhydroxyalkanoates(PHAs).It was determined that 37% of the tCOD could be recovered as PHAs without hindering the biogas generation.In this context,it was shown that PHAs and biogas production could be simultaneously achievable with a smart organic carbon utilization strategy which will also contribute to reduce energy requirement and carbon footprint of the industrial bulgur production process as well as create environmentally friendly solutions through resource recovery.
基金supported by the National Key Research and Development Program of China(2020YFC1909001)the Natural Science Foundation of Jiangxi Province(20202BABL214024)。
文摘The acid leaching residue(ALR)of ionic rare earth(IRE)concentrates containing radioactive elements such as thorium(Th)is classified as low-level radioactive waste.ALR holds valuable strategic resources such as rare earth and Th,while improper long-term heaping storage of ALR poses a substantial environmental risk.This paper proposes a comprehensive process involving low-temperature roasting,hydrochloric acid leaching,single extractant enrichment,and stepwise stripping to recover rare earth elements and thorium from ALR.The achieved leaching efficiencies are 80.11%of LnY,99.43%of Sc(Ⅲ),and 98.67%of Th(Ⅳ)after the carbonization of the organic phase in the ALR through low-temperature roasting.Despite large amounts of acid and impurities present in the leachate,2-ethylhexyl phosphonic acid mono 2-ethylhexyl ester(HEHEHP)still exhibits nearly 100%extraction efficiency for Sc(Ⅲ)and Th(Ⅳ).The effective separation of LnY,Th(Ⅳ),and Sc(Ⅲ)was achieved by implementing fractional extraction enrichment of Th(Ⅳ)and Sc(Ⅲ),followed by Th(Ⅳ)removal through H_(2)SO_(4)and Sc(Ⅲ)removal via NaOH from the loaded organic phase.This scheme successfully achieves a recovery of RE and Th and offers a viable solution for the safe disposal of ALR.
文摘Beyond energy efficiency,there are now urgent challenges around the supply of resources,materials,food and water.After debating energy-efficiency for the last decade,the focus has shifted to include resource and material-efficiency.In this context,urban farming has emerged as a valid urban design strategy in Europe,where food is produced and consumed locally within city boundaries,turning disused sites into productive urban landscapes and community gardens.Agricultural activities allow for effective composting of organic waste,returning nutrients to the soil and improving biodiversity in the urban environment.Urban farming will help to feed the 9 billion by 2050(predicted population growth,UN-Habitat forecast 2009).This paper reports on best practice of urban design principles in regard to materials flow,material recovery,adaptive re-use of building elements and components(‘design for disassembly’;prefabrication of modular building components),and other relevant strategies to implement zero waste by avoiding waste creation,reducing harmful consumption and changing behaviour.The paper touches on two important issues in regard to the rapid depletion of the world’s natural resources:the construction sector and the education of architects and designers.The construction sector:Prefabricated multi-story timber buildings for inner-city living can set new benchmarks for minimizing construction wastage and for sustainable on-site assembly.Today,the construction and demolition(C&D)sector is one of the main producers of waste;it does not engage enough with waste minimization,waste avoidance and recycling.Education and research:It’s still unclear how best to introduce a holistic understanding of these challenges and to better teach practical and affordable solutions to architects,urban designers,industrial designers,and so on.One of the findings of this paper is that embedding‘zero-waste’requires strong industry leadership,new policies and effective education curricula,as well as raising awareness(education)and refocusing research agendas to bring about attitudinal change and the reduction of wasteful consumption.
基金supported by National Natural Science Foundation of China(Nos.22176012,51878023)BUCEA Post Graduate Innovation Project(No.PG2023057)BUCEA Doctor Graduate Scientific Research Ability Improvement Project(No.DG2024022)。
文摘The nano-MOF-303 synthesized by microwave method exhibited efficient adsorption capacity(232 mg/g)toward Ag^(+),in which the adsorption behaviors were fitted by the pseudo-second-order kinetic and the Freundlich isotherm model.The outstanding Ag^(+)sorption ability of nano-MOF-303 could be contributed to electrostatic interactions,weak coordination interaction of Ag-N,and Ag Cl precipitates originating from the stored Cl^(-)in nano-MOF-303.Besides the adsorbent regeneration,the formed Ag/Ag Cl onto nano-MOF-303 could produce Ag/Ag Cl/MOF-303 as a photocatalyst for sulfamethoxazole degradation under visible light.In this work,both the adsorption and photocatalysis mechanisms were clarified,which might provide insight to develop more effective adsorbents for mining the critical resource from the wastewater.
基金Project supported by the Natural National Science Foundation of China(21707167)。
文摘Red mud is a byproduct of alumina refining of bauxite ores,and is a significant source for extracting scandium.However,a large amount of iron in red mud makes it difficult to recover scandium because Fe(III) and Sc(Ⅲ) have similar physicochemical properties.In this study,a new method was developed for selective separation of iron and scandium in acid leachate of red mud using D201 resin.Theoretical calculations indicate that the ferric species mainly exists as FeCl3 or FeCl4-at chloride concentration above 6.65 mol/L,while scandium still exists as SCl2+,making it possible to selectively separate iron fro m scandium through anion resin adso rption.The factors affecting the adso rption of iron and scandium such as chloride conce ntratio n,resin dosage,adso rption time,and temperature were evaluated in batch experiments,The Langmuir model was successfully applied to both iron and scandium adsorption,and the maximum adsorption capacities of iron and scandium are 147.06 and 0.95 mg/g,respectively,indicating a significant difference between iron and scandium.Raman analysis further demonstrates that the iron is adsorbed onto D201 resin as FeCl4 anion.
基金supported by the Fundamental Research Funds for the Central Universities(No.20822041B4013)Key Laboratory of Development and Application of Rural Renewable Energy,Ministry of Agriculture and Rural Affairs,China(No.18H0491)。
文摘A vacuum membrane distillation(VMD)process with permeate fractional condensation on membrane downstream has been developed for simultaneous recovery of phosphorus and nitrogen from liquid digestate.The polytetrafluoroethylene(PTFE)membrane flux could reach 6000 g·m-2·h-1 with the rejection efficiency of total phosphorus(TP)over 0.99,under the condition of flowrate being 120 L·h-1 and temperature being 40°C.Membrane fouling occurred with a film of organics and microorganism deposited on the surface of the membrane.Membrane flux could be reversed after the membrane was rinsed by water.Higher feed temperature and flowrate could improve the membrane flux,while hardly affect the rejection efficiency of total phosphorus.The concentration of TP could reach 1600 mg·L-1 after membrane distillation,which is about 5 times of that in initial liquid digestate.On the downstream of the membrane,some of the permeate vapor was condensed under the vacuum condition and most of water was collected here.The remaining vapor enriched with total nitrogen(TN)was compressed and pumped to the atmospheric condition to condense.The TN concentration in atmospheric condensate was as high as 7000 mg·L-1 with the process separation factor for ammonia being enhanced to 114.
文摘Based on the principle of bacterial leaching and bacterial metallurgy,a novel technology for the detoxification of chromium-containing slag by Achromobacter sp.CH-1 and chromium recovery was proposed.Strain CH-1 cell morphology before and after Cr(Ⅵ) reduction was observed with a scanning electron microscope(SEM),and the reduction product is found to adhere to terminals of CH-1 cells.Energy-dispersive X-ray(EDX) and electron paramagnetic resonance(EPR) analyses reveal that the main component of the reduction product is Cr(Ⅲ).Furthermore,small and large-scale demonstration projects reveal that Achromobacter sp.can be used to detoxify chromium-containing slag and to selectively recover chromium by using this novel technique.Chromium recovery rate increases with decreasing particle sizes of chromium-containing slag and slagheap height.Chromium recovery rates in 10 t/batch and 20 t/batch of on-site demonstration projects for chromium-containing slag detoxification are more than 90%.
基金supported by the National Natural Science Foundation of China“Behavioral Experiment and Policy Research of Pig Farmers when Diseased Dead Pigs Entering the Market”[Grant number 71540008]the Key Projects of the National Natural Science Foundation of China“Experimental Assessment of Agricultural Producer Safety Production Policy and Its Combined Design:Taking the Treatment of Diseased Dead Pigs as an Example”[Grant number.71673115]+3 种基金the Fundamental Research Funds for the Central Universities“Food Safety Risk Management Logic and Realistic Path Based on Big Data”[Grant number JUSRP1808ZD]the National College Student Innovation Training Program[Grant number 201810295025]the National Key R&D Program Funding Project[Grant number 2018YFC1603303]the National Key R&D Program Funding Project[Grant number 2018YFC1604000].
文摘Ecological compensation is widely considered a policy that encourages farmers to recycle livestock and poultry waste for economic and ecological benefits.Therefore,based on field data from 30 counties(districts)in six cities of Shandong Province,China,this study systematically analyzes farmers'willingness to accept compensation for livestock and poultry waste resource utilization as well as its determinants.It does so using the UTAUT theoretical analysis framework,as well as the contingent valuation method and Heckman two-stage selection model.The results show that,first,72.4%of the farmers in the sample are willing to accept a certain amount of compensation—the expected value of which is RMB 98.02 per month per household—as an incentive to utilize livestock waste.Second,the key determinants of farmers'willingness to accept compensation are marital status,family annual income,concurrent business,farming scale,economic performance expectation,social performance expectation,knowledge reserve,public relations,and technical convenience.Finally,the factors that affect farmers’willingness in terms of the compensation amount are gender,age,family annual income,social performance expectation,subjective norms,and public relations.Therefore,to promote the recycling of livestock and poultry waste,this study proposes policies that promote education and technology popularization in relation to livestock and poultry waste resource utilization,provide subsidies for waste recycling,and strengthen government control and social supervision over the non-standard disposal of such waste.
文摘Recovery of Ni-Cd batteries was studied by a self-designed vacuum-aided recovering system under laboratory conditions. The fundamental research on a process of disassembling and recovering selected materials from Ni-Cd batterieswas conducted. The impacts of temperature, pressure and time were studied respectively. The mechanism of vacuum thermal recovering was also discussed. The results show that: Ni-Cd batteries can be recovered effectively byvacuum-aided recovering system at 573~1173 K. At constant pressure, the increase of temperature can improve theseparating efficiency of cadmium. When the temperature is 1173 K, the cadmium can evaporate completely fromthe residue during 3 h at 10 Pa. The reduction of pressure in the certain range is effective to separate cadmium byvacuum distillation. Distillation time is a very important factor affecting separation of cadmium.
基金supported by the National Natural Science Foundation of China(52125001,52370033,and 31970106).
文摘Wastewater treatment significantly contributes to greenhouse gas emissions,which are further exacerbated by the environmental impact of external chemical additions.In response,microbial electrochemical wastewater refining has gained prominence at the interdisciplinary frontier of wastewater resource recovery and green bio-manufacturing.Significant progress has been made in utilizing active electrodes to stimulate CO_(2) fixation rates,applying“binary electron donors”to produce high-value-added chemicals,and developing novel processes and equipment.This review explores various aspects of microbial electrochemical wastewater refining,including microbial electrochemical monitoring of water quality,chemical synthesis from diverse carbon sources,and the deployment of pilot-scale systems for generating electricity,hydrogen,and methane,as well as for in-situ remediation.Additionally,it discusses the challenges and future directions,highlighting the importance of understanding mechanisms,advancing electrocatalyst and microbial engineering,and innovating hybrid processes.In conclusion,the widespread adoption of microbial electrochemical wastewater refining is emphasized for resource recovery and sustainable chemical production,ultimately reducing environmental impact.
基金Supported by the Project of Practical Innovation Training Program of Undergraduates in Jiangsu Province in 2012(232)
文摘Firstly, the water-quality characteristics of intestinal lavage wastewater and enzymolysis wastewater from the typical heparin sodium pro- ductive process were analyzed, and then the segregation treatment was applied in the treatment of enteric coating and heparin sodium manufacturing wastewater. Finally, the treatment of the two kinds of wastewater by different methods were discussed. The results showed that, COD of enzymolysis wastewater treated by centrifugation-coagulation-Fenton reagent oxidation-adsorption process was lower than 100 mg/L, while intestinal lavage wastewater treated by coagulation-ASBR-SBR process could meet the first standard of Comprehensive Discharge Standard of Sewage （GB8978-1996） after one month of continuous operation.
文摘At present, in the process of rural environmental treatment, the garbage problem has become the main problem that currently affects the rural environmental pollution. In view of this problem, the relevant departments should adopt effective solutions to classify the rural solid garbage, and at the same time, recycle the valuable garbage for secondary treatment. At present, the garbage in the rural areas of China mainly comes from domestic garbage, livestock breeding waste, agricultural straw and other solid wastes. Aiming at the problems existing in the treatment process of the above pollutants, in-depth research and discussion are carried out to obtain valuable recyclable remediation plan.
基金supported by the National Natural Science Foundation of China“Behavioral Experiment and Policy Research of Pig Farmers when Diseased Dead Pigs Entering the Market”[Gant number 71540008]the Key Projects of National Natural Science Foundation of China“Experimental Assessment of Agricultural Producer Safety Production Policy and Its Combined Design:Taking the Treatment of Diseased Dead Pigs as an Example”[Grant number 71673115]+3 种基金the Fundamental Research Funds for the Central Universities“Food Safety Risk Management Logic and Realistic Path Based on Big Data”[Grant number.JUSRP1808ZD]the National College Student Innovation Training Program[grant number.201810295025]the National Key R&D Program Funding Project[Grant number.2018YFC1603303]the National Key R&D Program Funding Project[Grant number.2018YFC1604000].
文摘Based on field research data on farmers in 30 counties(districts)of six cities in Shandong Province,this study systematically examines the methods of disposal of livestock and poultry waste and the factors that influence them,that is,the determinants of farmers’waste disposal behaviors,using the UTAUT theoretical framework and a disordered multi-class logit model.The results show that,first,economic performance expectancy,subjective norms,farming population,and poultry and livestock breeding numbers have significant effects on the four waste recycling methods considered:direct return,compost fermentation,biogas fermentation,and fresh-packed sale.Second,annual family income has a positive effect on the direct return method.Third,compost fermentation is positively affected by farmers'knowledge,distance from sources of water,and farming scale,and negatively affected by gender and marital status.Fourth,biogas fermentation is negatively affected by the age of farmers and positively affected by the farming income ratio and environmental convenience.Finally,the most important factors affecting the four methods are subjective norms,farming scale,economic performance expectancy,and farming population.Therefore,this study proposes that policies to promote resource utilization of livestock and poultry waste must prioritize raising awareness among the farmers of the advantages of resource disposal of waste;provide reasonable subsidies for waste recycling and enhance policy applicability,pertinence,and motivation;strengthen the promotion of waste recycling technology and improve the practicality of lectures or training content;and improve relevant laws and regulations and enhance authority and usability.
基金supported by the National Natural Science Foundation of China(21876131)the National Key Research and Development Program of China(2022YFC3702101)the Foundation of State Key Laboratory of Pollution Control and Resource Reuse of China(PCRRY).
文摘Industries such as non-ferrous metal smelting discharge billions of gallons of highly toxic heavy metal wastewater(HMW)worldwide annually,posing a severe challenge to conventional wastewater treatment plants and harming the environment.HMW is traditionally treated via chemical precipitation using lime,caustic,or sulfide,but the effluents do not meet the increasingly stringent discharge standards.This issue has spurred an increase in research and the development of innovative treatment technologies,among which those using nanoparticles receive particular interest.Among such initiatives,treatment using nanoscale zero-valent iron(nZVI)is one of the best developed.While nZVI is already well known for its site-remediation use,this perspective highlights its application in HMW treatment with metal recovery.We demonstrate several advantages of nZVI in this wastewater application,including its multifunctionality in sequestrating a wide array of metal(loid)s(>30 species);its capability to capture and enrich metal(loid)s at low concentrations(with a removal capacity reaching 500 mg·g^(-1)nZVI);and its operational convenience due to its unique hydrodynamics.All these advantages are attributable to nZVI’s diminutive nanoparticle size and/or its unique iron chemistry.We also present the first engineering practice of this application,which has treated millions of cubic meters of HMW and recovered tons of valuable metals(e.g.,Cu and Au).It is concluded that nZVI is a potent reagent for treating HMW and that nZVI technology provides an eco-solution to this toxic waste.
基金funded by the Deanship of Scientific Research at the University of Jordan.
文摘The composition of paper cups creates a challenge for the recycling industry,as the paperboard–plastic film composite is hard to separate.Therefore,paper cups are sent to landfills or waste incinerators.This study explores the combined use of red worms(Eisenia fetida)and Greater wax moth(Galleria mellonella)in the biodegradation of paper cups.The study investigates the conditions and combinations that promote using Eisenia fetida and Galleria mellonella for degrading paper cups.The study considered the influence of environmental temperature,the presence of food waste,varying the number of Eisenia fetida worms,and the presence of a Galleria mellonella growth-slowing agent on the degradation process.To achieve the study objectives,the study followed a quantitative approach.The study monitored the degradation of paper cup cuts that were placed in jars containing different combinations of Eisenia fetida worms,Galleria mellonella larvae,food waste,bedding material,and Galleria mellonella growth-slowing agents.The study found that the best operating temperature is 30oC.The study found that using food waste improves the performance of Eisenia fetida worms and Galleria mellonella larvae significantly.The study found that adding a Galleria mellonella growth-slowing agent slightly enhances the degradation of the paper cup.Finally,a numerical model was obtained to simulate the paper cup degradation efficiency.
文摘Given the conditions of residual coal from the boundary of a flat dipping open-pit mine,which uses strip areas mining and inner dumping with slope-covering,we propose an open-pit and underground integrated mining technology for residual coal of end slopes.In the proposal a conveyance road and ventilation conveyance near the slope are built,corresponding to the pit mining area and the surface coal mine dump,as well as an interval haulage tunnel and air-inlet tunnel.The outcome shows that such mining method may reduce the effect to slope stability from underground mining,it does not affect the dumping advance and has a high recovery rate of residual coal resources.The working face is timbered by single hydraulic props,transported by a scraper conveyor and supported by coal walls.This method of mining is one of layered top coal caving,with high resource recovery,low production cost where positive economic benefit can be realized.
