Environmental assessment of different management options for individual waste fractions by means of life-cycle assessment modelling

Several alternatives exist for handling of individual waste fractions, including recycling, incineration and landfilling. From an environmental point of view, the latter is commonly considered as the least desirable option. Many studies based on life-cycle assessment (LCA) highlight the environmental benefits offered by incineration and especially by recycling. However, the landfilling option is often approached unjustly in these studies, maybe disregarding the remarkable technological improvements that landfills have undergone in the last decades in many parts of the world.This study, by means of LCA-modelling, aims at comparing the environmental performance of three major management options (landfilling, recycling and incineration or composting) for a number of individual waste fractions. The landfilling option is here approached comprehensively, accounting for all technical and environmental factors involved, including energy generation from landfill gas and storage of biogenic carbon. Leachate and gas emissions associated to each individual waste fraction have been estimated by means of a mathematical modelling. This approach towards landfilling emissions allows for a more precise quantification of the landfill impacts when comparing management options for selected waste fractions.Results from the life-cycle impact assessment (LCIA) show that the environmental performance estimated for landfilling with energy recovery of the fractions “organics” and “recyclable paper” is comparable with composting (for “organics”) and incineration (for “recyclable paper”). This however requires high degree of control over gas and leachate emissions, high gas collection efficiency and extensive gas utilization at the landfill. For the other waste fractions, recycling and incineration are favourable, although specific emissions of a variety of toxic compounds (VOCs, PAHs, NO_x, heavy metals, etc.) may significantly worsen their environmental performance.     

A system dynamics model for evaluating the alternative of type in construction and demolition waste recycling center - The case of Chongqing, China

This paper presents a system dynamics computer model to evaluate alternative type of recycling center under different policy and economy environments through comparison on the economic feasibility of recycling centers and ratio of savings to costs in C&D waste management. A case study for the City of Chongqing, China is selected. Simulated results show three key factors can contribute to the economic feasibility of recycling and the ratio of savings to costs in C&D waste management: (a) profit; (b) unit recycling cost; (c) extra revenue from location advantage (It was assumed that the mobile centers can attain extra revenue from the location advantage compared with fixed recycling centers). The sensitive analysis and comparison on ratios between public and private sector indicate that to achieve the optimum ratio of savings to costs, design of recycling centers and selection of governmental instruments are determined by the priority list: (1) low extra revenue from location advantage; (2) low profit; (3) low unit recycling cost. Meanwhile, the fluctuation of the three factors must be prior to achieve economic feasibility of corresponding recycling centers.     

Optimizing the treatment and disposal of municipal solid wastes using mathematical programming—A case study in a Greek region

Goal of the work is to present a simplified methodology to optimize an integrated solid waste management system. The methodology performs two optimizations, namely: (i) minimization of the total cost of the MSW system and (ii) minimization of the equivalent carbon dioxide emissions (CO_2e) generated by the whole system. The methodology is modeled via non-linear mathematical equations, uses 32 decision variables and does not require complex LCA databases. The proposed model optimally allocates eight MSW components (paper, cardboard, plastics, metals, glass, food wastes, yard wastes and other wastes) to four MSW management technologies (incineration, composting, anaerobic digestion, and landfilling) after source separation of recyclables has taken place. The Region of East-Macedonia and Thrace in Greece was selected as a case study. Results showed that there is a trade off between cost and CO_2e emissions. Incineration and composting were favored as the principal treatment technologies, while landfilling was always the least desirable management technology under both objective functions. The recycling participation rate significantly affected all optimum scenarios.     

Assessment of the greenhouse effect impact of technologies used for energy recovery from municipal waste: A case for England

Waste management activities contribute to global greenhouse gas emissions approximately by 4%. In particular the disposal of waste in landfills generates methane that has high global warming potential. Effective mitigation of greenhouse gas emissions is important and could provide environmental benefits and sustainable development, as well as reduce adverse impacts on public health. The European and UK waste policy force sustainable waste management and especially diversion from landfill, through reduction, reuse, recycling and composting, and recovery of value from waste. Energy from waste is a waste management option that could provide diversion from landfill and at the same time save a significant amount of greenhouse gas emissions, since it recovers energy from waste which usually replaces an equivalent amount of energy generated from fossil fuels. Energy from waste is a wide definition and includes technologies such as incineration of waste with energy recovery, or combustion of waste-derived fuels for energy production or advanced thermal treatment of waste with technologies such as gasification and pyrolysis, with energy recovery. The present study assessed the greenhouse gas emission impacts of three technologies that could be used for the treatment of Municipal Solid Waste in order to recover energy from it. These technologies are Mass Burn Incineration with energy recovery, Mechanical Biological Treatment via bio-drying and Mechanical Heat Treatment, which is a relatively new and uninvestigated method, compared to the other two. Mechanical Biological Treatment and Mechanical Heat Treatment can turn Municipal Solid Waste into Solid Recovered Fuel that could be combusted for energy production or replace other fuels in various industrial processes. The analysis showed that performance of these two technologies depends strongly on the final use of the produced fuel and they could produce GHG emissions savings only when there is end market for the fuel. On the other hand Mass Burn Incineration generates greenhouse gas emission savings when it recovers electricity and heat. Moreover the study found that the expected increase on the amount of Municipal Solid Waste treated for energy recovery in England by 2020 could save greenhouse gas emission, if certain Energy from Waste technologies would be applied, under certain conditions.     

Bioethanol from waste: Life cycle estimation of the greenhouse gas saving potential

This paper considers two alternative feedstocks for bioethanol production, both derived from household waste—Refuse Derived Fuel (RDF) and Biodegradable Municipal Waste (BMW). Life Cycle Assessment (LCA) has been carried out to estimate the GHG emissions from bioethanol using these two feedstocks. An integrated waste management system has been considered, taking into account recycling of materials and production of bioethanol in a combined gasification/bio-catalytic process. For the functional unit defined as the ‘total amount of waste treated in the integrated waste management system’, the best option is to produce bioethanol from RDF—this saves up to 196 kg CO₂ equiv. per tonne of MSW, compared to the current waste management practice in the UK.However, if the functional unit is defined as ‘MJ of fuel equiv.’ and bioethanol is compared with petrol on an equivalent energy basis, the results show that bioethanol from RDF offers no saving of GHG emissions compared to petrol. For example, for a typical biogenic carbon content in RDF of around 60%, the life cycle GHG emissions from bioethanol are 87 g CO₂ equiv./MJ while for petrol they are 85 g CO₂ equiv./MJ. On the other hand, bioethanol from BMW offers a significant GHG saving potential over petrol. For a biogenic carbon content of 95%, the life cycle GHG emissions from bioethanol are 6.1 g CO₂ equiv./MJ which represents a saving of 92.5% compared to petrol. In comparison, bioethanol from UK wheat saves 28% of GHG while that from Brazilian sugar cane – the best performing bioethanol with respect to GHG emissions – saves 70%. If the biogenic carbon of the BMW feedstock exceeds 97%, the bioethanol system becomes a carbon sequester. For instance, if waste paper with the biogenic carbon content of almost 100% and a calorific value of 18 MJ/kg is converted into bioethanol, a saving of 107% compared to petrol could be achieved. Compared to paper recycling, converting waste paper into bioethanol saves 460 kg CO₂ equiv./t waste paper or eight times more than recycling.     

A model for cost-benefit analysis of construction and demolition waste management throughout the waste chain

Economic instrument is indubitably perceived as effective for encouraging or forcing contractors to conduct environmentally friendly construction practices. Previous studies in relation to this topic mainly put emphasis on economic analysis of construction and demolition (C&D) waste management from a static point of view, which failed to consider its dynamics nature by integrating all essential activities throughout the waste chain. This paper is thus intended to highlight the dynamics and interrelationships of C&D waste management practices and analyze the cost-benefit of this process using a system dynamics approach. Data related to concrete and aggregate of a construction project in Shenzhen was collected for the application of the proposed model. The findings reveal that net benefits from conducting C&D waste management will occur, but a higher landfill charge will lead to a higher net benefit, as well as an earlier realization of the net benefit. In addition, the general public under a higher landfill charge will suffer from a higher environmental cost caused by illegal dumping. The simulation results also suggest that current regulation in Shenzhen should be promoted to facilitate a dramatic increase in net benefit from the implementation of C&D waste management. This research is of value in facilitating better understanding on the dynamics of C&D waste management activities throughout the waste chain, as well as providing a tool for simulating the cost-benefit of C&D waste management practices over the project duration.     

Waste‐to‐energy recovery potential: A case study at Jaipur railway station

A study was conducted at the Jaipur railway station in Jaipur, India, to give the perspectives of the actual waste management practices there. Required information was collected from the stakeholders by means of semi‐structured questionnaires, individual and group interviews, and recorded, official data regarding waste generation, collection, transportation, and disposal. Further quantitative and compositional analyses were performed by means of surveys and measurements. Field visits were made for collection of waste samples for quantification and for the study of its management. The field data were compiled and analyzed by sorting the waste into different components. It was found that 1.8 tons of solid waste is collected per day, and a considerable percentage of it comprises paper, plastic, and glass. Excluding the inerts, which are irrelevant from the point of view of energy saving and recovery potential, the average moisture content was found to be 3.38%. From the perspective of life cycle analysis, the option of composting or recycling would give savings of 28.33 gigajoules (GJ) per day over landfilling, while combustion would give savings of 2.97 GJ per day in comparison to landfilling. Analysis based on a compositional model gives a heat value of 8,157.87 kilojoules per kilogram, which amounts to 14.68 GJ of energy per day.     

Assessing energy use and greenhouse gas emission savings from compact housing: a small-town case study

Data from the US Department of Energy show that single-family detached homes consume about 17% more energy per year than attached homes and roughly double that of units in large multi-family structures. While greater use of these compact housing types could reduce a community's energy use and greenhouse gas (GHG) emissions, most local climate action plans (CAPs) do not quantify those potential savings. This article describes how the climate action planning process in the Town of Blacksburg, Virginia has addressed residential sector GHG emissions and demonstrates a methodology applied in that community for estimating potential GHG reductions from compact housing. It finds that in an aggressive compact housing scenario GHG emissions from new housing could be decreased by as much as 36%, without factoring in additional energy conservation or efficiency measures. The article concludes with a discussion of the opportunities and challenges related to implementing compact housing in future residential development.     

Energy savings from solid waste management options

An essential difference in solid waste management systems lies in their treatment of the large paper component. This study reveals that in most cases considered for southern Ontario, net energy savings are attributable to recycling waste paper rather than using it as a source of energy. It was also found that recycling waste paper could result in a net decrease in air and water pollution. The energy savings attributable to reduction at source options are assessed separately.     

Concrete block production from construction and demolition waste in Tanzania

In Tanzania, construction and demolition (C&D) waste is not recycled and knowledge on how it can be recycled especially into valuable products like building materials are still limited. This study aimed at investigating the possibility of recycling the C&D waste (mainly cementitious rubble) into building material in Tanzania. The building materials produced from C&D waste was concrete blocks. The concrete blocks were required to have a load bearing capacity that meets the building material standards and specifications. Eight C&D waste samples were collected from C&D building sites, transported to the recycling site, crushed, and screened (sieved) to get the required recycled aggregates. Natural aggregates were also used as control. The recycled aggregates were tested in the laboratory following the standard methods as specified in Tanzanian standards. The physical, mechanical and chemical characteristics were determined. The physical and mechanical results showed that recycled aggregates were weaker than natural aggregates. However, chemically they were close to natural aggregates and therefore suitable for use in new concrete block production. In the production process, each experiment utilized 100% recycled aggregates for both fine and coarse portions to replace natural aggregates. The Fuller's maximum density theory was used to determine the mix proportions of materials in which a method that specifies concrete mix by system of proportion or ratio was used. The concrete blocks production processes included batching, mixing (that was done manually to get homogeneous material), compacting and moulding by hand machine and curing in water. After 28 days of curing, the concrete blocks were tested in the laboratory on compressive strength, water absorption ratio and density. The results showed that the blocks produced with 100% recycled aggregates were weaker than those with natural aggregates. However, the results also showed that there is a possibility of recycling the C&D waste into building material because 85% of the tested concrete block specimens from recycled aggregates achieved a compressive strength of 7 N/mm², which is defined as the minimum required load bearing capacity in Tanzania. Therefore, the C&D waste could be a potential resource for building material production for sustainable construction in Tanzania rather than discarding it. Further work should focus on the economic feasibility of production of concrete blocks with recycled aggregates in Tanzania.     

Modeling materials flow of waste concrete from construction and demolition wastes in Taiwan

Material flows of concrete from construction and demolition (C&D) waste in Taiwan have grown considerably over the last two decades, Hsiao et al. (2001). This increased flow puts pressure on limited national disposal capacity and has indirectly caused ecological damage to domestic riparian zones used as sources of natural aggregate. Using existing statistics and literature sources for C&D waste generation in Taiwan we have developed a dynamic model of domestic material flows of concrete waste and employ statistical analyses to obtain projections of future material flows. Our major findings are: (1) Taiwan’s rate of waste concrete generation in 2001 for the residential and commercial construction industry was approximately 2.4 Million Metric Tons (MMT) per year, averaging 0.11 metric tons of waste concrete generated annually by each Taiwanese; (2) Around the year 2009, the national rate will more than triple to exceed the spike in C&D concrete waste generation that occurred after the Chi Chi earthquake 9/21/99, 8.5 MMT. (3) Aside from pilot-scale development of waste concrete utilization technology, nationwide recycling rates remain negligible. Without resource recovery, the volume of C&D waste generation by 2009 is projected to occupy nearly 7% of all existing and planned domestic landfill capacity. A target is established to raise resource recovery rates for waste concrete to 50% by 2005 and a 100% nationwide recycling rate by 2009.     

Life cycle analysis of silane recycling in amorphous silicon-based solar photovoltaic manufacturing

Amorphous silicon (a-Si:H)-based solar cells have the lowest ecological impact of photovoltaic (PV) materials. In order to continue to improve the environmental performance of PV manufacturing using proposed industrial symbiosis techniques, this paper performs a life cycle analysis (LCA) on both conventional 1-GW scaled a-Si:H-based single junction and a-Si:H/microcrystalline-Si:H tandem cell solar PV manufacturing plants and such plants coupled to silane recycling plants. Both the energy consumed and greenhouse gas emissions are tracked in the LCA, then silane gas is reused in the manufacturing process rather than standard waste combustion. Using a recycling process that results in a silane loss of only 17% instead of conventional processing that loses 85% silane, results in an energy savings of 81,700 GJ and prevents 4400 tons of CO₂ from being released into the atmosphere per year for the single junction plant. Due to the increased use of silane for the relatively thick microcrystalline-Si:H layers in the tandem junction plants, the savings are even more substantial – 290,000 GJ of energy savings and 15.6 million kg of CO₂ eq. emission reductions per year. This recycling process reduces the cost of raw silane by 68%, or approximately $22.6 million per year for a 1-GW a-Si:H-based PV production facility and over $79 million per year for tandem manufacturing. The results are discussed and conclusions are drawn about the technical feasibility and environmental benefits of silane recycling in an eco-industrial park centered around a-Si:H-based PV manufacturing plants.     

Evaluation of life cycle inventory data for recycling systems

This paper reviews databases on material recycling (primary as well as secondary production) used in life cycle assessments (LCA) of waste management systems. A total of 366 datasets, from 1980 to 2010 and covering 14 materials, were collected from databases and reports. Totals for CO₂-equivalent emissions were compared to illustrate variations in the data. It was hypothesised that emissions from material production and the recycling industry had decreased over time due to increasing regulation, energy costs and process optimisation, but the reported datasets did not reveal such a general trend. Data representing the same processes varied considerably between databases, and proper background information was hard to obtain, which in turn made it difficult to explain the large differences observed. Those differences between the highest and lowest estimated CO₂ emissions (equivalents) from the primary production of newsprint, HDPE and glass were 238%, 443% and 452%, respectively. For steel and aluminium the differences were 1761% and 235%, respectively. There is a severe lack of data for some recycled materials; for example, only one dataset existed for secondary cardboard. The study shows that the choice of dataset used to represent the environmental load of a material recycling process and credited emissions from the avoided production of virgin materials is crucial for the outcome of an LCA on waste management. Great care and a high degree of transparency are mandatory, but advice on which datasets to use could not be determined from the study. However, from the gathered data, recycling in general showed lower emission of CO₂ per kg material than primary production, so the recycling of materials (considered in this study) is thus beneficial in most cases.     

Environmental impact evaluation of feeds prepared from food residues using life cycle assessment

There is increasing concern about feeds prepared from food residues (FFR) from an environmental viewpoint; however, various forms of energy are consumed in the production of FFR. Environmental impacts of three scenarios were therefore investigated and compared using life cycle assessment (LCA): production of liquid FFR by sterilization with heat (LQ), production of dehydrated FFR by dehydration (DH), and disposal of food residues by incineration (IC). The functional unit was defined as 1 kg dry matter of produced feed standardized to a fixed energy content. The system boundaries included collection of food residues and production of feed from food residues. In IC, food residues are incinerated as waste, and thus the impacts of production and transportation of commercial concentrate feeds equivalent to the FFR in the other scenarios are included in the analysis. Our results suggested that the average amounts of greenhouse gas (GHG) emissions from LQ, DH, and IC were 268, 1073, and 1066 g of CO(2) equivalent, respectively. The amount of GHG emissions from LQ was remarkably small, indicating that LQ was effective for reducing the environmental impact of animal production. Although the average amount of GHG emissions from DH was nearly equal to that from IC, a large variation of GHG emissions was observed among the DH units. The energy consumption of the three scenarios followed a pattern similar to that of GHG emissions. The water consumption of the FFR-producing units was remarkably smaller than that of IC due to the large volumes of water consumed in forage crop production.     

Best practice measures assessment for construction and demolition waste management in building constructions

Currently the construction and demolition (C&D) waste collection system in Spain is managed in a decentralized manner by each sub-contracted company. This lack of comprehensive strategy for C&D waste management causes a confusing and sometimes individual attitude regarding the different measures for C&D waste. Therefore effective waste management should be enforced. Construction stakeholders have wide range of best practices in C&D waste management that can be implemented, so they need to be assessed for their effectiveness.The aim of this research study is to assist construction stakeholders in making a decision on C&D waste management. This paper carries out a survey conducted among the construction agents in order to evaluate the effectiveness of 20 best practice measures regarding C&D waste management, identifying the most suitable types of building constructions to implement these practices and also the advantages and drawbacks of their performance in a building construction project.Results of this study show that among the highly effective best practices are: the use of industrialized systems and the contract of suppliers managing the waste. In addition, distributing small containers in the work areas is also another high valued practice, although only 36% of respondents usually implement this measure in their works.     

Reverse logistics in the Brazilian construction industry

In Brazil most Construction and Demolition Waste (C&D waste) is not recycled. This situation is expected to change significantly, since new federal regulations oblige municipalities to create and implement sustainable C&D waste management plans which assign an important role to recycling activities. The recycling organizational network and its flows and components are fundamental to C&D waste recycling feasibility. Organizational networks, flows and components involve reverse logistics. The aim of this work is to introduce the concepts of reverse logistics and reverse distribution channel networks and to study the Brazilian C&D waste case.     

Global Warming Impact of Electricity Generation from Beef Cattle Manure: A Life Cycle Assessment Study

We compare calculated greenhouse gas emissions for a North American beef feedlot operation, which includes biogas production by anaerobic digestion with subsequent electricity generation (the AD case), to the emissions for a “business as usual” case, which includes both a feedlot and an equivalent amount of grid-generated electricity. Anaerobic digestion, biogas production and electricity production are the major sources of differences in emissions. Fertilizer production, crop production, manure collection and spreading, as well as the associated transport stages are also considered within the LCA system boundaries; impacts on life cycle emissions from these sources are lower. Running a feedlot and producing electricity using typical grid power plants produces 3,845 kg CO_2?eq/MWh while running a feedlot, which generates biogas to produce electricity, produces 2,965 kg CO_2?eq/MWh. This savings of 880 kg CO_2?eq/MWh arises because the net power generation in the AD case emits about 90% less life cycle GHG emissions compared to grid-average electricity. The high overall emission levels arise due to emissions associated with enteric fermentation in beef cattle as the main source of GHG emissions in both the “business as usual” and the AD cases. It contributed 57% of total emissions for the feedlot /biogas /electricity system and 44% of total emissions for the feedlot /grid electricity system.     

Processing of Straw/Corn Stover: Comparison of Life Cycle Emissions

The LCA emissions from four renewable energy routes that convert straw/corn stover into usable energy are examined. The conversion options studied are ethanol by fermentation, syndiesel by oxygen gasification followed by Fischer Tropsch synthesis, and electricity by either direct combustion or biomass integrated gasification and combined cycle (BIGCC). The greenhouse gas (GHG) emissions of these four options are evaluated, drawing on a range of studies, and compared to the conventional technology they would replace in a western North American setting. The net avoided GHG emissions for the four energy conversion processes calculated relative to a “business as usual” case are 830 g CO₂e/kWh for direct combustion, 839 g CO₂e/kWh for BIGCC, 2,060 g CO₂e/L for ethanol production, and 2,440 g CO₂e/L for FT synthesis of syndiesel. The largest impact on avoided emissions arises from substitution of biomass for fossil fuel. Relative to this, the impact of emissions from processing of fossil fuel, e.g., refining of oil to produce gasoline or diesel, and processing of biomass to produce electricity or transportation fuels, is minor.     

Economics and GHG emission reduction of a PLA bio-refinery system—Combining bottom-up analysis with price elasticity effects

This paper analyses energy savings, GHG emission reductions and costs of bio-refinery systems for polylactic acid (PLA) production. The systems comprise ‘multi-functional’ uses of biomass resources, i.e. use of agricultural residues for energy consumption, use of by-products, and recycling and waste-to-energy recovery of materials. We evaluate the performance of these systems per kg of bio-based polymer produced and per ha of biomass production. The evaluation is done using data of Poland assuming that biomass and PLA production is embedded in a European energy and material market. First, the performance of different bio-refinery systems is investigated by means of a bottom-up chain analysis. Second, an analysis is applied that derives market prices of products and land depending on the own-price elasticity of demand. Thus, the costs of bio-refinery systems depending on the demand of land and material are determined. It is found that all PLA bio-refinery systems considered lead to net savings of non-renewable energy consumption of 70–220 GJ/(ha yr) and net GHG emission reductions of 3–17 Mg CO_2eq/(ha yr). Most of these PLA bio-refinery systems lead to net costs for the overall system of up to 4600 €/(ha yr). PLA production from short rotation wood leads to net benefits of about 1100 €/(ha yr) if a high amount of a high value product, i.e. fibres, is produced. Multi-functionality is necessary to ensure the viability of PLA bio-refinery systems from biomass with regard to energy savings and GHG emission reduction. However, the multi-functional use of biomass does not contribute much to overall incomes. Multifunctional biomass use – especially the use of biomass residues for energy consumption – contributes significantly to savings of non-renewable energy sources. Own-price elasticity of the demand for materials influences the overall costs of the bio-refinery system strongly. The own-price elasticity of land demand markets could become important if bio-refineries are introduced on a large scale.     

Decisions on recycling: Construction stakeholders’ decisions regarding recycled mineral construction materials

Construction and demolition (C&D) waste, being already the largest waste fraction in industrialized countries, is expected to increase in the future. C&D waste recycling has been considered to be a valuable option not only for minimizing C&D waste streams to landfills but also for mitigating primary mineral resource depletion. Even though the use of recycled mineral construction materials (RMCM) is regulated and successful application examples are available, construction stakeholders do not yet broadly apply them. Although various criteria hindering a transition towards a broader application of RMCM have been identified, it is yet unknown how these criteria differ among decisions, stakeholders and applications. We therefore analyze construction stakeholders’ behavior, and decision-making regarding RMCM for the construction material market in Switzerland. Stakeholders’ decision-making was quantified with the analytical hierarchy process (AHP) in a survey in combination with their behavior. The results demonstrate the importance of stakeholder interaction, i.e. most stakeholders decide which material to apply based on interaction with other stakeholders e.g., recommendations and specifications. However, the initial general specification by awarding authorities that construction should be sustainable has little relevance to the subsequent material decisions. On the contrary the role of the recommendation of engineers, have a high impact on the subsequent decisions by the other stakeholders. Results also confirm that RMCM are broadly accepted in civil engineering (CE), whereas in structural engineering (SE) RMCM are still a niche product. The good alignment of the outcome of decision modeling with observed behavior shows the usefulness of analyzing decision-making with AHP.