Life cycle assessment (LCA) of waste management strategies: Landfilling,sorting plant and incineration

This paper focuses on a Life Cycle Assessment (LCA) of four waste management strategies: landfill without biogas utilization; landfill with biogas combustion to generate electricity; sorting plant which splits the inorganic waste fraction (used to produce electricity via Refuse Derived Fuels, RDF) from the organic waste fraction (used to produce biogas via anaerobic digestion); direct incineration of waste. These scenarios are applied to the waste amount and composition of the Municipality of Roma (Italy) and are evaluated under different points of view: global and local emissions, total material demands, total energy requirements and ecological footprints. Results, reliable for most of the European big cities, show landfill systems as the worst waste management options and significant environmental savings at global scale are achieved from undertaking energy recycling. Furthermore, waste treatments finalized to energy recovery provide an energy output that, in the best case, is able to meet the 15% of Roma electricity consumption.     

From waste to electricity through integrated plasma gasification/fuel cell (IPGFC) system

The waste management is become a very crucial issue in many countries, due to the ever- increasing amount of waste material, both domiciliary and industrial, generated.The main strategies for the waste management are the increase of material recovery (MR), which can reduce the landfill disposal, the improvement of energy recovery (ER) from waste and the minimization of the environmental impact.These two last objectives can be achieved by introducing a novel technology for waste treatment based on a plasma torch gasification system integrated with a high efficiency energy conversion system, such as combined cycle power plant or high-temperature fuel cells.This work aims to evaluate the performance of an Integrated Plasma Gasification/Fuel Cell system (IPGFC) in order to establish its energy suitability and environmental feature.The performance analysis of this system has been carried out by using a numerical model properly defined and implemented in Aspen Plus™ code environment. The model is based on the combination of a thermochemical model of the plasma gasification unit, previously developed by the authors (the so-called EquiPlasmaJet model), and an electrochemical model for the SOFC fuel cell stack simulation.The EPJ model has been employed to predict the syngas composition and the energy balance of an RDF (Refuse Derived Fuel) plasma arc gasifier (that uses air as plasma gas), whereas the SOFC electrochemical model, that is a system-level model, has allowed to forecast the stack performance in terms of electrical power and efficiency.Results point out that the IPGFC system is able to produce a net power of 4.2 MW per kg of RDF with an electric efficiency of about 33%. This efficiency is high in comparison with those reached by conventional technologies based on RDF incineration (20%).     

垃圾衍生燃料热重法的燃烧特性

采用热重技术对由垃圾可燃物制备的垃圾衍生燃料(RDF)的燃烧特性进行了实验研究，并由微分热重曲线计算了它们燃烧反应的动力学参数．研究结果表明，草木类RDF存在二次着火现象，织物、塑料及混合原料RDF只存在固碳着火点．草木类RDF最易着火燃烧并且燃烧最猛烈但持续时间很短，塑料类RDF最耐烧，混合原料RDF的燃烧反应较平稳并且持续时间较长，易于实现稳定的燃烧．RDF的燃烧过程可由几个一级反应来描述．混合原料RDF中的各组成原料的燃烧相互影响，其燃烧特性不能由各组成原料燃烧特性简单叠加而成，各种原料RDF燃烧的难易程度可用表观活化能来表征。     

Municipal solid-waste in Port Harcourt,Nigeria

In Port Harcourt metropolis, municipal solid-waste (MSW) is generated and collected in large quantities, but some remains as litter in parts of the municipality. Refuse is mostly buried, but some reckless open-burning ensues, so posing environmental hazards. Waste collected from different receptacles and dumpsites in the city was subjected to analysis: on average, it consisted of 66.6% volatile solids, 13.5% fixed solids, 19.1% liquid and 0.8% other components. The average biodegradability fraction is 0.807, with a carbon-to-nitrogen ratio of 27:1. The energy content of the refuse was 7.25 MJ/kg as collected. These results indicate that such refuse is amenable to several disposal options with less adverse impact on the environment. It is also a source of energy.     

A feasibility study of energy recovery of RDF from municipal solid waste

Municipal Solid Waste (MSW) is being used in energy-to-waste plants and as fuel substitutes in different industrial processes. Particularly Refuse Derived Fuel (RDF) from MSW has been widely using in the current practice. This paper aims at conducting a feasibility study of energy recovery of RDF from MSW generated in Pyongyang per year. This study considers the combustibles as RDF resource (i.e. plastics, paper, textile, mixed organic waste, wood, and rubber) in an evaluation of energy recovery. This feasibility study is conducted in two ways: the evaluations of potential energy content and electricity from the RDF resource, which are carried out by methodologies based on heating values of RDF resource and efficiencies of energy recovery, respectively. The results show that the total energy content from RDF resource based on Lower Heating Value (LHV) is approximately 2,813,678.7 GJ/yr, while it is available to generate electricity in a range of 101,320,570?210,435,030 kWh/yr depending on different net efficiencies. This research findings provide a feasibility of RDF utilization for energy recovery to the local planners.     

基于源头提质制RDF中垃圾机械分选效率研究

城市生活垃圾的产量与日俱增,对现已产生的生活垃圾,最好的办法是回收其中的物质和能源,即垃圾资源化,实现垃圾资源化的首要问题就是垃圾的源头分类或提质。但是由于我国人口众多、居民的环境意识差、垃圾处于混合收集等原因,造成了我国源头分类难的问题。文章提出了垃圾按质分为干湿两类,然后再把干湿两类分别处理,其中干组分经过人工分选和机械分选后,进行破碎成型,制备RDF燃料;针对这种源头提质制备RDF环节中机械分选的效率进行研究,分析了滚筛、滚筒、风机等机械设备对分选效率的影响,最后得出最佳的机械分选参数,极大地优化了机械分选过程,起到了在制备RDF前处理过程中源头提质的作用。     

矿化垃圾制备RDF的工艺研究及应用前景分析

分析了我国矿化垃圾的产量和开发利用的资源以及环境意义。通过对比新鲜垃圾和矿化垃圾的成分、含量,发现从矿化垃圾中分选出的可燃物将更适合制备RDF,且其预测应用基低位热值约为24807kJk.g-1,相当于无烟煤的热值,具有较高的燃料品质,应用前景良好。还推荐了矿化垃圾制备RDF的工艺流程,并论述了其应用价值。     

Modelling and performance analysis of an integrated plasma gasification combined cycle (IPGCC) power plant

The waste management is become a very crucial issue in many countries, due to the ever-increasing amount of waste material, both domiciliary and industrial, generated. The main strategies for the waste management are the increase of material recovery (MR) which can reduce the landfill disposal, the improvement of energy recovery (ER) from waste and the minimization of the environmental impact.Recent studies have focused on an innovative technology, the plasma gasification, that has been demonstrated as one of the most effective and environmentally friendly methods for solid waste treatment and energy utilization.In this paper, a plasma gasification process based on plasma torch technology has been investigated by developing a thermochemical model (EPJ, EquiPlasmaJet) able to estimate both the syngas composition and the energy required for the gasification reactions. The EPJ model has been employed to predict the syngas composition and the energy balance of a RDF (refuse derived fuel) plasma arc gasification reactor using air as plasma gas, and, in order to define the optimal operating conditions three different configurations have been investigated.Results show that, in the better plant solution, the plasma gasification efficiency is 69.1% (LHV) and the lower heating value of the syngas generated is about 9 MJ/kg. Furthermore in order to evaluate the suitability of this technology for energy recovery from solid wastes, the integration of the optimum plasma gasification system (PGS) with a gas turbine combined cycle (GTCC) has been analysed and the performance of the resulting integrated plasma gasification combined cycle (IPGCC) has been evaluated. The system efficiency (31% LHV) is very high in comparison with the efficiency of conventional technologies based on waste incineration (20%).     

矿化垃圾一种可再生的燃料矿藏

分析了10年陈矿化垃圾组分特性，讨论了矿化垃圾用作可再生燃料的经济性与潜力及可行性。研究发现矿化垃圾中的可燃成分以塑料为主，另有木竹和纤维。与新鲜垃圾相比水份低，制作燃料（垃圾衍生燃料）无需干燥步骤，过程卫生，无臭气，制成工艺可望更简单。矿化垃圾作为再生燃料利用不仅可以回收能源，而且为城市垃圾的处理提供了经济、长效机制。     

废物衍生燃料_RDF_加压热解特性及其动力学研究

利用加压热重分析仪对城市固体废弃物衍生燃料（RDF）中厨余物等典型有机组份进行了加压热分析研究,实验载气为高纯氮气,加热速率为20K/min,终温773K。通过对热重（TG）、微分热量（DTG）曲线的深入分析,得出了加压条件下RDF中几种典型有机组份的热解反应动力学参数,并提出相应的热解机理。     

垃圾衍生燃料炭化物燃烧特性分析

利用热分析方法研究垃圾衍生燃料(RDF)和垃圾衍生燃料炭化物(cRDF)的燃烧特性,分析RDF和cRDF的燃烧TG-DTG曲线,得出RDF和cRDF的着火温度、燃烧特性指数和燃烧动力学参数等燃烧特性.研究表明,cRDF发热量比RDF高34%～43%,但由于挥发分含量较低,燃烧性能不及RDF,因此cRDF作为燃料时应和其它燃料配合使用,以改善其着火性能.     

宁波大岙垃圾卫生填埋场填埋气的综合利用

介绍了宁波大岙垃圾卫生填埋场在填埋气产生量估算的基础上,开发填埋气燃烧系统、填埋气砖厂利用项目、填埋气燃烧发电项目,实现了节能减排与综合利用。     

RDF production plants: I Design and costs

Municipal solid waste (MSW) management calls for the integration of different recovery, recycling and disposal technologies. Among these possible options, MSW may be treated in order to obtain a fuel to be sold to third party users or directly utilized to generate electricity provided it is of sufficient quality to be employed instead of traditional fuels. In this two-part paper the problem of producing refuse derived fuel (RDF) having a high heating value (LHV>4000 kcal/kg) has been examined from a technical and economic viewpoint. In the first part article a technical assessment of production plants is carried out. Different production lines have been thus compared in terms of mass efficiency, heating value of produced RDF and treatment cost highlighting how the choice of process equipment affects the system performances. As a result the process plant configurations enabling to meet the required product specifications are identified. The influence of mixing a high calorific waste such as scrap tires with the stream of household waste, in the limits allowed by current regulation, has been also analyzed and found to be a prerequisite to meet the prescribed heating value target. Economic feasibility and financial risk of RDF production plants have been successively evaluated in the second part article over a capacity range of 25–200 t/h considering also integrated facilities including compost production and/or electricity generation. The analysis has been carried out with reference to the current Italian market scenario even if it has a general applicability and its relevance is wider geographically.     

Optimization of municipal solid waste (MSW) disposal in Saudi Arabia

Municipal solid waste (MSW) mainly comprises organics, paper, glass, plastics, metals, wood, etc. Rapid industrialization, high population growth rate, and fast urbanization have resulted in increased levels of pollution and MSW in Saudi Arabia. The amount of waste has been steadily increasing due to increasing human population and urbanization. Recovery refers to materials removed from the waste stream for the purpose of recycling and/or composting. There are various options available to convert solid waste to energy. Mainly, the following types of technologies are available: (1) sanitary landfill, (2) incineration, (3) pyrolysis, (4) gasification, and (5) anaerobic digestion. An integrated MSW disposal policy comprises (1) reduction of MSW source, (2) reuse of MSW, (3) recycling of MSW, (4) landfill and gas-to-energy conversion, and (5) MSW-to-energy conversion. Traditionally, MSWs have been disposed in landfills. Landfill is the most inexpensive waste disposal option. The main MSW disposal policies and barriers have been concluded in this study.     

上海城市垃圾焚烧和发电技术分析

介绍了垃圾焚烧发电技术 ,并以上海两座生活垃圾焚烧发电厂为例 ,对垃圾的处理及污染防治进行了阐述。     

Process analysis of refuse derived fuel hydrogasification for producing SNG

Toxic emissions from waste thermal treatments are a major issue that in several countries hinders a full waste cycle. This paper addresses the specific topic of a sustainable exploitation of the refuse derived fuel (RDF). Because concerns still arise when using RDF as fuel, a new approach for its exploitation, the RDF hydrogasification for producing synthetic natural gas (SNG), is discussed herein.The process has been simulated with Aspen code. The best operating conditions to maximize methane yield, under thermodynamic equilibrium conditions, have been studied while the composition of the obtained SNG has been verified in order to comply with the requirements of the methane grid. Furthermore, the analysis looked at the effect of the hydrogen excess in promoting the methane yield and the reduction of the dioxins formation.The energy analysis of the process, that has considered the use of commercial alkaline electrolysers for producing hydrogen, has been found to be mainly affected by the electric power consumption and has exhibited values of energy efficiency around 61%.Finally, a preliminary assessment of the economic competitiveness of this process has been done in order to clarify if the benefits from costs avoided for waste disposal could be the breakthrough in making RDF a sustainable competitive fuel.     

Life cycle net energy and global warming impact assessment for hydrogen production via decomposition of ammonia recovered from source-separated human urine

Decomposition of ammonia derived from source-separated human urine is a renewable approach for hydrogen production. Life cycle net energy analysis and global warming impact of scaled-up hydrogen production via this technique are studied in this paper. Ammonia decomposition processes, including fixed-bed reactors with Ru/Al₂O₃ and Ni/Al₂O₃ as catalyst options are simulated using the Aspen Plus software, and the results are compared with published data for validation. The life cycle net energy indicators are assessed for three scenarios of ammonia generation: conventional air stripping, microbial fuel cell, and electrochemical cell methods at a unit basis of 1000 kg of H₂ production. Results show that the microbial fuel cell process is more energy-efficient and emits lower greenhouse gases. The net energy ratio of the microbial fuel cell method is 1.38, and 1.12, for Ru/Al₂O₃ and Ni/Al₂O₃, respectively. A comparative assessment of ammonia generation and decomposition options for environmentally-benign hydrogen production is discussed.     

From biogas-to hydrogen – Based integrated urban water,energy and waste solids system - Quest towards decarbonization

Three integrated systems of water and municipal solid waste (MSW) management were evaluated regarding their energy use, production and CO_2eq emissions:(1) Biogas based aerobic treatment of wastewater and waste solids disposal by landfilling wherein codigesting sludge with MSW and landfill gas capture produce electricity by a turbine and generator.(2) Biogas based wastewater treatment with codigestion of sludge with biodegradable solids combined with incineration of combustible sludge and other solids.(3) Hydrogen-based system replacing landfilling by indirect gasification of organic solids followed by hydrogen fuel cells.There are great differences between CO_2eq emissions of biogas and hydrogen-based systems. The first two systems are positive CO₂ and methane emitters. Achieving net zero carbon emissions is unlikely. The H₂ based system is fully decarbonized and in addition to clean water, energy and negative carbon dioxide emissions it produces valuable commodities such as energy, concentrated hydrogen, fertilizers, oxygen/ozone, and concentrated carbon dioxide.     

Assessment of environmental and economic performance of Waste-to-Energy facilities in Thai cities

Waste-to-Energy (WtE) technologies seem to be an option to tackle the growing waste management problems in developing Asia. This paper presents a quantitative assessment of the environmental and economic attributes of two major WtE technologies: landfill gas to energy (LFG-to-energy) and incineration in Thai cities. Net greenhouse gas (GHG) emissions, net fossil resource consumption and net life-cycle cost (LCC) were used as the basic indicators for measuring performance of these two technologies from a life cycle perspective. The assessment found that at the current efficiency level, both the LFG-to-energy project and the incineration facility contribute to GHG mitigation and fossil resource savings as compared to the Business as Usual (BAU) practice. However, the financial returns from these operations are very low and insufficient to compensate the costs. The paper argues that substantial improvements of WtE plants can be made by adopting proper management practices, enhancing the efficiencies of energy production. Such upgrading would further reduce GHG emissions, increase fossil resource savings and strengthen the financial performance to the benefit of local governments. The authors recognize the potential of incorporating other treatment options along with WtE technologies, for moving towards more sustainable waste management approaches like integrated waste management systems.     

Jet flames of a refuse derived fuel

This paper is concerned with combustion of a refuse derived fuel in a small-scale flame. The objective is to provide a direct comparison of the RDF flame properties with properties of pulverized coal flames fired under similar boundary conditions. Measurements of temperature, gas composition (O₂, CO₂, CO, NO) and burnout have demonstrated fundamental differences between the coal flames and the RDF flames. The pulverized coals ignite in the close vicinity of the burner and most of the combustion is completed within the first 300 ms. Despite the high volatile content of the RDF, its combustion extends far into the furnace and after 1.8 s residence time only a 94% burnout has been achieved. This effect has been attributed not only to the larger particle size of fluffy RDF particles but also to differences in RDF volatiles if compared to coal volatiles. Substantial amounts of oily tars have been observed in the RDF flames even though the flame temperatures exceeded 1300 °C. The presence of these tars has enhanced the slagging propensity of RDF flames and rapidly growing deposits of high carbon content have been observed.