Greenhouse gas emission and its potential mitigation process from the waste sector in a large-scale exhibition.

As one of the largest human activities, World Expo is an important source of anthropogenic Greenhouse Gas emission (GHG), and the GHG emission and other environmental impacts of the Expo Shanghai 2010, where around 59,397 tons of waste was generated during 184 Expo running days, were assessed by life cycle assessment (LCA). Two scenarios, i.e., the actual and expected figures of the waste sector, were assessed and compared, and 124.01 kg CO2-equivalent (CO2-eq.), 4.43 kg SO2-eq., 4.88 kg NO3--eq., and 3509 m3 water per ton tourist waste were found to be released in terms of global warming (GW), acidification (AC), nutrient enrichment (NE) and spoiled groundwater resources (SGWR), respectively. The total GHG emission was around 3499 ton CO2-eq. from the waste sector in Expo Park, among which 86.47% was generated during the waste landfilling at the rate of 107.24 kg CO2-eq., and CH4, CO and other hydrocarbons (HC) were the main contributors. If the waste sorting process had been implemented according to the plan scenario, around 497 ton CO2-eq. savings could have been attained. Unlike municipal solid waste, with more organic matter content, an incineration plant is more suitable for tourist waste disposal due to its high heating value, from the GHG reduction perspective.

Environmental impacts of a large-scale incinerator with mixed MSW of high water content from a LCA perspective.

Large-scale incinerators are applied widely as a result of the heavy burden of municipal solid waste (MSW) generated, while strong opposition is arising from the public living nearby. A large-scale working incineration plant of 1500 ton/day was chosen for evaluation using life cycle assessment. It was found that the corresponding human toxicity impacts via soil (HTs), human toxicity impacts via water (HTw) and human toxicity impacts via air (HTa) categories are 0.213, 2.171, and 0.012 personal equivalents (PE), and global warming (GW100) and nutrient enrichment (NE) impacts are 0.002 and 0.001 PE per ton of waste burned for this plant. Heavy metals in flue gas, such as Hg and Pb, are the two dominant contributors to the toxicity impact categories, and energy recovery could reduce the GW100 and NE greatly. The corresponding HTs, HTw and HTa decrease to 0.087, 0.911 and 0.008 PE, and GW100 turns into savings of -0.007 PE due to the increase of the heating value from 3935 to 5811 kJ/kg, if a trommel screener of 40 mm mesh size is used to pre-separate MSW. MSW sorting and the reduction of water content by physical pressure might be two promising pre-treatment methods to improve the combustion performance, and the application of stricter standards for leachate discharge and the flue gas purification process are two critical factors for improvement of the environmental profile identified in this work.

A model for estimation of potential generation of waste electrical and electronic equipment in Brazil.

Sales of electrical and electronic equipment are increasing dramatically in developing countries. Usually, there are no reliable data about quantities of the waste generated. A new law for solid waste management was enacted in Brazil in 2010, and the infrastructure to treat this waste must be planned, considering the volumes of the different types of electrical and electronic equipment generated. This paper reviews the literature regarding estimation of waste electrical and electronic equipment (WEEE), focusing on developing countries, particularly in Latin America. It briefly describes the current WEEE system in Brazil and presents an updated estimate of generation of WEEE. Considering the limited available data in Brazil, a model for WEEE generation estimation is proposed in which different methods are used for mature and non-mature market products. The results showed that the most important variable is the equipment lifetime, which requires a thorough understanding of consumer behavior to estimate. Since Brazil is a rapidly expanding market, the "boom" in waste generation is still to come. In the near future, better data will provide more reliable estimation of waste generation and a clearer interpretation of the lifetime variable throughout the years.

Reaching cost-saving effects by a mixed collection of light packagings together with residual household waste?

To enforce material recycling of household waste at high levels, separate collection schemes often under a producer's responsibility regime were implemented in Germany since the 1970s and 1990s, respectively. The separate collection of recyclables (Sorting-Transportation-Sorting-Recovery' system) is assumed, guaranteeing higher purities of the collected material streams but also causing higher costs for logistics and the processing of the waste fractions. Several authors argue that since the rapid development of automatic sorting systems in recent years, a mixed collection of recyclables and residual household waste with a downstream sorting strategy (Transportation-Sorting-Recovery system) is cheaper than the currents system while keeping the product quality constant. This paper evaluates the economic saving potentials in logistics and the extra costs for separation technologies when implementing a mixed collection system for light packagings together with residual household waste in an East German city. The results show that costs for process technologies in a mixed collection system can overcompensate cost-saving potentials in logistics.

Reduction of CO(2)-emissions by using biomass in combustion and digestion plants.

Climate protection is one of the main aims of environmental policy. One way to advance and push the progress is to reduce the use of fossil fuels for energy production through an increasing production of renewable and CO(2)-neutral energy for example through application of biomass. This paper sets the focus on biomass streams that can be used both thermal and biological for energy production like grass or energy crops. To calculate the potentials of decrease of CO(2)-emissions for treatment of biomass in either combustion or digestion plants some scenarios were set up with different assumptions regarding degree of efficiency of treatment plants which depends on size of plants and the treatment process itself. The energetic utilisation of the considered biomass streams is divided in different utilisation scenarios: combined heat and power generation (CHP) and heat generation or power generation only. Additionally four groups of plant sizes referring to electrical power (from 0.1 up to 10.0MW) were taken into consideration. The calculations of potential savings of CO(2)-emission in both types of treatment scenarios lead to the result that in comparison to biological technologies thermal processes show a much higher utilisation of the energy content in biomass.

Determination of heavy metals and halogens in plastics from electric and electronic waste.

The presence of hazardous substances and preparations in small waste electrical and electronic equipment (sWEEE) found in the residual household waste stream of the city of Dresden, Germany has been investigated. The content of sWEEE plastics in heavy metals and halogens is determined using handheld X-ray fluorescence analysis (HXRF), elemental analysis by means of atomic absorption spectrometry (AAS) and ion exchange chromatography (IEC). Mean value of results for heavy metals in samples (n=51) by AAS are 17.4 mg/kg for Pb, 5.7 mg/kg for Cd, 8.4 mg/kg for Cr. The mass fraction of an additive as shown by HXRF (n=161) can vary over a wide range. Precise deductions as regards sWEEE plastics content in hazardous substances and preparations cannot be made. Additional research would be expedient regarding the influence of hazardous substances to recycling processes, in particular regarding the contamination of clean fractions in the exit streams of a WEEE treatment plant. Suitable standards for calibrating HXRF for use on EEE plastics or complex electr(on)ic components do not exist and should be developed.

Small WEEE: determining recyclables and hazardous substances in plastics.

An examination regarding the determination of recyclables and hazardous substances in small waste electrical and electronic equipment (WEEE) found in the residual household waste stream of the city of Dresden, Germany, is described. Firstly, attitudes towards the disposal of small WEEE in the latter are assessed, and product types and categories which mostly contribute to its composition are identified. Physical parameters which could be used as mechanical sorting criteria are measured, and the material composition of the small WEEE found is determined. The hazardous substances' "base" charge in the residual waste is established by means of atomic absorption spectrometry and ionic chromatography, as a first step in estimating the contribution of small WEEE to its pollutant load. Consequently, the content of small WEEE plastics in key heavy metals and halogens is determined. Key conclusions are drawn concerning the future strategic development and practical implementation of the 2002/96/EC Directive, in relation to small WEEE management and recycling.

From traditional to modern fee systems.

This paper deals with the environmentally important issue regarding how best to motivate citizens to reduce their individual waste production. The paper discusses the pros and cons of the various financial incentives incorporated into the waste charging mechanism, pay-as-you-throw (PAYT). Pay-as-you-throw breaks with the tradition of paying for waste services through general blanket taxes or levies in the form of flat rates in that households are required to pay individually adjusted fees in the same way as water and electricity bills are calculated on an individual consumption basis. This difference is achieved through the interplay of three principal components which mark the technical implementation of PAYT: identification as a vehicle to attain accountability, measurement of the generated waste and/or corresponding services, and unit pricing as the basis for individual charges proportional to the extent of the obtained services. However, any motivating factor for inducing citizens to dispose of their recyclable discards and residual waste must be supported by a well developed collection infrastructure, good media information and an appropriate, transparent charging policy. Of particular importance is the use of a multi-tiered charge model, i.e., the charging of a fixed minimum fee plus certain variable components payable in respect of the service structure. The introduction of a basic charge, albeit reducing the intensity of the incentives created by the PAYT system, ensures that certain fixed costs for the provision of waste services will be covered independently from the actual waste developments and, at the same time, minimises the temptation to attempt to bypass the system. Such an arrangement for the waste charges neither contradicts the principle of pay-as-you-throw nor does it impair the waste diversion for which it is implemented. Waste statistics and figures representing the waste charging situation in Germany indicate that there is a relatively good correlation between the level of recycling and the amount of perceived financial motivation provided by PAYT. Waste stream developments in areas using such charging schemes generally suggest that the reduction goals are being achieved. Single figures on decreasing quantities of collected residual waste, however, say little about the actual efficiency of differentiated waste charging models and deliver little in the way of reasoned explanation as to why the diffusion of variable rate pricing is progressing painstakingly slowly. To evaluate the success, feasibility and problems of PAYT schemes, one needs to consider the various ways for technically implementing this approach in practice, and must take a broader look into the wide spectrum of available waste services and into more factors that influence their efficiency and acceptance. Urban structure settings assume a particular importance here as do the specific goals of social policy which, among others, are reflected in the charging mechanisms applied. Practical experience, however, shows that solutions can be found which allow most of the concerns and area specifics to be accommodated and waste streams to be influenced in the desired way. Aside from this, positive effects as to waste collection efficiency can also be achieved, which contribute towards long-term environmental improvements and countervail the incremental costs of implementing PAYT.

Thermal treatment of harzardous waste for heavy metal recovery.

In this study, a new method for recovering heavy metals from hazardous waste is introduced. The process is characterized by a separation of heavy metals and residues during the thermal treatment under a sub-stoichiometric atmosphere in a rotary kiln. After leaving the rotary kiln the separated heavy metals are precipitated in a hot gas ceramic filter. Using this technology, hazardous materials, both liquids and pasty hazardous waste containing heavy metals, can be treated and a product with a quasi-raw material condition can be formed. In contrast to current methods,the harmful substances should not be immobilized and disposed. In fact, a saleable product highly concentrated with heavy metals should be formed. During preliminary investigations with a solution containing sodium chromate tetrahydrate, the process was tested in a pilot plant. Here,the separation of chromium could be demonstrated with leaching tests and characterization of the filter dust. Analysis concerning the disposability of the residues had not been carried out because only the process and the characteristic of the filter dust were in the centre of attention.

Comparative evaluation of life cycle assessment models for solid waste management.

This publication compares a selection of six different models developed in Europe and America by research organisations, industry associations and governmental institutions. The comparison of the models reveals the variations in the results and the differences in the conclusions of an LCA study done with these models. The models are compared by modelling a specific case - the waste management system of Dresden, Germany - with each model and an in-detail comparison of the life cycle inventory results. Moreover, a life cycle impact assessment shows if the LCA results of each model allows for comparable and consecutive conclusions, which do not contradict the conclusions derived from the other models' results. Furthermore, the influence of different level of detail in the life cycle inventory of the life cycle assessment is demonstrated. The model comparison revealed that the variations in the LCA results calculated by the models for the case show high variations and are not negligible. In some cases the high variations in results lead to contradictory conclusions concerning the environmental performance of the waste management processes. The static, linear modelling approach chosen by all models analysed is inappropriate for reflecting actual conditions. Moreover, it was found that although the models' approach to LCA is comparable on a general level, the level of detail implemented in the software tools is very different.

Material flow analysis of RDF-production processes.

The authors evaluate the possibilities of modifying the chemical characteristics of refuse-derived fuels (RDF) that are processed from residual household waste by mechanical operations to achieve and assure quality targets for relevant chemical concentrations, especially for heavy metals and chlorine. Quality assurance in the production of RDF demands that, together with an enrichment of the calorific value, highly toxic waste components are selectively separated and concentrated in a small stream to produce high yields of a relatively low polluted fuel. Based on the method of material flow analysis, a process evaluation is developed that considers the aspect of minimizing hazardous chemicals along with classical process data such as yield and product quality. Data on specific concentration of hazardous chemicals in waste components and their distribution in residual household waste as well as the results from large-scale test runs using different separation techniques demonstrate that mechanical operations alone are insufficient for separating hazardous chemicals. In the test runs, chemical compounds such as chlorine, cadmium and lead were often concentrated in the product. Even using optimized techniques, the ability to reduce hazards in the product is limited due to the distribution of the element concentration in the various components of the waste stream.