Roland Pomberger

Design, quality and quality assurance of solid recovered fuels for the substitution of fossil feedstock in the cement industry

This paper describes the requirements for the production, quality, and quality assurance of solid recovered fuels (SRF) that are increasingly used in the cement industry. Different aspects have to be considered before using SRF as an alternative fuel. Here, a study on the quality of SRF used in the cement industry is presented. This overview is completed by an investigation of type and properties of input materials used at waste splitting and SRF production plants in Austria. As a simplified classification, SRF can be divided into two classes: a fine, high-calorific SRF for the main burner, or coarser SRF material with low calorific value for secondary firing systems, such as precombustion chambers or similar systems. In the present study, SRFs coming from various sources that fall under these two different waste fuel classes are discussed. Both SRFs are actually fired in the grey clinker kiln of the Holcim (Slovensko) plant in Rohožnik (Slovakia). The fine premium-quality material is used in the main burner and the coarse regular-quality material is fed to a FLS Hotdisc combustion device. In general, the alternative fuels are used instead of their substituted fossil fuels. For this, chemical compositions and other properties of SRF were compared to hard coal as one of the most common conventional fuels in Europe. This approach allows to compare the heavy metal input from traditional and alternative fuels and to comment on the legal requirements on SRF that, at the moment, are under development in Europe.

Climate impact analysis of waste treatment scenarios - thermal treatment of commercial and pretreated waste versus landfilling in Austria

A major challenge for modern waste management lies in a smart integration of waste-to-energy installations in local energy systems in such a way that the energy efficiency of the waste-to-energy plant is optimized and that the energy contained in the waste is, therefore, optimally utilized. The extent of integration of thermal waste treatment processes into regular energy supply systems plays a major role with regard to climate control. In this research, the specific waste management situation looked at scenarios aiming at maximizing the energy recovery from waste (i.e. actual scenario and waste-to-energy process with 75% energy efficiency [22.5% electricity, 52.5% heat]) yield greenhouse gas emission savings due to the fact that more greenhouse gas emissions are avoided in the energy sector than caused by the various waste treatment processes. Comparing dedicated waste-to-energy-systems based on the combined heat and power (CHP) process with concepts based on sole electricity production, the energy efficiency proves to be crucial with regard to climate control. This underlines the importance of choosing appropriate sites for waste-to-energy-plants. This research was looking at the effect with regard to the climate impact of various waste management scenarios that could be applied alternatively by a private waste management company in Austria. The research is, therefore, based on a specific set of data for the waste streams looked at (waste characteristics, logistics needed, etc.). Furthermore, the investigated scenarios have been defined based on the actual available alternatives with regard to the usage of treatment plants for this specific company. The standard scenarios for identifying climate impact implications due to energy recovery from waste are based on the respective marginal energy data for the power and heat generation facilities/industrial processes in Austria.

Monitoring of WEEE plastics in regards to brominated flame retardants using handheld XRF

This contribution is focused on the on-site determination of the bromine content in waste electrical and electronic equipment (WEEE), in particular waste plastics from television sets (TV) and personal computer monitors (PC) using a handheld X-ray fluorescence (XRF) device. The described approach allows the examination of samples in regards to the compliance with legal specifications for polybrominated biphenyls (PBBs) and polybrominated diphenyl ethers (PBDEs) directly after disassembling and facilitates the sorting out of plastics with high contents of brominated flame retardants (BFRs). In all, over 3000 pieces of black (TV) and 1600 pieces of grey (PC) plastic waste were analysed with handheld XRF technique for this study. Especially noticeable was the high percentage of pieces with a bromine content of over 50,000ppm for TV (7%) and PC (39%) waste plastics. The applied method was validated by comparing the data of handheld XRF with results obtained by GC-MS. The results showed the expected and sufficiently accurate correlation between these two methods. It is shown that handheld XRF technique is an effective tool for fast monitoring of large volumes of WEEE plastics in regards to BFRs for on-site measurements.

Landfill mining in Austria: Foundations for an integrated ecological and economic assessment

For the first time, basic technical and economic studies for landfill mining are being carried out in Austria on the basis of a pilot project. An important goal of these studies is the collection of elementary data as the basis for an integrated ecological and economic assessment of landfill mining projects with regard to their feasibility. For this purpose, economic, ecological, technical, organizational, as well as political and legal influencing factors are identified and extensively studied in the article. An important aspect is the mutual influence of the factors on each other, as this can significantly affect the development of an integrated assessment system. In addition to the influencing factors, the definition of the spatial and temporal system boundaries is crucial for further investigations. Among others, the quality and quantity of recovered waste materials, temporal fluctuations or developments in prices of secondary raw material and fuels attainable in the markets, and time and duration of dumping, play a crucial role. Based on the investigations, the spatial system boundary is defined in as much as all the necessary process steps, from landfill mining, preparing and sorting to providing a marketable material/product by the landfill operator, are taken into account. No general accepted definition can be made for the temporal system boundary because the different time-related influencing factors necessitate an individual project-specific determination and adaptation to the facts of the on-site landfill mining project.

Biogenic carbon-enriched and pollutant depleted SRF from commercial and pretreated heterogeneous waste generated by NIR sensor-based sorting

Mechanical processing using predominantly particle size and density as separation criteria is currently applied in the production of solid-recovered fuel or refuse-derived fuel. It does not sufficiently allow for the optimization of the quality of heterogeneous solid waste for subsequent energy recovery. Material-specific processing, in contrast, allows the separation criterion to be linked to specific chemical constituents. Therefore, the technical applicability of material-specific sorting of heterogeneous waste, in order to optimize its routing options, was evaluated. Two sorting steps were tested on a pilot and a large scale. Near infrared multiplexed sensor-based sorting devices were used (1) to reduce the chlorine (Cl) respectively pollutant content, in order to broaden the utilization options of SRF in industrial co-incineration, and (2) to increase the biogenic carbon (Cbio) content, which is highly relevant in the light of the EU emission trading scheme on CO2. It was found that the technology is generally applicable for the heterogeneous waste fractions looked at, if the sensor systems are appropriately adjusted for the sorting task. The first sorting step allowed for the removal of up to 40% of the Cl freight by separating only 3 to 5% of the material mass. Very low Cl concentrations were achieved in the output stream to be used as solid-recovered fuel stream and additionally, the cadmium (Cd) and lead (Pb) concentration was decreased. A two- to four-fold enriched Cbio content was achieved by the second sorting step. Due to lower yields in the large-scale test further challenges need to be addressed.

Landfill mining: Resource potential of Austrian landfills – Evaluation and quality assessment of recovered municipal solid waste by chemical analyses

Since the need for raw materials in countries undergoing industrialisation (like China) is rising, the availability of metal and fossil fuel energy resources (like ores or coal) has changed in recent years. Landfill sites can contain considerable amounts of recyclables and energy-recoverable materials, therefore, landfill mining is an option for exploiting dumped secondary raw materials, saving primary sources. For the purposes of this article, two sanitary landfill sites have been chosen for obtaining actual data to determine the resource potential of Austrian landfills. To evaluate how pretreating waste before disposal affects the resource potential of landfills, the first landfill site has been selected because it has received untreated waste, whereas mechanically–biologically treated waste was dumped in the second. The scope of this investigation comprised: (1) waste characterisation by sorting analyses of recovered waste; and (2) chemical analyses of specific waste fractions for quality assessment regarding potential energy recovery by using it as solid recovered fuels. The content of eight heavy metals and the net calorific values were determined for the chemical characterisation tests.

Landfill mining: Development of a cost simulation model.

Landfill mining permits recovering secondary raw materials from landfills. Whether this purpose is economically feasible, however, is a matter of various aspects. One is the amount of recoverable secondary raw material (like metals) that can be exploited with a profit. Other influences are the costs for excavation, for processing the waste at the landfill site and for paying charges on the secondary disposal of waste. Depending on the objectives of a landfill mining project (like the recovery of a ferrous and/or a calorific fraction) these expenses and revenues are difficult to assess in advance. This situation complicates any previous assessment of the economic feasibility and is the reason why many landfills that might be suitable for landfill mining are continuingly operated as active landfills, generating aftercare costs and leaving potential hazards to later generations. This article presents a newly developed simulation model for landfill mining projects. It permits identifying the quantities and qualities of output flows that can be recovered by mining and by mobile on-site processing of the waste based on treatment equipment selected by the landfill operator. Thus, charges for disposal and expected revenues from secondary raw materials can be assessed. Furthermore, investment, personnel, operation, servicing and insurance costs are assessed and displayed, based on the selected mobile processing procedure and its throughput, among other things. For clarity, the simulation model is described in this article using the example of a real Austrian sanitary landfill.

Future waste – waste future

‘Future waste’ is a term not yet established in the waste community; actually it is a paradoxon. ‘Future waste’ is not dealing with current solid waste, but products that will become waste in the future. Due to advances in science and technology and priorities in politics, large quantities of these, often technologically complex, products have already entered the anthropogenic stock within a short period of time or are about to do so in the near future. As the majority of these items have relatively long life spans they will not immediately play an important role in waste management, however, once the product life time is over meaningful quantities of this ‘future waste’ will be generated. At that time we need to have appropriate waste management solutions available as these wastes: (1) contain valuable resources (e.g. precious metals and critical raw materials, usually in very low concentrations) and (2) pose specific new challenges to prevent hazards associated with their treatment (e.g. nano-materials). What specifically does this term ‘future waste’ apply to? Some simple examples: lithium-ion batteries from hybrid and e-cars, wind turbines, photovoltaic cells and other components in renewable energy systems. These and similar products have a very long useful life and a substantial amount of this material has already entered the anthropogenic stocks – in Europe mainly during the last one to two decades. In the same way, China and other parts of the world are likely to follow. Based on political priorities and targets for renewable energy facilities, one can assume that this trend will continue indefinitely. New composite materials, such as glass and carbon fibre components, used in vehicles or in the construction of buildings are also proliferating. As a result of the respective product life-times these materials will probably remain in the anthropogenic stocks for the coming decades and will then become ‘future waste’. Apart from the long lived ‘future waste’ products, there are also examples with a short life cycle such as biodegradable plastics, the use of which is rapidly expanding in some countries, although consumption is relatively low today. A common feature of ‘future waste’ streams is that the waste sector will be dealing with relatively low quantities of these wastes in the near term. In the beginning it is mainly production waste and broken components which result from accidents and technical breakdowns that enter the waste sector. Currently there are no high-quality recycling or treatment solutions in place for this ‘future waste’; at best scientists and engineers are researching and developing innovative solutions for future applications. Some research projects in Germany and Austria, such as LIBRI, LITHOREC or LIBRES, developed the basic principles of lithium-ion battery recycling and provide fundamentals to recycling plant development. Other recovery options for ‘future waste’ are, for example, investigated in the CD laboratory on anthropogenic resources at the Technical University of Vienna. As another example researchers in Germany work on disposal solutions with regard to components of wind turbines. At present, in most cases the currently existing waste disposal options are used to deal with the small quantities of ‘future wastes’. Waste management companies are not yet interested in this ‘future waste’ because profits from treatment fees and revenues from processed recyclables will stay on a low level for many years because of the low volumes to be handled and the lack of markets for the processed recyclables from these emerging types of solid waste. How do we overcome this hurdle as feedback from the waste/ recycling sector is needed in order to improve the product design and, in turn, to increase recycling rates? Eco-design, currently not more than a buzzword, must attain higher relevance and must be closely linked to the recycling process. The whole supply chain must be evaluated by life-cycle assessment in addition to an economic assessment to define the benefits of developing suitable end-of-life recycling measures as part of the eco-design process for new products. How should we prepare for management of these ‘future wastes’? In fact, due to the absence of current economic stimuli, the development of recycling processes and new technologies for these ‘future waste’ streams probably needs to be initiated by regulatory measures such as producer responsibility and obligatory recycling rates. Legal requirements also promote re-use solutions, but re-use will only be a niche and special solution for minor quantities. Based on the European Union waste framework directive, EU member states are obliged to implement the waste hierarchy and producer responsibility regulations into national laws, which leads to pressure on waste management stakeholders to invest in the development and construction of waste treatment plants. In that context it is important that frontrunners (early adaptors) can rely on stable political priorities in order to minimize the potential for stranded investments in recycling and treatment plants. The concept of ‘future waste management’ suggested here thus comprises the following steps to be implemented in parallel:

Current issues on the production and utilization of medium-calorific solid recovered fuel: a case study on SRF for the HOTDISC technology

The HOTDISC technology allows the use of Solid Recovered Fuel (SRF) of a coarse grain size in cement rotary kilns. A suitable medium-calorific SRF is produced by mechanical treatment of mixed municipal and commercial waste that was previously used in fluidized bed incineration systems. Through a modification of the production process the quality of the SRF could be improved and its energetic utilization within a cement kiln with an integrated HOTDISC technology was realized. In course of a material flow analysis changes in quality and mass due to planned process changes were simulated on a theoretical basis. Due to a good agreement of the mass and quality prediction with the real data of the material flow analysis conducted after the system implementation it can be stated that by simulation beforehand the security in planning increases while the economic risk can be significantly reduced. Both the material flow analysis as well as practical operational experience confirms that the industrially produced HOTDISC SRF is applicable and can be produced from mixed municipal and commercial solid waste. An improvement in quality of the produced HOTDISC SRF can be shown by positive changes of essential parameters. From a waste management perspective the production and energetic utilization of HOTDISC SRF is reasonable by all means. This is shown by the conduction of an energy and CO2-balance. A growing international importance of the HOTDISC technology and the increased use of medium-calorific SRF are expected.

Landfill mining: Development of a theoretical method for a preliminary estimate of the raw material potential of landfill sites.

In recent years, the rising need for raw materials by emerging economies (e.g. China) has led to a change in the availability of certain primary raw materials, such as ores or coal. The accompanying rising demand for secondary raw materials as possible substitutes for primary resources, the soaring prices and the global lack of specific (e.g. metallic) raw materials pique the interest of science and economy to consider landfills as possible secondary sources of raw materials. These sites often contain substantial amounts of materials that can be potentially utilised materially or energetically. To investigate the raw material potential of a landfill, boreholes and excavations, as well as subsequent hand sorting have proven quite successful. These procedures, however, are expensive and time consuming as they frequently require extensive construction measures on the landfill body or waste mass. For this reason, this article introduces a newly developed, affordable, theoretical method for the estimation of landfill contents. The article summarises the individual calculation steps of the method and demonstrates this using the example of a selected Austrian sanitary landfill. To assess the practicality and plausibility, the mathematically determined raw material potential is compared with the actual results from experimental studies of excavated waste from the same landfill (actual raw material potential).