Waste Management & Research: The Journal for a Sustainable Circular Economy

Thermal utilization of municipal solid waste and commercial wastes has become of increasing importance in European waste management. As waste materials are generally composed of fossil and biogenic materials, a part of the energy generated can be considered as renewable and is thus subsidized in some European countries. Analogously, CO₂ emissions of waste incinerators are only partly accounted for in greenhouse gas inventories. A novel approach for determining these fractions is the so-called balance method. In the present study, the implementation of the balance method on a waste-to-energy plant using oxygen-enriched combustion air was investigated. The findings of the 4-year application indicate on the one hand the general applicability and robustness of the method, and on the other hand the importance of reliable monitoring data. In particular, measured volume flows of the flue gas and the oxygen-enriched combustion air as well as corresponding O₂ and CO₂ contents should regularly be validated. The fraction of renewable (biogenic) energy generated throughout the investigated period amounted to between 27 and 66% for weekly averages, thereby denoting the variation in waste composition over time. The average emission factor of the plant was approximately 45 g CO₂ MJ⁻¹ energy input or 450 g CO₂ kg⁻¹ waste incinerated. The maximum error of the final result was about 16% (relative error), which was well above the error (<8%) of the balance method for plants with conventional oxygen supply.

Energy and greenhouse gas balances for a waste incineration plant (Reno–Nord I/S, Aalborg, Denmark) as a function of time over a 45-year period beginning 1960 are presented. The quantity of energy recovered from the waste increased over time due to increasing waste production, increasing lower heating value of the waste and implementation of improved energy recovery technology at the incineration plant. Greenhouse gas (GHG) balances indicated progressively increasing GHG savings during the time period investigated as a result of the increasing energy production. The GHG balances show that the Reno–Nord incineration plant has changed from a net annual GHG emission of 30 kg CO₂-eq person⁻¹ year⁻¹ to a net annual GHG saving of 770 kg CO₂-eq person⁻¹ year⁻¹ which is equivalent to approximately 8% of the annual emission of GHG from an average Danish person (including emissions from industry and transport). The CO₂ emissions associated with combustion of the fossil carbon contained in the waste accounted for about two-thirds of the GHG turnover when no energy recovery is applied but its contribution reduces to between 10 and 15% when energy recovery is implemented. The reason being that energy recovery is associated with a large CO₂ saving (negative emission).

Waste-to-energy (WtE) plants are traditionally designed for clean and economical disposal of waste. Design for output on the other hand was the guideline when projecting the HRC (HoogRendement Centrale) block of Afval Energie Bedrijf Amsterdam. Since commissioning of the plant in 2007, operation has continuously improved. In December 2010, the block's running average subsidy efficiency for one year exceeded 30% for the first time. The plant can increase its efficiency even further by raising the steam temperature to 480°C. In addition, the plant throughput can be increased by 10% to reduce the total cost of ownership. In order to take these steps, good preparation is required in areas such as change in heat transfer in the boiler and the resulting higher temperature upstream of the super heaters. A solution was found in the form of combining measured data with a computational fluid dynamics (CFD) model. Suction and acoustic pyrometers are used to obtain a clear picture of the temperature distribution in the first boiler pass. With the help of the CFD model, the change in heat transfer and vertical temperature distribution was predicted. For the increased load, the temperature is increased by 100°C; this implies a higher heat transfer in the first and second boiler passes. Even though the new block was designed beyond state-of-the art in waste-to-energy technology, margins remain for pushing energy efficiency and economy even further.

Waste-to-energy (WtE) facilities have been established worldwide as a sustainable method for the disposal of residual waste. In the present study the following competing WtE systems were compared: (1) municipal solid waste incinerators (MSWIs) with energy recovery; (2) co-incineration of waste in old lignite or coal-fired power plants; (3) substitute [refuse-derived fuel (RDF)] incinerators with energy recovery; and (4) co-incineration of defined waste fractions in cement kilns. In general the municipal solid waste incinerators in Europe are designed for a broad range of municipal and commercial waste without a pre-treatment of the waste. All other WtE processes including the cement kilns require a pre-treatment and are more limited in terms of RDF composition; namely particle size, chlorine content, calorific value. As to Germany, the emission limit values for all facilities are similar. A sensitivity analysis of the economics of boilers using RDF and municipal solid waste leads to the conclusion that the feasibility of RDF incinerators might partially recover if the prices for primary energy increase again. On the other hand, pre-treatment of waste leads to higher costs for RDF. Incineration and recycling capacities are large enough in middle Europe to avoid landfilling of organic waste. The steep decline of gate fees observed in some national spot markets is a clear indicator of an already existing overcapacity. Considering the enormous amount of greenhouse gas emissions saved by WtE facilities in comparison with landfilling, free capacities of WtE installations should be used to incinerate waste from EU member states where waste disposal is still predominantly based on landfilling.

Bottom ashes (BA) obtained from a municipal solid waste incineration plant, have shown different pH and lead concentrations in leachate for different lines. In order to explain this behaviour, combustion tests were performed concerning the lines and the effect of the type of wastes. The BA obtained from the same waste has shown the same raw chemical composition, but different leachate characteristics for the different lines. The bottom ash from different wastes burned on the same line instead showed very similar leachate behaviour. The results suggest that the quality of leach ate depends on the plant and process conditions (in particular the ash quenching phase) and not on the composition of the waste. During ash quenching, the formation and dissolution of soluble alkalis depends on the washing ratio and on the residence time. A different washing degree leads to a different residual alkalinity in the bottom ash, and consequently to a different value of leachate pH with different metal releases. Therefore, with the practical aim of establishing the best conditions for the final disposal of bottom ash, a careful planning of this phase could be proposed as an alternative to a weathering process.

Risk assessment is a well established procedure for the analysis of the adverse impacts of pollutant substances emitted by waste treatment plants. The aim of the present study was the determination of the impact on human health associated with the activities of an incinerator in the Emilia-Romagna region (Northern Italy). The dispersion of heavy metals and organic pollutants monitored at plant stacks was predicted by the Gaussian model ISC3 (US-EPA). This analysis led to the estimation of risk, connected with various pollutants showing toxic and carcinogenic activities, for different receptors. The values obtained were first compared with the acceptability limits set by US-EPA, and then graphically represented as a territorial dispersion. A cautious approach was followed to calculate risk, by considering the worst, albeit realistic and reliable, estimate for the different parameters. The calculated exposure pathways resulted in different contributions depending on the receptor category (children and adults), even if direct exposure (via inhalation) is generally predominant. However, the resulting risk for both single pollutants studied and their combination all together proved to be within the acceptable limits (all lifetime individual risks being below 10^–6), according to the procedure followed. The obtained results highlight the importance of using reliable monitoring data on the studied contamination source and, in particular, suggest the advisability of a more in-depth study on the pollution from incineration stacks.

Waste incineration can be considered a robust technology for energy recovery from mixed waste. Modern incinerators are generally able to maintain relatively stable performance, but changes in waste input and furnace operation may affect emissions. This study investigated how inorganic air emissions and residue composition at a full-scale incinerator were affected by known additions of specific waste materials to the normal municipal solid waste (MSW) input. Six individual experiments were carried out (% ww of total waste input): NaCl (0.5%), shoes (1.6%), automobile shredder waste (14%), batteries (0.5%), poly(vinyl chloride) (5.5%) and chromate-cupper-arsenate impregnated wood (11%). Materials were selected based on chemical composition and potential for being included or excluded from the waste mix. Critical elements in the waste materials were identified based on comparison with six experiments including ‘as-large-as-possible’ changes in furnace operation (oxygen levels, air supply and burnout level) only using normal MSW as input. The experiments showed that effects from the added waste materials were significant in relation to: air emissions (in particular As, Cd, Cr, Hg, Sb), element transfer coefficients, and residue composition (As, Cd, Cl, Cr, Cu, Hg, Mo, Ni, Pb, S, Sb, Zn). Changes in furnace operation could not be directly linked to changes in emissions and residues. The results outlined important elements in waste which should be addressed in relation to waste incinerator performance. Likely ranges of element transfer coefficients were provided as the basis for sensitivity analysis of life-cycle assessment (LCA) results involving waste incinerator technologies

This article focuses on analysing the development of waste-generated energy in the countries of the European Union (EU 27). Besides elaborating the relevant legal and political framework in the waste and energy sector as well as climate protection, the results from correlation analyses based on the databases of the energy statistics from Eurostat are discussed. The share of energy from waste is correlated with macro-economic, waste- and energy-sector-related data, which have been defined as potentially relevant for energy recovery from waste in the countries of the European Union. The results show that a single factor influencing the extent of waste-generated energy could not be isolated as it is being influenced not only by the state of economic development and the state of development of waste management systems in the respective countries but also by energy-sector-related factors and the individual priority settings in those countries. Nevertheless the main driving force for an increase in the utilization of waste for energy generation can be seen in the legal and political framework of the European Union leading to the consequence that market conditions influence the realization of waste management infrastructure for waste-generated energy.

In Europe, about 20% of municipal solid waste is incinerated. Large differences can be found between northern and southern Europe regarding energy recovery efficiencies, flue gas cleaning technologies and residue management. Life-cycle assessment (LCA) of waste incineration often provides contradictory results if these local conditions are not properly accounted for. The importance of regional differences and site-specific data, and choice of LCA model itself, was evaluated by assessment of two waste incinerators representing northern and southern Europe (Denmark and Italy) based on two different LCA models (SimaPro and EASEWASTE). The results showed that assumptions and modelling approaches regarding energy recovery/substitution and direct air emissions were most critical. Differences in model design and model databases mainly had consequences for the toxicity-related impact categories. The overall environmental performance of the Danish system was better than the Italian, mainly because of higher heat recovery at the Danish plant. Flue gas cleaning at the Italian plant was, however, preferable to the Danish, indicating that efficient flue gas cleaning may provide significant benefits. Differences in waste composition between the two countries mainly affected global warming and human toxicity via water. Overall, SimaPro and EASEWASTE provided consistent ranking of the individual scenarios. However, important differences in results from the two models were related to differences in the databases and modelling approaches, in particular the possibility for modelling of waste-specific emissions affected the toxicity-related impact categories. The results clearly showed that the use of site-specific data was essential for the results.

This evaluative research study aimed to assess the effects of the central healthcare incinerator project on waste management in Yala Province. The study data were collected twice: at baseline and during the operational phase. A combination of structured interview and observation were used during data collection. The study covered 127 healthcare facilities: government hospitals, healthcare centres, and private clinics. The results showed 63% of healthcare risk waste (HCRW) handlers attended the HCRW management training. Improvements in each stage of the HCRW management system were observed in all groups of facilities. The total cost of the HCRW management system did not change, however; the costs for hospitals decreased, whereas those for clinics increased significantly. It was concluded that the central healthcare waste incinerator project positively affected HCRW management in the area, although the costs of management might increase for a particular group. However, the benefits of changing to a more appropriately managed HCRW system will outweigh the increased costs.