Johann Fellner

Determination of biogenic and fossil CO2 emitted by waste incineration based on 14CO2 and mass balances

A field application of the radiocarbon ((14)C) method was developed to determine the ratio of biogenic vs. fossil CO(2) emissions from waste-to-energy plants (WTE). This methodology can be used to assign the Kyoto relevant share of fossil CO(2) emissions, which is highly relevant for emission budgets and emission trading. Furthermore, heat and electricity produced by waste incinerators might be labelled depending on the fossil or biogenic nature of the primary energy source. The method development includes representative on-site CO(2) absorption and subsequent release in the laboratory. Furthermore, a reference value for the (14)C content of pure biogenic waste (f(M,bio)) was determined as 1.130+/-0.038. Gas samples for (14)CO(2) analysis were taken at three WTEs during one month each. Results were compared to an alternative approach based on mass and energy balances. Both methods were in excellent agreement and indicated a fraction of biogenic CO(2) slightly above 50%.

Comparing field investigations with laboratory models to predict landfill leachate emissions

Investigations into laboratory reactors and landfills are used for simulating and predicting emissions from municipal solid waste landfills. We examined water flow and solute transport through the same waste body for different volumetric scales (laboratory experiment: 0.08 m(3), landfill: 80,000 m(3)), and assessed the differences in water flow and leachate emissions of chloride, total organic carbon and Kjeldahl nitrogen. The results indicate that, due to preferential pathways, the flow of water in field-scale landfills is less uniform than in laboratory reactors. Based on tracer experiments, it can be discerned that in laboratory-scale experiments around 40% of pore water participates in advective solute transport, whereas this fraction amounts to less than 0.2% in the investigated full-scale landfill. Consequences of the difference in water flow and moisture distribution are: (1) leachate emissions from full-scale landfills decrease faster than predicted by laboratory experiments, and (2) the stock of materials remaining in the landfill body, and thus the long-term emission potential, is likely to be underestimated by laboratory landfill simulations.

Methods for determining the biomass content of waste

As CO2 emission trading in Europe has been established it is of essential importance to distinguish between biogenic and fossil emissions. Emissions resulting from bio-fuels and biogenous fractions are categorized as climate-neutral. Determination of plants using only fossil or bio-fuels is simple but categorization becomes more difficult for plants using a mix of fossil and biofuel such as solid recovered fuels. In the meantime, different methods for solving this problem have been developed. Using different approaches and technologies, all of these methods have the same goal: determining the biomass content (biogenic fraction), for example, in solid recovered fuels or in the off-gas of a mono- or co-incineration plant in order to calculate the biogenic carbon dioxide emissions. In the following article, the most common methods for determining the biogenic fraction of fuels, namely the Selective Dissolution Method, the Balance Method and the 14C-Method will be explained in detail.

Modeling of leachate generation from MSW landfills by a 2-dimensional 2-domain approach.

The flow of water through Municipal Solid Waste (MSW) landfills is highly non-uniform and dominated by preferential pathways. Thus, concepts to simulate landfill behavior require that a heterogeneous flow regime is considered. Recent models are based on a 2-domain approach, differentiating between channel domain with high hydraulic conductivity, and matrix domain of slow water movement with high water retention capacity. These models focus on the mathematical description of rapid water flow in channel domain. The present paper highlights the importance of water exchange between the two domains, and expands the 1-dimensional, 2-domain flow model by taking into account water flows in two dimensions. A flow field consisting of a vertical path (channel domain) surrounded by the waste mass (matrix domain) is defined using the software HYDRUS-2D. When the new model is calibrated using data sets from a MSW-landfill site the predicted leachate generation corresponds well with the observed leachate discharge. An overall model efficiency in terms of r(2) of 0.76 was determined for a simulation period of almost 4 years. The results confirm that water in landfills follows a preferential path way characterized by high permeability (K(s)=300 m/d) and zero retention capacity, while the bulk of the landfill (matrix domain) is characterized by low permeability (K(s)=0.1m/d) and high retention capacity. The most sensitive parameters of the model are the hydraulic conductivities of the channel domain and the matrix domain, and the anisotropy of the matrix domain.

A novel approach to characterize data uncertainty in material flow analysis and its application to plastics flows in Austria

Material flow analysis (MFA) is widely used to investigate flows and stocks of resources or pollutants in a defined system. Data availability to quantify material flows on a national or global level is often limited owing to data scarcity or lacking data. MFA input data are therefore considered inherently uncertain. In this work, an approach to characterize the uncertainty of MFA input data is presented and applied to a case study on plastics flows in major Austrian consumption sectors in the year 2010. The developed approach consists of data quality assessment as a basis for estimating the uncertainty of input data. Four different implementations of the approach with respect to the translation of indicator scores to uncertainty ranges (linear- vs. exponential-type functions) and underlying probability distributions (normal vs. log-normal) are examined. The case study results indicate that the way of deriving uncertainty estimates for material flows has a stronger effect on the uncertainty ranges of the resulting plastics flows than the assumptions about the underlying probability distributions. Because these uncertainty estimates originate from data quality evaluation as well as uncertainty characterization, it is crucial to use a well-defined approach, building on several steps to ensure the consistent translation of the data quality underlying material flow calculations into their associated uncertainties. Although subjectivity is inherent in uncertainty assessment in MFA, the proposed approach is consistent and provides a comprehensive documentation of the choices underlying the uncertainty analysis, which is essential to interpret the results and use MFA as a decision support tool. [ABSTRACT FROM AUTHOR]

Abundance of 14C in biomass fractions of wastes and solid recovered fuels

In recent years thermal utilization of mixed wastes and solid recovered fuels has become of increasing importance in European waste management. Since wastes or solid recovered fuels are generally composed of fossil and biogenic materials, only part of the CO(2) emissions is accounted for in greenhouse gas inventories or emission trading schemes. A promising approach for determining this fraction is the so-called radiocarbon method. It is based on different ratios of the carbon isotopes (14)C and (12)C in fossil and biogenic fuels. Fossil fuels have zero radiocarbon, whereas biogenic materials are enriched in (14)C and reflect the (14)CO(2) abundance of the ambient atmosphere. Due to nuclear weapons tests in the past century, the radiocarbon content in the atmosphere has not been constant, which has resulted in a varying (14)C content of biogenic matter, depending on the period of growth. In the present paper (14)C contents of different biogenic waste fractions (e.g., kitchen waste, paper, wood), as well as mixtures of different wastes (household, bulky waste, and commercial waste), and solid recovered fuels are determined. The calculated (14)C content of the materials investigated ranges between 98 and 135pMC.

Urban Mining in Times of Raw Material Shortage

By means of material flow analysis, the management of copper, an important and relatively scarce metal that is difficult to substitute, is examined. The combination of increased demand for copper (for ammunition) and constraints on supply from sources other than the domestic anthroposphere highlights the importance of planning for and surveying urban mining activities. The results also indicate limitations to extracting a large share of copper from the anthroposphere, even in the face of a critical shortage. Although extreme measures, such as confiscation, were taken, only 1.7 kilograms of copper per capita (kg Cu/cap), amounting to perhaps as little as 10% of the anthropogenic stock, could be made available through the end of the war. The present article investigates to what extent and level of success urban mining—the recovery of resources from anthropogenic stock — has been applied in the past during shortages of primary resources. As a case study, the Austrian economy during World War I — when raw materials indeed had to be substituted from secondary sources — is analyzed here. By means of material flow analysis, the management of copper, an important and relatively scarce metal that is difficult to substitute, is examined. The combination of increased demand for copper (for ammunition) and constraints on supply from sources other than the domestic anthroposphere highlights the importance of planning for and surveying urban mining activities. The results also indicate limitations to extracting a large share of copper from the anthroposphere, even in the face of a critical shortage. Although extreme measures, such as confiscation, were taken, only 1.7 kilograms of copper per capita (kg Cu/cap), amounting to perhaps as little as 10% of the anthropogenic stock, could be made available through the end of the war.

GIS-based Analysis of Vienna's Material Stock in Buildings

Summary The building stock is not only a huge consumer of resources (for its construction and operation), but also represents a significant source for the future supply of metallic and mineral resources. This article describes how material stocks in buildings and their spatial distribution can be analyzed on a city level. In particular, the building structure (buildings differentiated by construction period and utilization) of Vienna is analyzed by joining available geographical information systems (GIS) data from various municipal authorities. Specific material intensities for different building categories (differentiated by construction period and utilization) are generated based on multiple data sources on the material composition of different building types and combined with the data on the building structure. Utilizing these methods, the overall material stock in buildings in Vienna was calculated to be380 million metric tonnes (t), which equals 210 t per capita (t/cap). The bulk of the material (>96%) is mineral, whereas organic materials (wood, plastics, bitumen, and so on) and metals (iron/steel, lead, copper, aluminum, and so on) constitute a very small share, of which wood (4.1 t/cap) and steel (3.2 t/cap) are the major contributors. Besides the overall material stock, the spatial distribution of materials within the municipal area can be assessed. This research forms the basis for a resource cadaster, which provides information about gross volume, construction period, utilization, and material composition for each building in Vienna.

Flooding of municipal solid waste landfills ― An environmental hazard?

Municipal solid waste (MSW) landfills pose a long-lasting risk for humans and the environment. While landfill emissions under regular operating conditions are well investigated, landfill behaviour and associated emissions in case of flooding are widely unknown, although damages have been documented. This paper aims at developing a methodology for determining the proportion of MSW landfills endangered by flooding, and at evaluating the impact flooded landfills might have on the environment during a flood event. The risk of flooding of MSW landfills is assessed by using information about flood risk zones. Out of 1064 landfills investigated in Austria, 312 sites or about 30% are located in or next to areas flooded on average once in 200 years. Around 5% of these landfills are equipped with flood protection facilities. Material inventories of 147 landfill sites endangered by flooding are established, and potential emissions during a flood event are estimated by assuming the worst case of complete landfill leaching and erosion. The environmental relevance of emissions during flooding is discussed on the basis of a case study in the western part of Austria. Although environmental hazards need to be assessed on a site- and event-specific basis, the results indicate that flooded MSW landfills represent in general small environmental risks for the period of flooding. The longer term consequences of flooding are discussed in a next paper.

Evaluation of resource recovery from waste incineration residues--the case of zinc.

Solid residues generated at European Waste to Energy plants contain altogether about 69,000 t/a of Zn, of which more than 50% accumulates in air pollution control residues, mainly boiler and filter ashes. Intensive research activities aiming at Zn recovery from such residues recently resulted in a technical scale Zn recovery plant at a Swiss waste incinerator. By acidic leaching and subsequent electrolysis this technology (FLUREC) allows generating metallic Zn of purity>99.9%. In the present paper the economic viability of the FLUREC technology with respect to Zn recovery from different solid residues of waste incineration has been investigated and subsequently been categorised according to the mineral resource classification scheme of McKelvey. The results of the analysis demonstrate that recovery costs for Zn are highly dependent on the costs for current fly ash disposal (e.g. cost for subsurface landfilling). Assuming current disposal practice costs of 220€/ton fly ash, resulting recovery costs for Zn are generally higher than its current market price of 1.6€/kg Zn. With respect to the resource classification this outcome indicates that none of the identified Zn resources present in incineration residues can be economically extracted and thus cannot be classified as a reserve. Only for about 4800 t/a of Zn an extraction would be marginally economic, meaning that recovery costs are only slightly (less than 20%) higher than the current market price for Zn. For the remaining Zn resources production costs are between 1.5 and 4 times (7900 t/a Zn) and 10-80 times (55,300 t/a Zn) higher than the current market value. The economic potential for Zn recovery from waste incineration residues is highest for filter ashes generated at grate incinerators equipped with wet air pollution control.