Standardization of the Determination of the Biomass Content in Refuse Derived Fuels

Recent regulations of the European Community (2001/77/EC und 2009/29/EC) require operators of industrial incineration plants to report the amount of fossil CO2 emissions and the fraction of energy produced from biomass, respectively. Municipal solid waste, industrial waste, and solid recovered fuels processed out of them have been recognized as a source for energy recovery. Since these fuels generally consist of an unknown mixture of different organic materials, operates are interested in reliable and cost effective methods to determining the content of biogenic and fossil organic carbon. Until now the standard methods to characterize mixed wastes have been the manual sorting, the selective dissolution method and the radiocarbon method. In the recent years the applicant and his colleagues have developed an alternative method, the so called balance method (BM), for calculating the content of fossil organic carbon, and the portion of electricity produced from renewable (biogenic) materials in waste by solving a set of equations. All data required for this approach are either available from literature or from operating data routinely measured in combustion plants. So far the application of the balance method has been limited to retrospectively characterizing the feed of waste to energy plants. In recent investigations of the applicant the balance method has been adapted, so that results of the elementary analysis (C, H, N, S, and O content of the fuel) have been instrumental in conjunction with data about the chemical composition of moisture-and-ash-free biogenic and fossil organic matter to determine the biomass content of defined fuels mixtures. Hence the aim of the proposed project is to validate the adapted balance method (aBM) by further experiments with defined mixtures of biogenic and fossil organic matter. In addition it is planned to apply the method to 3 different types of refuse derived fuels RDF, in order to test the practical applicability of the approach. Finally comparative analyses of the biomass content of RDF samples will be conducted using the selective dissolution method and the radiocarbon method: In the frame of project the following research question will be addressed: 1. Is the adapted balance method (already tested against defined fuels mixtures) appropriate to determine the biomass content of "real" RDF, and which modifications are probably necessary? 2. How should the fuels samples be taken and conditioned in order to to obtain representative results? 3. Which variations in the chemical composition of moisture-and-ash-free biogenic and fossil organic matter in refused derived fuels are to be considered? 4. How does the aBM perform in comparison to standardized analyses methods? The results of the project will give on the one hand valuable information about the potentials and limitations of the balance method. On the other hand criteria (e.g., regarding sample conditioning, amount of analysis samples, data analysis) for a standardized application of the balance method will be provided.

In frame of the project StaMProC, a new method to determine the climate relevance of combustible wastes was developed and subsequently validated. In comparison to commonly applied methods, the new approach is connected with lower uncertainties and/or lower analysis costs. The results of the project represent the foundation for the planned standardization of the method at European level.Motivation of the project was the global increase in thermal recovery of waste. This results in the substitution of fossil fuels (such as fuel oil or natural gas) as energy carriers. This substitution is typically accompanied by a reduction of greenhouse gas emissions as waste usually contains biogenic matter (such as paper or wood), which is considered as carbon neutral when combusted. Thus, in order to evaluate the climate relevance of waste mixtures, knowledge about their contents of biomass (biogenic) and plastics (fossil) are crucial. The distinction between biomass and plastics is, however, not straightforward, mainly caused by a highly variable composition and heterogeneity of the waste and thereof derived fuels.The present project investigated a new method to determine the biomass content and thus, the climate relevance of combustible wastes. The method was tested for its suitability, reliability and practicability. In particular, the investigations focused on refuse derived fuels, which are fuels prepared from waste by different mechanical processing steps and are increasingly utilized in industrial plants (predominantly in cement kilns). The developed method utilizes the distinct difference in the elemental composition of plastics and biomass. Plastics contain high amounts of carbon (C) but low quantities of oxygen (O), whereas biomass includes both elements in similar quantities. Thus, elementary analyses (content of C, H, and O) of different refuse derived fuel samples in conjunction with data about the elemental composition of biomass and plastics were used to calculate the biomass content in the samples (and thus their climate relevance). In addition to the analysis real samples from the waste industry, predefined mixtures of biomass and plastics were analyzed to validate the methodology and to assess potential sources for errors (such as changes in composition due to sample preparation). The results of the investigations demonstratethe overall capability of the method to evaluate the climate relevance of refused derived fuels with high precision (relative error <8%) and at comparatively low costs,a good agreement of results with alternative methods (e.g. radiocarbon method),the importance of sample preparation (steps from waste sampling until elemental analysis) for reliable outcomes of the method,the low variability in the elemental composition of biomass and plastics present in different refuse derived fuels, which confirms the general applicability of the method.