Study on methodological aspects regarding limit values for pollutants in aggregates in the context of the possible development of end-of-waste criteria under the EU Waste Framework Directive

This report provides a methodology proposal for establishing limit values for pollutants in waste-derived aggregates with a view of using such aggregates in a wide variety of construction projects, as part of possible end-of-waste criteria for aggregates in accordance with Article 6 of the Waste Framework Directive (2008/98/EC). More specifically, the study centres on aggregate substances that are subject to leaching and/or release through wear. The report focuses on identifying and assessing the pollution risks of using aggregates derived from waste, on reviewing how the use of aggregates is regulated today in the EU with respect to avoiding pollution, on assessing the need for including limit values for pollutants in end-of-waste criteria, on assessing the suitability of different types of pollutant limit values, on identifying and assessing the different methodological approaches for deriving pollutant limit values and on identifying the most suitable testing approaches and methods, including simplified modes of compliance.JRC.J.5-Sustainable Production and Consumptio

Investigation of possible leaching control mechanisms for chromium and vanadium in electric arc furnace (EAF) slags using combined experimental and modeling approaches

In this study, possible leaching control mechanisms for Cr and V in electric arc furnace slags were investigated by using a multi-methodological approach. Aside from chemical and mineralogical bulk analyses, special emphasis was given to surface investigations of the slags prior to and after leaching. In addition, pH dependence leaching tests were performed and the obtained data were evaluated with hydrogeochemical models. Investigations revealed that Cr and V are mainly bound in spinel and wuestite as well as minor amounts of olivine. Spinel and wuestite do not dissolve during water leaching for 48 h, whereas, depending on the composition of olivine, this phase either dissolves and releases V and Cr congruently, or does not dissolve but may hydrate. Melilite may also hydrate, but neither V nor Cr were detected in this phase. It appears that leached V is subsequently adsorbed onto these newly hydrated phases. The combination of the applied methods further showed that the abundance of calcium silicates, spinel, and wuestite is influenced by the FeO/SiO2 and CaO/SiO2 ratio in the slag. Therefore, it is assumed that the leaching of V and Cr can be minimized by changing these ratios to favor the formation of Fe bearing calcium silicate and spinel instead of wuestite

Evaluating Biomass Ash Properties as Influenced by Feedstock and Thermal Conversion Technology towards Cement Clinker Production with a Lower Carbon Footprint

Purpose: This study evaluates the potential of biomass ash as raw clinker material and the influence of biomass feedstock and thermal conversion technology on biomass ash properties. Methods: A set of criteria for biomass feedstock and ash properties (i.e. CaO/SiO2 ratio and burnability) are established. A large dataset was collected and the best combination of biomass feedstock and conversion technology regarding the desired ash quality was identified. Results: Wood biomass has the highest potential to provide the right CaO/SiO2 ratio which is needed to form clinker minerals. Bark content and exogenous Si inclusion in wood biomass have a large influence on the CaO/SiO2 ratio. Paper sludge is composed of Ca, Si and Al and can potentially serve as a source of cement elements. Wood fly ash from pulverized fuel combustion can substitute a considerable amount of raw clinker materials due to its similar burnability. The replacement ratio is determined by the content of adverse elements in the ash (i.e. MgO2 and P2O5). Conclusion: Using biomass ash to lower the CO2 emission from clinker production depends on the joint effort of bioenergy producers, by providing higher quality biomass ash, and cement makers, by adapting the kiln operation to enable a high level of raw material replacement by biomass ash.The presented evaluation of the ash production chain, from biomass selection through combustion technology and ash management, provides new insights and recommendations for both stakeholders to facilitate this sustainable development. Graphic Abstract: [Figure not available: see fulltext.].</p

Chloride Interference during Analysis of Dissolved Organic Carbon Using Wet Chemical Oxidation Methods

Analysis of dissolved organic carbon (DOC) is widely used to quantify the sum of organic carbon species in water. Analyzers based on wet chemical oxidation (WCO) usually have a relatively low detection limit (±1 μg of C/L) and are, therefore, well suited for analyses of DOC in environmental samples (e.g., surface water, groundwater, or seawater). However, these matrices might contain relatively high concentrations of chloride that can affect the DOC oxidation efficiency. We validated the DOC analysis using a combined persulfate and ultraviolet oxidation method in various prepared samples (humic and fulvic acids and selected organic acids) with different background concentrations of chloride. The results show that chloride is an effective radical scavenger (at concentrations of >355 mg of Cl–/L) that reduces the oxidation efficiency of DOC analyses based on WCO. The oxidation efficiency correlates well with the proton dissociation constant of the selected organic acids. Our findings imply that the DOC analyses by WCO methods should include an assessment of the chloride concentrations in the samples to check for potential interference. The results are relevant for DOC analysis in samples containing high background levels of chloride (e.g., brackish water) and for samples from DOC fractionation methods to quantify humic substances

Technical and environmental performance of lower carbon footprint cement mortars containing biomass fly ash as a secondary cementitious material

This study evaluated the mechanical and environmental properties of cement mortars containing fly ash from biomass combustion as a secondary cementitious material. Cement mortars with 20 and 40% wt. replacement of Portland cement with fly ash from two types of installations were tested for their compressive strength and leaching behaviour. Substitution of 20% Portland cement with wood fly ash complied with the reference standard for compressive strength of 42.5öMPa at 28ödays. Replacement rates of 40% developed a lower strength (30 and 33.5öMPa), but were still suitable for applications. The pulverized fuel ash perform substantially worse. We conclude that the biomass fly ash from fluidized bed combustion performs as a functional secondary cementitious material in cement, whereas the functionality of pulverized fuel fly ash is insufficient. The release of environmentally relevant elements from all the tested specimens fulfilled the Dutch leaching criteria for reuse. During second life as a granular construction material the release of Ba, Cr, Mo and V increased to a level of concern. However, this release was found to be similar to that of existing blended cements and was controlled by cement chemistry. The technical performance of cement mortars was influenced by the type and ratio of fly ash mixed with cement. However, the environmental performance was driven by the cement matrix that controlled the release of contaminants. Using biomass fly ash as a secondary cementitious material can reduce the carbon footprint of concrete by 40% while maintaining good technical and environmental performance