Improved selection of the functional unit in environmental impact assessment of cement

The outcome of Life Cycle Assessment (LCA) studies is strongly influenced by the selection of the functional unit, which must be defined in such a way that, when products are compared, the amounts compared have identical utilities. LCA studies of cements mostly use mass based functional units (MFU). However, since different cements have a different composition and binding capacity, they result in different compressive strength and durability in their applications, so that MFUs are inadequate. Therefore, this study introduces as functional unit the Cement Functional Performance (CFP): mass of cement needed to obtain 1 MPa of compressive strength during one year of durability (kg/(MPa∙year)). To evaluate the effect of the CFP, the environmental performance of three cements is compared. Results show that adding 5% of zeolite to cement results in a similar strength and 1.78 times higher durability of the produced concrete, which is explained by the reduction of chloride diffusion. Moreover, adding 19% of zeolite to cement increases its durability 2.75 times, but reduces compressive strength by 29%. As a result, cement with 5 and 19% of zeolite added has respectively 54 and 36% of the environmental impacts of Portland cement

Disposición de colas en aguas profundas (DCAP) como alternativa para la gestión de residuales en la industria minera

The article aims to clarify how the deep sea tailings depositions have been used worldwide as alternative mining practice. The paper is a checking of case studies where this technology is used. The available information sources were consulted, which included: case reports, scientific papers, theses and reports by proper authorities. It is achieved to expose the fundamental principles of operation and environmental impact of this technology in the marine environment by applying empirical methods and theoretical research, as well as an assessment of main cases in the world

The deep sea tailings placement (DSTP) as alternative for the residuals management in the mining industry

The article aims to clarify how the deep sea tailings depositions have been used worldwide as alternative mining practice. The paper is a checking of case studies where this technology is used. The available information sources were consulted, which included: case reports, scientific papers, theses and reports by proper authorities. It is achieved to expose the fundamental principles of operation and environmental impact of this technology in the marine environment by applying empirical methods and theoretical research, as well as an assessment of main cases in the world

Acumulación de metales en sedimentos superficiales de la zona costera urbana e industrial del municipio de Moa (Cuba): distribución y evaluación de la contaminación

The investigation is to evaluate the accumulation of ten elements (Al, Cr, Fe, Mn, Ni, Co, As, Cu, Pb and Zn) in surface sediments from the urban and industrial coastal area of Moa. Human activity has influenced the region, which has been developing in one of the most important mining regions of Cuba since the middle of the past century. Two methods were used to assess the contamination of the sediments: the estimation of metal enrichment by calculating the index of geo-accumulation (Igeo) and the interpretation of the data obtained based on quality criteria. The overall range of concentrations is 15.7 - 83.5 mg g-1 for aluminum, 1.4 - 17.9 mg g-1 for chromium, 22.8 - 379.5 mg g-1 for iron, 1.5 - 56.2 mg g-1 for manganese, 0.9 - 6.2 mg g-1 for nickel, 56 - 1094 μg g-1 for cobalt, 6 - 126 μg g-1 for arsenic, 17 to 146 μg g-1 for copper, 6 - 66 μg g-1 for lead, and 64 - 576 μg g-1 for zinc. The results obtained from the studied coastal zone show a high level of pollution in surface sediments. The spatial distribution of the elements varied according to the analyzed elements: Al, Cr, Fe and Ni showed high levels of concentration throughout the studied zone; Mn, Co, Cu, As and Zn are in a higher proportion in Moa Bay Cay. In the case of As and Pb, higher concentrations were located at the deltas of Moa and Cayo Guam rivers and also in some areas in the west of the bay

Legal situation and current practice of waste incineration bottom ash utilisation in Europe

Almost 500 municipal solid waste incineration plants in the EU, Norway, and Switzerland generate about 17.6 Mt/a of incinerator bottom ash (IBA). IBA contains minerals and metals. Metals are mostly separated and sold to the scrap market and minerals are either disposed of in landfills or utilised in the construction sector. Since there is no uniform regulation for IBA utilisation at EU level, countries developed own rules with varying requirements for utilisation. As a result from a cooperation network between European experts an up-to-date overview of documents regulating IBA utilisation is presented. Furthermore, this work highlights the different requirements that have to be considered. Overall, 51 different parameters for the total content and 36 different parameters for the emission by leaching are defined. An analysis of the defined parameter reveals that leaching parameters are significantly more to be considered compared to total content parameters. In order to assess the leaching behaviour nine different leaching tests, including batch tests, up-flow percolation tests and one diffusion test (monolithic materials) are in place. A further discussion of leaching parameters showed that certain countries took over limit values initially defined for landfills for inert waste and adopted them for IBA utilisation. The overall utilisation rate of IBA in construction works is approximately 54 wt.%. It is revealed that the rate of utilisation does not necessarily depend on how well regulated IBA utilisation is, but rather seems to be a result of political commitment for IBA recycling and economically interesting circumstances

Characterisation of polycyclic aromatic hydrocarbons in flue gas and residues of a full scale fluidized bed combustor combusting non-hazardous industrial waste

This paper studies the fate of PAHs in full scale incinerators by analysing the concentration of the 16 EPA-PAHs in both the input waste and all the outputs of a full scale Fluidized Bed Combustor (FBC). Of the analysed waste inputs i.e. Waste Water Treatment (WWT) sludge, Refuse Derived Fuel (RDF) and Automotive Shredder Residue (ASR), RDF and ASR were the main PAH sources, with phenanthrene, fluoranthene and pyrene being the most important PAHs. In the flue gas sampled at the stack, naphthalene was the only predominant PAH, indicating that the PAHs in FBC's combustion gas were newly formed and did not remain from the input waste. Of the other outputs, the boiler and fly ash contained no detectable levels of PAHs, whereas the flue gas cleaning residue contained only low concentrations of naphthalene, probably adsorbed from the flue gas. The PAH fingerprint of the bottom ash corresponded rather well to the PAH fingerprint of the RDF and ASR, indicating that the PAHs in this output, in contrast to the other outputs, were mainly remainders from the PAHs in the waste inputs. A PAH mass balance showed that the total PAH input/output ratio of the FBC ranged from about 100 to about 2600 depending on the waste input composition and the obtained combustion conditions. In all cases, the FBC was clearly a net PAH sink.publisher: Elsevier articletitle: Characterisation of polycyclic aromatic hydrocarbons in flue gas and residues of a full scale fluidized bed combustor combusting non-hazardous industrial waste journaltitle: Waste Management articlelink: http://dx.doi.org/10.1016/j.wasman.2014.06.001 content_type: article copyright: Copyright © 2014 Elsevier Ltd. All rights reserved.status: publishe

Predicting melt formation and agglomeration in fluidized bed combustors by equilibrium calculations

Thermal valorization of biomass or waste in a fluidized bed combustor may result in agglomeration of the bed material, coated with ash, potentially causing defluidization. In this paper, the causes of agglomeration for various fuels are critically reviewed, based on thermodynamic grounds. It is shown that even for phosphorus rich biomass types, in most cases the largest melt phase consists of alkali silicates: Ca phosphates are formed instead of Ca silicates, leading to lower melting points in the CaO-K2O-SiO2 system. Although thermodynamic optimization of the four main ash forming elements (K, Ca, Si and P) only provides an estimate of the amount of melt phase, it is shown that for various fuels the agglomeration behavior can be explained consistent with experimental findings from literature. As a consequence, for most biomass and waste types a similar thermodynamic estimation can be made to predict agglomeration problems and incorporate countermeasures in the design and operation of the fluidized bed combustor. © 2013 Springer Science+Business Media Dordrecht.status: publishe

Is a further reduction of the emission limit value for SOx in waste incinerators meaningful from an LCA perspective?

From a life-cycle perspective, a system reducing the SOx concentration from 1500 to the current emission limit value (ELV) of 50 mg/Nm³ in the flue gas of a hazardous waste incinerator, significantly reduces the overall environmental impact of the incinerator in the impact categories acidification and photochemical oxidation, at the expense of relatively limited impacts in other impact categories. In case the ELV for SOx would be lowered from 50 to 25 mg SOx/Nm³, the existing installation has to be optimised or additional equipment has to be added. It is shown that in this case, the environmental impact of the incinerator is further reduced in the impact categories acidification and photochemical oxidation, but at the expense of considerable impacts in other impact categories, mainly global warming and abiotic resource depletion.status: publishe

Destruction and formation of dioxin-like PCBs in dedicated full scale waste incinerators

Destruction and formation of dioxin-like PCBs in full scale waste incinerators is studied by analysing input waste streams and boiler and fly ash of a grate furnace incinerator (GFI) incinerating MSW, of a Fluidised Bed Combustor (FBC) incinerating a mix of 50% sludge, 25% refuse derived fuel (RDF) and 25% automotive shredder residue (ASR) and of a rotary kiln incinerator (RKI) incinerating hazardous waste. The dioxin-like PCB fingerprints of the waste inputs show that PCB oils Aroclor 1242 and Aroclor 1254 late are the major dioxin-like PCB contamination source of sludge, RDF and ASR. The dioxin-like PCB fingerprints of the waste inputs are clearly different from the fingerprints of the outputs i.e. boiler and fly ash, indicating that in full scale waste incinerators dioxin-like PCBs in the input waste are destroyed and other dioxin-like PCBs are newly formed in the post combustion zone. The dioxin-like PCB fingerprint of boiler and fly ash of all three incinerators corresponds well to the fly ash fingerprint obtained in lab scale de novo synthesis experiments, indicating that dioxin-like PCBs are mainly formed through this mechanism. The high PCB concentration in the input waste mix of the RKI does not promote the formation of dioxin-like PCBs through precursor condensation.publisher: Elsevier articletitle: Destruction and formation of dioxin-like PCBs in dedicated full scale waste incinerators journaltitle: Chemosphere articlelink: http://dx.doi.org/10.1016/j.chemosphere.2013.09.008 content_type: article copyright: Copyright © 2013 Elsevier Ltd. All rights reserved.status: publishe

Indication of PCDD/F formation through precursor condensation in a full-scale hazardous waste incinerator

This paper gives the PCDD/F fingerprint of boiler and fly ash of a full scale hazardous waste incinerator and demonstrates that, when the waste to be incinerated contains high concentrations of PCBs and chlorinated pesticides, heterogeneous precursor condensation is the dominant PCDD/F formation mechanism rather than de novo synthesis. This is in contrast to full-scale municipal solid waste incinerators, where de novo synthesis has been shown to be the dominant PCDD/F formation mechanism. This paper agrees with earlier predictions based on numerous lab scale experiments.status: publishe