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The large amounts of sewage sludge (11 million tonnes in Europe in 2005) produced in paper manufacturing plants require the introduction of recycling and/or alternative recovery solutions to minimize the amounts of generated waste, such as its use in soil remediation or in the cement industry. A feasible alternative to valorize that waste is the use of paper sludge as raw material in the production of structural ceramic or clay bricks.Previous studies tried to incorporate sewage sludge from different sources into ceramic matrices, unfortunately with little success in the final result for most types of sludge. However, those experiments carried out using as additive sludge from the paper industry succeeded in producing a material suitable for the red ceramic industry.In this paper, binary mixtures of clay and paper sludge under different formulations were produced and and their physico-chemical properties were studied. Increasing the paper sludge content in the clay mixture provides the material with improved properties regarding its thermal and acoustic insulation, but in turn it decreases its mechanical strength. However, this fragility of the material is compensated by an increased ductility. Regarding metal leaching, the studied ceramics have no environmental restrictions as far as their use as building material is concerned, as the obtained results were virtually identical to those for the blank samples (100% clay). Results showed that the presence of dichloromethane (373.2 μg m -− 3 ) and propanone (61.2 μg m -− 3 ) in the samples with added sludge was relatively relevant with respect to concentrations in samples made of 100% clay. All monocyclic aromatics detected showed a concentration level far below theirodour odor threshold. In general, thus, it can be concluded that volatile organic compounds compound (VOCsVOC) emissions during firing of the new ceramic material do not involve any particular problem. Finally, the experience obtained after more than 10 years of industrial production of this new mixed ceramic product was also analyzed. This analysis allowedto confirm confirmation that clay brick production with incorporation of paper sludge waste is a feasible solution from a technical point of view. As a key outcome, this fact has helped to reduce the reduction in a large proportion the amount of sludge produced by the Spanish paper industry ending up in landfills.

a b s t r a c tUse of sewage sludge from wastewater treatment plants as a raw material for making clay bricks has been analyzed to be an option to dumping sludges into landfills. This alternative has been shown feasible and interesting due to the high rate of use of ceramic materials in the building sector. However, it meets with some environmental issues and some prejudices on the part of users.This work shows some leachability and toxicity tests (outgassing and offgassing) which demonstrate the environmental compatibility of these ceramic products to be used as building materials and even in deconstruction of the building once its useful life is ended.

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Multi-criteria decision-making methods support decision makers in all stages of the decision-making process by providing useful data. However, criteria are not always certain as uncertainty is a feature of the real world. MCDM methods under uncertainty and fuzzy systems are accepted as suitable techniques in conflicting problems that cannot be represented by numerical values, in particular in energy analysis and planning. In this paper, a modified TOPSIS method for multi-criteria group decision-making with qualitative linguistic labels is proposed. This method addresses uncertainty considering different levels of precision. Each decision maker's judgment on the performance of alternatives with respect to each criterion is expressed by qualitative linguistic labels. The new method takes into account linguistic data provided by the decision makers without any previous aggregation. Decision maker judgments are incorporated into the proposed method to generate a complete ranking of alternatives. An application in energy planning is presented as an illustrative case example in which energy policy alternatives are ranked. Seven energy alternatives under nine criteria were evaluated according to the opinion of three environmental and energy experts. The weights of the criteria are determined by fuzzy AHP, and the alternatives are ranked using qualitative TOPSIS. The proposed approach is compared with a modified fuzzy TOPSIS method, showing the advantages of the proposed approach when dealing with linguistic assessments to model uncertainty and imprecision. Although the new approach requires less cognitive effort to decision makers, it yields similar results.