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- Evaluation of activated carbons produced from Maize Cob Waste for adsorption-based CO2 separation and biogas upgradingPublication . Surra, Elena; Ribeiro, Rui P.P.L.; Santos, Tiago; Bernardo, Maria; Mota, José P.B.; Lapa, Nuno; Esteves, Isabel A.A.C.Two activated carbons (AC) resulting from CO2 activation of Maize Cob Waste (MCW) were investigated as adsorbent materials for biogas upgrading to bio-methane applying a biorefinery concept. The porous carbons were originated from different times of activation and the one resulting from 3 h with CO2 (MCW(PA)3 h) showed better textural properties, higher working capacity, and selectivity towards CO2 than the carbon resulting from 2 h of activation (MCW(PA)2 h), making it the best candidate for biogas purification. The adsorption equilibrium measurements of CO2 and CH4 on MCW(PA)3 h carbon showed that the Sips isotherm model, as well as the Adsorption Potential Theory (APT), can be confidently employed to accurately correlate the adsorption equilibrium data of the adsorbates employed. In the range of the partial pressures typical for biogas upgrading units, MCW(PA)3 h showed higher CO2 uptakes than the ones reported for coal-based commercial ACs and similar uptakes to the ones reported for bio-based ACs. Moreover, the axial dispersed plug-flow and Linear Driving Force (LDF) approximation for lumped solid-diffusion mass transfer model used for the prediction of the dynamic behaviour of the adsorbate-adsorbent system, provided a good agreement with the experimental results, demonstrating its applicability to the studied system. This work represents the basis of future modelling works of a Pressure Swing Adsorption (PSA) cycle based on the use of MCW(PA)3 h as adsorbent material and demonstrates the high potential of this novel material to be applied in biogas upgrading processes
- Advantages of structural inspection and diagnosis for traditional buildings’ refurbishment: A Life Cycle Assessment perspectivePublication . Silva, Renata; Surra, Elena; Quelhas, Bruno; Costa, Alexandre A.; Lapa, Nuno; Delerue-Matos, CristinaThis work demonstrated, through Life Cycle Assessment (LCA), the environmental advantages brought by the application of the Structural Inspection and Diagnosis (SID) methodology to the structural refurbishment of 7 traditional buildings located in the city of Porto (Portugal), when compared to the common total demolition and reconstruction approach. The early diagnosis of the conservation state of the existing structural elements, and their characterization provides fundamental information for optimizing the design of the refurbishment towards environmental sustainability. SID approach can reduce by 75.3%, on average, the demolished material and provide the lowest environmental burdens in the environmental categories of Global Warming, Acidification, Eutrophication, Ozone, and Abiotic Depletion, Photochemical Ozone Creation potential, Human Toxicity as well as Energy Demand when compared with the total demolition and reconstruction scenarios. In terms of relative environmental impact for the reconstruction scenarios, it was concluded that reinforced concrete, in the form of lightweight and solid slabs, presents the worst performance due to the concrete production process. Furthermore, timber structures show better environmental performance when compared to the use of glued laminated timber. The establishment of the SID tool as a consolidated methodology can be a unique opportunity to systematically include, in the refurbishment of traditional buildings, the principles of the environmental sustainability required by EU policies in the construction sector, providing a significant reduction of demolition wastes and the maximization of the preservation of existing structural materials.
- BioH2 from Dark Fermentation of OFMSW: Effect of the Hydraulic Retention Time and Organic Loading RatePublication . Martins, Inês; Surra, Elena; Ventura, Márcia; Lapa, NunoFood wastes represent one third of all food produced worldwide. It is crucial to both prevent the production of food waste and recover the wasted fraction with the aim to valorizing it. In this context, the conversion of the organic fraction of municipal solid wastes (OFMSW) into bioH2 by dark fermentation (DF) is an important technology to valorize these wastes into renewable fuel. Nevertheless, the DF of OFMSW needs to be optimized for critical operational parameters. The main purposes of this study were to investigate (i) the effect of HRT during continuous bioH2 production through DF and (ii) the effect of organic loading rate (OLR) ruled by HRT. In this work, three HRTs (4, 5, and 6 d) were tested in a mesophilic continuous stirred-tank reactor (CSTR). The HRTs of 4, 5, and 6 days, corresponding to OLRs of 23.6, 18.0, and 10.6 g volatile solids (VS)·L−1·d−1, respectively, showed bioH2 yields of 8.48, 18.2, and 1.64 L·kg−1 VSinfluent with an H2 content of approximately 25, 32, and 5% v/v, respectively. An accumulation of volatile fatty acids (VFAs) was registered with the decrease in HRT, causing a decrease in bioH2 production. The 5 d HRT was the most favorable condition.