Process integration for emerging challenges: optimal allocation of antivirals under resource constraints

Clean Technologies and Environmental Policy - The global scientific community has intensified efforts to develop, test, and commercialize pharmaceutical products to deal with the COVID-19 pandemic....     

A fuzzy analytic hierarchy process for the site selection of the Philippine algal industry

Clean Technologies and Environmental Policy - The Philippine algae industry is a multi-billion dollar industry that requires restructuring to further gain global market share. Through the...     

Modelling vicious networks with P-graph causality maps

Clean Technologies and Environmental Policy - P-graph causality maps were recently proposed as a methodology for systematic analysis of intertwined causal chains forming network-like structures....     

Study of microalgae cultivation systems based on integrated analytic hierarchy process–life cycle optimization

Optimization of sustainable process plant configurations requires the use of systematic assessment methods based on the usage of natural resources, release of pollutants and generation of environmental impact. This paper presents an integrated life cycle optimization framework for the synthesis of microalgae cultivation systems, using a multiple objective linear program formulation; in the model, individual objective functions are aggregated and weighted using the analytic hierarchy process. Four different cultivation alternatives were used as case study to demonstrate the capability of this formulated integrated model. The model takes into account three main environmental criteria in assessing different cultivation alternatives, namely energy, water (direct and indirect water) and carbon footprints. It is determined in the case study that the open pond cultivation system is preferred compared to other alternatives.     

Fuzzy analytic hierarchy process (FAHP) for multi-criteria selection of microalgae harvesting and drying processes

Microalgae are considered to be a promising source of biomass compared with first and second generation feedstocks. However, the high energy requirement for harvesting and drying of the algal biomass poses challenge to commercialization due to implications on both carbon footprint (CF) and cost. In this work, we propose a systematic methodology for the multi-criteria evaluation of alternatives for the harvesting and drying processes. A fuzzy analytic hierarchy process (FAHP) approach is used, where the pairwise comparison of the multiple criteria and alternatives were done to prioritize the best harvesting and drying method within the fuzzy bounds of the value judgment that satisfies the consistency index. FAHP also allows the degree of confidence of the expert to be quantified. A case study of four alternatives each for the harvesting and drying process is used to demonstrate the process. Technology capability, cost and environmental impacts (comprised CF, land footprint and water footprint) are identified as the selection criteria for harvesting and drying process, respectively. Results show that flotation is the best alternative for harvesting process, while sun drying is the best among the drying alternatives. Sensitivity analysis is used to give insights on the robustness of the decision model and enables the understanding of critical criteria that would significantly influence the ranking of the alternatives. The proposed FAHP approach therefore can effectively deal with the uncertainty of judgment in the decision-making process in the evaluation of microalgae harvesting and drying processes.     

A methodology for augmenting sparse pairwise comparison matrices in AHP: applications to energy systems

Multiple-attribute decision making (MADM) techniques can be used to provide a systematic approach to selection problems in energy engineering and management. They may be used for selecting the best technologies or policies based on environmental, technical, and socio-economic criteria. Among the many available MADM techniques, the analytic hierarchy process (AHP) has become one of the most widely used due to its effective hierarchical decomposition of complex problems. However, AHP may be tedious due to the large number of pairwise comparisons needed in large problems. Furthermore, in many cases, relevant information may also be available for determining criteria weights based on past decisions that have proven satisfactory in retrospect. Thus, we propose a simple methodology for augmenting sparse pairwise comparisons in AHP through a non-linear programming model that extracts a set of consistent weights from a priori ranking of a subset of alternatives. Two case studies on the ranking of bioethanol feedstocks and of CO₂ storage sites are then shown to illustrate this technique.     

Application of synchrotron microtomography for pore structure characterization of deteriorated cementitious materials due to leaching

Deteriorated mortars and cement pastes (w/c = 0.50) were prepared by an accelerated leaching test using electrochemical migration technique. This technique enabled the reduction of the CaO/SiO₂ molar ratio to less than 2.0. Non-destructive three-dimensional imaging of the internal microstructure of the deteriorated cement matrix in hardened cement paste and mortar was performed using synchrotron X-ray computed microtomography at SPring-8, Japan. After image analysis at a spatial resolution of 0.5 μm/voxel the microtomographic images successfully visualized increased pore spaces in the deteriorated cement matrix with the effective porosity ranging from 0.31 to 0.38. In addition the diffusion tortuosity in the pore space derived from random walk simulation was also evaluated as a pore structure-transport parameter. Indications suggest that the deterioration of the cement matrix due primarily to the dissolution of portlandite decreases the diffusion tortuosity to a single digit as the degree of pore connectivity becomes larger at the submicron scale.     

A design of experiments approach to the sensitivity analysis of the life cycle cost of biodiesel

Clean Technologies and Environmental Policy - Economic feasibility is one of the major factors that has to be considered in the decision to continue with alternative fuel development. Economic...     

Quantification of tortuosity in hardened cement pastes using synchrotron-based X-ray computed microtomography

Tortuosity, as being influenced by the 3D pore micro-geometry, is an important physical quantity to understand better the effect of pore structure on transport properties of cement-based materials. This study attempts to evaluate directly this pore structure-transport parameter from the microtomographic images at spatial resolution of 0.5 μm. This resolution, is by far, to our knowledge, the highest resolution reported for 3D non-invasive imaging of hardened cement pastes. The results show the feasibility of using synchrotron microtomography coupled with 3D image analysis and random walk simulation to measure the diffusion tortuosity that has a direct bearing on transport properties. The tortuosity associated with the percolating pore space seems to reflect the pore morphology that mainly controls the transport properties in young cement pastes; thus, explaining the rough agreement of the results with the computer model or experimental evidence.     

Prediction of CO2 storage site integrity with rough set-based machine learning

Clean Technologies and Environmental Policy - CO2 capture and storage (CCS) and negative emissions technologies (NETs) are considered to be essential carbon management strategies to safely...