Multilayer Approach for Product Portfolio Optimization: Waste to Added-Value Products.

A multistage multilayer systematic procedure has been developed for the selection of the optimal product portfolio from waste biomass as feedstock for systems involving water-energy-food nexus. It consists of a hybrid heuristic, metric-based, and optimization methodology that evaluates the economic and environmental performance of added-value products from a particular raw material. The first stage preselects the promising products. Next, a superstructure optimization problem is formulated to valorize or transform waste into the optimal set of products. The methodology has been applied within the waste to power and chemicals initiative to evaluate the best use of the biomass residue from the olive oil industry toward food, chemicals, and energy. The heuristic stage is based on the literature review to analyze the feasible products and techniques. Next, simple metrics have been developed and used to preselect products that are promising. Finally, a superstructure optimization approach is used to design the facility that processes leaves, wood chips, and olives into final products. The best technique to recover phenols from "alperujo", a wet solid waste/byproduct of the process, consists of the use of membranes, while the adsorption technique is used for the recovery of phenols from olive leaves and branches. The investment required to process waste adds up to €110.2 million for a 100 kt/yr for the olive production facility, while the profit depends on the level of integration. If the facility is attached to an olive oil production, the generated profit ranges between 14.5 MM €/yr (when the waste is purchased at prices of €249 per ton of alperujo and €6 per ton of olive leaves and branches) and 34.3 MM €/yr when the waste material is obtained for free.

Correction to "Synthesis and Sustainability Evaluation of a Lignocellulosic Multifeedstock Biorefinery Considering Technical Performance Indicators".

[This corrects the article DOI: 10.1021/acsomega.0c00114.].

A novel CO2 utilization technology for the synergistic co-production of multi-walled carbon nanotubes and syngas.

Dry reforming of methane (DRM) is a well-known process in which CH4 and CO2 catalytically react to produce syngas. Solid carbon is a well-known byproduct of the DRM but is undesirable as it leads to catalyst deactivation. However, converting CO2 and CH4 into solid carbon serves as a promising carbon capture and sequestration technique that has been demonstrated in this study by two patented processes. In the first process, known as CARGEN technology (CARbon GENerator), a novel concept of two reactors in series is developed that separately convert the greenhouse gases (GHGs) into multi-walled carbon nanotubes (MWCNTs) and syngas. CARGEN enables at least a 50% reduction in energy requirement with at least 65% CO2 conversion compared to the DRM process. The second process presents an alternative pathway for the regeneration/reactivation of the spent DRM/CARGEN catalyst using CO2. Provided herein is the first report on an experimental demonstration of a 'switching' technology in which CO2 is utilized in both the operation and the regeneration cycles and thus, finally contributing to the overall goal of CO2 fixation. The following studies support all the results in this work: physisorption, chemisorption, XRD, XPS, SEM, TEM, TGA, ICP, and Raman analysis.

Synthesis and Sustainability Evaluation of a Lignocellulosic Multifeedstock Biorefinery Considering Technical Performance Indicators.

Nowadays, green-chemistry principles offer an approach that fits to ensure chemical process sustainability by the use of low-cost renewable raw materials, waste prevention, inherent safer designs, among others. Based on this motivation, this study presents a novel methodology for sustainable process design that comprises the synthesis of a multifeedstock optimal biorefinery under simultaneous optimization of economic and environmental targets and further sustainability evaluation using the sustainability weighted return on investment metric (SWROIM). The first step of the proposed method is the formulation of an optimization model to generate the most suitable process alternatives. The model took into account various biomasses as available raw materials for production of ethanol, butanol, succinic acid, among others. Process technologies such as fermentation, anaerobic digestion, gasification, among others, were considered for biorefinery design. Once the model synthesizes the optimal biorefinery, we used environmental, safety, economic, and energy analyses to assess the process, which is a case study for north Colombia. Process simulation generated the data needed (extended mass and energy balances, property estimation, and modeling of downstream) to develop the process analysis stage via the Aspen Plus software. Results for the environmental and economic analyses showed that the assumption considered to solve the optimization problem was adequate, yielding promising environmental and economic outcomes. Finally, the overall sustainability evaluation showed a SWROIM of 27.29%, indicating that the case study showed higher weighted performance compared to the return on investment (ROI) metric of 14.33%.

Technology review and data analysis for cost assessment of water treatment systems.

A wide variety of water sources, treatment methods, and recycling options have created a myriad of water management options. For modeling of sustainable water treatment options, computationally efficient models may be required. This paper provides a comprehensive and comparative review of the water management systems and the associated economic, environmental, and performance metrics. The water management systems are represented as a network of sources, users, technologies, recycling options, and quality of water. Special attention is given to desalination systems. The two main technology categories currently used for desalination are thermal (e.g., Multistage Flash "MSF", Multi-Effect Distillation "MED", and Mechanical Vapor Compression "MVC") and membrane (e.g., seawater reverse osmosis "SWRO", brackish water reverse osmosis "BWRO"). The cost assessment includes a capital cost comparison (for which regression analysis has been used to account for the non-linear nature of the capacity-cost curves), an operating cost comparison, which includes energy requirements, labor costs, chemicals used, maintenance and repair costs, membrane replacement costs and a unit product cost ($/m3) breakdown, which combines the capital and operating costs. Numerous data were collected for the cost of desalination systems. Statistical methods were then used to analyze these collected data to establish deeper understanding of the relationship to capital cost, operating cost, capacity, constraints due to treatment method capabilities, requirements of the users. The paper also briefly discusses other cost considerations such as the water intake and distribution costs. The environmental impacts (concentrate disposal and CO2 footprint) have also been compared for the various technologies considered. Some integration strategies such as use of hybrid systems, cogeneration plants and use of renewable energy have shown reductions in cost associated due to energy consumption and thereby, reducing the unit product cost. Finally, the paper provides a selection guide suitable for various situations with consideration of the different factors affecting cost, environmental impact and energy demands.

A hierarchical approach for the design improvements of an Organocat biorefinery.

Lignocellulosic biomass has emerged as a potentially attractive renewable energy source. Processing technologies of such biomass, particularly its primary separation, still lack economic justification due to intense energy requirements. Establishing an economically viable and energy efficient biorefinery scheme is a significant challenge. In this work, a systematic approach is proposed for improving basic/existing biorefinery designs. This approach is based on enhancing the efficiency of mass and energy utilization through the use of a hierarchical design approach that involves mass and energy integration. The proposed procedure is applied to a novel biorefinery called Organocat to minimize its energy and mass consumption and total annualized cost. An improved heat exchanger network with minimum energy consumption of 4.5 MJ/kgdry biomass is designed. An optimal recycle network with zero fresh water usage and minimum waste discharge is also constructed, making the process more competitive and economically attractive.

Techno-economic analysis for a sugarcane biorefinery: Colombian case.

In this paper a techno-economic analysis for a sugarcane biorefinery is presented for the Colombian case. It is shown two scenarios for different conversion pathways as function of feedstock distribution and technologies for sugar, fuel ethanol, PHB, anthocyanins and electricity production. These scenarios are compared with the Colombian base case which simultaneously produce sugar, fuel ethanol and electricity. A simulation procedure was used in order to evaluate biorefinery schemes for all the scenarios, using Aspen Plus software, that include productivity analysis, energy calculations and economic evaluation for each process configuration. The results showed that the configuration with the best economic, environmental and social performance is the one that considers fuel ethanol and PHB production from combined cane bagasse and molasses. This result served as the basis to draw recommendations on technological and economic feasibility as well as social aspects for the implementation of such type of biorefinery in Colombia.

Optimal planning for the sustainable utilization of municipal solid waste.

The increasing generation of municipal solid waste (MSW) is a major problem particularly for large urban areas with insufficient landfill capacities and inefficient waste management systems. Several options associated to the supply chain for implementing a MSW management system are available, however to determine the optimal solution several technical, economic, environmental and social aspects must be considered. Therefore, this paper proposes a mathematical programming model for the optimal planning of the supply chain associated to the MSW management system to maximize the economic benefit while accounting for technical and environmental issues. The optimization model simultaneously selects the processing technologies and their location, the distribution of wastes from cities as well as the distribution of products to markets. The problem was formulated as a multi-objective mixed-integer linear programing problem to maximize the profit of the supply chain and the amount of recycled wastes, where the results are showed through Pareto curves that tradeoff economic and environmental aspects. The proposed approach is applied to a case study for the west-central part of Mexico to consider the integration of MSW from several cities to yield useful products. The results show that an integrated utilization of MSW can provide economic, environmental and social benefits.

Synthesis of Hybrid Gas Permeation Membrane/Condensation Systems for Pollution Prevention.

Pollution prevention is a major economic and environmental issue in the chemical processing industries. This paper addresses the design of cost-effective recovery systems for vaporous emissions, systems that allow environmentally sound recycling of the recovered components for re-use within the process as a means of pollution prevention. A methodology is proposed to design optimal hybrid systems that involve gas permeation membranes and vapor condensation systems. The design methodology is presented as a mixed-integer, nonlinear program. Based on a fixed structure of the system, a short-cut formulation is derived. Additionally, the incorporation of the system into the emerging mass integration methodology is presented. It is demonstrated, through an industrial case study, that hybrid membrane/condensation systems possess advantages over either separation technique alone.