Heriberto Cabezas

7003847757

Publications - 9

Exergy-Based Sustainability Assessment of Gold Mining in Colombia: A Comparative Analysis of Open-Pit and Alluvial Mining

Natalia A. Cano-Londoño Javier Ordoñez-Loza Héctor I. Velásquez Heriberto Cabezas

Publication Name: Energies

Publication Date: 2025-07-01

Volume: 18

Issue: 13

Page Range: Unknown

Description:

Highlights: Exergy analysis quantifies the sustainability of a process based on the environmental burden generated by using energy resources. Open-pit mining relies on fossil fuels (53%), while alluvial mining is mostly water-dependent (94%) Strategies include improving efficiency, minimizing exergy losses, using renewables, and adopting circular economy principles. Exergy efficiency is improved by reduction in exergy inputs and exergy emissions/waste, i.e., reduction in the loss of useful energy. Findings highlight inefficiencies, guiding resource optimization, and reduced environmental impact. Thermodynamic methods such as exergy analysis enable the evaluation of environmental load (environmental impacts) by quantifying entropy generation and exergy destruction associated with using renewable and non-renewable resources throughout a production system. Based on the principle that environmental impacts occur when exergy is dissipated into the environment, this study applies exergy analysis as a tool for assessing the sustainability of gold mining in Colombia. Two extraction technologies—open-pit and alluvial mining—are evaluated by calculating exergy efficiencies, cumulative exergy demand (CExD), and associated environmental impacts. The results reveal significant differences between the two methods: open-pit mining is heavily dependent on fossil fuels (53% of input exergy), with 99.62% of total exergy destroyed, resulting in an exergy efficiency of just 0.37% and a sustainability index (SI) of 1.00. In contrast, alluvial mining relies predominantly on water (94%), with 69% of input exergy destroyed, an exergy efficiency of 31%, and an SI of 1.46. Four strategies are proposed to reduce environmental burdens: improving efficiency, minimizing exergy losses, integrating renewable energy, and adopting circular economy principles. This study presents the first application of exergy analysis to comprehensively assess the exergy cost of gold production, from extraction through refining, casting, and molding, highlighting critical exergy hotspots and offering a thermodynamic foundation for optimizing resource use in mineral processing.

Open Access: Yes

DOI: 10.3390/en18133247

Designing cost-effective supply chains for plastics at the end-of-life

Gerardo Ruiz-Mercado Natalia A. Cano-Londoño Jean Pimentel Csaba T. Deak Baibhaw Kumar Heriberto Cabezas

Publication Name: Journal of Cleaner Production

Publication Date: 2025-04-10

Volume: 501

Issue: Unknown

Page Range: Unknown

Description:

Increased global plastic consumption and production boosted the amount of end-of-life (EoL) plastic. Also, 90 % of plastic EoL is either landfilled or incinerated. These unsustainable EoL pathways impact the environment and human health and waste valuable materials. Thus, improvements to the existing recycling infrastructure for sustainable plastic management are needed to enhance plastic circularity. Therefore, this contribution addresses optimizing cost-effective pathways for plastic recycling within the supply chain. The research uses mathematical optimization and the P-graph theoretical framework to calculate recycling costs, encompassing both capital expenditure and operational expenditure for various pathways of plastic recycling. The proposed methodology is applied through a detailed case study in Miskolc, Hungary, revealing estimated recycling costs ranging from 54.9 to 59.28 EUR/ton. This finding provides crucial insights into the economic implications of diverse recycling methods. Also, the study highlights the P-graph model's untapped potential as a resource for decision-makers in plastic recycling, particularly the enumeration of options for further consideration. The work's utility and novelty lie in the model's capability to design cost-effective pathways, offering a tangible contribution to the plastic recycling supply chain. Finally, this contribution offers economic solutions needed to ensure cost-effective sustainable plastic management solutions.

Open Access: Yes

DOI: 10.1016/j.jclepro.2025.145227

Editorial overview: Climate Change Special Issue

Vasilios I. Manousiouthakis Heriberto Cabezas

Publication Name: Current Opinion in Chemical Engineering

Publication Date: 2025-03-01

Volume: 47

Issue: Unknown

Page Range: Unknown

Description:

No description provided

Open Access: Yes

DOI: 10.1016/j.coche.2024.101076

Water stress-based price for global sustainability: a study using generalized global sustainability model (GGSM)

Urmila Diwekar Neeraj Hanumante Apoorva Nisal Heriberto Cabezas Yogendra Shastri

Publication Name: Clean Technologies and Environmental Policy

Publication Date: 2025-03-01

Volume: 27

Issue: 3

Page Range: 1131-1150

Description:

Abstract: Considering the importance of water in the global Food-Energy-Water nexus, stress-dependent water pricing can be a valuable tool to achieve water sustainability. Given the large variability in water availability and demands across the globe, such mechanism should be implemented at regional scale. However, water pricing explicitly incorporating regional water stress has been rarely studied and used. Here, the generalized global sustainability model is modified and used to model continent-level stress-based water price and its effectiveness as a policy tool. The water price model includes a constant component representing the base price and a variable component which is a linear function of the water stress. The water stress feedback is modeled through the demand elasticity of water price. These models are parameterized for six global regions and three water-consuming sectors. Regional distribution of parameters is carried out based on GDP per capita, whereas sectoral distribution is obtained based on literature. The simulation results indicate that incorporating stress-based water price feedback reduces water stress for otherwise high water stress regions like Africa. Since the response to water price changes can reduce water stress, a water stress-based price model can be used as a policy instrument. This model can also capture the systemic progression of the influence of water price rise. The African continent may experience a reduction in food production by about 26% due to rising water prices. Because of the trade-off between regional food production and water stress, cooperation between various regions could help reduce the impact of the impending water crisis. North America and Europe may produce surplus food products and play a pivotal role in alleviating the critical situation in Africa.

Open Access: Yes

DOI: 10.1007/s10098-024-02888-x

Modeling of a Biomass-Based Energy Production Case Study Using Flexible Inputs with the P-Graph Framework

András Éles István Heckl Heriberto Cabezas

Publication Name: Energies

Publication Date: 2024-02-01

Volume: 17

Issue: 3

Page Range: Unknown

Description:

In this work, a modeling technique utilizing the P-Graph framework was used for a case study involving biomass-based local energy production. In recent years, distributed energy systems gained attention. These systems aim to satisfy energy supply demands, support the local economy, decrease transportation needs and dependence on imports, and, in general, obtain a more sustainable energy production process. Designing such systems is a challenge, for which novel optimization approaches were developed to help decision making. Previous work used the P-Graph framework to optimize energy production in a small rural area, involving manure, intercrops, grass, and corn silage as inputs and fermenters. Biogas is produced in fermenters, and Combined Heat and Power (CHP) plants provide heat and electricity. A more recent result introduced the concept of operations with flexible inputs in the P-Graph framework. In this work, the concept of flexible inputs was applied to model fermenters in the original case study. A new implementation of the original decision problem was made both as a Mixed-Integer Linear Programming (MILP) model and as a purely P-Graph model by using the flexible input technique. Both approaches provided the same optimal solution, with a 31% larger profit than the fixed input model.

Open Access: Yes

DOI: 10.3390/en17030687

Enabling technology models with nonlinearities in the synthesis of wastewater treatment networks based on the P-graph framework

Ákos Orosz Kirti M. Yenkie Jean Pimentel Emmanuel A. Aboagye Mihály Csaba Markót Heriberto Cabezas Ferenc Friedler

Publication Name: Computers and Chemical Engineering

Publication Date: 2022-11-01

Volume: 167

Issue: Unknown

Page Range: Unknown

Description:

Designing effective wastewater treatment networks is challenging because of the large number of treatment options available for performing similar tasks. Each treatment option has variability in cost and contaminant removal efficiency. Moreover, their mathematical models are highly nonlinear, thus rendering them computationally intensive. Such systems yield mixed-integer nonlinear programming models which cannot be solved properly with contemporary optimization tools that may result in local optima or may fail to converge. Herein, the P-graph framework is employed, thus generating all potentially feasible process structures, which results in simpler, smaller mathematical models. All potentially feasible process networks are evaluated by nonlinear programming resulting in guaranteed global optimum; furthermore, the ranked list of the n-best networks is also available. With the proposed tool, better facilities can be designed handling complex waste streams with minimal cost and reasonable environmental impact. The novel method is illustrated with two case studies showing its computational effectiveness.

Open Access: Yes

DOI: 10.1016/j.compchemeng.2022.108034

The P-graph approach for systematic synthesis of wastewater treatment networks

Ákos Orosz Kirti M. Yenkie Jean Pimentel Heriberto Cabezas Ferenc Friedler

Publication Name: Aiche Journal

Publication Date: 2021-07-01

Volume: 67

Issue: 7

Page Range: Unknown

Description:

Wastewater treatment consists of three or four sequential stages: preliminary, primary, secondary, and tertiary. Each stage can comprise multiple alternative technologies that can perform the same tasks with different efficiencies, operating times, and costs. Thus, we propose a systematic approach for designing wastewater treatment networks by utilizing principles of mathematical modeling and generating an exhaustive enumeration of all the possible technologies and their connections during the early stages of designing a treatment facility. Some of these structures are nonintuitive and include recycling, reprocessing, bypasses, and multiple technologies in parallel or series to remove the same contaminant. The nonintuitive structures with multiple technologies may provide a measure of resilience compared to typical heuristic designs. Thus, the combination of P-graph methodology and the sequence of treatment technologies predicted via the optimization algorithm from the maximal structure is based on holistic considerations and does not lead to suboptimal solutions.

Open Access: Yes

DOI: 10.1002/aic.17253

Efficient Design and Sustainability Assessment of Wastewater Treatment Networks using the P-graph Approach: A Tannery Waste Case Study

Ákos Orosz Kirti M. Yenkie Jean Pimentel Emmanuel A. Aboagye Heriberto Cabezas Ferenc Friedler

Publication Name: Chemical Engineering Transactions

Publication Date: 2021-01-01

Volume: 88

Issue: Unknown

Page Range: 493-498

Description:

In the tannery industry approximately, 30 - 35 m3 of wastewater (WW) is generated per ton of rawhide processed. The WW comprises high concentrations of salts, ammonia, dye, solvents, and chromium. Of particular interest is chromium, which has been proven to cause dermatological, developmental, and reproductive issues on exposure. Thus, there is a need for appropriate treatment of the tannery WW before it is discharged for natural remediation. However, designing a treatment process is multifaceted due to the availability of multiple technologies that can perform similar tasks and the complex composition of waste streams. This necessitates the treatment to be performed in stages namely, primary, secondary, and tertiary. In some cases, pretreatment is required to enhance the recovery in the following stages. Due to the combinatorial nature of this problem, the P-graph approach, which uses principles from graph theory, can be used to synthesize a treatment pathway by selecting appropriate technologies at each stage, while meeting required purity specifications. Furthermore, the P-graph approach can provide alternate feasible treatment structures ranked based on Economics as well as Sustainability indicators, such as the Sustainable Process Index (SPI). In this work, a tannery WW case study is investigated with multiple stages and treatment technologies. A complex maximal structure is generated comprising all possible technologies, flows, connections, bypasses, mixers, and splitters. The models for each technology involve capital and operating costs, efficiency, and SPI at each stage of the treatment process. This problem is formulated in P-graph and solved using the Accelerated Branch-and-Bound algorithm.

Open Access: Yes

DOI: 10.3303/CET2188082

Socio-ecological network structures from process graphs

Angelyn Lao Ákos Orosz Raymond R. Tan Heriberto Cabezas Ferenc Friedler

Publication Name: Plos One

Publication Date: 2020-08-01

Volume: 15

Issue: 8 August

Page Range: Unknown

Description:

We propose a process graph (P-graph) approach to develop ecosystem networks from knowledge of the properties of the component species. Originally developed as a process engineering tool for designing industrial plants, the P-graph framework has key advantages over conventional ecological network analysis techniques based on input-output models. A P-graph is a bipartite graph consisting of two types of nodes, which we propose to represent components of an ecosystem. Compartments within ecosystems (e.g., organism species) are represented by one class of nodes, while the roles or functions that they play relative to other compartments are represented by a second class of nodes. This bipartite graph representation enables a powerful, unambiguous representation of relationships among ecosystem compartments, which can come in tangible (e.g., mass flow in predation) or intangible form (e.g., symbiosis). For example, within a P-graph, the distinct roles of bees as pollinators for some plants and as prey for some animals can be explicitly represented, which would not otherwise be possible using conventional ecological network analysis. After a discussion of the mapping of ecosystems into P-graph, we also discuss how this framework can be used to guide understanding of complex networks that exist in nature. Two component algorithms of P-graph, namely maximal structure generation (MSG) and solution structure generation (SSG), are shown to be particularly useful for ecological network analysis. These algorithms enable candidate ecosystem networks to be deduced based on current scientific knowledge on the individual ecosystem components. This method can be used to determine the (a) effects of loss of specific ecosystem compartments due to extinction, (b) potential efficacy of ecosystem reconstruction efforts, and (c) maximum sustainable exploitation of human ecosystem services by humans. We illustrate the use of P-graph for the analysis of ecosystem compartment loss using a small-scale stylized case study, and further propose a new criticality index that can be easily derived from SSG results.

Open Access: Yes

DOI: 10.1371/journal.pone.0232384