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• This research aims to quantify the contribution of NETs in reducing carbon emissions with minimum cost to achieve net-zero emissions. • Life cycle optimisation study provides an optimal solution by optimising the system's life cycle impacts. • DACCS shows a different economic performance when different comparison basis is used. • Minimum carbon emission is achievable with minimum system cost. • The resulting NETs portfolios provide a new benchmark for selecting an optimal carbon removal approach. Negative emission technologies (NETs) have been identified as the key to achieve carbon dioxide (CO 2) emission targets in most coutries. However, selecting the most appropriate and cost-efficient NET to meet these targets is challenging. Thus, a deeper understanding of the system impacts of NETs is necessary for effective decision-making. This work presents a life cycle optimisation (LCO) study of a set of NET technologies. LCO study combines life cycle analysis with techno-economic analysis to optimise and screen process alternatives such as bioenergy carbon capture and storage (BECCS), direct air carbon capture and storage (DACCCS), and biochar. The proposed methodology was demonstrated with a case study with five scenarios to achieve two objectives: to minimise total system cost and to minimise net CO 2 emissions. The case study analysed different NET configurations to decarbonise an existing coal-fired power plant in East Malaysia (Sarawak). In this work, an existing Balingian Coal-Fired Power Plant was considered. NET configurations were assessed based on critical performance aspects such as total life cycle carbon emissions (TLCCE) and total life cycle cost input (TLCCI). However, it is worth emphasising that the proposed methodology can be revised to handle other NET configurations that were not explicitly addressed in this paper. This can be done by utilising relevant data and assumptions that are specific to each NET configuration. Results from the case study show that the minimum cost case provides an optimum NET configuration with TLCCE and TLCCI ranging from -0.02 kgCO 2 eq to 100.28 kgCO 2 eq and 23.99 USD/MWh to 1466.70 USD/MWh, respectively. In terms of life cycle analysis, DACCS shows a favourable TLCCI of 23.99 USD/MWh and TLCCE of -0.02 kgCO 2 eq/MWh. On the other hand, minimising CO 2 emissions results in a 7% to 17% higher TLCCI in Scenario 2 and 3 but a similar trend in each sub-system can still be observed. This has proven that higher cost is required in the case when the CO 2 emissions were to be minimised. [ABSTRACT FROM AUTHOR]

This paper presents a novel methodology for solving multi-objective Computer Aided Molecular Design (CAMD) problems. One of the major challenges in multi-objective CAMD problems is the subjectivity involved in assigning the weighting factors to each property that is optimised. It is difficult to define the relative importance of each property in CAMD problems as target properties that belong to different categories cannot be compared on a common scale. It is crucial to solve this issue as distinct solutions will be generated due to different weighting factors of each property. In this work, a systematic framework that combines CAMD and Analytic Hierarchy Process (AHP) is developed to deal with the ambiguities involved in assessing the relative importance weightings of target properties in multi-objective molecular design problem. Through AHP, molecular design problems can be approached as a hierarchical decision structure and different categories of target properties are combined in the same analysis. Besides, AHP has the ability to generate numerical priorities from the subjective knowledge in evaluating the relative importance of properties using pairwise comparison. A case study on solvent design for oil extraction from palm pressed fibre is solved to illustrate the proposed methodology. [ABSTRACT FROM AUTHOR]

RCNet is a spreadsheet-based software for the synthesis of resource conversation networks (RCNs) for planning the efficient use of material resources (e.g., water, utility gases, solvents) in industrial plants. The software is developed based on the well-established process integration tools, namely pinch analysis and mathematical programming techniques. In the first stage, pinch analysis is used to determine maximum resource conservation targets prior to detailed RCN design. In the second stage, mathematical optimisation is then used to determine the optimal flowrate allocation between process sources and sinks of the RCN, to achieve the performance targets. RCNet is applicable for various industrial applications. To date, no generic software has been developed to handle water minimisation, hydrogen recovery and property integration, which is the main subject of this work. In the developed software, same interface and platform can be used to solve abovementioned problems independently. For illustration, three literature examples on water minimisation, hydrogen recovery and property integration, as well as an industrial case study are solved using RCNet. [ABSTRACT FROM AUTHOR]

Most of the established methods for utility targeting in a heat exchanger network (HEN) are mainly focusing on fixed stream conditions, where the flow rate, heat capacity, supply and target temperatures are fixed. However, in the process industries, the stream conditions (flow rates and temperatures) are not fixed. Therefore, the established HEN targeting methods cannot be directly applied to locate the hot and cold utility targets for HEN problem with varying flow rates and temperatures. To address this issue, a revised floating pinch method which uses binary variables to parameterise the stream locations on the composite curves, is presented in this work to identify the minimum utilities targets. The revised method simplify the earlier version of floating pinch method presented by Duran and Grossmann (1986) by avoiding the non-differentiability in the mathematical program. Two cases, one with fixed parameters while another with temperature-dependent properties and varying operating parameters are solved to illustrate the revised model. [ABSTRACT FROM AUTHOR]

Pretreatment is often necessary when the fresh water available to industrial plants is impure, and when some processes are particularly sensitive to contaminants. Partitioning processes such as membrane separation units are often used for such applications. However, the use of pretreatment units adds to capital and operating costs for a water system. Hence, it is of interest to develop design procedures to minimize the cost for such system. This work presents a graphical pinch analysis approach for targeting minimum flowrate of partitioning water pretreatment systems in single component problem. The approach determines how product and reject streams from the treatment unit can be allocated, along with bypassed freshwater, to satisfy multiple process sinks with their respective flowrate and purity requirements. Hypothetical case studies are presented to illustrate the approach, and generalized design principles based on pinch analysis heuristics are drawn from the examples. [ABSTRACT FROM AUTHOR]

This paper presents a novel superstructure-based optimization model for the synthesis of industrial water networks with partitioning regenerators. Such regenerators function by splitting a contaminated water stream into a regenerated lean stream and a low-quality reject stream. Membrane separation-based processes are examples of these types of regenerators. The optimization model presented in this work integrates a single, centralized partitioning regenerator with a source-sink superstructure under the assumption that the processes within the plant are of the fixed flow rate type. The formulation is non-linear as a result of the presence of bilinear terms in the regenerator balance equations, but global optimal solutions can be found using commercial software The features of the model are illustrated by solving case studies from the literature It is notable from these examples that considerable design flexibility exists in networks of this type, since potentially both the lean and reject streams from the partitioning regenerator can be reused/recycled within the plant. [ABSTRACT FROM AUTHOR]

Assessment on sustainability of production pathway is an important step to promote the sustainability features during early process design. The early process design can be divided into three stages, which are research and development (R&D), preliminary engineering and basic engineering. Note that, the assessment frameworks for R&D and preliminary engineering stages have been presented in our previous works. As continuation, a systematic framework for the assessment of chemical production pathway in basic engineering design stage is presented in this work (0105 and 0110). This framework emphasises on the inherent safety, health and environment (SHE) and economic performance (EP) assessment of chemical production pathway, with the integration of fuzzy optimisation approach as the multi-objective analysis tool. Following the proposed assessment framework, selection of pipe size and types of fittings is considered in this framework for improvement of inherent SHE and EP, as those selection criteria are the key design parameters at this design stage. To illustrate the application of the proposed framework, a case study on biodiesel production pathway assessment is presented. [ABSTRACT FROM AUTHOR]

This paper presents a heuristic framework that can be used for the debottlenecking of a palm oil-based integrated biorefinery with multiple processes and products. In current industrial practice, any individual unit within these systems is generally designed for a required size. Besides, it also takes into account of an additional margin for safety to meet the requirement of the baseline state of the process. In case there is a variation in the quality of the supplied feedstock or an increase for product demand, it becomes necessary to identify the bottleneck process unit in order to handle the new variation and meet all requirements. In response, the system has to be debottlenecked by altering important operating parameters from the baseline state that limits the change. This stage entails formulating and solving a detailed model for this particular process. In this paper, frameworks are presented to aid decision makers to first identify a bottleneck and subsequently debottleneck the process. The frameworks are essentially a guide for design and safety engineers for decision making at conceptual design stage. A design stage palm oil-based integrated biorefinery case study is solved to demonstrate the proposed approach. [ABSTRACT FROM AUTHOR]

Carbon capture and storage (CCS) is a means for reducing carbon dioxide (CO2) emissions from fossil fuel combustion in power generation and industrial processes. It involves the capture of CO2 for subsequent storage in various geological formations. The selection and matching of the power plants and storage sites are often an issue of optimisation due to various constraints, i.e., time of availability, injection rate, and storage capacity limits. In this work, a novel graphical targeting tool based on pinch analysis is proposed to address the planning problem of the storage of captured CO2 from power generating plants into corresponding reservoirs. The main consideration for the problem is the time of availability of the latter, since reservoirs need to be developed prior to CO2 storage. The time limitation is addressed by the graphical technique where time is taken as the governing element in solving the problem. Hypothetical examples are used to elucidate the proposed approach. [ABSTRACT FROM AUTHOR]

Depletion of fossil fuels and increasing public awareness of environmental issues has stimulated the search for alternative energy sources. Biofuels are recognised as one of the most promising alternatives to fossil fuels, as they can be produced from various types of feedstock. The efficiency and sustainability of biomass-based production can be maximised by producing biofuels along with other valuable coproducts in a "biorefinery". This concept was proposed to make the production of biofuels and biochemicals more economically viable by taking advantage of opportunities for process integration and waste recovery. In this work, a novel hybrid optimisation model that combines superstructure-based optimisation approach and insight-based automated targeting for the synthesis of a sustainable integrated biorefinery is presented. In addition, fuzzy optimisation is also adapted to synthesize such integrated facility with the simultaneous consideration of both economic and environmental performance. Note that the proposed approach is a generic synthesis strategy that can be applied even without detailed modelling of individual processes. [ABSTRACT FROM AUTHOR]

An introduction to the journal is presented in which the editors discuss various reports within the issue on topics including the development of advanced waste treatment technologies, boron removal using electrocoagulation, and work on process integration.

Palm pressed fibre (PPF) is one of the by-products from palm oil milling process which is conventionally burned as fuel to produce energy to support the milling operation. PPF typically contains 5-6% of residual palm oil, which can be further recovered as by-product before using it as fuel ir. boiler. Therefore, it has propagated great interest in developing technologies to extract the residual oil from PPF. Based on the currently available technologies, hexane cold extraction is the most established method for recovering the residual oil. However, the extracted residual oil via hexane is not suitable for food applications due to the toxicity of hexane. Besides, the low recovery of carotene from the residual oil is another major concern of using hexane as solvent in the cold extraction. Therefore, there is a need to identify an alternative solvent to recover the residual oil from PPF. In this work, Computer Aided Molecular Design (CAMD) technique is adapted to identify alternative solvents which possess the most desirable attributes for this application. This application of CAMD is unique because it is important to optimize the physical properties of the potential solvent along with safety and health attributes in order to use in food industries. Moreover, the safety and health indexes depend on the physical properties of the final solvent and the abrupt changes of these indexes must be tracked simultaneously with the changes in properties. The proposed approach can identify alternative solvents that extract residual oil from PPF with the highest retention of carotene. To trade off the optimisation objective of the recovery of carotene and total health and safety impacts, fuzzy optimisation based approach for solvent design has been developed. [ABSTRACT FROM AUTHOR]

Carbon capture and storage (CCS) techniques are considered as one of the promising approaches to reduce carbon dioxide (CO2) emissions from fossil fuel based power generation, which still accounts for a significant portion of greenhouse gas emissions in the world. CCS technology can be used to mitigate greenhouse gas emissions, with the additional advantage that it allows continuing use reliable and inexpensive fossil fuels. However, CCS retrofit entails major capital costs as well as a reduction of overall thermal efficiency and power output. Thus, it is essential for planning purposes to implement the minimal extent of CCS retrofit while meeting the specified carbon emission limits for the power sector. At the same time, it is necessary to plan for compensatory power generation capacity to offset energy losses resulting from CCS retrofit. In this paper, an algebraic targeting technique is presented for planning of grid-wide CCS retrofits in the power generation sector with compensatory power. The targeting technique is developed based on pinch analysis. In addition, the proposed methodologies are illustrated through case studies based on grid data in India and the Philippines. Sensitivity analysis is carried out to determine the suitable CCS technology and compensatory power source which satisfy emission limits. [ABSTRACT FROM AUTHOR]

With the increasing pressures imposed upon industries on the environmental impacts of the manufacturing industry and chemical processes, numerous methodologies have been developed for the quantification, assessment and minimisation of waste and emissions. Meanwhile, methods for the simultaneous maximisation of economic performance within a product life cycle have also been developed. Similarly, various methodologies for screening of process alternatives based on the above factors have also been developed. However, the human lives put at risk in a supply chain constituting a life cycle tend to be overlooked as a factor of assessment, selection and optimisation of the process. Despite having life cycle assessment (LCA) methodologies for environmental assessment, no methodology has been developed for the minimisation of work-related casualties due to the unpredictable nature of workplace accidents. To address this problem, this paper develops a multi-objective optimisation model that utilises realistic statistical data for estimating the best possible pathway. The model results in the least potential fatality directly involved within the product life cycle while simultaneously minimising operating costs throughout the entire life cycle. A case study involving the utilisation of palm-based biomass formed for the production of value-added green products in Malaysia is used to demonstrate the model. [ABSTRACT FROM AUTHOR]

Synthesis of distributed waste treatment systems has been extensively researched on in the past decades. Although the use of centralised treatment systems is widespread in the process industries, distributed treatment systems are proven to be superior to the former, particularly in terms of cost effectiveness. In this work, a recent-developed graphical targeting technique is extended to determine the minimum treatment flowrate for a single-contaminant system with multiple distributed effluent treatment units. Treatment units of fixed outlet concentration and removal ratio types are considered. Apart from locating the minimum treatment flowrate, additional constraints on maximum inlet concentration and specified regulatory limit are also considered in this work. In addition, the targeting technique is extended for cases with multiple treatment units and two-contaminant system. Case studies were solved to illustrate the proposed approach. [ABSTRACT FROM AUTHOR]