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Process efficiency optimisation and integration for cleaner production
Accepted Manuscript Process efficiency optimisation and integration for cleaner production Yee Van Fan, Petar Sabev Varbanov, Jiří Jaromír Klemeš, Andreja Nemet PII:
S0959-6526(17)32632-X
DOI:
10.1016/j.jclepro.2017.10.325
Reference:
JCLP 11117
To appear in:
Journal of Cleaner Production
Received Date: 17 October 2017 Accepted Date: 17 October 2017
Please cite this article as: Fan YV, Varbanov PS, Klemeš JJ, Nemet A, Process efficiency optimisation and integration for cleaner production, Journal of Cleaner Production (2017), doi: 10.1016/ j.jclepro.2017.10.325. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Process Efficiency Optimisation and Integration for Cleaner Production Yee Van Fana, Petar Sabev Varbanova, Andreja Nemetb, Jiří Jaromír Klemeša a
Sustainable Process Integration Laboratory – SPIL, NETME Centre, Faculty of Mechanical
Engineering, Brno University of Technology - VUT Brno, Technická 2896/2, 616 00 Brno, Czech Republic Faculty of Chemistry and Chemical Engineering, University of Maribor, Smetanova ulica 17,
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b
Maribor, Slovenia ABSTRACT
Achieving and attaining sustainability of a society’s existence and functioning
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constitutes a problem of enormous breadth, involving complex interactions among actors of varying backgrounds, personal and institutional goals. The contribution of process
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optimisation by engineering communities to the development of concepts and tools for improved sustainability has been substantial. This article presents an overview of process optimisation and Process Integration paradigms and the most relevant recent works, relevant to sustainability improvement. Based on this background, recent contributions to the field published in the current Special Issue of Process Integration Contribution to Cleaner Production have been analysed. The analysis shows the progress that has been made in
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energy and water efficiency, and waste management, including waste-to-energy, pollution prevention and remediation. 1.
Introduction
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Sustainable development can be achieved by harmonising the three pillars of economic development, social inclusion and environmental protection (UN, 2017). Environmental and
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safety factors have a direct relation to social sustainability, impacting significantly both the quality of human life and other Earth habitants. The initial Kuznets curve (Grossman and Krueger, 1993) representing the relationship between economic inequality and income per capita has been extended to consider the relationship between economics and the environment, hypothesised by the environmental Kuznets curve (Jebli et al., 2016). This concept has been recognised by several studies, such as that by Li et al. (2016) in evaluating the agricultural-related environmental indices and GDP per capita in China. However, it has also been subjected to debate, as the environmental Kuznets curve conveys the message of grow now clean later (Dasgupta et al., 2002). Gill et al. (2017) also highlighted that the proposed relationship, an inverted U-shaped curve, did not necessary apply to all types of
ACCEPTED MANUSCRIPT environmental issues. Process Optimisation (PO) and the efficient use of Process Integration (PI) in the cleaner production have been proven to ensure the healthy functioning of the world economy. Both approaches minimise resource consumption of energy, water and materials, and waste generation, usually improving process efficiency and leading to higher net profit. PO and PI play a significant role in sustainable development (Klemeš and
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Varbanov, 2013) and cover a wider scope than direct Total Site Heat Integration (Klemeš et al., 1997) energy planning for industrial and urban systems for renewable energy integration (Liew et al., 2017). They also include water planning, which is a field experiencing emerging development; see, for example, the cost-optimal water network design presented by Sujak et
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al., (2017), waste recycling and waste to wealth planning (Sadef et al., 2016), chemical reaction (Eblagon et al., 2016) and supply chain/ distribution networks (Govindan et al.,
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2014), and safety of process systems (Stevanovic et al., 2015).
For continued functioning and development of the economy, large inputs of resources are required and waste flows of large magnitude are generated. High energy use, water consumption and waste disposal have been discussed by Kennedy et al. (2015) in an analysis of the energy and material flows of megacities. While it is necessary to cope with the main consequences of economic activities, optimal design and policy solutions without
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compromising development are very much needed. Figure 1 shows the energy production and consumption of the top five countries with regard to Gross Domestic Product (GDP). China has the highest energy consumption (1,987 Mtoe) followed by the United States (1,537 Mtoe), Japan (295.7 Mtoe), Germany (216.3 Mtoe) and the United Kingdom (123 Mtoe). The energy
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consumption and production rates of a country, as shown in Figure 1, are not equal where energy consumption is 36-53% less than energy production. The differences can be
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interpreted as energy loss, or as energy exported to the other countries. When referring to global consumption, illustrated in Figure 2, energy loss is the more likely the explanation, as 51% has not been consumed. A similar discussion on the amount of energy that is lost through inefficiency has been provided by LLNL (2017) in a study of US energy flows. The share of renewable energy (RE) of each country is also shown in Figure 1. This proposes that countries with a lower share of RE have a lower difference between energy production and consumption, and a resulting lower energy loss (e.g. Japan). However, this can also be affected by the maturity and efficiency of renewable technologies, as well as the energy exports needed by a country. (Desjardins, 2016) declared that RE is one of the contributors to high energy loss and low energy efficiency. Consequently, he suggested that more research
ACCEPTED MANUSCRIPT attention is needed to further promote the development of better dispatch ability and efficiency, as well as to lower the cost of renewable energy technologies. Energy supply sufficiency and security are strongly viewed as the main drivers ensuring the welfare and economic development of a society. In this context, ensuring cleaner energy is one of the cornerstones for cleaner overall production, especially in reducing emissions of greenhouse
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gases (GHGs) and other pollutants which are directly related to the types and loads of the
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energy sources used.
Figure 1. Energy production and consumption (IEA, 2015) of the top GDP countries (IMF,
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2017) and the share of renewable energy (OECD, 2017)
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Figure 2. Global energy consumption by sector for the year 2015. Dataset extracted from IEA (2015) RE provides diversification of energy supplies and reduces dependency on fossil fuel imports. The sources of RE can be classified into natural resources (such as sun, water, wind,
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waves, geothermal and biomass) and waste (such as agricultural, plastic, industrial and municipal solid waste). In the context of total energy production and imports, global final energy consumption is only 49%, with 51% not being utilised. This can be seen in Figure 2, which also breaks down the total amount by sectors, where the energy flows from the source
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to the final destination. Industry and transport sectors are energy intensive, taking 2,712 Mtoe/y and 2,704 Mtoe/y of energy consumption respectively. The residential sector
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contributes (2,051 Mtoe/y) to the high energy consumption of the “Other” category. It is reported as the main consumer of renewable energy, including geothermal (5 Mtoe/y), solar/tidal/wind (24 Mtoe/y), biofuels and waste (745 Mtoe/y) (IEA, 2015). Biomass energy is the largest renewable energy source, with 14% out of a total of 18% renewables in the energy mix, and supplies 10% of the global energy supply (REN21, 2016). The main source of RE consumed in industry and transportation comes from biofuels and waste, but the RE share of total energy consumption is rather low (IEA, 2015). It has been reported as only 7% (193 Mtoe) and 2.8% (76 Mtoe) in the industry and transportation sectors (IEA, 2015). The industry sector operates with a low proportion of RE because of the intermittent nature of renewables. Deployment and exploitation of RE technologies are highly
ACCEPTED MANUSCRIPT dependent on the availability and supply of resources, which vary from country to country. Paraguay has been listed as the country with the highest share of RE by the OECE (2017). The share of RE to the total primary energy supply in Paraguay is as high as 135.19%, dominated by hydroelectricity (OECD, 2017). The RE generated is even exported to neighbouring countries. Unscheduled power flows from variable energy sources, such as
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peaks in wind electricity supplies (Korab and Owczarek, 2016), have caused serious and costly (especially the cost of transformers) problems in Central Europe, for example between the Czech Republic and Germany (50 Hertz and CEPS, 2017).
Most of the time, one type of RE supply is not sufficient to cover the demand. RE
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integration is usually performed using distributed generation (Čucek et al., 2010) and energy storage (Varbanov and Klemeš, 2011). Hybrid solar PV and wind energy systems (Krishna
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and Kumar, 2015) are among the prevalent and the more common combinations because of the natural synergies of sun and wind (co-located) (FS-UNEP, 2017). Different types of hybrid systems (Solar and Wind), including stand-alone hybrid systems with a common direct current (DC) and alternating current (AC) bus, grid-connected hybrid systems with a common DC and AC bus, as well as the hybrid systems with AC microgrids have been presented in a study by Badwawi et al. (2015). Transportation is also an active area in
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research supporting sustainable development with low GHGs and pollutant emissions with outcomes including the utilisation of biofuels and the development of electric cars. Figure 3 shows the EU28 share of renewable energy in transportation. The average is still below 10% of the EU28 target by 2020, however. Recently, countries such as the UK, France and China
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(FT, 2017) have considered banning the production of petrol and diesel cars. A range of battery issues (such as charging duration) needs to be solved for meeting the targets. It still a
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question whether the electric car will completely displace the roles of petrol and diesel. This again highlights the need for optimisation and integration studies to incorporate existing technologies into real-world solutions.
30.0
Top Five
25.0 20.0 15.0 10.0 5.0 6.7
8.5
8.9
11.4
Norway
Austria
0.0 EU28 Slovak (Average) Republic
2020 target
22.0
24.0
Finland
Sweden
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2015
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Share of Energy from Renewable Sources in Transport (%)
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Figure 3. The share of renewable energy in transportation, EU28. Data from (Eurostat, 2017)
Waste to Energy (WtE) and Waste to Wealth (WtW) are the two-fold green approaches to mitigating the impact of waste currently ending up in landfills by converting it into resources. The global WtE market was valued at USD 25.32 · 109 in 2013, a growth of 5.5%
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over the previous year (WEC, 2016).
Thermal energy conversion leads the WtE market and accounted for 88.2% of total market revenue in 2013 (WEC, 2016). The EU is the largest market for WtE (47.6%), while the fastest market growth is in China (WEC, 2016). Table 1 summarises the current WtE
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technologies for various forms of energy. It has been reported that WtE plant can save 100350 kg CO2eq/t of waste processed (WEC, 2016). Inconsistent supply, the burdening effect of waste collection and pre-treatment for different waste characteristics are the key barriers to
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the current implementation. The conversion or recycling processes also create a burdening footprint (emission and pollution). Process optimisation, assessment and measurement are important to ensure that the burdening footprint is offset by the unburdening footprint (Klemeš et al., 2015). Waste-to-Energy is an important discovery and leap forward for a sustainable future. It is driven mainly by concerns regarding inappropriate waste management and energy security; however, reliability and affordability are yet to be improved as discussed. This is becoming even more important in relation to the development of smart cities.
ACCEPTED MANUSCRIPT Table 1. The summary of WtE technologies. Information from WEC (2016) WtE technologies
Form of energy produced
Thermochemical 1. Incineration
Heat, power, Combined heat and
(Mass burn >1,000oC, Co-combustion with coal, biomass, power (CHP)
2. Thermal gasification
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Refuse-derived fuel) Hydrogen, methane, syngas
o
o
(Conventional 750 C, Plasma arc 4,000-7,000 C) 3. Pyrolysis (300-800oC, absence of O2)
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Biochemical
Char, gases, aerosols, syngas
1. Fermentation
Ethanol, hydrogen, biodiesel Methane
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2. Anaerobic digestion 3. Sanitary landfill
Methane
4. Microbial Fuel cell
Power
Chemical 1. Esterification
Ethanol, biodiesel
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Despite the relatively smaller emphasis, the roles of PO and PI in water planning and supply chain planning (de Jong et al., 2017), including the storage (Kavadias et al., 2017), distribution (Theo et al., 2017), and safety (Tan et al., 2016) of industrial processes, as well as
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energy conversion and supply, is also important for achieving a holistic and sufficiently complete set of technologies for enabling smart cities, as discussed in an overview by
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Prakash et al., (2016).
Acting upon the necessity for providing technology solutions for the issues discussed in this introductory analysis of sustainable development, the 19th Conference “Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction - PRES 2016 conference was held in Prague, Czech Republic, from 27 to 31 August 2016, coorganised with CHISA 2016 (PRES, 2017). The PRES conference series serves as a platform for sharing and exchanging knowledge and ideas for improving processes, procedures and energy-saving practices. After a thorough peer-review process, 17 articles were selected for the current Virtual Special Issue (VSI). This review presents the key information from the selected articles, supplemented by the current state of the art in the corresponding study scope.
ACCEPTED MANUSCRIPT The Special Issue content can be broadly classified into two themes relating to sustainability improvement: (i) Experimental Assessment: Novel Approaches and Potential Assessment (ii) Methodology Development and Modelling: Optimisation. 2.
Sustainability
Improvement
Through
Experimental
Assessment:
Novel
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Approaches and Potential Assessment Liquid biofuels can be generally classified into ethanol, biodiesel and hydrated vegetable oil. In 2015, ethanol production increased by 4%, whereas global biodiesel production fell (by less than 1%) mainly because of the growth of the use of ethanol fuel in
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Asia (REN21, 2016). Figure 4 shows the share of biofuel global production by type and country. Biodiesel offers fewer emissions in PM (Shi et al., 2006), CO (Nantha Gopal et al. 2017), unburned hydrocarbon (Nantha Gopal et al. 2017), SOx (Aziz et al., 2005), and offers
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security of supply. Other advantages of biodiesel include its better lubricability, reasonable cold filter plugging point, better cetane number and high flash point (Liew et al., 2014) compared to fossil fuels. These properties make it a promising alternative fuel for engines. However, emissions of NOx are higher than from petroleum diesel (Nantha Gopal et al. 2017). These reaction optimisation studies play an important part in outlining the limitations of
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biodiesel (NOx emission). Emission reduction performance and process efficiency can be improved by identifying suitable raw materials, varying the production process, using blends, and the addition of catalysts as summarised by Jeevahan et al., (2017). Asif et al., (2017) investigated the non-edible oils (Salvadora alii and Thespesia populneoides) for biodiesel
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synthesis via a novel ultrasonic-assisted cavitation system. The methyl ester was produced by using an ultrasonically assisted cavitation reactor with the addition of calcium oxide catalyst.
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The biodiesel produced was found to comply with standards of fuel properties. Biofuels have a high impact on changing the quality of land, as they are mostly produced from agricultural raw materials. A study by Sági et al. (2017) highlighted the possibility of integration biofuel production in a refinery. The main barriers to utilisation of first-generation biofuels (bioethanol) are low thermal and oxidation stability, higher fuel consumption compared to fossil diesel fuel, and the requirement that the fatty acid content of feedstocks should be kept low. Despite some of the disadvantages, the application of biofuels is encouraged, especially when produced from waste biomass fraction that does not compete with food production. The main advantage of biofuel utilisation are the replacement of crude oil use and lowering the dependence on the import of crude oil. (Sági et al. 2017).
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Figure 4. The share of biofuel global production by type and country. Adapted from REN21 (2016)
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Not limited to biofuel, lignocellulosic biomass also serves as a sustainable alternative of precursor for phenolic platform chemicals, syngas-based products, hydrocarbon derivatives, polymer alloys and adhesives, etc (de Jong et al., 2012). However, its complex aromatic polymer structure requires pre-treatment to make the components suitable for processing steps in order to achieve higher yields of production. It has a critical impact on the feasibility (resources demand, energy input, process efficiency, cost) of the overall
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conversion process. Weinwurm et al., (2017) investigated a two-stage combination of liquid hot water (LHW) and ethanol organosolv (EO) treatment for wheat straw. The aim of this study was to produce a hemicellulose free substrate by LHW pre-hydrolysis and quantitative lignin recovery by EO treatment afterwards. In this way, the three different parts of
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lignocellulose (lignin, cellulose and hemicellulose) could be utilised separately for different products. However, the experimental results indicated that excessively harsh conditions had
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been set during LHW, as one-third of the lignin content was removed, presenting an unacceptably high loss rate of lignin. Based on the results, an upper limit of LHW pretreatment could be set (approximately 30 min at 180°C), and carbohydrate reactions were modelled. Future study is needed to evaluate the economic feasibility of this hybrid treatment as evaluated by Crimes et al. (2017). Post-treatment is a key step in waste to energy utilisation. Energy in the form of gases needs to be upgraded for more efficient usage. Biogas, which consists of CH4, CO2, N2, O2, H2O and H2S from anaerobic digestion (see Figure 5) has been studied the most, particularly desulphurisation, H2O and CO2 removal processes. Miltner et al. (2017) reviewed various upgrading technologies to optimise the quality of biogas natural gas grid injection or for
ACCEPTED MANUSCRIPT vehicle fuel. They suggested that besides the usual local utilisation of biogas for producing heat and power, alternative routes and technologies will have to be considered to obtain costeffective biogas production plants. The efficiency and flexibility of biogas upgrading to enhance economic viability of biogas plants were investigated. The desulphurization process was studied in order to obtain sweetened gas that could be used as local vehicle fuel or in the
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natural gas grid. For utilisation as vehicle fuel, the separation of high and fluctuating amounts of hydrogen sulphide from raw biogas was studied. For CO2 removal, a method of membrane-based gas permeation was presented. The latter is estimated to present a reduction
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potential of 20 to 40% for TOC (Total Cost of Ownership).
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Figure 5. Anaerobic digestion and the biogas constituents. 1(American Biogas Council, 2017)
The handling of fluctuating electrical excess energy is another challenge of RE. The
efficiencies and long-term stability o f storing and transport technologies are promising solutions to this problem. The technologies summarised by Aneke and Wang (2016) include pumped hydrostorage, flywheels, batteries, and thermal storage. Power to gas is a relatively new approach. In line with the power to the gas concept, Liemberger et al. (2017) present a hybrid approach based on membrane separation and pressure swing adsorption that separates hydrogen, which is transported as a co-stream in the natural gas grid. The aim was to achieve hydrogen at fuel cell quality of 99.97 % v/v. Technological feasibility has been achieved at a
ACCEPTED MANUSCRIPT required energy of 0.8-1.5 kWh/m3. The experimental outcome could facilitate the development of simulation models toward energy and costs optimisation to gain the full process potential. Recently, a load-shifting product for energy storage has been proposed by California ISO (Maloney, 2017). In contrast to load consumption patterns that incentivize the consumption of more electricity during periods of high RE generation, load shift product
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means excess clean energy can be absorbed and stored. The energy will be used productively at a different time to benefit both the economy and the environment. This approach is in the early stages; however, it has attracted several organisations, such Tesla, CESA, Stem and Green Charge (CAISO, 2017).
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Hydrogen is widely used as a clean and high efficient energy carrier for electricity generation through fuel cell systems. Hydrogen production from ethanol reforming is
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regarded as a sustainable alternative. However, the yield of hydrogen is highly dependent on operating conditions, and more importantly, the catalyst (including the nature of the selected metal and the support). Hou et al. (2015) identified metals such as Ni, Co, Rh, Ir and Ru to have a reasonable amount of intrinsic activity for ethanol reforming, while CeO2, Al2O3, MgO and ZrO2 are suitable as a support. Palma et al. (2017) introduced a highly active and stable Pt-Ni/CeO2-SiO2 combination for ethanol reforming to modulate hydrogen yield and
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coke formation. The catalyst, prepared by sequential wet impregnation, is evaluated as a promising catalyst for ethanol reforming in the low-temperature range with high activity and low-carbon formation rate at 500°C, 20,000 h−1 and water/ethanol molar ratio of 4.
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Azmi et al. (2017) investigated the potential of CO2 capture by a combination of two processes, adsorption and gas hydrate, on CaO from low cost waste seashells. The adsorption capacity depends on the amount of water present in the shell pores. The water ratio in pores
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of seashell at optimum values of 0.32 and 0.67, with about 7.26 and 9.79 mmol/g increment of CO2 uptake, has been proposed for commercial and synthesized CaO. A freeze-drying process based on a self-heat recuperation technology that reduces and recovers waste heat was proposed by Bando et al. (2017), who reported that it can reduce total energy consumption by 70 – 87 % compared to conventional counterparts. Experimental assessment and specific reaction process optimisation as presented in this section are stepping stones to further integration and development. Both fundamental and advanced research studies have been conducted simultaneously, according to the maturity of the introduced concept, methodologies or technologies.
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Sustainability Improvement Through Methodology Development and Modelling: Integration This section presents an initiative for minimising the gaps between fundamental
improvement studies and real case implementation, beyond technical feasibility. AlMohannadi et al. (2017) studied natural gas utilisation in industrial clusters. Their systematic
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approach to explore synergistic effects of natural gas allocation, power generation and CO2 reduction has been proposed and illustrated in a case study of an industrial cluster.
Aviso et al. (2017) have applied P-graph to the synthesis of community-level energy
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conversion and supply networks. They thoroughly analysed and exploited the multi-period optimisation capability of P-graph Studio (P-graph, 2017). The authors developed a pattern for formulating the relevant superstructures, allowing the design of energy networks that cope
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with varying operation conditions, focusing on seasonal variations of product demand and resource availability. The proposed procedure has been demonstrated in two case studies, allowing users to obtain optimal, as well as near-optimal, solutions for further detailed analysis by decision makers.
Synthesis of integrated biorefineries has been the topic of many investigations,
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including those focusing on process-level synthesis (Martín and Grossmann, 2013) and distributed regional biorefineries using P-graph (Halász et al., 2005) or multi-objective optimisation accounting simultaneously for economics and various environmental impacts (Čuček et al., 2012). Sy et al. (2017) introduced the consideration of uncertainty in seasonal
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changes or fluctuations in product demand when obtaining a design for an integration biorefinery. Their approach identifies the optimal design of an integrated biorefinery by
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maximizing a robustness index against uncertainties, using a multi-objective mathematical optimisation model. Different scenarios were considered via Monte Carlo simulations. The latter considers both profit and environmental footprints, while ensuring that the solutions identified are relatively robust and capable of handling variations in demands and resources. Minimising water consumption has also been viewed as a key building block for smart city development. A concentration potential concept for the design of water networks with multiple contaminants has been reviewed by Li et al. (2017). Several recommendations, including total water networks and interplant water networks using multi-objective optimisation of property-based water networks have been suggested to improve the implementation of water-using networks with multiple contaminants. A water assessment
ACCEPTED MANUSCRIPT study quantifying the overall environmental performance of wastewater treatment plants has been presented by Mustapha et al. (2017). Its aim is to enable a facility manager to efficiently monitor, analyse and improve the performance of a Wastewater Treatment Plant in a cleaner production program. The aim of the study has been achieved through the developed green index based on the stock market composite index. Soil contamination often contributes to
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water pollution and has a significant effect on the ecosystem, as well as on food security. Smart farming (Wolfert et al., 2017) and precision agriculture (Hedley, 2015) are two of the prevention approaches to minimising the waste of resources (especially fertiliser and pesticides) for a sustainable environment. End of pipes solution and remediation technologies
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has been presented by Yao et al., (2012) for contaminated soils (not limited to pollution from agricultural activities). Vocciante et al. (2017) suggested a method originally developed for the early detection of leaks in landfill liners to accommodate the estimation of soil
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characteristics. This method is an inexpensive estimation for soil parameters which can improve the performance of remediation technologies.
A holistic view of the entire extended value chain is also important for an organisation interested in achieving a sustainable future. However, implementation remains a problem. Pavlas et al. (2017) observed that supply chain models are rarely filled with precise
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forecasted quantitative data. Hence, a mathematical model to handle the problem of forecasting with spatially distributed and uncertain data has been proposed. This approach is suitable for supply-chain and network flow models where future amounts of commodities (the flow of which is optimised) are to be forecasted for a number of nodes (such as dealing
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with several waste streams). Sustainable Enterprise Resource Planning systems (Chofreh et al., 2014) enables the integration of sustainable processes, information and data on every
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value chain level of the organisation. Chofreh et al. (2017) developed a roadmap consisting of pre-implementation, implementation and post implementation for practitioners toward the master plan and S-ERP implementation. The safety aspect is another component that should not be overlooked for economic benefit, environmental protection and social acceptance of sustainable development. An industrial area layout method has been proposed by Wang et al. (2017) to enhance safety and to reduce pipe usage in an industrial area with 16 plants. The total cost reduction was as high as 19.2 %, accounting for risk cost and piping cost. Other indirect savings include steel resources and energy, as well as reduced emissions from transportation. These findings aiming to enable real case implementation are important for bridging the gap between industrial process integration implementations.
ACCEPTED MANUSCRIPT 4. Conclusions Ensuring cleaner energy and water supply is one of the cornerstones for cleaner production and overall economic and social development. This is also very important for reducing the emissions of greenhouse gases (GHGs) and other pollutants while preserving the economic viability of the key economic and social activities.
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Treating energy issues as a key pillar of sustainability improvement, minimising waste of energy and materials should be considered first, and only after that, harvesting and utilisation of external renewable resources. In this light, giving the priority to energy and resource recovery, including waste management, gives a starting point on the path to
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sustainability. This includes industrial waste streams for fuel recovery, as well as classical waste-to-energy processes and their supply chains. The works reviewed clarify the key issue
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of obtaining adequate and reliable data for performing process optimisation. Following the principle of maximising the use of the renewable resources base as the second pillar, biorefinery processes for converting biomass to various chemicals are being investigated, maximising process efficiency. The research done to date has accounted for uncertainties in energy and biorefinery networks optimisation, using P-graph and directly
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Mathematical Programming. Future efforts need to assess and maximise their economic viability.
In terms of handling fluctuations in the availability of renewable resources, as well as market energy demands, power-to-gas is a potential storage-enabling technology, where in
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the current SI, hydrogen has been considered as an energy carrier. As the last priority in emission control and mitigation, CO2 capture and storage have
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also attracted research attention. Adsorption of CO2 and the minimisation of the parasitic energy demands of the process have been evaluated, reporting significant energy reduction figures – up to 87%.
Considering the third pillar of sustainable and efficient processing, water networks have been researched in the current VSI, formulating the “concentration potential” concept for seamless treatment of multiple contaminants, including a water management tool based on a composite performance index. Restoring ecosystems after pollution has occurred is an important activity. The landfill monitoring and soil remediation studies reviewed show remarkable potential for improving
ACCEPTED MANUSCRIPT landfill sites performance in a cost-efficient way. Enterprise safety and management aspects have been also discussed, also enable the holistic management of these issues in combination with the key process properties. ACKNOWLEDGEMENT
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This work has been supported by the project Sustainable Process Integration Laboratory – SPIL, funded as project No. CZ.02.1.01/0.0/0.0/15_ 003/0000456, by the Czech Republic Operational Programme Research and Development, Education under a collaboration agreement with the University of Maribor in Slovenia and was financially supported by the
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Slovenian Research Agency (program P2-0032 and project L2-7633).
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S0959-6526(17)32632-X
DOI:
10.1016/j.jclepro.2017.10.325
Reference:
JCLP 11117
To appear in:
Journal of Cleaner Production
Received Date: 17 October 2017 Accepted Date: 17 October 2017
Please cite this article as: Fan YV, Varbanov PS, Klemeš JJ, Nemet A, Process efficiency optimisation and integration for cleaner production, Journal of Cleaner Production (2017), doi: 10.1016/ j.jclepro.2017.10.325. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Process Efficiency Optimisation and Integration for Cleaner Production Yee Van Fana, Petar Sabev Varbanova, Andreja Nemetb, Jiří Jaromír Klemeša a
Sustainable Process Integration Laboratory – SPIL, NETME Centre, Faculty of Mechanical
Engineering, Brno University of Technology - VUT Brno, Technická 2896/2, 616 00 Brno, Czech Republic Faculty of Chemistry and Chemical Engineering, University of Maribor, Smetanova ulica 17,
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b
Maribor, Slovenia ABSTRACT
Achieving and attaining sustainability of a society’s existence and functioning
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constitutes a problem of enormous breadth, involving complex interactions among actors of varying backgrounds, personal and institutional goals. The contribution of process
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optimisation by engineering communities to the development of concepts and tools for improved sustainability has been substantial. This article presents an overview of process optimisation and Process Integration paradigms and the most relevant recent works, relevant to sustainability improvement. Based on this background, recent contributions to the field published in the current Special Issue of Process Integration Contribution to Cleaner Production have been analysed. The analysis shows the progress that has been made in
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energy and water efficiency, and waste management, including waste-to-energy, pollution prevention and remediation. 1.
Introduction
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Sustainable development can be achieved by harmonising the three pillars of economic development, social inclusion and environmental protection (UN, 2017). Environmental and
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safety factors have a direct relation to social sustainability, impacting significantly both the quality of human life and other Earth habitants. The initial Kuznets curve (Grossman and Krueger, 1993) representing the relationship between economic inequality and income per capita has been extended to consider the relationship between economics and the environment, hypothesised by the environmental Kuznets curve (Jebli et al., 2016). This concept has been recognised by several studies, such as that by Li et al. (2016) in evaluating the agricultural-related environmental indices and GDP per capita in China. However, it has also been subjected to debate, as the environmental Kuznets curve conveys the message of grow now clean later (Dasgupta et al., 2002). Gill et al. (2017) also highlighted that the proposed relationship, an inverted U-shaped curve, did not necessary apply to all types of
ACCEPTED MANUSCRIPT environmental issues. Process Optimisation (PO) and the efficient use of Process Integration (PI) in the cleaner production have been proven to ensure the healthy functioning of the world economy. Both approaches minimise resource consumption of energy, water and materials, and waste generation, usually improving process efficiency and leading to higher net profit. PO and PI play a significant role in sustainable development (Klemeš and
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Varbanov, 2013) and cover a wider scope than direct Total Site Heat Integration (Klemeš et al., 1997) energy planning for industrial and urban systems for renewable energy integration (Liew et al., 2017). They also include water planning, which is a field experiencing emerging development; see, for example, the cost-optimal water network design presented by Sujak et
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al., (2017), waste recycling and waste to wealth planning (Sadef et al., 2016), chemical reaction (Eblagon et al., 2016) and supply chain/ distribution networks (Govindan et al.,
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2014), and safety of process systems (Stevanovic et al., 2015).
For continued functioning and development of the economy, large inputs of resources are required and waste flows of large magnitude are generated. High energy use, water consumption and waste disposal have been discussed by Kennedy et al. (2015) in an analysis of the energy and material flows of megacities. While it is necessary to cope with the main consequences of economic activities, optimal design and policy solutions without
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compromising development are very much needed. Figure 1 shows the energy production and consumption of the top five countries with regard to Gross Domestic Product (GDP). China has the highest energy consumption (1,987 Mtoe) followed by the United States (1,537 Mtoe), Japan (295.7 Mtoe), Germany (216.3 Mtoe) and the United Kingdom (123 Mtoe). The energy
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consumption and production rates of a country, as shown in Figure 1, are not equal where energy consumption is 36-53% less than energy production. The differences can be
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interpreted as energy loss, or as energy exported to the other countries. When referring to global consumption, illustrated in Figure 2, energy loss is the more likely the explanation, as 51% has not been consumed. A similar discussion on the amount of energy that is lost through inefficiency has been provided by LLNL (2017) in a study of US energy flows. The share of renewable energy (RE) of each country is also shown in Figure 1. This proposes that countries with a lower share of RE have a lower difference between energy production and consumption, and a resulting lower energy loss (e.g. Japan). However, this can also be affected by the maturity and efficiency of renewable technologies, as well as the energy exports needed by a country. (Desjardins, 2016) declared that RE is one of the contributors to high energy loss and low energy efficiency. Consequently, he suggested that more research
ACCEPTED MANUSCRIPT attention is needed to further promote the development of better dispatch ability and efficiency, as well as to lower the cost of renewable energy technologies. Energy supply sufficiency and security are strongly viewed as the main drivers ensuring the welfare and economic development of a society. In this context, ensuring cleaner energy is one of the cornerstones for cleaner overall production, especially in reducing emissions of greenhouse
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gases (GHGs) and other pollutants which are directly related to the types and loads of the
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energy sources used.
Figure 1. Energy production and consumption (IEA, 2015) of the top GDP countries (IMF,
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2017) and the share of renewable energy (OECD, 2017)
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Figure 2. Global energy consumption by sector for the year 2015. Dataset extracted from IEA (2015) RE provides diversification of energy supplies and reduces dependency on fossil fuel imports. The sources of RE can be classified into natural resources (such as sun, water, wind,
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waves, geothermal and biomass) and waste (such as agricultural, plastic, industrial and municipal solid waste). In the context of total energy production and imports, global final energy consumption is only 49%, with 51% not being utilised. This can be seen in Figure 2, which also breaks down the total amount by sectors, where the energy flows from the source
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to the final destination. Industry and transport sectors are energy intensive, taking 2,712 Mtoe/y and 2,704 Mtoe/y of energy consumption respectively. The residential sector
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contributes (2,051 Mtoe/y) to the high energy consumption of the “Other” category. It is reported as the main consumer of renewable energy, including geothermal (5 Mtoe/y), solar/tidal/wind (24 Mtoe/y), biofuels and waste (745 Mtoe/y) (IEA, 2015). Biomass energy is the largest renewable energy source, with 14% out of a total of 18% renewables in the energy mix, and supplies 10% of the global energy supply (REN21, 2016). The main source of RE consumed in industry and transportation comes from biofuels and waste, but the RE share of total energy consumption is rather low (IEA, 2015). It has been reported as only 7% (193 Mtoe) and 2.8% (76 Mtoe) in the industry and transportation sectors (IEA, 2015). The industry sector operates with a low proportion of RE because of the intermittent nature of renewables. Deployment and exploitation of RE technologies are highly
ACCEPTED MANUSCRIPT dependent on the availability and supply of resources, which vary from country to country. Paraguay has been listed as the country with the highest share of RE by the OECE (2017). The share of RE to the total primary energy supply in Paraguay is as high as 135.19%, dominated by hydroelectricity (OECD, 2017). The RE generated is even exported to neighbouring countries. Unscheduled power flows from variable energy sources, such as
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peaks in wind electricity supplies (Korab and Owczarek, 2016), have caused serious and costly (especially the cost of transformers) problems in Central Europe, for example between the Czech Republic and Germany (50 Hertz and CEPS, 2017).
Most of the time, one type of RE supply is not sufficient to cover the demand. RE
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integration is usually performed using distributed generation (Čucek et al., 2010) and energy storage (Varbanov and Klemeš, 2011). Hybrid solar PV and wind energy systems (Krishna
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and Kumar, 2015) are among the prevalent and the more common combinations because of the natural synergies of sun and wind (co-located) (FS-UNEP, 2017). Different types of hybrid systems (Solar and Wind), including stand-alone hybrid systems with a common direct current (DC) and alternating current (AC) bus, grid-connected hybrid systems with a common DC and AC bus, as well as the hybrid systems with AC microgrids have been presented in a study by Badwawi et al. (2015). Transportation is also an active area in
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research supporting sustainable development with low GHGs and pollutant emissions with outcomes including the utilisation of biofuels and the development of electric cars. Figure 3 shows the EU28 share of renewable energy in transportation. The average is still below 10% of the EU28 target by 2020, however. Recently, countries such as the UK, France and China
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(FT, 2017) have considered banning the production of petrol and diesel cars. A range of battery issues (such as charging duration) needs to be solved for meeting the targets. It still a
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question whether the electric car will completely displace the roles of petrol and diesel. This again highlights the need for optimisation and integration studies to incorporate existing technologies into real-world solutions.
30.0
Top Five
25.0 20.0 15.0 10.0 5.0 6.7
8.5
8.9
11.4
Norway
Austria
0.0 EU28 Slovak (Average) Republic
2020 target
22.0
24.0
Finland
Sweden
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2015
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Share of Energy from Renewable Sources in Transport (%)
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Figure 3. The share of renewable energy in transportation, EU28. Data from (Eurostat, 2017)
Waste to Energy (WtE) and Waste to Wealth (WtW) are the two-fold green approaches to mitigating the impact of waste currently ending up in landfills by converting it into resources. The global WtE market was valued at USD 25.32 · 109 in 2013, a growth of 5.5%
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over the previous year (WEC, 2016).
Thermal energy conversion leads the WtE market and accounted for 88.2% of total market revenue in 2013 (WEC, 2016). The EU is the largest market for WtE (47.6%), while the fastest market growth is in China (WEC, 2016). Table 1 summarises the current WtE
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technologies for various forms of energy. It has been reported that WtE plant can save 100350 kg CO2eq/t of waste processed (WEC, 2016). Inconsistent supply, the burdening effect of waste collection and pre-treatment for different waste characteristics are the key barriers to
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the current implementation. The conversion or recycling processes also create a burdening footprint (emission and pollution). Process optimisation, assessment and measurement are important to ensure that the burdening footprint is offset by the unburdening footprint (Klemeš et al., 2015). Waste-to-Energy is an important discovery and leap forward for a sustainable future. It is driven mainly by concerns regarding inappropriate waste management and energy security; however, reliability and affordability are yet to be improved as discussed. This is becoming even more important in relation to the development of smart cities.
ACCEPTED MANUSCRIPT Table 1. The summary of WtE technologies. Information from WEC (2016) WtE technologies
Form of energy produced
Thermochemical 1. Incineration
Heat, power, Combined heat and
(Mass burn >1,000oC, Co-combustion with coal, biomass, power (CHP)
2. Thermal gasification
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Refuse-derived fuel) Hydrogen, methane, syngas
o
o
(Conventional 750 C, Plasma arc 4,000-7,000 C) 3. Pyrolysis (300-800oC, absence of O2)
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Biochemical
Char, gases, aerosols, syngas
1. Fermentation
Ethanol, hydrogen, biodiesel Methane
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2. Anaerobic digestion 3. Sanitary landfill
Methane
4. Microbial Fuel cell
Power
Chemical 1. Esterification
Ethanol, biodiesel
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Despite the relatively smaller emphasis, the roles of PO and PI in water planning and supply chain planning (de Jong et al., 2017), including the storage (Kavadias et al., 2017), distribution (Theo et al., 2017), and safety (Tan et al., 2016) of industrial processes, as well as
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energy conversion and supply, is also important for achieving a holistic and sufficiently complete set of technologies for enabling smart cities, as discussed in an overview by
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Prakash et al., (2016).
Acting upon the necessity for providing technology solutions for the issues discussed in this introductory analysis of sustainable development, the 19th Conference “Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction - PRES 2016 conference was held in Prague, Czech Republic, from 27 to 31 August 2016, coorganised with CHISA 2016 (PRES, 2017). The PRES conference series serves as a platform for sharing and exchanging knowledge and ideas for improving processes, procedures and energy-saving practices. After a thorough peer-review process, 17 articles were selected for the current Virtual Special Issue (VSI). This review presents the key information from the selected articles, supplemented by the current state of the art in the corresponding study scope.
ACCEPTED MANUSCRIPT The Special Issue content can be broadly classified into two themes relating to sustainability improvement: (i) Experimental Assessment: Novel Approaches and Potential Assessment (ii) Methodology Development and Modelling: Optimisation. 2.
Sustainability
Improvement
Through
Experimental
Assessment:
Novel
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Approaches and Potential Assessment Liquid biofuels can be generally classified into ethanol, biodiesel and hydrated vegetable oil. In 2015, ethanol production increased by 4%, whereas global biodiesel production fell (by less than 1%) mainly because of the growth of the use of ethanol fuel in
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Asia (REN21, 2016). Figure 4 shows the share of biofuel global production by type and country. Biodiesel offers fewer emissions in PM (Shi et al., 2006), CO (Nantha Gopal et al. 2017), unburned hydrocarbon (Nantha Gopal et al. 2017), SOx (Aziz et al., 2005), and offers
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security of supply. Other advantages of biodiesel include its better lubricability, reasonable cold filter plugging point, better cetane number and high flash point (Liew et al., 2014) compared to fossil fuels. These properties make it a promising alternative fuel for engines. However, emissions of NOx are higher than from petroleum diesel (Nantha Gopal et al. 2017). These reaction optimisation studies play an important part in outlining the limitations of
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biodiesel (NOx emission). Emission reduction performance and process efficiency can be improved by identifying suitable raw materials, varying the production process, using blends, and the addition of catalysts as summarised by Jeevahan et al., (2017). Asif et al., (2017) investigated the non-edible oils (Salvadora alii and Thespesia populneoides) for biodiesel
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synthesis via a novel ultrasonic-assisted cavitation system. The methyl ester was produced by using an ultrasonically assisted cavitation reactor with the addition of calcium oxide catalyst.
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The biodiesel produced was found to comply with standards of fuel properties. Biofuels have a high impact on changing the quality of land, as they are mostly produced from agricultural raw materials. A study by Sági et al. (2017) highlighted the possibility of integration biofuel production in a refinery. The main barriers to utilisation of first-generation biofuels (bioethanol) are low thermal and oxidation stability, higher fuel consumption compared to fossil diesel fuel, and the requirement that the fatty acid content of feedstocks should be kept low. Despite some of the disadvantages, the application of biofuels is encouraged, especially when produced from waste biomass fraction that does not compete with food production. The main advantage of biofuel utilisation are the replacement of crude oil use and lowering the dependence on the import of crude oil. (Sági et al. 2017).
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Figure 4. The share of biofuel global production by type and country. Adapted from REN21 (2016)
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Not limited to biofuel, lignocellulosic biomass also serves as a sustainable alternative of precursor for phenolic platform chemicals, syngas-based products, hydrocarbon derivatives, polymer alloys and adhesives, etc (de Jong et al., 2012). However, its complex aromatic polymer structure requires pre-treatment to make the components suitable for processing steps in order to achieve higher yields of production. It has a critical impact on the feasibility (resources demand, energy input, process efficiency, cost) of the overall
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conversion process. Weinwurm et al., (2017) investigated a two-stage combination of liquid hot water (LHW) and ethanol organosolv (EO) treatment for wheat straw. The aim of this study was to produce a hemicellulose free substrate by LHW pre-hydrolysis and quantitative lignin recovery by EO treatment afterwards. In this way, the three different parts of
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lignocellulose (lignin, cellulose and hemicellulose) could be utilised separately for different products. However, the experimental results indicated that excessively harsh conditions had
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been set during LHW, as one-third of the lignin content was removed, presenting an unacceptably high loss rate of lignin. Based on the results, an upper limit of LHW pretreatment could be set (approximately 30 min at 180°C), and carbohydrate reactions were modelled. Future study is needed to evaluate the economic feasibility of this hybrid treatment as evaluated by Crimes et al. (2017). Post-treatment is a key step in waste to energy utilisation. Energy in the form of gases needs to be upgraded for more efficient usage. Biogas, which consists of CH4, CO2, N2, O2, H2O and H2S from anaerobic digestion (see Figure 5) has been studied the most, particularly desulphurisation, H2O and CO2 removal processes. Miltner et al. (2017) reviewed various upgrading technologies to optimise the quality of biogas natural gas grid injection or for
ACCEPTED MANUSCRIPT vehicle fuel. They suggested that besides the usual local utilisation of biogas for producing heat and power, alternative routes and technologies will have to be considered to obtain costeffective biogas production plants. The efficiency and flexibility of biogas upgrading to enhance economic viability of biogas plants were investigated. The desulphurization process was studied in order to obtain sweetened gas that could be used as local vehicle fuel or in the
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natural gas grid. For utilisation as vehicle fuel, the separation of high and fluctuating amounts of hydrogen sulphide from raw biogas was studied. For CO2 removal, a method of membrane-based gas permeation was presented. The latter is estimated to present a reduction
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potential of 20 to 40% for TOC (Total Cost of Ownership).
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Figure 5. Anaerobic digestion and the biogas constituents. 1(American Biogas Council, 2017)
The handling of fluctuating electrical excess energy is another challenge of RE. The
efficiencies and long-term stability o f storing and transport technologies are promising solutions to this problem. The technologies summarised by Aneke and Wang (2016) include pumped hydrostorage, flywheels, batteries, and thermal storage. Power to gas is a relatively new approach. In line with the power to the gas concept, Liemberger et al. (2017) present a hybrid approach based on membrane separation and pressure swing adsorption that separates hydrogen, which is transported as a co-stream in the natural gas grid. The aim was to achieve hydrogen at fuel cell quality of 99.97 % v/v. Technological feasibility has been achieved at a
ACCEPTED MANUSCRIPT required energy of 0.8-1.5 kWh/m3. The experimental outcome could facilitate the development of simulation models toward energy and costs optimisation to gain the full process potential. Recently, a load-shifting product for energy storage has been proposed by California ISO (Maloney, 2017). In contrast to load consumption patterns that incentivize the consumption of more electricity during periods of high RE generation, load shift product
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means excess clean energy can be absorbed and stored. The energy will be used productively at a different time to benefit both the economy and the environment. This approach is in the early stages; however, it has attracted several organisations, such Tesla, CESA, Stem and Green Charge (CAISO, 2017).
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Hydrogen is widely used as a clean and high efficient energy carrier for electricity generation through fuel cell systems. Hydrogen production from ethanol reforming is
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regarded as a sustainable alternative. However, the yield of hydrogen is highly dependent on operating conditions, and more importantly, the catalyst (including the nature of the selected metal and the support). Hou et al. (2015) identified metals such as Ni, Co, Rh, Ir and Ru to have a reasonable amount of intrinsic activity for ethanol reforming, while CeO2, Al2O3, MgO and ZrO2 are suitable as a support. Palma et al. (2017) introduced a highly active and stable Pt-Ni/CeO2-SiO2 combination for ethanol reforming to modulate hydrogen yield and
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coke formation. The catalyst, prepared by sequential wet impregnation, is evaluated as a promising catalyst for ethanol reforming in the low-temperature range with high activity and low-carbon formation rate at 500°C, 20,000 h−1 and water/ethanol molar ratio of 4.
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Azmi et al. (2017) investigated the potential of CO2 capture by a combination of two processes, adsorption and gas hydrate, on CaO from low cost waste seashells. The adsorption capacity depends on the amount of water present in the shell pores. The water ratio in pores
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of seashell at optimum values of 0.32 and 0.67, with about 7.26 and 9.79 mmol/g increment of CO2 uptake, has been proposed for commercial and synthesized CaO. A freeze-drying process based on a self-heat recuperation technology that reduces and recovers waste heat was proposed by Bando et al. (2017), who reported that it can reduce total energy consumption by 70 – 87 % compared to conventional counterparts. Experimental assessment and specific reaction process optimisation as presented in this section are stepping stones to further integration and development. Both fundamental and advanced research studies have been conducted simultaneously, according to the maturity of the introduced concept, methodologies or technologies.
ACCEPTED MANUSCRIPT 3.
Sustainability Improvement Through Methodology Development and Modelling: Integration This section presents an initiative for minimising the gaps between fundamental
improvement studies and real case implementation, beyond technical feasibility. AlMohannadi et al. (2017) studied natural gas utilisation in industrial clusters. Their systematic
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approach to explore synergistic effects of natural gas allocation, power generation and CO2 reduction has been proposed and illustrated in a case study of an industrial cluster.
Aviso et al. (2017) have applied P-graph to the synthesis of community-level energy
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conversion and supply networks. They thoroughly analysed and exploited the multi-period optimisation capability of P-graph Studio (P-graph, 2017). The authors developed a pattern for formulating the relevant superstructures, allowing the design of energy networks that cope
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with varying operation conditions, focusing on seasonal variations of product demand and resource availability. The proposed procedure has been demonstrated in two case studies, allowing users to obtain optimal, as well as near-optimal, solutions for further detailed analysis by decision makers.
Synthesis of integrated biorefineries has been the topic of many investigations,
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including those focusing on process-level synthesis (Martín and Grossmann, 2013) and distributed regional biorefineries using P-graph (Halász et al., 2005) or multi-objective optimisation accounting simultaneously for economics and various environmental impacts (Čuček et al., 2012). Sy et al. (2017) introduced the consideration of uncertainty in seasonal
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changes or fluctuations in product demand when obtaining a design for an integration biorefinery. Their approach identifies the optimal design of an integrated biorefinery by
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maximizing a robustness index against uncertainties, using a multi-objective mathematical optimisation model. Different scenarios were considered via Monte Carlo simulations. The latter considers both profit and environmental footprints, while ensuring that the solutions identified are relatively robust and capable of handling variations in demands and resources. Minimising water consumption has also been viewed as a key building block for smart city development. A concentration potential concept for the design of water networks with multiple contaminants has been reviewed by Li et al. (2017). Several recommendations, including total water networks and interplant water networks using multi-objective optimisation of property-based water networks have been suggested to improve the implementation of water-using networks with multiple contaminants. A water assessment
ACCEPTED MANUSCRIPT study quantifying the overall environmental performance of wastewater treatment plants has been presented by Mustapha et al. (2017). Its aim is to enable a facility manager to efficiently monitor, analyse and improve the performance of a Wastewater Treatment Plant in a cleaner production program. The aim of the study has been achieved through the developed green index based on the stock market composite index. Soil contamination often contributes to
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water pollution and has a significant effect on the ecosystem, as well as on food security. Smart farming (Wolfert et al., 2017) and precision agriculture (Hedley, 2015) are two of the prevention approaches to minimising the waste of resources (especially fertiliser and pesticides) for a sustainable environment. End of pipes solution and remediation technologies
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has been presented by Yao et al., (2012) for contaminated soils (not limited to pollution from agricultural activities). Vocciante et al. (2017) suggested a method originally developed for the early detection of leaks in landfill liners to accommodate the estimation of soil
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characteristics. This method is an inexpensive estimation for soil parameters which can improve the performance of remediation technologies.
A holistic view of the entire extended value chain is also important for an organisation interested in achieving a sustainable future. However, implementation remains a problem. Pavlas et al. (2017) observed that supply chain models are rarely filled with precise
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forecasted quantitative data. Hence, a mathematical model to handle the problem of forecasting with spatially distributed and uncertain data has been proposed. This approach is suitable for supply-chain and network flow models where future amounts of commodities (the flow of which is optimised) are to be forecasted for a number of nodes (such as dealing
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with several waste streams). Sustainable Enterprise Resource Planning systems (Chofreh et al., 2014) enables the integration of sustainable processes, information and data on every
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value chain level of the organisation. Chofreh et al. (2017) developed a roadmap consisting of pre-implementation, implementation and post implementation for practitioners toward the master plan and S-ERP implementation. The safety aspect is another component that should not be overlooked for economic benefit, environmental protection and social acceptance of sustainable development. An industrial area layout method has been proposed by Wang et al. (2017) to enhance safety and to reduce pipe usage in an industrial area with 16 plants. The total cost reduction was as high as 19.2 %, accounting for risk cost and piping cost. Other indirect savings include steel resources and energy, as well as reduced emissions from transportation. These findings aiming to enable real case implementation are important for bridging the gap between industrial process integration implementations.
ACCEPTED MANUSCRIPT 4. Conclusions Ensuring cleaner energy and water supply is one of the cornerstones for cleaner production and overall economic and social development. This is also very important for reducing the emissions of greenhouse gases (GHGs) and other pollutants while preserving the economic viability of the key economic and social activities.
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Treating energy issues as a key pillar of sustainability improvement, minimising waste of energy and materials should be considered first, and only after that, harvesting and utilisation of external renewable resources. In this light, giving the priority to energy and resource recovery, including waste management, gives a starting point on the path to
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sustainability. This includes industrial waste streams for fuel recovery, as well as classical waste-to-energy processes and their supply chains. The works reviewed clarify the key issue
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of obtaining adequate and reliable data for performing process optimisation. Following the principle of maximising the use of the renewable resources base as the second pillar, biorefinery processes for converting biomass to various chemicals are being investigated, maximising process efficiency. The research done to date has accounted for uncertainties in energy and biorefinery networks optimisation, using P-graph and directly
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Mathematical Programming. Future efforts need to assess and maximise their economic viability.
In terms of handling fluctuations in the availability of renewable resources, as well as market energy demands, power-to-gas is a potential storage-enabling technology, where in
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the current SI, hydrogen has been considered as an energy carrier. As the last priority in emission control and mitigation, CO2 capture and storage have
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also attracted research attention. Adsorption of CO2 and the minimisation of the parasitic energy demands of the process have been evaluated, reporting significant energy reduction figures – up to 87%.
Considering the third pillar of sustainable and efficient processing, water networks have been researched in the current VSI, formulating the “concentration potential” concept for seamless treatment of multiple contaminants, including a water management tool based on a composite performance index. Restoring ecosystems after pollution has occurred is an important activity. The landfill monitoring and soil remediation studies reviewed show remarkable potential for improving
ACCEPTED MANUSCRIPT landfill sites performance in a cost-efficient way. Enterprise safety and management aspects have been also discussed, also enable the holistic management of these issues in combination with the key process properties. ACKNOWLEDGEMENT
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This work has been supported by the project Sustainable Process Integration Laboratory – SPIL, funded as project No. CZ.02.1.01/0.0/0.0/15_ 003/0000456, by the Czech Republic Operational Programme Research and Development, Education under a collaboration agreement with the University of Maribor in Slovenia and was financially supported by the
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Slovenian Research Agency (program P2-0032 and project L2-7633).
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