Search

Current management of solid waste from pulp and paper activities represents an environmental and economic burden worldwide due to pollution emissions. This study investigates the potential of hydrothermal carbonisation (HTC) treatment as a sustainable alternative for producing cleaner and energy-dense solid fuel from paper mill sludge. The effect of process parameters (temperature, reaction time and solid load) on hydrochar fuel formation from paper sludge was evaluated and, for the first time, the paper sludge-derived hydrochar was optimised to maximise the mass yield and calorific value using response surface methodology (RSM). The physicochemical characteristics, thermal fuel behaviour, energy recycling efficiency and electricity generation potential were assessed by proximate and ultimate analysis, thermogravimetry, bomb calorimeter, scanning electron microscopy and process energy assessment. Results showed that hydrochar fuel formation and properties were mainly influenced by the process temperature and residence time, and governed by dehydration and decarboxylation reactions which reduced the atomic H/C and O/C ratios by 35.5% and 64%, respectively. The produced hydrochars presented low sulphur, nitrogen and ash content with a maximum calorific value (HHV) of 22.9 MJ/kg, equivalent to the HHV of coal for commercial utility in South Africa. The HHV of the hydrochar corresponded to a 49.80% increase over the HHV of the initial feedstock. The optimum operating conditions were 231 ± 1 °C and 1.99 h for a hydrochar yield of 74.4% and calorific value of 18.5 MJ/kg. The energy assessment showed that up to 58.34% of the energy produced by hydrochar fuel combustion may be recycled as heat or power, while the remaining 41.66% of the combustion energy could be utilised to sustain the HTC treatment of paper sludge. The substantial water demand was concluded to be a drawback. Thus, water recirculation and the potential to catalyse the HTC reactions to increase overall process efficiency will constitute a future study to make the process more environmentally friendly for industrial-scale application. [Display omitted] • Dehydration and decarboxylation were predominant. • Optimum energy yield of 18.5 MJ/kg and 74.4% hydrochar was achieved under 231 ± 1 °C and 1.99 h. • Higher HTC reaction severity enhanced the physicochemical properties of the hydrochar. • Hydrochars produced have low nitrogen and sulphur (<1%) content. [ABSTRACT FROM AUTHOR]

Understanding the connection between water supply and energy consumption in a circular economy is crucial for managing the demands of these resources. Sankey diagrams have the potential to enhance the visualisation of resource flows. However, there is a knowledge gap regarding the effective use of Sankey diagrams to capture the water-energy nexus and circularity of water. This study focused on effectively utilizing Sankey diagrams to model the nexus of water and energy flows and to assess the circularity of water. A comprehensive literature review was conducted on major studies on water material flows and modelling. This was supported by a review of approaches for modelling circularity, which have evolved from the material circularity index. The newly developed framework in this paper models water resource flows at all stages of the water supply chain, embedding the nexus as an interaction and considering resource intensity and material circularity index at each node. A city-level case study in South Africa was then used to apply the recommendations, model circularity, and the water-energy nexus using Sankey diagrams. In terms of circularity, the results indicate that water loss in the study area was very high, accounting for up to 40% of the total water supply and the water recycle rate was still very low, ranging from 3% to 7%. In terms of the nexus, the residential sector was found to have the highest energy intensity for water supply, primarily due to energy demand for water heating. Exploring the use of renewable or solar energy for water heating will be of interest and value. The new approach presented in this study allows for the simultaneous consideration of objectives, enabling a more robust analysis of energy-effective water use and water circularity along the water supply chain. [Display omitted] • A new framework for modelling the water energy nexus enriched by circularity options, energy intensity factors and confidence modelling. • Options for embedded circularity through the water supply chain. • The urgent challenge to address massive water loses in water supply systems for water scarce regions. • New Sankey diagrams showcasing how to model nexus and circularity. [ABSTRACT FROM AUTHOR]

Socio-economic development and economic growth is connected with the intensive use of energy resources, which poses also risks to long-term viability of the biosphere by causing natural resource depletion and environmental degradation. One of the options to reduce Human and environmental risks from extensive energy generation are renewable energy sources. However, there are several barriers for transformation of energy sector towards a greater share of renewable energies. Human factors such as social support or opposition are crucial drivers for this transition. This paper examines the state of infrastructure projects in South Africa and assesses how lessons from these projects can contribute to improve development of energy transformation in the country. It analyses the challenges of applying participatory governance in the energy transition in South Africa, as a critical component of successful infrastructure project implementation, and of insights into fostering environmental leadership. The paper is based on the case studies analysis of ten large infrastructure projects in South Africa and focuses on public participation in these projects, its effects and challenges by applying the ladder of public participation methodology. Findings from the study support the scientific arguments that public participation in decision-making regarding deployment infrastructure projects creates an enabling environment for successful implementation. In conclusion public participation was only in the context of environmental impact assessment which is a mandatory requirement for infrastructure projects in South Africa. Currently public participation is manly regarded as a reactive measure to conflict resolution. It is organized to provide feedback on the results of environmental impact assessment, mainly as a way to address conflict, which has already emerged. Our results show that provision of information and consultation are the two most frequent levels of public participation. Land use issues and questions about benefits and impacts from infrastructure projects on local communities are the most frequent concerns. [ABSTRACT FROM AUTHOR]

Packaging can play a key role in reducing food waste and enabling resource efficient logistics operations. This paper offers insights into why this potential is not fully adopted by companies in food supply chains by exploring adoption barriers for sustainable packaging practices in ten companies in South Africa and Sweden. The paper develops an analytical framework from theory and applies it to the empirical data. This resulted in ten propositions that structure adoption barriers for sustainable packaging practices in food supply chains and explain the reasons for their occurrence. The propositions can form a basis for researchers to understand why the adoption of sustainable packaging practices in food supply chains may be lacking. Corporate decision-makers can use the propositions to form strategies and initiatives to overcome adoption barriers. The study also identified some contextual differences, but overall, the contextual impact on adoption barriers was surprisingly low. To deepen research and practice insights about the complexity of adopting sustainable packaging practices, the paper offers a process view on the adoption barriers in which their relationships are linked. The analytical framework and the process view offer integrative views on adoption barriers for sustainable packaging practices that enable researchers and practitioners to address them with a structured approach. This explorative study finally unfolds further research opportunities. • Explore adoption barriers for sustainable packaging practices in food supply chains in South Africa and Sweden. • Ten propositions structure adoption barriers explain the reasons for their occurrence. • Help to understand why the adoption of sustainable packaging practices may be lacking. • Support corporate decision-makers to form strategies to overcome adoption barriers. • Identify contextual differences, which overall were surprisingly low. [ABSTRACT FROM AUTHOR]

Abstract Responsible tourism is embraced globally as one of the vectors to achieving the United Nations' 2030 Sustainable Development Goals (SDGs). Through the Theory of Planned Behaviour, this article attempts to establish the understanding of responsible tourism among owners of small budget hotels in the Johannesburg West Rand Region, South Africa. The conclusion it reaches is that a general appreciation of responsible tourism does not translate into being responsible in daily operations. The paper proposes a 'Best Responsible Tourism Model', which identifies four ways that small hotels can be encouraged by the public sector to participate in responsible tourism, including education, economic motivation, marketing motivation and building social networks. Combined, these feed into the Theory of Planned Behaviour variations, normative beliefs, behavioural beliefs and control beliefs, which will determine the behaviour and perceptions of hoteliers on Responsible Tourism Practice. Participatory democracy should be adopted by hoteliers and other key responsible tourism actors to augment understanding and practice of responsible tourism in small hotels. Highlights • The Theory of Planned Behaviour, established the understanding of responsible tourism among owners of small budget hotels. • A 'Best Responsible Tourism Model', identifies four ways that small hotels can be encouraged by the public sector to participate in responsible tourism. • Participatory democracy should be adopted by hoteliers and other key responsible tourism actors. [ABSTRACT FROM AUTHOR]

Electricity production has a significant impact on the Water-Energy-Food nexus sectors as it requires substantial amounts of water and land, whilst also being a primary polluter of these resources. In addition, electricity production is a key contributor to global carbon emissions. With electricity production predicted to increase by over 50% by 2050, the impact of electricity production on water and land resources, as well as on carbon emissions, will need to be significantly reduced. This is particularly important in countries facing water, energy, and food scarcity and insecurity, such as South Africa. This paper therefore investigates the impact of electricity production on the Water-Energy-Food nexus sectors and on carbon emissions in South Africa. To do this, we conduct a lifecycle assessment of the water and land required for electricity production, as well as its carbon emissions in South Africa, by electricity source, and under key scenarios. The results from the Integrated Resource Plan 2030 scenario show that despite a 34% increase in electricity production targeted from 2018 to 2030 in South Africa, the water and land requirements, and the carbon emissions of electricity production would decrease by 29%, 9%, and 5.5%, respectively. Compared to the Business-as-Usual 2030 scenario, it was shown that the water and land requirements and carbon emissions of electricity production would be 55.5%, 42.6%, and 41.5% lower in the Integrated Resource Plan 2030 scenario, respectively. Overall, the results show that to reduce the impact of electricity production on the Water-Energy-Food nexus sectors and on carbon emissions, switching away from fossil fuels (particularly coal), and promoting the use of non-hydro and non-biomass renewables is required. [Display omitted] • We quantify the water and land requirements, and carbon emissions, of electricity. • In 2018, it required 312 Gl of water, 929 km2 land, and emitted 152MtCO₂eq. • If the electricity mix does not change, all impacts will increase by 63% by 2030. • With planned changes, the impacts could decrease by 29%, 9%, and 5.5%, respectively. [ABSTRACT FROM AUTHOR]

Exploring the influencing factors of ecological footprint is a hot issue. However, the impacts of energy consumption and globalization on ecological footprint are inconclusive due to the complex and nonlinear relationships among variables. The objective of this paper is to explore the nonlinear effects of energy consumption and globalization on ecological footprint in BIRCS countries. The quantile-on-quantile approach is employed, and the results display that in China and India, energy consumption has a positive impact on ecological footprint at most quantiles, while in South Africa, the negative impact appears at most quantiles. Furthermore, a positive effect of globalization on the ecological footprint is found at the most quantiles of the ecological footprint in China, South Africa. For Brazil, India, and Russia, the negative impact occurs at most quantiles of the ecological footprint. Finally, some policy recommendations are presented for the BRICS to achieve long-term sustainability. [Display omitted] • A quantile-on-quantile method is used to explore the effects of energy consumption and globalization on ecological footprint. • The impact of energy consumption and globalization on ecological footprint is heterogeneous among different quantiles. • We provide some policy recommendations for the BRICS to achieve long-term sustainability. [ABSTRACT FROM AUTHOR]

Water footprint assessment is a developing method that is being increasingly applied to quantify water use, prioritise reductions, assess sustainability and provide information to achieve sustainable, efficient, and equitable water use. The objectives of this paper were to conduct a water footprint assessment of primary citrus production within the Lower Sundays River Valley in South Africa using local, high-resolution data and to examine indicators (water scarcity, pollution, efficiency, productivity and access) to determine the sustainability of blue, green and grey water footprints of a wet, dry and average year. Lemons were found to have the lowest blue and combined green-blue water footprint per ton of production across all climatic years, followed by soft citrus, valencias and navels. Valencias had the lowest, and navels the highest grey WF (relating to inorganic nitrogen). Lemons, despite their high crop water and fertiliser requirements, were regarded more economically efficient in comparison to valencias, soft citrus and navels, in that they provided higher net income and more employment hours per m 3 of water in comparison to other citrus crops. In an average season, lemons generated approximately 39% more income per m 3 of water than navels, despite navels being the dominant cultivar. Blue water consumption for citrus in the catchment was calculated to be 58.7 Mm 3 for an average season and 89.2 Mm 3 for a dry season. Due to an inter-basin transfer scheme, no physical water scarcity occurred, and both environmental and basic human needs are met. Water pollution levels related to nitrogen however, exceeded the assimilative capacity of the run-off in dry years. The area also experiences institutional and infrastructural scarcity and 14% of the population do not have access to piped water. Stakeholders and governments may use the results of water footprint assessments to determine the status of river basins, make evaluations for future water usage and the potential impacts of expanding agriculture and different management strategies. Including environmental and socio-economic indicators will also improve the integrity of water footprint assessments. [ABSTRACT FROM AUTHOR]

This paper reports the analyses of the social and environmental disclosures of listed South African mining companies and compares the disclosures of larger companies with those of smaller companies using several different categories of comparison. The prior literature suggests that larger companies almost invariably disclose more social and environmental information due to their greater visibility. The expected differences are found in social disclosures, but not in environmental disclosures. An institutional theory framework explains these unexpected environmental disclosure findings. Specifically, normative isomorphism, usually driven by professionalization, becomes more prominent when a field reaches maturity and the field of corporate environmental disclosures among mining companies has reached a level of maturity and professionalization causing disclosures to be similar. These similarities have now reached the stage where small companies disclose the same amount of environmental information, in the same general format, as large companies. [ABSTRACT FROM AUTHOR]

Water supply in an increasing number of rural and peri-urban communities can be described as marginal i.e. subject to failure, becoming unaffordable or increasingly difficult to access. A range of common factors contribute to water marginalisation or access bias. Firstly, communities may be poorly served by formal water infrastructure by being on the margins of urban settlements. Secondly, where water infrastructure exists, this may be prone to failure as local municipalities and water utilities with limited capacity and resources struggle to maintain a widely dispersed system. Thirdly, when local water systems fail, they are often not repaired quickly, if repaired at all. This results in people, often with very limited resources having to obtain water from far distances or having to pay someone to transport water to them in order to meet their basic water needs. Thus, where water supplies are unreliable, unaffordable and difficult to access, geography, urban settlement patterns, the choice of water distribution systems, and the management capacity result in water marginality. This paper investigates water marginality in communities in rural and peri-urban areas in South Africa. It utilises surveys and interviews of communities, the local authority, water and urban planning officials, to understand the nature of this marginality, and investigates the key contributory factors. This forms the basis for recommendations on how access and marginalisation challenges can be addressed. The paper provides valuable insights on how, and why, water marginality occurs, and proposes strategies for sustainable solutions. As climate change and rural-urban migration accentuate water marginality, the study offers important and timely insights in an area that urgently requires further research. [ABSTRACT FROM AUTHOR]

The aim of this paper is to select appropriate waste-to-energy (WtE) technology considering both subjective perspective of decision-maker and objective evaluation of the actual performance metrics of each alternative. Based on this premise, a novel hybrid multi-criteria decision making method based on Fuzzy-analytic hierarchy process (Fuzzy-AHP), Fuzzy-Entropy and Fuzzy-Multi-Objective Optimization on the basis of Ratio Analysis plus full multiplicative form (Fuzzy-MULTIMOORA) is applied as a decision tool. In this study, four (4) alternative WtE technologies (i.e., anaerobic digestion, incineration, pyrolysis and gasification) with fourteen (14) sub-factors that cut across four sustainability aspects (i.e., technical, economic, environmental and social factors) are considered. The applicability of the model is tested for a WtE technology selection in the City of Cape Town, South Africa. The result obtained reveals that for all the alternatives considered, the most sustainable WtE technology for investment in the City of Cape Town follows the order: anaerobic digestion > gasification > pyrolysis > incineration. Sensitivity analysis shows a high degree of consistency, robustness, and stability in the obtained results. The current work recommends that the integration of anaerobic digestion and gasification should be promoted as it has the potential to offer a well-balanced WtE technology compared to the stand-alone systems. Although, the case study is a city in South Africa, the methodology could be applied for selecting WtE technology in any developing countries' city with similar waste characteristic and economic nature like that of South Africa. • An objective-subjective hybrid MCDM model is put forward. • The criteria weights are determined using Fuzzy-AHP and Fuzzy-Entropy methods. • The waste-to-energy technologies are ranked using Fuzzy-MULTIMOORA approach. • Managerial implications of the most sustainable waste-to-energy technology is presented. [ABSTRACT FROM AUTHOR]

Acid mine Drainage (AMD) is a low pH, sulphate and heavy metal rich leachate that is produced from oxidation of sulphide bearing minerals commonly found in the host rocks of some mineral ores. The pH augmentation, and sulphate and metal removal in AMD is often achieved by adding alkaline reagents in it. CaCO 3 and/or its derivatives are commonly used for this purpose due to their abundance and affordability as compared to other neutralizing reagents. The problems associated with the use of this naturally occurring reagent do not only include the emission of greenhouse gases and ecological disturbances but also include a disastrous implication of depleting their reserves. To avoid these predicaments, green liquor dregs (GLD) from two Kraft pulp manufactures in South Africa were used as alternative alkaline reagents to neutralize AMD originating from Witwatersrand goldfields in Johannesburg. These GLD samples were referred to as GLD A and B. CaCO 3 was used as a reference material. The GLD samples had neutralizing values that are comparable to that of CaCO 3. Thus, CaCO 3 , GLD A, and GLD B had a neutralizing value of, 26.0, 21.2, and 21.0% CaO respectively. Different dosages 1, 2, 6, 10, and 20 g/L of these neutralizing reagents were used to neutralize the AMD. Results of this study showed that raising the pH of AMD was possible even at a low dosages of 1 g/L. At this dosage, the acidity of the AMD sample changed from 183.36 to 21.7, 36.4, and 48.72 mg/L CaCO 3, and changed the pH from 5.6 to 8.84, 8.21, and 8.0 respectively. However, the SO 4 2− and Ec had increased from 2093 to 2360, 2538, and 2407 mg/L and from 3.6 to 4.0, 4.3, 4.2 mS/cm respectively, indicating that caution should be taken to keep these values low by keeping the reagent dosage low and being cognizant of the carbonate mineral present in GLD. The x-ray diffraction patterns of the reacted samples confirmed the presence of metal oxides and Ca and Mg compounds that were depicted by SEM/EDX micrographs. In conclusion, the results from this study showed that the pH of AMD can be raised to optimum pH process value and reduce the acidity at a low dosage, a competitive advantage over commercial CaCO 3. The proposed concept can be adopted by both the mining and pulp and paper industries, for the upscaling of co-disposing GLD and AMD contaminants as an eco-friendly alternative for the CaCO 3. [ABSTRACT FROM AUTHOR]

This paper presents international co-inventor networks as both a predictor variable of countries' ability to produce and disseminate internationally green inventions, and an alternative mechanism to support development of relevant programmes and policies in that regard. It includes cases from three developing countries with limited resources for clean technology development, Brazil, India and South Africa, which have shown successes owing to the potentials of co-inventor networks. It contributes the extent literature on this topic, which predominantly emphasizes firms' responses to conventional governments' interventions (subsidies, market price, standards, and interagency cooperation) to achieve cleaner production plans and particularly the Targets 17.6; 17.7 and 17.8 of the sustainable development goals. Broadly, such targets aim at enhancing countries' technological capabilities through partnership. The paper finds various correlations between co-inventor networks and growth of patents in solar energy, air pollution management and biofuels in the sample countries. Correlations are linear in India, followed by Brazil owing to the larger sizes of co-inventor networks but nonlinear in South Africa, which has smaller networks. The paper argues that co-inventor networks accelerate transnational exchanges of core human capital, and are fitting predictors of production and flows of green inventions. They are worth adopting in national and transnational industrial and innovation cluster policies globally to support sustainable production plans. [ABSTRACT FROM AUTHOR]

This paper aims to understand the relationship between patterns of lean practice implementation, farm size and sustainable performance among fruit horticultural primary producers in South Africa. Utilizing a comprehensive lean framework, addressing 10 lean practice dimensions, the authors collected data from a sample of 132 fruit farming operations in South Africa. First, cluster analysis was applied to identify distinct clusters of farms with common lean practice implementation characteristics. Next, the distinct clusters were tested to identify significant differences in lean practice implementation and sustainable performance, with farm size incorporate as a control variable. In terms of common lean implementation characteristics, the analysis identified two distinct clusters of farms, labelled as the high lean practice cluster and the low lean practice cluster. It is determined that these two clusters differ significantly in practice implementation across all 10 dimension of lean management practice. It is further established that the two clusters differ significantly in terms of sustainable performance. Furthermore, farm size is found to significantly differentiate (i) lean practice implementation across 5 of the 10 lean practice dimensions and (ii) levels of sustainable performance between medium and large sized farms. This empirical analyses of lean practices and sustainable performance outcomes in the primary production domain represents a novel contribution to the existing literature on lean management and horticultural management. • Lean management practice implementation is a determinant of sustainable performance in horticultural primary production. • Farm size supports sustainable performance outcomes, but the effects are only significant for relatively larger farming operations. • Farm size significantly influences lean implementation, but only for 5 of the 10 lean practice dimensions considered. • The findings allude to a set of market leading growers, who operate at a higher degree of lean managerial professionalism than the general population of primary producers. [ABSTRACT FROM AUTHOR]

This paper presents an integrated rainwater harvesting and greywater recycling system to tackle the energy-water nexus in residences with unreliable water and electricity supply. The system is made up of the municipal water and energy supplies, a rainwater harvesting system and a greywater recycling system to supply the residential water demand. A combined sizing and operational optimization approach is developed. In particular, a mixed integer linear programming model is formulated to determine the optimal sizes of the water tanks and optimal operation of pumps to reduce potable water consumption and electricity cost under the time-of-use tariff. The model formulated is applied to a practical case study of a single-family house in Durban, Kwa-Zulu Natal province of South Africa. Simulations results with measured rainfall intensity over five years show that the proposed integrated rainwater harvesting and greywater recycling system is beneficial for the household in terms of both water savings and financial cost savings with an acceptable payback period of 4.39 years. To investigate the validity of the results obtained in different applications, a sensitivity analysis was performed concerning uncertainties in water demand, rainfall intensity, the cost of electricity and discount rate. The findings confirm that the model developed is robust against uncertainties in these parameters. It is also concluded that payback period of the project can be even shorter if applied to a case with a higher water demand. • Develops an integrated rainwater harvesting and greywater recycling sys-tem. • Optimizes the sizes of tanks and operation of pumps for cost-e_ectiveness. • 56.46% potable water and 50.51% wastewater cost savings are achieved. • Reduces operating cost by 54.9% with a payback period of 4.39 years. • System performance is verified using measured 5-year rainfall data. [ABSTRACT FROM AUTHOR]

Although the steel industry has brought economic benefits to many countries, it also has non-negligible impacts on the environment. To understand how steel production impacts are shared among trading countries, it is necessary to conduct a large scale research from environmental and economic perspectives. This study applies the life cycle assessment method (LCA) to analyze 12 major iron-mining and steel-making countries, calculate a "unit GDP impact intensity" and finally raise an issue of "pollution allocation" among actors in international trade. Results firstly indicate that normalized ecotoxicity impacts over the entire production chain are among the most crucial consequences of iron and steel production, even higher than the non-negligeble impacts from carbon emissions. Secondly, performance indicators indicating the relation between environmental impacts and economic activities can be calculated as Total Normalized Impacts/GDP, an inverse measure of environmental versus economic efficiency. South Africa has the highest unit GDP impact intensity (4.35E-4 TNI/US $) in iron mining, while Canada has the largest intensity in steel manufacturing (5.81E-3 TNI/US $). Thirdly, countries that largely benefit from importing "pollution-free" materials, should share a proportional responsibility for the environmental pollution caused by iron&steel processing activities occurring in their trade partner countries: this is especially true for China and US, which are major iron ore/steel importing economies. Finally, this paper proposes policy implications at local, national and international levels, from a perspective of global sustainable development. • Environmental impacts of iron mining and steel production are assessed by using LCA. • Toxicity is the most important problem. • South Africa and Canada have the highest UNI among iron/steel producing countries, respectively.. • Importing countries should take responsibility of generated impacts. [ABSTRACT FROM AUTHOR]

In this paper, a hierarchical control strategy for Venlo-type greenhouse climate control under South Africa climate is proposed to improve energy efficiency and reduce operating cost. The proposed hierarchical control architecture includes two layers. The upper layer is to generate set points by solving different optimization problems. Three different strategies with different optimization objectives are studied. The meteorological data of a typical winter day is used. Strategy 1 is to minimize the energy consumption. Strategy 2 is to minimize the energy cost under the time-of-use (TOU) tariff. Strategy 3 is to minimize the total cost of energy consumption, ventilation and carbon dioxide (CO 2) supply. The lower layer is to track the trajectories obtained from the upper layer. A closed-loop model predictive control (MPC) strategy is introduced to address model plant mismatch and reject system disturbances. Two performance indices, relative average deviation (RAD) and maximum relative deviation (MRD), are introduced to compare the tracking performance of the proposed MPC and an open loop control under three different levels of system disturbances (2%, 5%, 10%). Simulation results show that the proposed strategy can effectively reduce the operating cost while keeping the temperature, relative humidity and CO 2 concentration within required ranges. Compared with Strategy 1 and Strategy 2, the total cost of Strategy 3 is reduced by 72.07% and 71.41% respectively. Moreover, the proposed MPC has better tracking performance than the open loop control. Therefore, the proposed hierarchical MPC strategy could be an effective way to improve greenhouse energy efficiency and achieve sustainable cleaner production. • A hierarchical control architecture is adopted for greenhouse system optimization. • Not only energy consumption but also ventilation and CO2 supply are considered for operating cost calculation. • The time-of-use tariff is considered for the calculation of electricity cost. • A model predictive control strategy is proposed to address model plant mismatch and reject system disturbances. [ABSTRACT FROM AUTHOR]