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The extensive utilisation of microorganisms namely fungi and bacteria for treating organic wastes has been attributed to their efficiency in eliminating pathogen and accelerating the degradation process. Their uses have been found considerably efficient for enhancing waste treatment. Among many methods employed, composting mediated by indigenous microbial communities has gained significant popularity in treating organic waste. Use of cellulolytic microorganisms to expedite the degradation rate of wastes, notably the lignocellulosic components, may prove useful. This paper reviews the application of microorganisms in the waste management technologies that include anaerobic digestion and composting of organic waste with a high lignocellulosic portion, composting of heavy metal contaminated organic waste, and composting at low temperature.

The demands and consumption of energy in the world are increasing, despite major developments towards more efficient energy production and use. Most energy supply still comes from non-renewable sources, and greenhouse gas emissions are constantly increasing, despite the development of various international policies on climate change, such as the Kyoto Protocol or the not yet ratified Paris Agreement. In this study, the potential for enhancing the efficiencies of utility transport and use, as well as cross-sectorial energy integration, are estimated for the current state of energy production, energy conversion, and energy use within and between the main sectors. Improving energy integration between different sectors can lead to significant savings in energy sources, resulting in significantly lower greenhouse gas emissions. Integrating different sectors is not a straightforward task since they use different types and loads of utilities at different levels. The first step toward integration of different energy sectors is to properly assess the primary energy source demand. A methodology for estimating primary energy requirements by tackling different types of and loads on utilities was developed. The results indicate that the primary energy source utilisation can be 2.6 times higher compared to the initial energy consumption in different sectors. The energy consumption should be addressed holistically considering at least three different aspects: i) utility transport efficiency, ii) energy efficiency within the sectors (intensification) and iii) energy integration between different sectors.

The sound handling of municipal solid waste (MSW) is of high priority to minimise environmental degradation and pollution. MSW can be treated via various technologies including landfilling, incineration, composting, anaerobic digestion (AD) and more. Landfill without landfill gas capturing serves as an enclosed bioreactor to store and stabilise waste. Other technologies such as incineration, composting and AD allow substantial volume reduction and generate value-added products. The treatment for MSW is commonly focusing on the solid part. Organic waste contains high moisture content of 70 - 90 %. The pressing of the water content before entering treatment unit, the release of water during and after the treatment, can generate high strength wastewater, known as leachate. Leachate is rich in organic matter, organic pollutants, pathogens, heavy metals and more, which can lead to severe secondary environmental pollution if not properly treated. Leachate from different treatment units showed certain unique characteristics, such as high Na, high Ca , different species and availability of heavy metals. This review summarised some of the important characteristics of different leachates and the suitability of AD as a mean of treatment. The efficiency of AD to treat leachate was presented in terms of the removal efficiency of chemical oxygen demand (COD) and biogas production. The COD removal efficiency was between 60 - 98 %, following the treatment of different leachates under different reactors and operational parameters. Among the different stream of leachates, the leachate from landfill is most commonly studied as a co-digestion substrate for AD, as compared to leachate from the composting facility.

This paper explores the macro optimisation decisions of energy sources selection and the structural design of the utility system within the framework of Total Site Heat Integration (TSHI). Most TSHI research on utility systems focuses on optimisation of conventional Combined Heat and Power systems. To build a new Utility Systems Planner (USP) tool, P-graph has been selected as the optimisation tool. A critical element of USP is the inclusion of low-grade heat utilisation technologies within the considered superstructure. The USP outputs include the optimal structure of the utility system including the arrangement and size of each component and estimates for Greenhouse Gas and Water Footprints. The successful application of the USP to a representative industrial case study with district energy integration shows an optimal solution with a natural gas boiler, reciprocating gas engine, condensing economiser, steam turbine, thermocompressor, organic Rankine cycle, cooling tower, and electric chiller with a total cost of 14.893 M€/y. The new tool is a platform for launching further research including site-specific application, multi-period optimisation, and sensitivity analysis.

Lignocellulosic waste is one of the most abundant and potential feedstocks for anaerobic digestion (AD), but the energy efficiency is limited by the lignocellulosic composition which is recalcitrant to biodegradation. Pre- treatment of feedstock and the post-treatment of biogas and digestate play a significant role in enhancing the AD efficiency as well as the product utilisation. This study aims to determine the cost-optimal pre-and post- treatment pathway for an AD of lignocellulosic waste by applying P-graph. The economic balance between the main operating cost, yield and quality of products were considered. The treatment options were overviewed followed by a case study considered a different combination of physical, chemical and biological pre- treatments, biogas post-treatment (combine heat and power, fuel cell, biomethane, biofuel) and digestate treatments. A total of 9 pre-treatments for lignocellulosic waste, 2 digestate post-treatments and 9 post- treatments for biogas were evaluated in this study. Chemical pre-treatment by CaO, post-treatment by H2S removal with membrane separation for biomethane production and without the composting of digestate is suggested as the optimal treatment pathway for lignocellulosic waste.

Pressure drop is an important consideration in Total Site Heat Integration (TSHI). This is due to the typically large distances between the different plants and the flow across plant elevations and equipment, including heat exchangers. Failure to consider pressure drop during utility targeting and heat exchanger network (HEN) synthesis may, at best, lead to optimistic energy targets, and at worst, an inoperable system if the pumps or compressors cannot overcome the actual pressure drop. Most studies have addressed the pressure drop factor in terms of pumping cost, forbidden matches or allowable pressure drop constraints in the optimisation of HEN. This study looks at the implication of pressure drop in the context of a Total Site. The graphical Pinch-based TSHI methodology is extended to consider the pressure drop factor during the minimum energy requirement (MER) targeting stage. The improved methodology provides a more realistic estimation of the MER targets and valuable insights for the implementation of the TSHI design. In the case study, when pressure drop in the steam distribution networks is considered, the heating and cooling duties increase by 14.5% and 4.5%.

The strong demand for sustainable energy supplies had escalated the discovery, and intensive research into cleaner energy sources, as well as efficient energy management practices. In the context of the circular economy, the efforts target not only the optimisation of resource utilisation at various stages, but the products’ eco-design is also emphasized to extend their life spans. Based on the concept of comprehensive circular integration, this review discusses the roles of Process Integration approaches, renewable energy sources utilisation and design modifications in addressing the process of energy and exergy efficiency improvement. The primary focus is to enhance the economic and environmental performance through process analysis, modelling and optimisation. The paper is categorised into sections to show the contribution of each aspect clearly, namely: (a) Design and numerical study for innovative energy-efficient technologies; (b) Process Integration—heat and power; (c) Process energy efficiency or emissions analysis; (d) Optimisation of renewable energy resources supply chain. Each section is assessed based on the latest contribution of this journal’s Special Issue from the 21st conference on Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction (PRES 2018). The key results are highlighted and summarised within the broader context of the state of the art development.

Research and development on integrated energy systems such as cogeneration and trigeneration to improve the efficiency of thermal energy as well as fuel utilisation have been a key focus of attention by researchers. Total Site Utility Integration is an established methodology for the synergy and integration of utility recovery among multiple processes. However, Total Site Cooling, Heating and Power (TSCHP) integration methods involving trigeneration systems for industrial plants have been much less emphasised. This paper proposes a novel methodology for developing an insight-based numerical Pinch Analysis technique to simultaneously target the minimum cooling, heating and power requirements for a total site energy system. It enables the design of an integrated centralised trigeneration system involving several industrial sites generating the same utilities. The new method is called the Trigeneration System Cascade Analysis (TriGenSCA). The procedure for TriGenSCA involves data extraction, constructions of a Problem Table Algorithm (PTA), Multiple Utility Problem Table Algorithm (MU PTA), Total Site Problem Table Algorithm (TS PTA) and estimation of energy sources by a trigeneration system followed by construction of TriGenSCA, Trigeneration Storage Cascade Table (TriGenSCT) and construction of a Total Site Utility Distribution (TSUD) Table. The TriGenSCA tool is vital for users to determine the optimal size of utilities for generating power, heating and cooling in a trigeneration power plant. Based on the case study, the base fuel source for power, heating and cooling is nuclear energy with a demand load of 72 GWh/d supplied by 10.8 t of Uranium-235. Comparison between conventional PWR producing power, heating and cooling seperately, and trigeneration PWR system with and without integration have been made. The results prove that PWR as a trigeneration system is the most cost-effective, enabling 28% and 17% energy savings as compared to conventional PWR producing power, heating and cooling separately.

The design of heat exchanger networks (HEN) in the process industry has largely focused on minimisation of operating and capital costs using techniques such as pinch analysis or mathematical modelling. Aspects of operability and flexibility, including issues of disturbances affecting downstream processes during the operation of highly integrated HEN, still need development. This work presents a methodology to manage temperature disturbances in a HEN design to achieve maximum heat recovery, considering the impact of supply temperature fluctuations on utility consumption, heat exchanger sizing, bypass placement and economic performance. Key observations have been made and new heuristics are proposed to guide heat exchanger sizing to consider disturbances and bypass placement for cases above and below the HEN pinch point. Application of the methodology on two case studies shows that the impact of supply temperature fluctuations on downstream heat exchangers can be reduced through instant propagation of the disturbances to heaters or coolers. Where possible, the disturbances have been capitalised upon for additional heat recovery using the pinch analysis plus-minus principle as a guide. Results of the case study show that the HEN with maximum HE area yields economic savings of up to 15% per year relative to the HEN with a nominal HE area.

Seawater desalination is considered a technique with high water supply potential and has become an emerging alternative for freshwater supply in China. The increase of the capacity also increases energy consumption and greenhouse gases (GHG) emissions, which has not been well investigated in studies. This study has analyzed the current development of seawater desalination in China, including the capacity, distribution, processes, as well as the desalted water use. Energy consumption and GHG emissions of overall desalination in China, as well as for the provinces, are calculated covering the period of 2006⁻2016. The unit product cost of seawater desalination plants specifying processes is also estimated. The results showed that 1) The installed capacity maintained increased from 2006 to 2016, and reverse osmosis is the major process used for seawater desalination in China. 2) The energy consumption increased from 81 MWh/y to 1,561 MWh/y during the 11 years. The overall GHG emission increase from 85 Mt CO2eq/y to 1,628 Mt CO2eq/y. Tianjin had the largest GHG emissions, following are Hebei and Shandong, with emissions of 4.1 Mt CO2eq/y, 2.2 Mt CO2eq/y. and 1.0 Mt CO2eq/y. 3) The unit product cost of seawater desalination is higher than other water supply alternatives, and it differentiates the desalination processes. The average unit product cost of the reverse osmosis process is 0.96 USD and 2.5 USD for the multiple-effect distillation process. The potential for future works should specify different energy forms, e.g. heat and power. Alternatives of process integration should be investigated—e.g. efficiency of using the energy, heat integration, and renewables in water desalination, as well as the utilization of total site heat integration.