Adisa Azapagic’s research while affiliated with University of Manchester and other places

Soil salinization has become one of the major environmental and socioeconomic issues globally and this is expected to be exacerbated further with projected climatic change. Determining how climate change influences the dynamics of naturally-occurring soil salinization has scarcely been addressed due to highly complex processes influencing salinization. This paper sets out to address this long-standing challenge by developing data-driven models capable of predicting primary (naturally-occurring) soil salinity and its variations in the world’s drylands up to the year 2100 under changing climate. Analysis of the future predictions made here identifies the dryland areas of South America, southern and western Australia, Mexico, southwest United States, and South Africa as the salinization hotspots. Conversely, we project a decrease in the soil salinity of the drylands in the northwest United States, the Horn of Africa, Eastern Europe, Turkmenistan, and west Kazakhstan in response to climate change over the same period.

Offshore wind electricity is becoming an important source of renewable energy due to its global warming potential (GWP). However, the GWP can vary significantly, depending on many factors, including the capacity of the installation, distance from the shore, supporting structure and maintenance requirements. Currently, there is a lack of life cycle assessment (LCA) studies that take these specific conditions into account. As a consequence, developers and policy makers rely on average GWP values which could lead to inaccurate estimates of the GWP and other impacts. To address this gap, this paper presents a new model for estimating the life cycle impacts of offshore wind electricity taking into account specific technical characteristics of individual installations and whole wind farms. Aimed at non-experts, the model provided freely with this paper is developed in Excel and follows the ISO 14040/44 LCA methodology. Supported by the built-in background LCA databases, it requires users to specify only a few key characteristics of an existing or proposed installation, thus facilitating quick and yet robust estimations of impacts. Eleven impacts can be considered, including GWP, depletion of resources, human toxicity and eco-toxicities. The application of the model is illustrated by quantifying the LCA impacts of 20 offshore wind farms (OWF) operating in the UK. The results show that the impacts vary considerably with the specific characteristics of OWF, including the age, type and size of wind turbines, their capacity and distance from the shore. For example, the GWP ranges by a factor of three (6.4-19.5 g CO2 eq./kWh) and the other impacts by a factor of 2.2-3.2. The developed model can be used by designers, developers and policy makers to customise the inputs for a specific OWF and estimate the impacts quickly and cost-efficiently, without the need for prior expertise in LCA and extensive data collection.

This paper combines process design and modelling with life cycle sustainability assessment to identify opportunities for improving the environmental and economic performance in the cheese industry. Considering both the production and consumption perspectives, the study considers first a range of improvement options in the cheese manufacturing process, followed by an assessment of the rest of the life cycle. For the manufacturing process, the focus is on energy efficiency and valorisation of waste with the following four options considered: Option 1 is a base case that reflects current manufacturing practice and therefore excludes energy recovery and waste utilisation; Option 2 includes heat integration applied to recover waste heat from the process; Option 3 considers the combination of heat integration with treatment of cheese whey via anaerobic digestion to produce biogas; in Option 4, heat integration is combined with treatment of whey via fermentation to produce bioethanol and animal feed. Cheddar cheese has been selected by way of example as one of the most consumed types of cheese in different countries, including the US and the UK. Using life cycle assessment and life cycle costing, the environmental and economic sustainability of cheese have been assessed for these options from farm gate to cheese-plant gate for the production perspective, and from cradle to grave for the consumption perspective. Option 4 is found to be the best alternative across all impacts and costs for both perspectives. For example, compared to the base case, the climate change impact and life cycle costs of cheese are reduced respectively by 148% and 158% for the production perspective, and by 3.4% and 8% for the consumption perspective. These reductions are mainly due to the co-production of bioethanol and animal feed. Production of biogas from whey in Option 3 has higher environmental impacts than the base case, making it the worst alternative. Taking the consumption of cheese at the UK level as an example, improvements in the manufacturing process via Option 4 could reduce the annual climate change impact of the food sector by around 209 kt CO2 eq./yr and primary energy demand by 6.7 PJ/yr, while increasing the value added of cheese by up to 11%. These results will be of interest to cheese producers, food manufacturers, consumers and policy makers.

A large portion of plastic produced each year is used to make single-use packaging and other short-lived consumer products that are discarded quickly, creating significant amounts of waste. It is important that such waste be managed appropriately in line with circular-economy principles. One option for managing plastic waste is chemical recycling via pyrolysis, which can convert it back into chemical feedstock that can then be used to manufacture virgin-quality polymers. However, given that this is an emerging technology not yet used widely in practice, it is not clear if pyrolysis of waste plastics is sustainable on a life cycle basis and how it compares to other plastics waste management options as well as to the production of virgin plastics. Therefore, this study uses life cycle assessment (LCA) to compare the environmental impacts of chemical recycling of mixed plastic waste (MPW) via pyrolysis with the established waste management alternatives: mechanical recycling and energy recovery. Three LCA studies have been carried out under three perspectives: waste, product and a combination of the two. To ensure robust comparisons, the impacts have been estimated using two impact assessment methods: Environmental footprint and ReCiPe. The results suggest that chemical recycling via pyrolysis has a 50% lower climate change impact and life cycle energy use than the energy recovery option. The climate change impact and energy use of pyrolysis and mechanical recycling of MPW are similar if the quality of the recyclate is taken into account. Furthermore, MPW recycled by pyrolysis has a significantly lower climate change impact (-0.45 vs 1.89 t CO2 eq./t plastic) than the equivalent made from virgin fossil resources. However, pyrolysis has significantly higher other impacts than mechanical recycling, energy recovery and production of virgin plastics. Sensitivity analyses show that some assumptions have notable effects on the results, including the assumed geographical region and its energy mix, carbon conversion efficiency of pyrolysis and recyclate quality. These results will be of interest to the chemical, plastics and waste industries, as well as to policy makers.

The circular economy (CE) literature has so far focused on the implementation of the CE philosophy in teaching and research at universities. However, studies on the implementation of CE principles for sustainable campus management are lacking. This chapter shows how the latter may be achieved using the University of Manchester as an illustrative case. A CE decision-support framework was used for these purposes to help the university identify opportunities and develop a pragmatic action plan for implementation of a CE. The chapter also illustrates the first steps that need to be taken to build a CE business case. Future research should focus on quantifying the sustainability implications of implementing a CE in universities, including definition of meaningful performance indicators, stakeholder benefits and how university living labs can be used for experimentation towards CE implementation. This could help monitor CE progress and benchmark universities on their circularity and sustainability performance. Book and chapter: https://www.e-elgar.com/shop/gbp/catalog/product/view/_ignore_category/1/id/16687/s/handbook-of-the-circular-economy-9781788972710/

Significance Land degradation due to soil salinization has detrimental impacts on vegetation, crops, and human livelihoods, leading to a need for a methodologically consistent analysis of the variability of different aspects of salt-affected soils. However, previous studies on the soil salinity issue have been primarily spatial and localized, leaving the large-scale spatiotemporal variations of soil salinity widely ignored. To address this gap, we present a globally validated analysis quantifying the long-term variations (40 y) of topsoil salinity at high spatial resolutions using machine-learning techniques. The results have significant implications for agroecological modelling, land assessment, crop growth simulation, and sustainable water management.

Information on the scale of food waste, its sources, causes and associated environmental impacts is critical for devising food waste prevention strategies. A number of studies have focused on these issues, but there are still significant knowledge gaps, both in terms of the amount of food waste generated in various parts of the supply chain and the related impacts. In an attempt to address some of these gaps, this study focuses on food waste in the UK to estimate its quantities along the whole supply chains and to assess the resulting life cycle environmental impacts. Furthermore, the contributions of various food groups to food waste and their impacts in different life cycle stages are also quantified. The findings suggest that 13.1 Mt of food waste is generated annually in the UK across all the supply chain, leading to the greenhouse gas emissions of 27 Mt of CO2 eq./yr. The highest volume of waste is generated in the cereals (31%) and vegetables & roots subsectors (28%). However, meat and fish are the major contributors to the total life cycle environmental impacts, even though they account for only 10% of the overall food waste. Although post-consumer waste has the highest contribution, both in terms of waste quantities and environmental impacts, the contribution of other stages (primary production, food processing and distribution) is also significant. These findings emphasise the need to consider environmental impacts of food waste and engage all supply chain actors in formulating food waste reduction strategies.

Biofuels are being promoted as a low-carbon alternative to fossil fuels as they could help to reduce greenhouse gas (GHG) emissions and the related climate change impact from transport. However, there are also concerns that their wider deployment could lead to unintended environmental consequences. Numerous life cycle assessment (LCA) studies have considered the climate change and other environmental impacts of biofuels. However, their findings are often conflicting, with a wide variation in the estimates. Thus, the aim of this paper is to review and analyse the latest available evidence to provide a greater clarity and understanding of the environmental impacts of different liquid biofuels. It is evident from the review that the outcomes of LCA studies are highly situational and dependent on many factors, including the type of feedstock, production routes, data variations and methodological choices. Despite this, the existing evidence suggests that, if no land-use change (LUC) is involved, first-generation biofuels can—on average—have lower GHG emissions than fossil fuels, but the reductions for most feedstocks are insufficient to meet the GHG savings required by the EU Renewable Energy Directive (RED). However, second-generation biofuels have, in general, a greater potential to reduce the emissions, provided there is no LUC. Third-generation biofuels do not represent a feasible option at present state of development as their GHG emissions are higher than those from fossil fuels. As also discussed in the paper, several studies show that reductions in GHG emissions from biofuels are achieved at the expense of other impacts, such as acidification, eutrophication, water footprint and biodiversity loss. The paper also investigates the key methodological aspects and sources of uncertainty in the LCA of biofuels and provides recommendations to address these issues.

Growing uncertainty in the future availability of freshwater sources has led to an increase in installations for desalination of seawater. Reverse osmosis (RO), currently the most widely adopted technique, has caused environmental concerns over the high associated greenhouse gas emissions and generation of large amounts of chemicals-containing brine. Significant consumption of electricity for RO desalination is an additional challenge, particularly in remote locations. In this review, forward osmosis (FO), membrane distillation (MD) and capacitive deionisation (CDI) are assessed as potential substitute technologies and the major recent advancements in each field are discussed. These emerging technologies offer significant advantages over RO, such as higher salt rejection (CDI, MD), higher recovery of water (MD), fewer pre-treatment stages (MD, FO) and the ability to use low-grade energy (MD, FO). In their current state, stand-alone technologies cannot compete with RO until certain challenges are addressed, including pore-wetting (MD) and high energy consumption (MD, CDI, FO). Hybrid systems that combine RO and emerging technologies may be useful for feed waters that cannot be treated by RO alone and their benefits may be able to offset the increase in capital costs. These and other aspects, such as operational stability should be considered in larger-scale, long-term studies.