Carbon dioxide emissions must be dramatically reduced to avoid the potentially dangerous effects of climate change. The steel and aluminium industries produce large amounts of carbon dioxide, accounting for 6% of anthropogenic emissions. Previous studies have shown that in these industries there is limited scope for further improvements in energy efficiency. Material efficiency strategies can, however, further reduce emissions. This thesis focuses on materially efficient reuse without melting. A scoping study of current reuse found three opportunities, an examination of which forms the basis of this thesis: reusing components at end of product life; extending the lifespan of products; and reusing manufacturing scrap. The opportunity to reuse components has received little attention to date and there is no clearly defined set of strategies or barriers to enable assessment of appropriate component reuse; neither is it possible to predict future levels of reuse. This thesis presents a global assessment of the potential for reusing steel and aluminium components. A combination of top-down and bottom-up analyses is used to allocate the final destinations of current global steel and aluminium production to final products. A substantial catalogue has been compiled for these products characterizing key features of steel and aluminium components including design specifications, requirements in use, and current reuse patterns. To estimate the fraction of end-of-life metal components that could be reused for each product, the catalogue formed the basis of a set of semi-structured interviews with industrial experts. The results suggest that approximately 30% of steel and aluminium used in current products could be reused. Barriers against reuse are examined, prompting recommendations for redesign that would facilitate future reuse. In order to understand how product lifespans can be extended it must first be understood why products are replaced. A simple framework with which to analyse failure is applied to the products that dominate steel use, finding that they are often replaced because a component/sub-assembly becomes degraded, inferior, unsuitable or worthless. In light of this, four products, which are representative of high steel content products in general, are analysed at the component level, determining profiles of cumulative steel mass over the lifespan of each product. The results show that the majority of the steel components are underexploited – still functioning when the product is discarded. In particular, the potential lifespan of the steel-rich structure is typically much greater than its actual lifespan. Evidence from twelve case studies, in which product or component life has been increased, is used to tailor life-extension strategies to each reason for product failure, providing practical guidelines for designers. There is currently no commercial method of reusing small manufacturing scrap; however, previous research has demonstrated that extruded profiles can be created from small clean aluminium scrap, the scrap fragments solid-state welding together when extruded. In order to evaluate potential applications for these profiles four case studies are conducted in collaboration with aluminium producers and product manufacturers. It was found that strong and formable profiles could be produced from scrap. However, contaminated scrap sources, unreliable bonding and poor surface quality limited their potential for commercial use. No model exists for solid-state weld strength that is applicable to scrap extrusion. This prevents optimisation of the existing extrusion process and the development of new, potentially better, processes. Subsequently, this thesis presents a new model of weld strength as a function of relevant deformation parameters. The model is evaluated using a new experiment in which the deformation conditions can be varied independently. The experiments establish the basic relationships between deformation parameters and weld strength. The model correctly predicts these trends with predicted weld strengths typically lying within the experimental error range. The technical assessment of reuse presented in this thesis demonstrates the scope of potential change. If implemented, the opportunities presented would greatly increase the reuse of steel and aluminium, reducing the emissions emitted from liquid metal production in conventional recycling.

This research has developed a novel sustainability assessment framework for electricity technologies and scenarios, taking into account techno-economic, environmental and social aspects. The methodology uses a life cycle approach and considers relevant sustainability impacts along the supply chain. The framework is generic and applicable to a range of electricity technologies and scenarios. To test the methodology, sustainability assessments have been carried out first for different technologies and then for a range of possible future electricity scenarios for the UK. The electricity options considered either contribute significantly to the current UK electricity mix or will play a greater role in the future; these are nuclear power (PWR), natural gas (CCGT), wind (offshore), solar (residential PV) and coal power (subcritical pulverised). The results show that no one technology is superior and that certain tradeoffs must be made. For example, nuclear and offshore wind power have the lowest life cycle environmental impacts, except for freshwater eco-toxicity for which gas is the best option; coal and gas are the cheapest options, but both have high global warming potential; PV has relatively low global warming potential but high cost, ozone layer and resource depletion. Nuclear, wind and PV increase certain aspects of energy security but introduce potential grid management problems; nuclear also poses complex risk and intergenerational questions. Five potential future electricity mixes have also been examined within three overarching scenarios, spanning 2020 to 2070, and compared to the present-day UK grid. The scenarios have been guided by three different approaches to climate change: one future in which little action is taken to reduce CO2 emissions (‘65%’), one in which electricity decarbonises by 80% by 2050 in line with the UK’s CO2 reduction target (‘80%’), and one in which electricity is virtually decarbonised (at the point of generation) by 2050, in line with current policy (‘100%’).In order to examine the sustainability implications of these scenarios, the assessment results from the present-day comparison were projected forward to describe each technology in future time periods. Additional data were compiled so that coal with carbon capture and storage (CCS) – a potentially key future technology – could be included. The results of the scenario analyses show that the cost of generating electricity is likely to increase and become more capital-intensive. However, the lower-carbon scenarios are also at least 87% less sensitive to fuel price volatility. Higher penetration of nuclear and renewables generally leads to better environmental performance and more employment, but creates unknown energy storage costs and, in the case of nuclear power and coal CCS, the production of long-lived waste places a burden of management and risk on future generations. Therefore, the choice of the ‘most sustainable’ electricity options now and in the future will depend crucially on the importance placed on different sustainability impacts; this should be acknowledged in future policy and decision making. A good compromise requires strategic government action; to provide guidance, specific recommendations are made for future government policy.

Many companies acknowledge the threat from global carbon emissions and how it affects climate change. Despite the continuous warnings, many organizations lack the necessary and recommended action plans that can hamper their negative impact on the environment. One of the managerial tools that companies use globally in order to work proactively and strategically on issues related to the environment, is to set up carbon reduction targets. With time companies have in-house strategies on how to reach the carbon reduction targets by creating a roadmap of cutting measures. Unfortunately, the majority of companies do not have carbon reduction targets that are in line with what science think is needed to avoid contributing to global warming. Nonetheless, forward-thinking early adopters have been using “science-based” methods to challenge the status quo by developing ambitious carbon targets that are in line with today’s best carbon science. This qualitative research investigates the challenging steps from setting a long-term carbon target, using the guidelines and methods presented by the Science-based target initiative. With an exploratory research approach, a case study was conducted at a global leader in appliance manufacturing and industry leader within sustainability. The data was gathered by using semistructured interviews combined with observational findings with a focus to examine how carbon targets emerge in a situated organizational setting. The interviewee's representatives come from two categories, internal company representatives and, external companies that have used the guidelines to set science-based carbon targets. For manufacturing firms, the findings from investigating three steps of the process: calculating the base-year, target integration and predicting future technology development. Calculating the base-year was identified as the most challenging step. The empirical findings helped build an understanding of the different dimensions that facilitate corporate sustainability management. This research has helped to contribute to the lack of empirical findings within the carbon management and carbon target area. Specifically, the sciencebased carbon target topic. / Många företag har idag uppmärksammat det globala hotet från de enorma utsläppen av koldioxid och dess drivande roll i framtidens klimatförändringar. Trots att många företag kontinuerligt arbetar mot att minska sina koldioxidutsläpp, saknar många de nödvändiga handlingsplanerna för att hämma deras negativa påverkan på miljön. Ett av verktygen företag globalt har för att arbeta med proaktivt och strategiskt i frågor som rör miljö, är att sätta upp koldioxidreduktionsmål. Men tyvärr har flertalet av företagen idag mål som inte ligger i linje med vad vetenskapen anser är nödvändigt för att undvika den framtida globala uppvärmningen.Vad ett företag bidrar med har visat sig ofta bygga på okunskap och är därför hamnar sällan målen i linje med vad naturen efterfrågar. För att utmana detta problem har några banbrytande företag använt sig av metoder som kallas "science-based". Dessa metoder är en samling ramverk för att skapa långsiktiga koldioxidreduktionsmål som bättre ligger i linje med vad forskningen tror är nödvändigt för att undvika den globala uppvärmningen. Denna kvalitativa studie undersöker hur ett tillverkningsföretag skapar långsiktiga koldioxidreduktionsmål genom att använda vetenskapligt baserade metoder. En explorativ fallstudie genomfördes hos en global ledare inom tillverkning av vitvaror och hushållsapparater och, som även är branschledare inom hållbarutveckling. Uppgifterna samlades in genom att använda halvstrukturerade intervjuer i kombination med observationer med fokus på att undersöka målsättningsprocessen i ett företags miljöer. De intervjuade kommer från två kategorier, representanter inom företaget och, externa företag som redan har använt dessa ramverk för att skapa vetenskapligt baserade koldioxidreduktionsmål. Resultaten visar att för tillverkningsföretag finns det tre utmanande steg: att beräkna basåret, målintegration och förutspå nödvändig framtida teknikutveckling. De empiriska fynden bidrar till att skapa en bättre förståelse kring hur företag idag arbetar med att sätta upp koldioxidreduktionsmål med fokus på att använda ”science-based” ramverken.