Conventional farming practices and land-use conversions drive carbon out of soil and into the atmosphere, where it contributes to climate change. Biochar, a soil amendment produced by pyrolyzing organic feedstocks under low-oxygen conditions, is a promising tool to restore soil carbon and draw down atmospheric carbon dioxide. Biochar has received considerable attention from scientists, growers, and environmentalists in the last 20 years, but there is still a gap between academic research and practical recommendations on biochar production and application that are relevant to small-scale growers. Here I present the results from two complementary studies that demonstrate the utility of local-scale biochar systems and provide some recommendations for those looking to work with biochar. The first study sought to determine the impact of biochar amendments on soil carbon and nutrient retention on three working farms across a variety of soil types, cropping systems, and climates in the United States. The effect of biochar amendment depended on initial soil characteristics and the properties of the biochar applied. Biochar amendments increased soil carbon in all three sites and increased soil nitrogen at two of the three. In this study pyrolysis conditions appeared to be as important as local soils and climate influences on the efficacy of biochar treatments. The second study was a life cycle assessment using SimaPro software to quantify the carbon balance and global warming potential of biochar produced from three local feedstocks (softwood, hardwood, and hay) applied to pasture soils in Southwest Virginia. Feedstock type, pyrolysis gas yield, and transportation distance significantly contributed to variation in the carbon balance of each agro-ecosystem. Biochar made from softwood lumber scraps performed best, with the highest net carbon storage and lowest global warming potential, followed by biochar made from hardwood scraps. Hay biochar performed worst, with positive carbon emissions (i.e., more carbon released than stored over its life cycle) in most scenarios tested, mainly because of its low biochar yield and the carbon emissions associated with agronomic production and transportation. Together these studies demonstrate the potential of local biochar systems to improve both soil health and carbon sequestration, and reinforce how important it is to know the characteristics of the soil and the production history and properties of the biochar being applied in order to meet soil health and carbon sequestration goals. / Master of Science / Conventional farming practices break down organic material in the soil, which decreases the capacity of soils to sustain crop growth and contributes to climate change as the soil releases carbon dioxide and other greenhouse gasses into the atmosphere. Biochar, or charcoal that is deliberately incorporated into soil, is gaining popularity among farmers, gardeners, and climate scientists for its ability to improve soil health and draw carbon out of the atmosphere to create stable long-term pools of carbon underground. Unfortunately, much of the research on biochar does not translate easily into recommendations for growers and land-managers to make and use biochar. Here I discuss the results from two studies examining the effect of biochar on soil health and carbon sequestration on local scales. In the first experiment I analyzed soil samples shared by farmers in New Mexico, Minnesota and Virginia who applied locally-sourced biochar to their soils. I found that the initial characteristics of the soil and of the biochar affected how the biochar application changed agriculturally-relevant soil properties. In general, biochar improved soil carbon and nitrogen levels, had mixed effects on soil pH depending on the biochar's pH, and had no effect on electrical conductivity (a measure of soil salinity). The second study was a life cycle assessment that quantified and compared greenhouse gas emissions of three different types of biochar, from feedstock harvest to biochar application to soil. I found that the type of feedstock used to make biochar, the amount of gas emitted during the conversion process, and the distance the feedstocks and biochar were transported all played a role in the overall carbon balance of the life cycle. The biochar made from softwood scraps performed best from a carbon storage perspective, followed by biochar made from hardwood. These two biochars tended to return more carbon to the soil than they emitted over their life cycle. The biochar made from hay performed worst, and emitted more carbon than it stored in most of the scenarios I tested. Together these studies show the potential of local biochar systems to improve both soil health and carbon sequestration and reinforce how important it is to be familiar with the soil and the production history and properties of the biochar being applied in order to meet soil health and carbon sequestration goals.

Life Cycle Cost Analysis (LCCA) forms an important part of asset management practices and provides an informed decision support. The holistic nature of LCCA includes life cycle assessment (LCA) as an important component alongside economic life cycle cost analysis. The drinking water industry is right now lacking a reliable cost data structure which will ensure that all the utilities capture the same set of cost data. Also, models and tools currently available in the academia and industry are purely deterministic in nature and do not cater to uncertainty in the data. This study provides a framework for a holistic life cycle cost analysis tool which will help drinking water utilities to prioritize the activities and optimize the cost spending of the utility. The methodology includes the development of a cost data structure, a life cycle cost analysis and a life cycle assessment model in the form of an excel spreadsheet. The LCCA model has the capability to compare different pipe materials, installation, condition assessment, rehabilitation and replacement technologies. Whereas, LCA model can compare different pipe materials based on greenhouse gas emissions calculations. The final step of the methodology includes piloting the model with data from utility A. The analysis has been shown in the form of three case studies - comparison of two pipe materials, two pipe installation technologies and two pipe rehabilitation technologies. The case studies provide results in the form of comparison of total life cycle costs for different alternatives and hence a better alternative can be chosen. / Master of Science

A Avaliação do Ciclo de Vida é uma das principais técnicas de avaliação ambiental de bens e serviços e pode ser classificada em duas abordagens: atribucional e consequencial. A atribucional, caracterizada pelo uso de dados médios de ICV e de alocação de coprodutos, tem como objetivo a avaliação dos impactos ambientais de um produto do berço ao túmulo, em um sistema estático. A ACV consequencial consiste na avaliação das consequências ambientais em um sistema dinâmico, orientado por mudanças. Esta abordagem vem sendo intensamente discutida na literatura internacional, porém, no Brasil ainda se trata de um tema pouco explorado. O presente trabalho visa aprofundar a discussão entre as duas abordagens da ACV. Para isso, utilizaram-se os seguintes procedimentos metodológicos: revisão da literatura e aplicação das abordagens ao biocombustível etanol hidratado de cana-de-açúcar. Os resultados apontam que a ACV atribucional apresentou maiores cargas ambientais em todas as categorias de impacto, com principalmente nas categorias de Ecotoxicidade Aquática, Ecotoxicidade Terrestre e Depleção Abiótica. Isto se deve à subtração das cargas ambientais referentes aos produtos evitados, considerados na análise devido à expansão do sistema realizada na abordagem consequencial com a finalidade de evitar a alocação que, por sua vez, foi utilizada na abordagem atribucional. Notou-se que, em teoria, a principal diferença entre as abordagens da ACV consiste em seus distintos alinhamentos quanto à aplicação pretendida, sendo a atribucional voltada ao conhecimento dos impactos ambientais do ciclo de vida de um produto e identificação de pontos críticos no sistema, e a abordagem consequencial voltada à identificação das consequências ambientais geradas por uma mudança no sistema de produto investigado. Na prática, entretanto, foram encontradas algumas limitações que comprometeram a operacionalização do estudo consequencial, distanciando-a do seu propósito teórico. Dentre estas limitações merecem destaque: o grande número de simplificações intrínsecas ao método aplicado e a falta de transparência quanto à base de dados de background utilizada. Notou-se que a operacionalização da ACV consequencial é bastante complexa, pois despende muito tempo e recursos, principalmente na coleta e validação de informações de mercado. Portanto, reforça-se a necessidade de esforços no sentido do desenvolvimento de métodos menos subjetivos e mais sistemáticos para a abordagem consequencial além de diretrizes mais esclarecedoras explicitando as diferenças quanto ao conteúdo, contextos e formas de aplicação das abordagens atribucional e consequencial da ACV e indicando em quais situações elas podem ser complementares. / Life Cycle Assessment is one of the most used tool to asses environmental impact of goods and services. It can be classified into two approaches: attributional and consequential.Attributional LCA, characterized by the use of average data ICV and coproducts allocation is aimed at assessing the environmental impacts of a product from the cradle to the grave, in a static system. The consequential LCA is the evaluation of the environmental consequences in a dynamic system driven by changes. Both approaches have been intensively discussed in the literature in recent years, but in Brazil it is still a little discussed and explored topic. Thus, this study aims to deepen the discussion between the two LCA approaches. For this, the following methodological procedures are used: literature review and application of the approaches on hydrated bioethanol from sugarcane. The results show that the attributional LCA has higher environmental burdens in all impact categories, with greater difference with consequential in the categories of aquatic and terrestrial ecotoxicity and abiotic depletion. This is due to the subtraction of environmental charges related to avoided products, considered at the time of system expansion in consequential approach, which did not occur in attributional (where co- products were treated by means of allocation). The main differences between the approaches reflect their different alignments on the intended application, the attributional approach is mostly focused on the knowledge of the environmental impacts of the life cycle of a product and identification of improvement points to the system, while the consequential approach aims to verify potential environmental consequences generated by the change in product system investigated. In practice, however, it was observed that the consequential LCA results should be interpreted with great caution due to the fact that the application has brought a large number of limitations, such as: great number of simplifications of the method applied, consideration of standard assumptions when the lack of information for the collection of data and lack of transparency as to the basis of background data used. Moreover, its implementation is still quite complex, requiring much time and resources to collect data and market information. Therefore, we reinforce what has already been established through the literature review: efforts are needed towards the development of less subjective methods and more systematic for consequential approach as well as more enlightening guidelines explaining the differences in the content, context and application forms of attributional and consequential LCA approaches.

A Avaliação do Ciclo de Vida é uma das principais técnicas de avaliação ambiental de bens e serviços e pode ser classificada em duas abordagens: atribucional e consequencial. A atribucional, caracterizada pelo uso de dados médios de ICV e de alocação de coprodutos, tem como objetivo a avaliação dos impactos ambientais de um produto do berço ao túmulo, em um sistema estático. A ACV consequencial consiste na avaliação das consequências ambientais em um sistema dinâmico, orientado por mudanças. Esta abordagem vem sendo intensamente discutida na literatura internacional, porém, no Brasil ainda se trata de um tema pouco explorado. O presente trabalho visa aprofundar a discussão entre as duas abordagens da ACV. Para isso, utilizaram-se os seguintes procedimentos metodológicos: revisão da literatura e aplicação das abordagens ao biocombustível etanol hidratado de cana-de-açúcar. Os resultados apontam que a ACV atribucional apresentou maiores cargas ambientais em todas as categorias de impacto, com principalmente nas categorias de Ecotoxicidade Aquática, Ecotoxicidade Terrestre e Depleção Abiótica. Isto se deve à subtração das cargas ambientais referentes aos produtos evitados, considerados na análise devido à expansão do sistema realizada na abordagem consequencial com a finalidade de evitar a alocação que, por sua vez, foi utilizada na abordagem atribucional. Notou-se que, em teoria, a principal diferença entre as abordagens da ACV consiste em seus distintos alinhamentos quanto à aplicação pretendida, sendo a atribucional voltada ao conhecimento dos impactos ambientais do ciclo de vida de um produto e identificação de pontos críticos no sistema, e a abordagem consequencial voltada à identificação das consequências ambientais geradas por uma mudança no sistema de produto investigado. Na prática, entretanto, foram encontradas algumas limitações que comprometeram a operacionalização do estudo consequencial, distanciando-a do seu propósito teórico. Dentre estas limitações merecem destaque: o grande número de simplificações intrínsecas ao método aplicado e a falta de transparência quanto à base de dados de background utilizada. Notou-se que a operacionalização da ACV consequencial é bastante complexa, pois despende muito tempo e recursos, principalmente na coleta e validação de informações de mercado. Portanto, reforça-se a necessidade de esforços no sentido do desenvolvimento de métodos menos subjetivos e mais sistemáticos para a abordagem consequencial além de diretrizes mais esclarecedoras explicitando as diferenças quanto ao conteúdo, contextos e formas de aplicação das abordagens atribucional e consequencial da ACV e indicando em quais situações elas podem ser complementares. / Life Cycle Assessment is one of the most used tool to asses environmental impact of goods and services. It can be classified into two approaches: attributional and consequential.Attributional LCA, characterized by the use of average data ICV and coproducts allocation is aimed at assessing the environmental impacts of a product from the cradle to the grave, in a static system. The consequential LCA is the evaluation of the environmental consequences in a dynamic system driven by changes. Both approaches have been intensively discussed in the literature in recent years, but in Brazil it is still a little discussed and explored topic. Thus, this study aims to deepen the discussion between the two LCA approaches. For this, the following methodological procedures are used: literature review and application of the approaches on hydrated bioethanol from sugarcane. The results show that the attributional LCA has higher environmental burdens in all impact categories, with greater difference with consequential in the categories of aquatic and terrestrial ecotoxicity and abiotic depletion. This is due to the subtraction of environmental charges related to avoided products, considered at the time of system expansion in consequential approach, which did not occur in attributional (where co- products were treated by means of allocation). The main differences between the approaches reflect their different alignments on the intended application, the attributional approach is mostly focused on the knowledge of the environmental impacts of the life cycle of a product and identification of improvement points to the system, while the consequential approach aims to verify potential environmental consequences generated by the change in product system investigated. In practice, however, it was observed that the consequential LCA results should be interpreted with great caution due to the fact that the application has brought a large number of limitations, such as: great number of simplifications of the method applied, consideration of standard assumptions when the lack of information for the collection of data and lack of transparency as to the basis of background data used. Moreover, its implementation is still quite complex, requiring much time and resources to collect data and market information. Therefore, we reinforce what has already been established through the literature review: efforts are needed towards the development of less subjective methods and more systematic for consequential approach as well as more enlightening guidelines explaining the differences in the content, context and application forms of attributional and consequential LCA approaches.

Research on historical developments that lead to the establishment of global organizations for climate change has shown that the phenomenon of surface temperature is not a new topic of focus. Increased policy restrictions, brand image, fear of resource scarcity, growing market trends towards sustainability and consumer awareness are among the several external factors that have influenced the growing research in corporate transition towards carbon neutrality. The main aim of this study is to understand through data accounting of major material and energy carrier changes, how a non-production facility could transition to become a carbon-neutral facility. Therefore, an exploratory case study has been performed and conducted at Volvo CE Customer center in Eskilstuna, Sweden, with two objectives: i) to identify and quantify the customer center current footprint by mapping the main contributors to greenhouse gases emissions, and ii) to recommend specific & general measures that can mitigate the carbon footprint of the facility. Three research questions related to the facility’s current carbon footprint, measures implemented so far, and the best applied assessment method, have guided us throughout the study. The methodology has been framed to give a theoretical underpinning for understanding the project from a holistic perspective. The split of the methodology has been constructed in line with the theoretical framework that gave the foundation to the needed theories to be taken into account i.e. GHG protocol, which is the tool that has been adopted by the study to attain the desired aim, including the three scopes under the protocol which were also defined accordingly. ‘Scope 1’ has been taken into account and is a representation of direct emissions, ‘Scope 2 represents the indirect emissions, and ‘Scope 3’ (according to the GHG protocol) takes into account the rest of the indirect emissions arranged into 15 categories, from which applicable to our study were 4 categories (1, 3, 4 and 6). The results showed that during the base year (2019) the highest user within Scope 1 was diesel, followed by HVO, and under Scope 2, The results from Scope 1 and 2, together with the results of Scope 3 category, were analyzed using the attributional LCA approach recommended by the GHG protocol to calculate their contribution to the customer centers’ total carbon footprint. It was found that Scope 1 stands for 128.52 t CO₂-eq while Scope 2 stands only for 1.16 t CO₂-eq and finally Scope 3 stands for most of the emissions with 3719 t CO₂-eq. It has been found that in 2019, the customer center has saved 101.05 tonnes of GHG by implementing measures, such as switching from using Diesel to HVO and switching from the mixed electricity to the renewable ones, according to the attributional perspective presented in the GHG protocol. However, different results were found when these values were discussed and analyzed from the consequential perspective, since this perspective analyses the effects of the implemented measures on the global emission level. This concluded that implementation of conservation and efficiency measures must take priority before switching to higher priced renewables. Thus, the resulting carbon neutrality will be consequentially safer. The recommendations stated in this study also follows the same principle “Conserve before investing”. Suggestions and recommendations outlined in the study for future implementation approach carbon neutrality as a strategy and not a burden, helping the customer neutral achieve the goal in an Environment, Economic and Socially sustainable manner.

<p dir="ltr">Controlled environment agriculture (CEA) is a practice of food production under optimized conditions to intensify production yield, and thus has potential for addressing food security for a growing population. Aquaculture and aquaponics are two types of CEA that can produce aquatic animals along with plants using non-arable lands and lower inputs of water and nutrients. However, their operations have high energy consumption and generate considerable nutrient-rich sludge and wastewater, making their environmental performance an emerging research focus. This thesis quantitively analyzed the environmental sustainability of aquaponics and aquaculture production using life cycle assessment (LCA).</p><p dir="ltr">The LCA on aquaponics evaluated a marine aquaponics production system that grew shrimp, red orache, minutina and okahajiki, and analyzed the effect of salinity, C/N ratio, and shrimp-to-plant stocking density. The grow-out stage accounted for over 90% of total environmental impacts with electricity use as the predominant contributor. The marine aquaponic production exhibited best environmental performance when operated at low salinity (10 ppt), and high C/N ratio (15) and stocking density (5:1), which can be further improved by 95–99% via the use of wind power as electricity source. Additionally, variation in the prices of aquaponic products was found to improve the system’s environmental impacts by up to 8%.</p><p dir="ltr">The aquaculture LCA focused on shrimp recirculating aquaculture systems (RAS) and evaluated the environmental feasibility of microalgae-based wastewater treatment. Microalgae treatment effectively removed 74% of phosphate in RAS wastewater and thus reduced the freshwater eutrophication potential by 55%. However, its remediation performance was inferior to activated sludge treatment due to different operation scales. Electricity was the principal hotspot of microalgae treatment and made up over 99% of all the environmental impacts, which can be considerably decreased by reducing coal use in the electricity supply. Three utilization pathways for algal biomass (feed ingredient, biodiesel and biogas) were investigated; however, only biogas production was found to show environmental benefits to marine eutrophication remediation owing to the low biomass quantity produced.</p><p dir="ltr">While <a href="" target="_blank">aquaculture and aquaponics</a> play important roles in meeting the globally growing demand for seafood, this thesis provides valuable life cycle inventory data for these fields. Moreover, the LCA models developed in this thesis are useful decision-making tools for aquaculture and aquaponic producers to adapt farming practices with lower environmental footprint.</p>

In order to reduce the environmental footprint of products, companies turn to Eco-design and associated tools. Life cycle assessment (LCA) is a holistic and quantitative tool that is widely accepted in companies, but it is too extensive to apply in product development; as an alternative, simplified versions are more suitable. By utilising CAD models of components, material data and a database, weight can be calculated and LCA data estimated. This thesis aims to evaluate the feasibility of utilising CAD-integrated LCA software in product development process and explore the barriers in doing so. A case study was conducted to evaluate the software Sustainable Innovation Intelligence by thoroughly describing the tool, the database used as well as the product life cycle management (PLM) system used. Two research questions have been formulated regarding the barriers and to what extent they can be overcome using the new CAD-integrated tool. The first one is answered by a literature review, where 22 barriers were identified and related to different sociotechnical levels, while the second is answered by using pattern matching following the case study. The evaluation covers human and technical aspects of the tool itself, what is required by the practitioner, as well as additional aspects to consider when implementing the tool in a company. The final result shows that 11 of the barriers are to some extent being overcome by the tool. While showing promise, the novelty of the software makes it immature and lacking full functionality, while requiring a lot of the practitioner in terms of LCA specific knowledge.

This studyh focuses on thermal comfort and cost effectiveness of stratum ventilation in subtropical Hong Kong Special Adminstation Region (HKSAR). The need for studying thermal comfort with various air distribution strategies becomes a significant issue recently due to climate change, increasing energy prices and the governmental energy efficiency policy. Stratum ventilation, with air supplied at breathing level, can probably provide satisfactory thermal comfort at a relatively elevated indoor temperature in which less energy use is consumed. It seems that only limited studies on the evaluation of neutral temperature, which is a condition of neither slightly warm nor slightly cool, are supported by actual human comfort surveys. Moreover, study on the related thermal comfort and cost effectiveness as other paradigms in comparison with the mixing and displacement air distribution design is rare. New environmental chamber of laboratory-based air-conditioning systems has been developed for investigating the actual benefit of cost effectiveness and balance of thermal comfort satisfaction with the stratum air distribution strategy under subtropical climates. American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) 7-point questionnaires have been collected from human comfort tests so as to estimate the neutral temperature of stratum ventilation in comparison with mixing and displacement ventilation at pre-set conditions. The neutral temperatures of HKSAR people under the mode of mixing, displacement, stratum, modified-stratum-1, modified-stratum-2, and modified-stratum-3 are found to be 24.6℃, 25.1℃, 25.6℃, 26.0℃, 27.1℃ and 27.3℃ at 10 air change per hour (ACH) respectively, which become 24.8℃, 25.3℃, 26.6℃, 27.4℃, and 27.9℃ at 15 ACH respectively. Life cycle assessment results in 10 service year indicate that 7.73% and 7.32% of cost reduction, and 14.52% and 11.91% of greenhouse gas emission reduction in stratum ventilation by comparing with mixing and displacement ventilation. As a result, stratum ventilation should be the best option on both of cost reduction, and less carbon emission in small-to-medium size air-conditioned space for new building and retrofitting existing works.

The continued drive to reduce Greenhouse Gas (GHG) emissions in order to mitigate climate change has led to an increase in demand for low-carbon energy sources, and the development of new technologies to harness the available energy in the wind, waves and tides. Many controversies surround these technologies, however, particularly with regards to their economic cost, environmental impacts and the implications of the variability of their output for security of the electricity supply. In order to make informed policy decisions on future developments of the electricity system, it is necessary to address these controversies and confirm the environmental, economic and social sustainability of these new renewable generators. This thesis specifically examines two key issues: whether new variable-output renewable energy generators actually deliver a net reduction in greenhouse gas emissions over their lifetimes, and whether they produce a viable energy return on energy investment. Although renewable energy sources are themselves ‘carbon free’, GHG emissions (and energy consumption) occur during the construction, maintenance and decommissioning of the generator infrastructure required to convert this energy into electricity. Furthermore, the variability of the output power from such generators has implications for the operation of the grid - there may be a requirement for additional reserve capacity and the increased part-loading of conventional plant is likely to reduce its operating efficiency. Carbon and energy paybacks are measures of the time required for a new renewable installation to offset these life cycle impacts. The work presented in this thesis examines both the life cycle impacts and the GHG emissions displacement of variable renewable generation, using Great Britain as a case study, in order to provide a basis for significantly more robust and reliable estimates of carbon and energy paybacks. The extensive literature survey concentrates on two key areas: current calculation methodologies and estimates for life cycle carbon and energy consumption of power generators; and the marginal emissions displacement of variable renewable generation. A detailed life cycle assessment of the Pelamis wave energy converter is presented, which sets the embodied carbon and energy in the context of the wider environmental impacts and includes an examination of the effect of different assumptions on the analysis results. In order to investigate the true emissions displacement of renewable generation, a historical analysis of real data from the National Grid was carried out, identifying the marginal displacement factor of wind power and taking into account the effect of the efficiency penalties of conventional plant. The findings of the analyses presented in this thesis are combined with information from the literature to examine the actual carbon and energy payback of existing renewable generation infrastructure on the British grid, and to provide detailed recommendations for future carbon and energy payback calculations.

Thesis (MEng)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Sustainability is becoming an increasingly important aspect in all facets of engineering. It is in particular an important consideration in the structural engineering industry, due to the prominence of the negative impact this industry has on the environment, both on a national and international scale. The problem, however, is that sustainability is a mostly unknown and highly debated topic. It is not only difficult to quantify, but even difficult just to define. In the field of structural engineering it is an especially difficult task to consider sustainability. It is still a very new field of research and difficult to apply. It is therefore important that continued research be done in order for there to be a better understanding of how sustainability should be considered and applied in the context of structures. In an attempt to assess the environmental impact of building structures, there are two basic approaches that are followed. The first, the application-oriented method, is a simple, points-based system. The second, the analysis-oriented method, makes use of detailed indices and factors to quantify the impact. This study aims to develop an analysis-oriented method, specifically designed for the complete life cycle of buildings in the South African environment. This is accomplished by continuing the work that was started by Brewis (2011), and continued by Brits (2012). Brewis developed the approach for the pre-use phase, while Brits developed the approach for the end-of-life phase. Both focussed their application on low-cost housing development. However, the approach is defined for the use of the analysis of a building envelope. The details of developing the environmental life cycle assessment (LCA), as well as the approaches for the pre-use phase and the end-of life phase are discussed in Chapter 3. The study develops the use phase of the proposed environmental life cycle assessment for buildings in Chapter 4. It discusses in detail the two main components of the use phase, namely maintenance and operation. While maintenance is concerned with the replacement of building materials in the structure, the operation component is concerned with the energy needs during the use phase. It is determined that the energy use that is directly related to the building envelope is the energy required for the space heating and cooling of the building. This is due to the fact that the thermal properties of the building envelope influence the thermal environment within the building, and thereby impact the use of energy to regulate that thermal environment. In order to make the most use of both of these components within the application of the proposed LCA, it was decided to model a residential building structure that uses consistent energy to regulate the thermal environment within the structure. However, it is not only the objective to use the proposed LCA as an assessment tool, but also as a comparative and optimisation tool. Therefore one component, the external walls, was selected as a variable component. This component was varied to form a total of nine different buildings. These nine buildings were then used in a comparative study in order to try to determine an optimum choice of external walling system, based on the results of the environmental impacts determined in the LCA. It is also used to try to explain exactly how and to what extent the external walling system contributes to the environmental impact, and what useful application value we can gain from this knowledge. The results showed that a minor increase in the materials impact (due to attempts to improve the thermal capacity of the external walls) were in most cases countered by a decrease in the energy impact, which in seven of the eight alternative external walling systems led to a net decrease in environmental impact (EI) categories one to four. It was also found that with the increase of the R-value of the external walling systems, the environmental impact of the building steadily decreased, in terms of four of the five impact categories. The only exception to these trends was found in the fifth impact category: waste generation. The reason for this is the fact that energy impact in this environmental impact category is negligible, and therefore does not contribute much to the net change in environmental impact. / AFRIKAANSE OPSOMMING: Die belangrikheid van volhoubaarheid neem al hoe meer toe in alle aspekte van ingenieurswese. In die industrie van struktuuringenieurswese is dit van besonderse belang as gevolg van die prominente negatiewe impak van hierdie industrie op die omgewing, op beide ’n nasionale en internasionale skaal. Die probleem is egter dat volhoubaarheid nog meestal gesien word as ʼn onderwerp wat onbekend en hoogs debatteerbaar is. Dit is nie net moeilik om te kwantifiseer nie, maar selfs moeilik om dit net te definieer. In struktuuringenieurswese is dit veral ʼn moeilike taak om volhoubaarheid in ag te neem. Dit is nog ʼn baie jong studieveld wat moeilik is om toe te pas. Dit is dus van uiterse belang dat verdere navorsing gedoen word sodat daar ʼn beter begrip kan wees van hoe volhoubaarheid op die lewensiklus van strukture toegepas kan word. In 'n poging om die omgewingsimpak van die geboustrukture te evalueer, is daar twee basiese benaderings wat gevolg kan word. Die eerste, die toepassingsgeoriënteerde metode, is 'n eenvoudige, punte-gebaseerde stelsel. Die tweede, die analise-georiënteerde metode maak gebruik van gedetailleerde indekse en faktore om die omgewingsimpak te kwantifiseer. Hierdie studie beoog om 'n analise-georiënteerde metode te ontwikkel, wat spesifiek ontwerp is vir die analise van die volledige lewensiklus van geboue in die Suid-Afrikaanse omgewing. Dit word gedoen deur die voortsetting van die werk wat begin is deur Brewis (2011), en voortgesit is deur Brits (2012). Brewis het die benadering vir die eerste fase (voor-gebruik) ontwikkel, terwyl Brits die benadering vir die finale fase (einde-van-lewe) ontwikkel het. Beide het die fokus van hul toepassings geplaas op lae-koste behuising. Die benaderings is egter gedefinieer vir die algemene analise van ʼn gebou se raamwerk. Die besonderhede van die ontwikkeling van die omgewingslewensiklus analise (OLA), asook die benaderings vir die eerste en finale fases, word in Hoofstuk 3 bespreek. Die studie ontwikkel die gebruiksfase van die voorgestelde omgewingslewensiklus analise vir geboue in Hoofstuk 4. Dit bespreek die twee hoofkomponente van die gebruiksfase, naamlik die instandhouding en bedryf. Terwyl instandhouding gemoeid is met die vervanging van boumateriale in die struktuur, is die bedryfskomponent gemoeid met die energie behoeftes tydens die gebruiksfase. Dit word bepaal dat die energie verbruik wat ʼn direkte verband het met die gebou se raamwerk, die energie is wat nodig is vir die verhitting en verkoeling van die gebou. Dit is te danke aan die feit dat die termiese eienskappe van die gebou se raamwerk die termiese omgewing binne die gebou beïnvloed, en sodoende 'n impak het op die energie wat benodig word om die temperatuur te reguleer. In ʼn poging om die spektrum van die voorgestelde OLA ten volle te benut, is dit besluit om die toepassing daarvan te illustreer op 'n residensiële gebou wat van konsekwente energieverbruik gebruik maak om die termiese omgewing binne die gebou te reguleer. Dit is egter nie net die doel om die voorgestelde OLA te gebruik as 'n assesseringsinstrument nie, maar ook om die OLA se funksie as ’n vergelykende en optimaliseringshulpmiddel te illustreer. Dus is een komponent, die eksterne mure, gekies as 'n veranderlike komponent. Hierdie komponent is gewissel om 'n totaal van nege verskillende geboue te vorm. Hierdie nege geboue is gebruik in 'n vergelykende studie in 'n poging om 'n optimale keuse van eksterne mure te bepaal, gebaseer op die resultate van die omgewingsimpak wat in die OLA te bepaal is. Dit word ook gebruik om te probeer om te verduidelik presies hoe en tot watter mate die eksterne mure bydra by tot die omgewingsimpak, en watter nuttige toepassingswaarde geput kan word uit hierdie kennis. Die resultate het getoon dat 'n toename in die materiaal impak (weens pogings om die termiese kapasiteit van die eksterne mure te verbeter) in die meeste gevalle teengewerk is deur 'n afname in die energie impak. In sewe van die agt alternatiewe eksterne muurstelsels het dit gelei tot 'n netto afname in omgewingsimpak vir kategorieë een tot vier. Dit is ook gevind dat die omgewingsimpak van die gebou stelselmatig gedaal het met die toename van die Rwaarde van die eksterne muurstelsels, ook in terme van kategorieë een tot vier. Die enigste uitsondering op hierdie tendense is gevind in die vyfde impak kategorie: die afval wat gegenereer word. Die feit dat die effek van energie verbruik gering is in hierdie omgewingsimpak kategorie, lei tot die feit dat dit nie veel bydra tot die netto verandering in die omgewingsimpak nie.