OpenUCT :: Browsing by Author "Von Blottnitz, Harro"

Browsing by Author "Von Blottnitz, Harro"

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Open Access
Application of life cycle assessment in process design: case study on SO₂ abatement technologies in the PGM sector
(2016) Munyongani, Veronica; Von Blottnitz, Harro; Broadhurst, Jennifer Lee
Platinum group elements (PGEs) are increasingly being used in a variety of environmentally-related technologies such as catalysts and catalytic converters which have strong expected growth to meet environmental and technological challenges this century. The platinum industry is actively seeking to progress its commitment to sustainability principles by reducing the negative impacts of their mining and mineral processing operations. Technical innovation to improve future plant designs, as well as the development of management policies, guidelines and protocols for efficient operation of process plants has therefore become a strategic priority for the South African platinum industry. The industry has also made an effort to understand the environmental impacts of its products from mine to metal, using life cycle methods. However, very limited research has been done to investigate what environmental value could be created if strategic and design decisions in minerals processing were life cycle based, particularly in the context of PGMs. Seminal work by Stewart (1999) investigating the environmental life cycle consideration for design-related decision making in the minerals industry has not led to significant adoption. Forbes et al. (2000) analysed metal processing using LCA and were able to identify opportunities for improved environmental performance. They however did not explore how it would be incorporated into the decision making cycle. Therefore, the main objective of this research is to determine whether life cycle assessment could help inform design decision making in the minerals industry. In the years 2002-2008 several PGM-producing companies commissioned new SO₂ scrubbing technologies to meet the regulations that had been set to prevent the release of excessive amounts of sulphur dioxide from smelters in the Rustenburg area, a mining town located in the North West Province of South Africa. Using these cleanup process retrofits as case studies, this dissertation aims to determine whether the introduction of LCA as an environmental analysis tool would have provided additional value to the decision makers. The case study approach that was chosen compared and assessed the performance of SO₂ abatement technologies and the effect of efficiencies chosen on environmental performance by using life cycle assessment modelling. By doing the life cycle assessment on the different options that the companies had, it was possible to evaluate the indirect environmental impacts that could have been overlooked during the design decision making process. In addition , experts who were involved in the design processes of the SO₂ abatement retrofits were interviewed to establish: i) how the design decisions were made and ii) whether the life cycle based insights into technology performance would have been of use in the design work. The goal of the life cycle assessment was to identify whether there were design decisions that induced environmental burden shifting when platinum smelters in the Rustenburg area added SO₂ abatement technologies to their processes, which could have been avoided had the LCA perspective been taken into account. The assessments considered two key variables, namely extent of recovery and technology choice.
Open Access
Applications of systems thinking in integrated solid waste management planning for African cities: the case of Nairobi, Kenya
(2010) Kasozi, A; Von Blottnitz, Harro
The majority of solid waste generated by urban living cannot be assimilated in the city environment,and initial improvements in urban cleanliness and health were only realized when organized wastecollection and disposal outside of city limits was introduced in Europe in the late 19th century.Sanitary landfills were later invented to reduce the environmental effects of large unsecureddumpsites, it is now however increasingly being shown that this too as a waste management strategyoffers a worse environmental footprint than material and energy recovery and recycling (Cherubini et01., 2009). Modern approaches to solid waste management, collectively referred to as Integrated Solid Waste Management (ISWM), therefore increasingly incorporate strategies to reduce wastegeneration and to encourage re-use and recycling of materials, and recovery of energy; with landfilling as a last option for residual waste. This represents a shift in waste management paradigmsfrom a focus on collection for disposal, to an increasing integrated interest in the entire waste chainfrom waste generation to material and energy recovery and recycling, and to safe residual treatmentand disposal. The increasing acceptance of Mebratu's (1998) cosmic interdependence model as amore realistic conceptualisation of our world and how its natural, social, and economic spheresinteract however implies that sustainable waste management design needs to take a further leapinto a systems discourse, and cannot be considered in isolation of a rigorous understanding of thesystemic interactions of the social and economic circumstances unique to particular areas. This callsfor a greater understanding of how ISWM principles fit within the social and economic contexts ofgiven areas; an analytical gap that can be filled through the use of systems thinking and systemsbasedtools to multi-dimensionally investigate, and articulate the structures and relationships thatoften underlie complex situations. While systems thinking has found wide application in thesustainability sciences as a prerequisite to building truly sustainable systems (for example Capra,2002 and Hjorth & Bagheri, 2006), it has as yet found little application in waste management analysisand designs, which have evolved from simple problem-oriented to ""integrated"" engineeringmethods. In response to dire solid waste conditions in Nairobi, the government of Kenya agreed in 2009 tocollaborate with UNEP to develop an ISWM Strategy for Nairobi. The project was initiated in March2009, and a National Task Team was established to oversee the development of the plan along with ateam from the University of Cape Town, of which the author was part. The core elements of theresulting Nairobi City ISWM Strategy (CCN & UNEP, 2010) were finalised in April 2010 and included,alongside the formal use of the UNEP ISWM planning methodology, some application of systemsanalysis. These systems analyses could however only be partially developed due to project deliverytime constraints, and this dissertation extends these analyses to completion and explores theirimplications for ISWM in Nairobi.Systems based tools from the research area of system dynamics were applied to systematicallystructure the waste problem and situation in Nairobi, and to develop conceptual causal loop modelsarticulating the solid waste system in Nairobi as a whole. This enabled the highlighting of inherentwaste system strengths and weaknesses in Nairobi, system drivers, leverage points, behaviouralarchetypes, and resulting implications for ISWM planning in Nairobi. The insights generated wereused to inform an examination of whether the intervention strategies finally developed in theNairobi ISWM Strategy Plan (CCN & UNEP, 2010) were adequate at a fundamental level andsufficiently relevant. It was also determined that the bulk of Nairobi's solid waste is organic, and thatthe material recycling and reuse capacity in the city is a key system driver in its waste management towards ISWM, of which organic waste valorization comprises a significant part. It was therefore ofinterest to determine the current capacity, and potential for expansion of organic waste valorizationin the city towards amplifying material recycling as a system driver towards ISWM.The application of a systems based analysis of Nairobi's waste management identified the presenceof ten system drivers of varying nature and flexibility, through which to influence the achievement ofISWM objectives in the city. Potential system leverage points in Nairobi's waste sector were alsoidentified and allowed the development of additional systemic interventions through which largewaste sector changes towards ISWM may be achieved with relatively small inputs. The solid wastemanagement scene in Nairobi was also found to involve a combination of two systems archetypes asdefined by Braun (2002): a 'Success to the successful' trend of private waste collection relative to theCity Council, embedded within a larger 'Tragedy of the Commons' trend - the commons being thecity's economic, human, and natural capital; and implicitly its potential revenue base for collectionservice providers, whose tragic diminishing for all will be the inevitable result if the current operationand disposal practices of both the private collectors and the City Council continue. The interventionsproposed in the Nairobi ISWM Strategy (CCN & UNEP, 2010) were found to have targeted many ofthe fundamental causes leading to the current solid waste situation in Nairobi, due in part to thepartial use of systems analysis in their development by the author; additional insights were howevergenerated from the completed systems analysis discussed in this dissertation. These highlight a needfor the development of policy consistent with eight extra systemic interventions, six of which may beconsidered critical to the success of ISWM efforts in Nairobi.The latter focus on the potential of organic waste valorization to amplify Nairobi's material recyclingcapacity as a waste system driver towards ISWM revealed that there is a leakage of 14% to 23% of allwaste in the city due to organic waste degradation at open dumps or collection points. There is acurrent interest in the use of such organic wastes as animal feed in Nairobi City, and this userepresents a promising but seemingly under tapped organic waste valorisation potential that is likelyto gain in importance in future. Bulk compost production from organic waste is uneconomical underthe present market conditions in the city, and does not currently offer a rational option for the bulkvalorisation of organic wastes in Nairobi. The anaerobic digestion of organic waste for energyhowever shows potential to achieve radically improved organic waste valorisation levels in the city,and from techno-economic modelling undertaken of potential medium scale biogas-to-energy plantinvestments, seems feasible at the current biogas energy feed-in tariffs of 6 KShs/kWh (17-19 US Cents/kWh) and an organic waste tipping fee of KShs. l/kg organic wastetreated, is recommended to achieve more attractive investment payback periods of under five yearsfor especially private investors, and generally agrees with feed-in tarif
Open Access
An assessment of the potential for waste minimisation in small and medium enterprises in the South African metal finishing industry
(2000) Jänisch, Claire H; Von Blottnitz, Harro
The metal finishing industry has previously been found to be one of the most polluting industries of the manufacturing sector in South Africa. South African environmental legislation has recently (1998) been updated. The National Waste Management Strategy (NWMS), has clearly identified waste minimisation as an important part of future programs aimed at making waste handling practices in South Africa more sustainable. The waste minimisation approach has been applied in several countries in various industry sectors, including the metal finishing industry.
Open Access
A comparison of technical and environmental merits of producing bio-ethanol and bio-methane from waste paper sludge
(2012) Dalwai, Ilhaam; Von Blottnitz, Harro
The pressing need for alternative methods of waste management in developing countries has led to increased interest in energy recovery from waste. However, owing to the high proportion of wet organic waste, it will be necessary to take material-specific approaches going beyond bulk incineration. Life Cycle Assessments (LCAs) have shown that there is a large potential in bio-energy production from waste papers and cellulosic waste sludge, however, it is still unclear whether it would be more feasible to convert the mostly wet non-recyclable waste paper to bio-methane or to bio-ethanol. The primary objective of this study was to evaluate the technical and environmental feasibility of converting waste paper sludge to bio-ethanol and bio-methane for application as a vehicle fuel or for the generation of electricity. The focus of this study was on the conversion of waste paper sludge (WPS) in particular, which is generally sent directly to landfill and rarely treated.
Open Access
Contributions of a minerals industry cluster to sustainable development: A case study on human and social capital in Richards Bay, South Africa
(2017) Kato, Shuhei; Von Blottnitz, Harro; Black, Anthony
The South African economy has developed with its strong connection to the minerals extraction and processing industries. Rich endowments of coal and a well-established mining sector in the country enabled the generation and supply of competitively priced electricity to energy and capital intensive processing and chemical industries. Although the minerals industry cluster remains globally competitive at the present time, whether it can be a catalyst for sustainable development, economically, socially and environmentally is in question. Field work was carried out in Richards Bay to analyse the development contributions of the local aluminium industry cluster in terms of two of the five capitals essential for sustainable development, viz. human and social capital. This town is the host of world class aluminium smelters as well as mineral sands mining and smelting, amongst other energy intensive industries such as paper pulp and phosphate production. The analysis interrogates the importance of skills development and of collective action between various stakeholders centred on the Hillside smelter of South 32, and including interviews with representatives of ten further stakeholders. Evidence found shows that the minerals industry cluster has contributed to human capital development, and continues to do so, through well-established in-house training and mentorship programmes as well as their corporate social investment into enterprise and supplier development, education and primary health care. However, a more competitive and environmentally responsible industrial cluster would require continuous improvement through institutional and individual capabilities. Research and training institutions and government intervention have important roles to play in this regard. One of the major challenges is rooted in the lack of social capital development in the past. Although no single accepted definition nor standard for measuring exists, social capital can be defined as the norms and networks that enable people to act collectively. The racially segregated development pattern in the region had left residents with huge disparities and a trust deficit. This mitigated against collective actions within the community except in the few cases of natural disaster responses and crime prevention. This is evidenced in the free-riding of skilled labourers by some companies in the region and the failure of socio-economic development programmes in the past due to the low level of community buy-in. The research highlights that the significance of the local minerals industry cluster remains undoubtedly high; however, a facilitative process of social capital development is necessary to promote collective actions. The process requires accountable formal institutions who can mitigate social distrust, create dialogue and a cooperative environment between different interest groups. This is particularly important as the government resource-based industrialisation policy is centralised in developing linkages from extractive sector (downstream, upstream, and side-stream) but little attention has been paid to the aspect of social capital development. It is expected that the study itself contributes to social capital development and works as a communication platform to further promote studies in applying multidisciplinary learning-by-doing process across academia, policymakers, and practitioners.
Open Access
Creative deployment of technology in urban planning for sustainable energy use and supply in a south-north comparison
(2007) Nissing, Christian; Von Blottnitz, Harro; Heil, Jürgen
Includes bibliographical references (p. 297-324).
Open Access
Developing minerals beneficiation flowsheets for eco-efficiency : a systems approach
(2010) Guma, Mondli; Von Blottnitz, Harro; Broadhurst, Jennifer Lee
Eco-efficiency has been proposed by the World Business Council for Sustainable Development as a performance indicator framework that contributes to sustainability by assisting corporate decision makers improve the environmental performance of their operations and processes, while also extracting additional economic value. Given the emergent importance of eco-efficiency within the business community and the urgency with which environmental impacts generated by the minerals industry need to be mitigated, it becomes apparent that there is a need to assess whether eco-efficiency indicators can drive environmental sustainability performance improvement during process design within the minerals industry. This thesis aims to respond to this research need by assessing the strengths and limitations of eco-efficiency indicators as performance metrics in guiding decision making during minerals process design in the interests of environmental sustainability. The ultimate aim of this thesis is to contribute towards improved guidance for process design engineers in the selection of the appropriate tools for more environmentally sustainable design of minerals beneficiation processes.
Open Access
Development of a rapid laboratory predictive test method using fluidised bed techniques for the determination of oxidisability of residual CR (III) present in slags
(2006) Maidza, Teboho; Von Blottnitz, Harro
Slag arising from smelting in the production of ferrochrome alloys, stainless steel andPlatinum group metals (PGM) is known to contain residual chromium in variousphases within the slag matrix. Although the bulk of slag ends up on landfills, slag isused in the construction, agriculture and marine industry among others. Applicationsfor slag include as an aggregate in road construction and paving, buttressing, and as asource of lime in agriculture. Previous studies have shown that about 0.1-1 % of residual Cr(III) in slags with CaO/Si02 ratios greater than 2 can be slowly converted to a toxic and water-soluble hexavalent species in the presence of atmospheric oxygen, at ambient temperaturesalbeit at very slow rates. The produced Cr(VI) is potentially able to leach intounderground waterways and terrestrial water bodies, thus posing an environmentalhazard. In a landfill scenario, the oxidation kinetics are likely to be limited by the externaldiffusion resistance of the bulk of the landfill and the internal diffusion limitations tothe reactive phases within individual particles where CaO and Cr20 3 phases are inintimate contact. Earlier studies have also shown that the conversion of Cr(Ill) toCr(VI) in an ambient atmosphere increases, as the particle size decreases, with an increase in CaO and in the presence of moisture.
Open Access
Environmental and social dimensions of fuel ethanol production in Cradock, South Africa, in the context of the wider biofuels debate
(2013) Nasterlack, Tobias; Wynberg, Rachel; Von Blottnitz, Harro
Liquid biofuels are fossil fuel replacements in the form of fuel ethanol and biodiesel. Advocates of biofuels highlight their potential to mitigate climate change from reduced greenhouse gas emissions and socio-economic benefits for countries that achieve a higher degree of self-reliant energy supply. Critics emphasise social drawbacks from biofuel production and suggest that crop-based biofuels could jeopardise food security. The cultivation of biofuel feedstock has furthermore been reported to promote agricultural expansion and thus pose threats to biodiversity. Intense agricultural practices, coupled with land transformation, have also led to question as to whether or not biofuels reduce the carbon footprint of transportation fuels. The South African government established a biofuels strategy in 2007. Besides having declared self-imposed renewable fuel targets, the policy paper encourages the participation of black people in this emerging industry. The proposed fuel ethanol plant in Cradock, Eastern Cape, is likely to be the first operational bioethanol project in the country. As one of the first biofuels-related Black Economic Empowerment (BEE) programmes, 25 Cradock farms have already been purchased and allocated to black emerging farmers. The intention of this initiative is to enable part of the ethanol plant feedstock to be produced by these emerging farmers. The present dissertation aims to determine the magnitude and relevance of concerns highlighted in the global biofuels debate for fuel ethanol production at the proposed Cradock plant. This incorporates environmental impacts from agriculture, greenhouse gas emissions during the biofuel production chain, food security impacts, and the performance of socially equitable development. A total of 44 face-to-face interviews were held, comprising 22 commercial farmers, 12 emerging farmers, and representatives from the governmental, commercial and research sectors. The interviewees were questioned on the various socioeconomic, environmental and agricultural aspects of the Cradock fuel ethanol project. The inputs of the interviewees were complemented with descriptive statistics on food production, fertiliser and water use, biome maps and a life-cycle assessment of the carbon footprint of the biofuel that will be produced in Cradock.
Open Access
An environmental assessment of recycling options for used lubricating oil in South Africa
(2000) Rwodzi, Bryne; Von Blottnitz, Harro
A study carried out with the aim of overcoming the limitations of of current strategies for used oil management in the country is presented in this thesis. The goal of the study was to develop a Life Cycle Assessment (LCA) based tool for comparing and evaluating the environmental performance of selected used oil management scenarios in South Africa. The LCA based tool presented a broad based strategy for used oil management which not only compares two different options but which can predict the performance of a recycling option within the context of the entire lube oil manufacturing, use and re-use systems.
Open Access
An experimental investigation of leachate generation predictions of waste from copper sulphide ore processing
(2006) Maluleke, Wisani J; Von Blottnitz, Harro
The greatest environmental liability in the mineal processing industry is the prolonged environmental degredation of groundwater and land, resulting from Acid Mine Drainage (AMD) formation from mine wastes due to oxidation of sulphide minerals. AMD enhances the mobilisation of trace and minor metals contained in wastes, therby generating contaminated leachate, which may pollute the ground and surface water. It is imperative to minimise post-closure environmental impacts and liability associated with the long-term generation and dispersion of contaminated leachate from solid mien deposits. Therefore, prediction of the environmental aspects associated with soild mineral waste is essential to their effective management during all phases of a project life cycle including post-closure.
Open Access
Flows and fates of nickel-cadmium batteries in the City of Cape Town
(2009) Mason-Jones, Kyle; Von Blottnitz, Harro
Current patterns of economic activity entail high rates of material extraction from the natural environment and the generation of large amounts of waste. Alternative strategies must be found if we are to avoid the exhaustion of resources and the environment's capacity to safely absorb our wastes. Examining current resource use is an important step towards achieving a more sustainable society, and the toxic substances widely applied in our technologies form a crucial part of this examination. The heavy metal cadmium is one such substance. The use and disposal of nickel-cadmium secondary cells (the basic components of NiCd batteries) in Cape Town, South Africa, has been investigated with the objective of quantifying the associated flows of cadmium. This was achieved by applying substance flow analysis methodology to the year 2005 with a steady-state approach to quantify the disposal commitment arising from inflows in that year. Uncertainty in the calculated results was quantified by means of Monte Carlo simulation. Small sealed cells were found to make the dominant contribution to overall cadmium flows, with cordless power tools and separately imported cells accounting for most of these. Essentially all of these cells either have or will enter the municipal solid waste streams of the city. Large industrial cells made a smaller but significant contribution to overall inflows (3.4-14%), but none were known to have entered municipal waste. These went primarily to hazardous waste disposal outside the city or recycling abroad, with some going into storage. In order to assess the environmental significance of the cadmium sent to landfill, hypothetical "best worst-case" scenarios were developed which involved the worst case of total cadmium release from landfill, and best-case calculations of the potential contamination of agricultural land that could result from such release. A total release to agriculture was found to contaminate the city's croplands in under twenty years. Although these scenarios considered contamination potential but not the likelihood of contamination, and hence were not predictive, it could nevertheless be concluded that the amounts of cadmium destined for landfill disposal justified concern and caution. The disposal of environmentally significant amounts of cadmium in Cape Town and the very limited understanding of landfill behaviour necessitate the elimination ofNiCd batteries from municipal solid waste streams. Some approaches are briefly discussed by which this might be achieved, with regard to both environmental protection and resource conservation in general and the changing landscape of waste management in South Africa. Significant challenges were encountered from limited data availability during the application of substance flow analysis within a developing-world urban setting. This necessitated primary data collection and adaptation of data from other geographical and temporal scales. Adjusting national data to the city scale required the development of scaling factors which were more plausible than the use of population share or regional GDP Some similarities were noted between the cadmium metabolism of Cape Town and that of previously studied regions in the developed world. This supported the suggestion that some insights from substance flow analysis studies can be transferred to other regions when resources are not available for thorough local study. Important differences were also present, however, and further research is required to develop this possibility.
Open Access
Greenhouse gas intensity of South Africa's production and consumption : a study of the relationship between economic growth, income distribution and greenhouse gas emission in South Africa
(2013) Piaget, Stève Marc; Von Blottnitz, Harro
Includes abstract. Includes bibliographical references.
Open Access
Greenhouse gas mitigation cost of energy from biogas : a techno-economic analysis of co-digestion of three types of waste in Cape Town
(2011) Malla, Lesego; Hughes, Alison; Von Blottnitz, Harro
This paper investigates, in the context of Cape Town the emission reduction potential (ERP) of energy from biogas and related cost. Two project-scale models and a city-scale model were developed. Substrates for project model 1 were organic fraction of municipal solid waste (OFMSW) and primary sludge (PS) from sewage works. Project model 2 considered waste paper sludge (WPS) and PS. For the city-scale model, substrates for project model 1 were extended to include total amounts of OFMSW and PS generated in Cape Town. Financial results show that at the REFIT tariff model 1 would have a higher internal rate of return (20.5%) than model 2 (5.6%). The landfill ERP of the project-scale models is 98 600 CO2 equivalent tons per year, corresponding to a weighted average capital investment of R372 per CO2 equivalent ton saved in year 1. The results for the city-scale model indicate that a landfill ERP of 458 000 CO2 equivalent tons per year can be expected at an investment cost of R287 per CO2 equivalent ton saved in year 1. Energy emissions from fossil fuels at city-scale are most effectively mitigated if coal rather than other fossil fuel based power and heat generation are replaced.
Open Access
Hydrogen as an energy product from agriculturally produced sugars and starches in South Africa
(2008) Melamu, Rethabile; Von Blottnitz, Harro
Bio-fuels have a significant role to play in the South African energy economy. They have a potential to impact positively on the quality of life of a large number of people while providing environmental gains geared at addressing environmental challenges such as global warming. Technologies to produce bio-fuels are well established and processes mature, however energy yields are low to modest in relation to land used. More efficient technologies, the so called ‘second generation bio-fuels technologies’ are being developed in response to this challenge. On a parallel track, research to enable the ‘hydrogen economy’ is also being stimulated. This dissertation investigates the potential transfer of a ‘second generation bio-fuel technology’ developed elsewhere into the South African industry. The technology of interest is called Aqueous Phase Reforming (APR) and it is claimed to provide an efficient route for hydrogen production from intermediate process sugar streams.
Open Access
Identification of eco-efficient improvement opportunities in the industrial networks of small and medium-sized enterprises
(2000) Van Beers, Dick; Von Blottnitz, Harro; Raimondo, John
The central problem on which this Masters research project builds is the perceived limited ability of small and medium-sized enterprises (SMEs) in the South African manufacturing sector to improve their environmental performance on their own. Waste minimisation is a valid and proven tool for the identification of ways to reduce or eliminate wastes.
Open Access
An industrial ecology approach to salt-related environmental sustainability issues in a large industrial complex
(2011) Ras, Cornelia; Von Blottnitz, Harro
This thesis aims to demonstrate the application of industrial ecology (IE) theory to understand environmental sustainability problems relating to the accumulation of saline wastes and to study the potential for integrated technology interventions which take multi-party engagements and effects into account.
Open Access
Integrating bio-based resource recovery and treatment into municipal solid waste management in developing countries: a focus on anaerobic digestion
(2012) Munganga, Gracia; Von Blottnitz, Harro
Many authors, along with the United Nations Environment Programme (UNEP), argue that biological treatments such as anaerobic digestion (AD) and composting would be suitable in developing cities due the highly organic nature of their waste. AD entails the degradation of organic substances in the absence of oxygen, and its main products are CH 4-rich biogas and the remaining sludge. AD occurs in four main phases (hydrolysis, acidogenesis, acetogenesis and methanogenesis) and is a complex process, where microbiological, biochemical and physico-chemical phenomena are closely linked. Although composting the organic fraction of MSW (OFMSW) has been the preferred treatment method due to the low economic costs and operative ease, the production of biogas - a renewable energy source - has now positioned AD as the more energy efficient process as opposed to composting which requires energy inputs. A clear identification and understanding of the different organic waste streams available, their respective biogas potential, the engineering considerations and process limitations are needed to ensure good performance of AD plants. Location-specific data on the behaviour of different organic wastes in AD are, however, scarce, particularly in Africa. This dissertation is an attempt to generate Africa-relevant engineering knowledge through laboratory scale experiments of AD of organic waste streams typically disposed off in landfills. The main objectives of this dissertation are to (i) investigate the suitability for treatment by AD of typical organic waste streams in MSW, and (ii) consider the interplay between the nature of the available wastes and the temporal evolution of various process parameters. Finally, this dissertation aims to make sound recommendations from the data generated, building a preliminary source of knowledge for waste management officials and independent entrepreneurs.
Open Access
An investigation into increased productivity of small scale anaerobic digesters by means of temperature management
(2018) Carolissen, Sanchez; Hughes, Alison; Von Blottnitz, Harro
The use of biological waste as a primary energy source for the production of biogas, by the process of anaerobic digestion, has been commonly used in the past by small communities and on a larger scale by waste water treatment plants. In the latter, the biogas is traditionally used for heating of the digesters in order to increase process performance. Smaller scale anaerobic digesters using food waste as a primary energy source for biogas production could be implemented for residences and restaurants. The biogas produced could be used for cooking and heating purposes. Whilst common designs for such smaller digesters do not provide for heating, there may be warm waste water on site to elevate the operating temperature and thus improve gas yield. This dissertation reports an experiment aimed at improving the performance of an existing anaerobic digester located at the Leo Marquard Hall (LMH) residence of the University of Cape Town. The 6 m³ digester has been operated using food waste as its sole substrate. The volume of gas produced is unknown as there are no gas measurement devices on site. In the past it has been roughly estimated from pressure readings before and after gas use. The digester operates at ambient temperature which averages 16 °C over the year, which is suboptimal. The anaerobic digester is not equipped with a temperature measurement device to monitor operating temperature. Two hypotheses were formulated and tested. The first stated that the temperature profile of the waste water leaving the LMH residence will have peaks in the morning and evening periods when the majority of students shower. The peak temperature periods will be in the morning before breakfast and in the evening after dinner. The temperature during these times is expected to be above 30 °C. In order to test the first hypothesis, a thermocouple with temperature data logger was installed to record the temperature of waste water in the manhole drain leaving the LMH residence. The temperature data recordings confirmed the temperature peak of waste water leaving LMH residence at an average temperature of 30.5 °C in the morning. However, a clear evening temperature peak was not identified. Thus the hypothesis was only true for the morning temperature peak of waste water leaving LMH residence for weekdays when lectures take place. The second hypothesis stated that, adding a portion of the 30 °C waste water into the LMH anaerobic digester will result in the digester running at 5 °C above the normal average operating temperature, and thus increase the productivity of the anaerobic digester. In order to test the second hypothesis the design and installation of a pumped pipe system was completed in order to pump waste water from the LMH residence waste water outlet manhole gravity sewer to the LMH anaerobic digester. By loading the LMH anaerobic digester with 600 ℓ of warm waste water, the maximum digester temperature increase obtained was 5 °C relative to the normal cold water operation. The maximum increases in total weekly biogas and methane production achieved were 238 % and 260 % respectively, relative to the average weekly cold water operation. The operating temperature of small scale anaerobic digesters is a very important factor for the performance of the anaerobic digester. This research shows that increasing the operating temperature of a small scale anaerobic digester by as little as 5 °C could double the performance of the anaerobic digester. The site location for the installation of small scale anaerobic digesters should be investigated at design stage by taking into consideration the operating temperature. The digester could be installed in close proximity to both an organic waste stream and warm waste water stream that could affect the feasibility of a particular project installation.
Open Access
An investigation of carbon footprint reductions achievable in Cape Town social housing considering rebound effects
(2012) Dick, Jasper; Von Blottnitz, Harro; Lewis, Yvonne
Various life cycle studies have shown that solar water heaters (SWHs) have short greenhouse gas emission payback periods. Thus, it is believed that replacing electric geysers with SWHs will reduce a household’s carbon footprint. It is also believed that living in a well-located area close to jobs, schools, shops and public transport will reduce a household’s carbon footprint through reducing fuel consumption via private/public transport. These conclusions, however, do not take the rebound effect into account, where money saved from spending less on electricity or transport, is spent eventually, either on more electricity and transport, or on other goods and services with an associated carbon footprint.