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Fire plays an important role in the earth system by influencing ecosystems and climate, but climate in turn also influences fire. The system became more complex when humans started using fire as a tool. Understanding the interaction between humans, fire and climate is the major aim of paleofire research. Understanding changes in these three aspects in the past will help predicting future climate, fire and human interactions. The use of lake sediment cores as natural archives for reconstructing past fire activity by counting charcoal particles is well established. This present dissertation is dedicated to the evaluation and application of specific organic molecular markers for biomass burning: levoglucosan, mannosan and galactosan were used as proxies for reconstructing past fire activity in lake sediments thorough the entire Holocene. First, a new analytical method was developed using high-performance anion exchange chromatography combined with mass spectrometry to separate and detect these three monosaccharide anhydrides in lake sediments. The suitability of this analytical method was proven by comparing the levoglucosan, mannosan and galactosan results in selected lake sediment samples from Lake Kirkpatrick, New Zealand and by correlating the results with macroscopic charcoal. Furthermore, the method was successfully applied to a lake sediment core from Lake Petén Itzá, Guatemala to reconstruct regional Holocene fire history. The analyses of levoglucosan were combined with fecal sterols to reconstruct late Holocene human fire interactions at Lake Trasimeno, Italy, demonstrating low fire activity during the Roman period. This combination of studies proves that these molecular markers are valid fire proxies in sediments from multiple locations around the globe. Comparison of levoglucosan, mannosan and galactosan concentrations with macroscopic charcoal trends in Lake Kirkpatrick and Lake Petén Itzá, suggests that the molecular markers represent more regional fire history and low temperature fires in contrast to macroscopic charcoal, which is a local fire proxy. In addition, vegetation changes (Lake Kirkpatrick and Lake Petén Itzá) and charcoal morphotypes (Lake Petén Itzá) were compared to the levoglucosan/mannosan and levoglucosan/(mannosan+galactosan) ratios suggesting that these ratios may be a suitable tool to track burned fuel. Biodegradation tests demonstrate the potential degradation of levoglucosan, mannosan and galactosan if dissolved in water, but findings in ancient sediment samples suggest that particle-bound levoglucosan, mannosan and galactosan can be buried in sediments over millennial time scales. Although uncertainties still exist, the results of this research suggests that organic molecular markers are a suitable regional fire proxy and isomer ratios may help understand changes in burned vegetation.
Achieving the ‘Great Transformation’ demands a closer consideration of the material basis of technologies, whose broad-scale implementation is often associated with efficiency improvements and progress towards a post-fossil society, but which is largely disregarded as of today. At the same time, the discourse on resource-related issues only rarely evolves around achieving an actual fundamental shift towards sustainability in the sense of a ‘material transition’. The notion of this mutual disconnect – a ‘transformation-material gap’ that exists in both research and practice – is the main driver for this dissertation. Metals fulfill crucial functions in areas as diverse as renewable energy, digitization and life style appliances such as smart home concepts, mobility, communication, or medicine. In the context of sustainability, achieving a more sustainable metal use means (i) minimizing the adverse effects associated with metal production and use and (ii) sustaining the availability of metals in a way that benefits present and future generations. Urgent need to act to avoid bottlenecks as well as meeting the challenge of possible conflicts of use among those areas of application calls for appropriate strategy making to intervene in the complex field of metal production and use that involves various, often interlinked operating levels, actors, and spatial and temporal scales. Located within the field of sustainability science, this dissertation focuses on strategies as a means to intervene in a system. It pursues the question, which design features could guide future strategy making to foster sustainability along the whole metal life cycle, and especially, how a better understanding of temporalities – i.e. understanding time in a diverse sense – could improve strategy design and help to bridge the assumed ‘transformation-material gap’. My research converges the results from four research studies. A conceptual part explores the role of temporalities for interventions in complex and interlinked systems, which adds to the conceptual basis, on which the empirical part builds up to explore present and future interventions in metal production and use. The research revealed three essential needs that future strategies must tackle: (i) managing the complex interlinkages of processes and activities on various operational levels and spatial and temporal scales, (ii) providing clear guidance concerning the operationalization of sustainability principles, and (iii) keeping activities within the planet’s carrying capacity and embracing constant change as an inherent system characteristic. In response to these needs, I developed three guidelines with two design features each (one relating to content, and one to the process of formulating and implementing the strategy) to guide future strategy making: 1. Design strategies based on a profound understanding of the system and its interrelations, but bear in mind context-specific characteristics. (Comprehensive, but tailored.) 2. Design strategies to achieve fundamental change in a cooperative and inclusive manner. (Ambitious, but manageable.) 3. Design strategies to strengthen resilience in a constantly changing environment. (Dynamic, but consistent.) My results show that TIME MATTERS in this respect. If considered in close relation to space and diversely understood in the sense of temporalities, it serves to (i) understand the impact (duration and magnitude) of an intervention, (ii) recognize patterns of change that go beyond establishing linear, one-dimensional connections, and (iii) design interventions in a way that considers the resilience of a system. While these findings can contribute to closer considering our understanding of transformation processes towards sustainability in future interventions in metal production and use, more research is needed on approaches that bring the material basis into closer consideration of transformation processes in research and practice.
As modern society progresses, waste treatment becomes a pressing issue. Not only are global waste amounts increasing, but there is also an unmet demand for sustainable materials (e.g. bioplastics). By identifying and developing processes, which efficiently treat waste while simultaneously generating sustainable materials, potentially both these issues might be alleviated. Following this line of thought, this dissertation focuses on procedures for treatment of the organic fraction of waste. Organic waste is a suitable starting material for microbial fermentation, where carbohydrates are converted to smaller molecules, such as ethanol, acetic acid, and lactic acid. Being the monomer of the thermoplastic poly-lactic acid, lactic acid is of particular interest with regard to bioplastics production and was selected as target compound for this dissertation. Organic waste acted as substrate for non-sterile batch and continuous fermentations. Fermentations were initiated with inoculum of Streptococcus sp. or with indigenous consortium alone. During batch mode, concentration, yield, and productivity reached maximum values of 50 g L−1, 63%, and 2.93 g L−1 h −1. During continuous operation at a dilution rate of 0.44 d−1, concentration and yield were increased to 69 g L−1 and 86%, respectively, while productivity was lowered to 1.27 g L−1 h −1 . To fully exploit the nutrients present in organic waste, phosphate recovery was analyzed using seashells as adsorbent. Furthermore, the pattern of the indigenous consortium was monitored. Evidently, a very efficient Enterococcus strain tended to dominate the indigenous consortium during fermentation. The isolation and cultivation of this consortium gave a very potent inoculum. In comparison to the non-inoculated fermentation of a different organic waste batch, addition of this inoculum lead to an improved fermentation performance. Lactic acid yield, concentration, and molar selectivity could be increased from 38% to 51%, 49 g L−1 to 65 g L−1, and 46% to 86%, respectively. Eventually, fermentation process data was used to perform techno-economic analysis proposing a waste treatment plant with different catchment area sizes ranging from 50,000 to 1,000,000 people. Economically profitable scenarios for both batch and continuous operation could be identified for a community with as few as 100,000 inhabitants. With the experimental data, as well as techno-economic calculations presented in this dissertation, a profound contribution to sustainable waste treatment and material production was made.
