Papers by Sigrid Kusch-Brandt
Resources, Aug 2, 2019
the new edition of the annually updated Renewables Global Status Report (GSR) compiles the most r... more the new edition of the annually updated Renewables Global Status Report (GSR) compiles the most recent developments and trends in the adoption of renewable energies worldwide and in specific regions, countries and sectors. The report represents a rich resource for reliable and up-to-date information about individual renewable energy sources and their use. The analysis also covers a review of energy policies. Renewable energy policies still strongly concentrate on the power sector, while transport and heating and cooling are given less attention. Most investment in renewable energy today happens in developing and emerging countries, which is a major change to the situation some years ago. The 2019 edition of the GSR report includes a feature on renewable energy in cities, which highlights the importance of prioritising the urban context in order to achieve more sustainable schemes of energy supply and consumption. More than half of the global population today lives in cities, but around two-thirds of energy consumption happens in an urban environment. The GSR 2019 identifies that cities already are among the most active players in the adoption of renewable energies. One interesting finding is that in more than 100 cities worldwide at least 70% of the electricity already comes from renewables. This includes cities in both developed and developing countries.
Processes
Anaerobic digestion (AD) is a bio-based solution designed to convert organic materials into renew... more Anaerobic digestion (AD) is a bio-based solution designed to convert organic materials into renewable energy and other products, such as soil improver and organic fertiliser [...]
Environment, Development and Sustainability
Recycling of e-waste (waste electrical and electronic equipment) represents an important abatemen... more Recycling of e-waste (waste electrical and electronic equipment) represents an important abatement of pressure on the environment, but recycling rates are still low. This study builds on common environmental economics approaches to identify the main driving forces of the e-waste recycling rate. The environmental Kuznets curve hypothesis was applied in the context of the STIRPAT (stochastic impacts by regression on population, affluence and technology) model to analyze data from 30 European countries over the period 2008–2018. Panel quantile regression was conducted to determine the relationship between e-waste recycling rate and economic growth, population, population density, energy intensity, energy efficiency, credit to private sector and e-waste collected. Strong evidence was found that the relationship between economic growth and e-waste recycling rate is an N-shaped curve, i.e., the e-waste recycling rate first increases with economic growth, then decreases in maturing economi...
International Journal of Environmental Science and Technology, 2022
Previous studies have examined the relationship between total e-waste generation and its determin... more Previous studies have examined the relationship between total e-waste generation and its determinants. However, e-waste categories have not received appropriate attention, and thus important information is missing for policymakers. This paper advances the state of knowledge by studying e-waste categories individually. Statistical data of e-waste in the EU28 + 2 countries over the period 2000–2015 is disaggregated into single categories, namely temperature exchange equipment, screens and monitors, lamps, large equipment, small equipment, and small IT and telecommunication equipment. To examine the main driving forces of e-waste in each category, the STIRPAT model (Stochastic Impacts by Regression on Population, Affluence, and Technology) and the environmental Kuznets curve (EKC) hypothesis are applied, using panel quantile regression as main method and pooled OLS to control robustness of findings. Results show that population, renewable energy consumption, trade openness, and urbaniz...
Agriculture
Achieving high production with limited resources is a major challenge faced by poultry farmers in... more Achieving high production with limited resources is a major challenge faced by poultry farmers in countries with developing economies, such as Pakistan. Optimization of the technical efficiency (TE) of poultry business operations is a promising strategy. A representative sample of 210 poultry farms in the province of Punjab in Pakistan was analyzed for TE. The studied sample comprised 105 layer chicken farms (battery cage system, egg production) and 105 broiler chicken farms (environmental control shed system, meat production). A Cobb–Douglas stochastic frontier production analysis approach with the inefficiency effect model was used to simultaneously estimate TE levels and identify factors that influence efficiency. The results indicated that flock size, labor, feed, and water consumption are positively related to egg production, whereas vaccination was found to be insignificant. For broiler businesses, flock size, feed, and water consumption were positively related to the output, ...
it, 2012
It is difficult to compare the biogas yield of solid substrates from findings in literature becau... more It is difficult to compare the biogas yield of solid substrates from findings in literature because the substrate composition is rarely defined. This complicates not only the calculation of the potential biogas yield of a specific plant, but also the transferability of results to other sites and other countries (including municipal solid waste, source-segregated biowaste, agricultural residues). Based on a case example, an approach to solve this problem is presented and discussed. The studied anaerobic digestion plant is an innovative continuous two-phase two-stage prototype biogas plant operated with a mixture of excreta, straw and oat husks. The dry digestion concept, which is already widely applied to treat municipal solid waste, has demonstrated to also be suitable for this substrate type. Data obtained by this approach with looking at the individual fractions are potentially transferable to other sites. However, in substrate mixtures several factors may enhance both total methane yield and biogas production kinetics compared to digestion of single fractions.
Sustainability, 2018
Due to the ever-growing demand for natural resources, wastewater is being considered an alternati... more Due to the ever-growing demand for natural resources, wastewater is being considered an alternative source of water and potentially other resources. Using Qatar as an example, this study assesses the resources embodied in wastewater and paves the way to combine wastewater treatment with advanced resource recovery (water, energy, nitrogen, phosphorous, added value products) which can turn wastewater management from a major cost into a source of profit. In this sense, wastewater is no longer seen as a problem in need of a solution, rather it is part of the solution to challenges that societies are facing today. Based on estimated quantities of generated urban wastewater and its average composition, mass flow analysis is implemented to explore the maximum availability of major wastewater constituents (solids, organic compounds, nutrients, chloride, alkalinity, sulfide). An assessment analysis reveals that, in Qatar, more than 290,000 metric tons total solids, 77,000 metric tons organic...
Sustainable Production and Consumption
There is an urgent need to address interlinked sustainability issues in a world challenged by ine... more There is an urgent need to address interlinked sustainability issues in a world challenged by inequality, finite resources and unprecedented changes across Earth’s systems. As Future Earth Fellows, based on our collective expertise in a diverse range of sustainability issues, here we identify a specific need to recognise and respond appropriately to the nexus between human health and wellbeing, urbanisation, and ecosystem services (the ‘WUE nexus’). This nexus is a priority area for research, policy and practice. In particular, it provides a useful pathway to meet the challenges of successful implementation of the Sustainable Development Goals (SDGs). In this brief, we present the following policy recommendations: 1. By emphasising urban-rural linkages, foster an integrated approach to ensure food security, food safety, and health promotion; 2. Secure resilient livelihoods for all, in particular for vulnerable groups; and 3. Integrate co-production of knowledge in science for decisi...
Survey data for 'Estimating the Generation of Garden Waste in England and the Differences bet... more Survey data for 'Estimating the Generation of Garden Waste in England and the Differences between Rural and Urban Areas' Eades et al. 2020 DOI:10.3390/resources9010008
If valorisation strategies are implemented, horse manure is a valuable resource to be used as org... more If valorisation strategies are implemented, horse manure is a valuable resource to be used as organic soil amendment and for renewable energy generation. Huge amounts of equine residues are generated in the EU and elsewhere, most of which are currently considered as waste to be disposed of, which places an additional burden on the sector. Under a SWOT analysis perspective it becomes evident that one of the key challenges lies in the fact that horse manure varies widely with view to generated quantities and contents due to utilisation of different bedding materials and different management practices. This study further aims to evaluate the challenges related to valorisation of horse manure and to identify the most promising options. Anaerobic digestion and thermal treatment are currently the two key options that hold potential for more widespread implementation of bioenergy generation in practice. Keywordshorse manure; horse dung; equine residues; bioenergy
Cogeneration power plants simultaneously generate power and usable heat in a single, integrated s... more Cogeneration power plants simultaneously generate power and usable heat in a single, integrated system, which achieves a degree of overall efficiency that is much greater compared to electricity production alone. This makes better use of energy conversion and reduces greenhouse gas emissions. Combined heat and power production is already relatively common in Europe while it is less common, for example, in the USA. There is great potential for further implementation throughout Europe and worldwide, including in the industrial sector. Major challenges are the short potential distances for the transport of heat and the fact that consumers’ heat demands vary in quantity, mainly due to seasonal effects, and in quality as different applications require different temperature levels. Cleaner production schemes offer suitable frameworks to foster uptake of combined heat and power production by industry, in particular by small and medium sized enterprises.
There is an urgent need to address interlinked sustainability issues in a world challenged by ine... more There is an urgent need to address interlinked sustainability issues in a world challenged by inequality, finite resources and unprecedented changes across Earth’s systems. As Future Earth Fellows, based on our collective expertise in a diverse range of sustainability issues, here we identify a specific need to recognise and respond appropriately to the nexus between human health and wellbeing, urbanisation, and ecosystem services (the ‘WUE nexus’). This nexus is a priority area for research, policy and practice. In particular, it provides a useful pathway to meet the challenges of successful implementation of the Sustainable Development Goals (SDGs). In this brief, we present the following policy recommendations: 1. By emphasising urban-rural linkages, foster an integrated approach to ensure food security, food safety, and health promotion; 2. Secure resilient livelihoods for all, in particular for vulnerable groups; and 3. Integrate co-production of knowledge in science for decisi...
Through this assessment, the authors and the United Nations Environment Programme (UNEP) secretar... more Through this assessment, the authors and the United Nations Environment Programme (UNEP) secretariat are providing an objective evaluation and analysis of the pan-European environment designed to support environmental decision-making at multiple scales. In this assessment, the judgement of experts is applied to existing knowledge to provide scientifically credible answers to policy-relevant questions. These questions include, but are not limited to the following: • What is happening to the environment in the pan-European region and why? • What are the consequences for the environment and the human population in the pan-European region? • What is being done and how effective is it? • What are the prospects for the environment in the future? • What actions could be taken to achieve a more sustainable future?
Resources, 2019
While it is well known that particle size reduction impacts the performance of bioprocessing such... more While it is well known that particle size reduction impacts the performance of bioprocessing such as anaerobic digestion or composting, there is a relative lack of knowledge about particle size distribution (PSD) in pre-treated organic material, i.e., the distribution of particles across different size ranges. PSD in municipal solid waste (MSW) pre-treated for bioprocessing in mechanical–biological treatment (MBT) was researched. In the first part of this study, the PSD in pre-treated waste at two full-scale MBT plants in the UK was determined. The main part of the study consisted of experimental trials to reduce particle sizes in MSW destined for bioprocessing and to explore the obtained PSD patterns. Shredders and a macerating grinder were used. For shear shredders, a jaw opening of 20 mm was found favourable for effective reduction of particle sizes, while a smaller jaw opening rather compressed the wet organic waste into balls. Setting the shredder jaw opening to 20 mm does not ...
Separate collection of food waste from households is an efficient instrument for diversion of org... more Separate collection of food waste from households is an efficient instrument for diversion of organic material from landfill to biological treatment. There is widespread consensus that source-segregated food waste is a suitable substrate for valorisation through anaerobic digestion with biogas production. Source-segregation concepts are adopted by more and more municipalities in European countries and elsewhere. Food waste can be collected in separate food waste collection units or together with other organic materials. Based on a campaign of sorting seperatly collected materials in four European countries, along with physico-chemical analyses, the present manuscript is aimed at providing an overview of differences and similarities in food wastes enterenting the respective source segregation stream. Factors related to suitability of materials for anaerobic digestion are discussed.
Processes
The combination of a post-Brexit agricultural policy, the Global Methane Pledge announced during ... more The combination of a post-Brexit agricultural policy, the Global Methane Pledge announced during the last United Nations Climate Change Conference in Glasgow (COP26), and urgency of meeting climate goals means the UK has a unique opportunity to create an exemplar through recognition of the benefits of small-scale farm anaerobic digesters that valorise on-site wastes for renewable electricity and heat, cushioning agri-businesses against energy perturbations. To explore economic viability of farm-based biogas production, combinations of support levels, energy prices, capital cost, internal rate of return (IRR), and digestate value were analysed, employing a 550-cow dairy farm with access to other agricultural wastes. A 145 kWe system utilising 100% of CHP electricity (grid value: £0.1361 per kWh) and 70% of the heat (heating oil value: £0.055 per kWh) could achieve an IRR above 15.5% with a median electricity tariff of £0.1104 per kWh at a heat tariff from £0.0309 to £0.0873 per kWh t...
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Papers by Sigrid Kusch-Brandt
• What is happening to the environment in the pan-European region and why?
• What are the consequences for the environment and the human population in the pan-European region?
• What is being done and how effective is it?
• What are the prospects for the environment in the future?
• What actions could be taken to achieve a more sustainable future?
Experiments in laboratory-scale batch reactors and at a full-scale farm plant were conducted. Based on the experimental findings, suitable fields of application for the solid-phase digestion in this simple reactor type were identified, as were appropriate process conditions and problematic aspects. This may allow for more sustainable decisions in support of, or against, the use of such a process type during the planning of new biogas plants in the future. Moreover, possibilities to optimize process operation are discussed.
The experimental results show that, if process conditions are optimal, digestion of solid substrates in discontinuous solid-phase systems with percolation can achieve substrate specific methane yields that are comparable to those in common, slurrybased liquid-phase digestion installations. A higher risk of inactive zones with inhibited biodegradation was, however, observed at farm-scale. This may be explained as result of lack of mixing during fermentation and due to inhomogeneous conditions over the substrate stack height.
Homogeneous decomposition of stacked solids requires optimally preconditioned substrate. In order to avoid digester failure resulting from acidification by accumulation of volatile fatty acids, the microbial community should contain sufficient levels of methanogens during start-up. Therefore, in the percolation process fresh material should be mixed with solid inoculum (already digested substrate). The appropriate ratio of inoculum highly depends on the specific substrate characteristics and varies considerably. A proportion of around 20 % (w/w on a TS-basis) solid inoculum was sufficient for materials with slow degradability, such as municipal green cut or horse dung with straw. But easily degradable substrates such as ensiled maize or ensiled grass required up to 70 % inoculum. Further experimental results demonstrate that fractions should be carefully mixed prior to being filled in the reactor. A high degree of homogeneity within the stacked substrate body minimizes the risk of inactive zones. This not only ensures high methane yields, but it also prevents discharge of material that has only partly degraded.
The successful implementation of processes with percolation necessitates that liquid actually trickles through the whole substrate stack. Therefore, process water with low viscosity must be used as should substrate with sufficient structure. Materials with poor structure should be mixed with structure material, e.g. straw or green cut. Liquid manure (slurry) is not suitable for percolation, as it will not ensure a leachate flow through solid biomass.
Choosing one process type among several alternative systems should depend on the specific characteristics of the available materials. Easily hydrolysable biomasses with high energy density, e.g. ensiled maize or grass, are especially suitable for continuous digestion. For discontinuous digestion with percolation, structure-rich biomass, e.g. green cut or solid dung, is especially advantageous choice when considering process technology. Fibrous material, which in general is regarded as unsuitable for running a continuous digestion at elevated TS-contents, does not cause any problem in batch-operated solid-phase digestion with percolation. On the other hand, biogas production with such substrates is rather low. In order to maximize gas production per reactor volume, mixtures of fractions with high energy content and structure-rich fractions are advisable. Possible mixtures are maize with municipal green cut or with solid dung containing straw.
If biogas generation is envisaged exclusively with energy crops, continuously operated process alternatives should be given special consideration. Discontinuous digestion with percolation is not the optimal choice for such substrates due to their poor structure and the high inoculum proportion required. Especially for materials such as energy crops with high costs for cultivation and conservation, incomplete degradation may have critical effects on the profitability of a biogas plant. Therefore, compared to digestion of waste materials, special care should be taken so as to avoid inactive zones with inhibited degradation. Based on the experiments conducted, a mixture of 25 % (v/v) ensiled maize, 15 % green cut with woody components and 60 % solid inoculum is recommended for six-week cycles. This achieves a mean methane generation of around 0.45 m³N CH4/(m³RV,netto*d) [norm cubic meters of methane per usable reactor volume and day]. Using ensiled grass, a mixture of 50 % (v/v) silage, 10 % green cut with woody components and 40 % solid inoculum is advisable for six-week cycles and results in slightly lower methane generation than the abovementioned mixture with ensiled maize. With grass however, ammonia will accumulate in the recycled process water and will reach inhibitory levels quite quickly; therefore process water must be partly exchanged with fresh water.
In systems with several solid-phase digesters that are functionally coupled through the recirculated liquid phase (leachate collected from all reactors and reused for percolation of all reactors), gas production from one fermenter cannot be assessed with precision. Organic material is partly washed out from the substrate stack and metabolized either in the liquid tank or in other solid-phase digesters. Only part of the total methane production actually occurs in the substrate itself. Moreover, liquefied organic matter from other fermenters is poured in with the recirculated process water and mineralized in the biomass bed. Especially with easily degradable substrate, significant proportions of the total organic matter will be washed out from the stacked biomass. In experiments with ensiled maize, up to 2/3 of the total methane production occurred outside the actual substrate stack (in the percolate tank and in other solidphase digesters).
Gas from the percolate tank must be collected. Particularly when easily hydrolysable substrate is used, gas production in the process water tank can be considerably high. In experiments, > 10 % of the total methane production was measured in the exterior process water tank. Increasing the maize proportion in the substrate resulted in higher methane generation in the exterior percolate tank of up to 21 % of the total methane production.
The intensity of percolation influences methanisation in the biomass bed. Discontinuous process water recirculation encourages biogas production in the biomass bed itself. If a sufficient ratio of solid inoculum is added, intensified percolation will not achieve any advantage. Continuous percolation will rather enhance hydrolysation and acid generation, but it will not accelerate the development of the methanogenic population.
Compared to percolated systems, flooding the solid substrate with process water can both reduce and increase the risk of acidification, depending on individual substrate characteristics. Flooding seems to encourage hydrolysis and acid generation rather than methanogenesis, which might increase acidification risk for easily hydrolysable material. Since generated acids are diluted due to the higher ratio of liquid volume to solid material, the risk of acidification can also decrease. With slowly degradable substrate (horse dung, municipal green cut) no addition of solid inoculum was necessary in the flooded process. Therefore, methane production per reactor volume was higher compared to the percolated process, although methane generation from the fresh material itself was not enhanced by flooding. Nevertheless, the flooded process is technically more sophisticated and also more time consuming. During digestion, floating of solid material must be controlled by appropriate technical equippment. Prior to discharging the reactor, phase-separation (liquid/solid phase) is necessary. The digestion residue can become pasty and handling is more difficult during and after discharge.
Discontinuous systems are more appropriate with smaller throughputs. In contrast to continuous systems, no process automation is possible. Moreover, the amount of effort and labour required is constantly increasing with higher numbers of digestion boxes. For each load around 5 to 6 hours are required to charge the fermenter. The volume of one reactor is limited; therefore for higher throughputs high numbers of digestion boxes would be necessary.
Although planned, no thermophilic process was possible at the full-scale farm plant. Even in the mesophilic range marked temperature fluctuations were observed. It may be assumed that compared to flooded digesters, thermal energy transport is more difficult as pores inside the substrate stack are partly filled with gas and not with liquid. Therefore, a mesophilic process should be implemented with this type of digestion system rather than a thermophilic process.