Abstract: The quantities of e-waste are expected to increase sharply in Chile. The purpose of this paper is to provide a quantitative data basis on generated e-waste quantities. A material flow analysis was carried out assessing the generation of e-waste from computer equipment (desktop and laptop PCs as well as CRT and LCD-monitors). Import and sales data were collected from the Chilean Customs database as well as from publications by the International Data Corporation. A survey was conducted to determine consumers' choices with respect to storage, re-use and disposal of computer equipment. The generation of e-waste was assessed in a baseline as well as upper and lower scenarios until 2020. The results for the baseline scenario show that about 10,000 and 20,000tons of computer waste may be generated in the years 2010 and 2020, respectively. The cumulative e-waste generation will be four to five times higher in the upcoming decade (2010-2019) than during the current decade (2000-2009). By 2020, the shares of LCD-monitors and laptops will increase more rapidly replacing other e-waste including the CRT-monitors. The model also shows the principal flows of computer equipment from production and sale to recycling and disposal. The re-use of computer equipment plays an important role in Chile. An appropriate recycling scheme will have to be introduced to provide adequate solutions for the growing rate of e-waste generation.
Abstract: Bioenergy from woodfuel has a considerable potential to substitute fossil fuels and alleviate global xD;warming. One issue so far not systematically addressed is the question of the optimal size of bioenergy plants xD;with regards to environmental and economic performance. The aim of this work is to fill this gap by modeling xD;the entire production chain of wood and its conversion to bioenergy in a synthetic natural gas plant both with xD;respect to economic and environmental performance. Several spatially explicit submodels for the availability, xD;harvest, transportation and conversion of wood were built and joined in a multi-objective optimization model to xD;determine optimal plant sizes for any desired weighting of environmental impacts and profits. xD;We find a trade-off between environmental and economic optimal plant sizes. While the economic optima range xD;between 75 â 200 MW, the environmental optima are with 10 â 40 MW significantly smaller. Moreover, the xD;economic optima are highly location specific and tend to be smaller if the biomass resource in the geographic xD;region of the plant is scarcer. The results are robust with regards to the effect on global warming as well as with xD;respect to the aggregated environmental impact assessment methods Ecoindicator â99 and Ecological Scarcity xD;2006.
Abstract: This thesis addresses the availability and environmentally optimal use of bioenergy. A life cycle per-spective is adopted to consider the supply, the technical conversion, and the final use of bioenergy as well as its use for the substitution of fossil energy. In order to determine the sustainable energetic biomass potential in Switzerland, which is the geographic focus of this thesis, a bioenergy potential assessment is conducted using a sustainability constraints approach. Life cycle assessment (LCA) is performed to analyse the suitability of the conversion of wood to synthetic natural gas (SNG). Howev-er, individual technology LCAs are not sufficient to provide answers to the question of âhow energeti-cally available biomass resources can be used optimally for bioenergy from an environmental perspectiveâ. Instead, more comprehensive trans-sectoral assessments are required including all relevant bioenergy technologies and end-uses, as well as fossil energy technologies that can be substituted. To enable such analyses, an LCA-based system optimization (LCA-SO) framework is developed and applied to the Swiss and European cases. Finally, also spatial aspects need to be considered to determine optimal plant sizes. Therefore, a spatially explicit bioenergy value chain model was developed for the case of SNG plants in Switzerland.
One of the main findings of this thesis is that 82 PJ of biomass is available in Switzerland, which cor-responds to approximately 7% of its primary energy demand. Half of this potential has yet to be real-ized. By 2035, when optimally used in the business as usual scenario defined by the Swiss Energy Perspectives, biomass could mitigate about 5 megatons of CO2, which would be equal to 13% of Switzerlandâs total emissions. Simultaneously, the demand of fossil energy for heat, electricity, and transportation would be reduced by 13%, 3%, and 2%, respectively. In the European Reference Scenario (2030) 9%, 13%, and 1%, respectively, of fossil heat, electricity, and transportation could be replaced and 600 Mt of CO2, equal to about 15% of the EUâs total emissions, could be avoided.
To achieve these goals, woody biomass should be used mainly for heating and combined heat and power (CHP) generation. The production of SNG from wood to substitute fossil energy has been found environmentally beneficial from the GHG, Ecological Scarcity, and Eco-indicator 99 perspectives. However, the production of transportation fuel from woody biomass is, at the current technological development state, associated with important efficiency losses and is therefore not considered an optimal solution. For non-woody biomass (by which we refer to agricultural residues, manure, bio- and food industry wastes, and sewage sludge) the optimal use is to a large degree determined by the substitution of fossil energy and varies according to the environmental indicator applied. For all biomass, it is vital that a high substitution efficiency is achieved, which implies an efficient conversion of biomass and the choice of optimal substitutions.
Finally, the spatially explicit bioenergy modelling conducted in this work indicates that smaller bioenergy plant sizes are slightly preferable in terms of overall environmental benefits, mainly due to reduced transportation distances. However, further analyses would be required to generalise this finding.
