Alternative fuels for gas turbines: A consequential LCA for electricity generation in 2020

This master's project focuses on a LCA assessment of alternative fuels in disperse geographical locations for electricity generation through a gas turbine in 2020. Indeed, by then, the industrial partner's gas turbine technology should have the ability to burn these different fuels efficiently. The study's main objective is therefore to determine the location and alternative fuel types that should be used to operate the gas turbine, considering environmental impacts and market feasibility and according to the industrial partner's guidelines.;In order to achieve the main objective, the first task was to determine the geographical context and feedstock with the most potential for future supply and technical feasibility based on the alternative fuels and industrial partner's guidelines. The literature on the bioenergy market was therefore assessed, and several recurring important factors were taken into account, including the bioenergy policies in the assessed regions, feedstock supply and availability, the state of the art and current and projected fuel production volumes and costs (Smeets et al., 2007). In the end, the following scenarios were found to have future potential supply: syngas from forest residues and biogas from manure in Germany, biogas from MSW in Italy, biodiesel from palm oil in Indonesia, bioethanol from sugarcane in Brazil, syngas from coal, biodiesel from tallow, bioethanol from corn stover in the US and finally syngas from coal in China.;The second and third objectives were respectively to identify the alternative fuels with less overall potential environmental impacts considering their different feedstocks and geographical contexts and determine the locations where there is a greater potential benefit from the use of these fuels for electricity generation as compared to the competing source of electricity in the relative countries. Both objectives were answered by conducting a prospective consequential life cycle assessment (CLCA) on the scenarios determined by the first objective.;The CLCA methodology takes many different aspects into account, including system expansion for co-producing processes, indirect impacts from the use of constrained feedstock, indirect land use change (LUC) from energy crop cultivation and the impacts of electricity substitution. Weidema's (2003) approach was used to correctly implement the system expansion, which is an important issue, since there is no consensus on the applied methodology. When a knock-on (i.e. incidental) effect from crop production was shown on other market-linked energy crops, Schmidt and Weidema's (2008) approach was chosen to find the equilibrium state and calculate the avoided or additional crop production. Indirect impacts from the use of constrained resources were taken into account, since the materials were considered to have inelastic supply and thus could not respond to a change in demand.;Essentially, should these sources of biomass be used for alternate applications, their availability would be reduced for the current users or waste systems. Hence, indirect impacts linked to the former must be modeled. On the other hand, there is no denying that LCA studies on potential biofuel impacts now require assessments of ILUC impacts, which have been proven to be significant and could invert certain study conclusions (Searchinger et al., 2008). The causal-descriptive method, which maps out the ways additional biofuel production could be attained in various regions identified as marginal producers, was used (Bauen et al, 2010).;Finally, the marginal source of electricity in each scenario was determined, since the substitution of the electricity by the alternative fuels had to be assessed. The short-term and long-term approaches were used to evaluate the changes in installed power plants and future capacity investments, respectively. Weidema's approach (2008) was again used to assess the long-term affected technologies, and the method was adjusted. Indeed, in some cases, more than one technology was identified and the load following ability of the energy sources was taken into account in the identification process. Otherwise, the short-term approach was used and based on determining the affected technology through its marginal costs (i.e. fuel costs), and the technologies that shared the same marginal costs as the turbine running on its respective alternative fuel was identified as the affected technology.;Based on the results, the most dominant trends are that syngas from coal in the US and China have the worst environmental performance in all endpoint categories, followed closely by ethanol in Brazil and ethanol in the US. On the other hand, the most promising scenarios vary depending on the impact category taken into account. However, POME in Indonesia -- with the exeption of ecosystem quality- followed by syngas and biogas in Germany are always among the highest ranking options in terms of environmental performance. The remaining scenarios also vary considerably in their scores depending on the type of impact. Consequently, it is the industrial partner's responsibility to value one impact category over another according to its own standards.;Several sensitivity analyses were performed in order to verify fuel production, gas turbine operation, the impact characterization method and the electricity substitution assumptions in order to verify whether certain hypotheses invert some of the study's conclusions. For instance, many fuel production assumptions reversed the conclusions, especially for the climate change and resource depletion endpoint categories. The most significant changes arose from the deviation of tallow to the different market applications and are noted for every category of impact. Additionally, the impacts resulting from the identification of different affected power plants are most significant and change the scenario ranking. However, the aforementioned trends remain unchanged. In conclusion, the study enables the partner to position its priorities in subsequent alternative fuel studies, perfect its strategic planning for business development and possibly use this study as a marketing tool for clients and the public.