LCA and Methodological Choices for Identification of Improvement Potential - Case Study Bearing Unit
Examensarbete för masterexamen
The society focus on environmental issues in general and global warming in particular is constantly growing and a further improvement of the studied company’s environmental performance is increasingly important. Several corporate environmental targets have been launched and to meet these, new ways to use Life Cycle Assessments (LCA) are sought. A number of LCA’s have been performed within the studied company, but with limited utilisation of the results. This may be due to a lack of result credibility caused by diversified methodological choices and a want for recommendations on result use. In this study an LCA of a specific bearing unit, not a product average, is carried out to increase the knowledge of the product environmental performance from cradle to gate. The studied bearing unit is a high volume product manufactured with materials and processes that allow for generalisation and reuse of results and conclusions within the case study company. The results are related to corporate environmental targets and ways for homogenisation of methodological choices as well as presentation of improvement potential are found. The major potential environmental impact in the cradle to gate life cycle of the surveyed bearing unit is, for all studied impact categories, caused by the ring production including upstream processes. Steel production is the activity category with dominant contribution to potential environmental impact. When further surveyed it is shown that energy use for steel production is the major contributor to environmental impact. For similar products where average electricity mix is used for in-house processes, the environmental impact from in-house processes is significant as well. To decrease the sensitivity for choice of allocation methods, environmentally relevant flows should be quantified on channel, rather than facility level. The preferred allocation methods for bearing manufacturing in a system similar to the one surveyed here should be number of pieces and processing time, and not mass as generally used in earlier studies at the company. For channel energy use, further increased system detail by measurement of machine power use for process statuses and calculation of energy use from cycle time data gives a substantial mismatch compared to measurement of energy use on channel level. This methodology is though rewarding when improvement of manufacturing channel energy efficiency is of interest. It is indicated that the highest improvement of product cradle to gate life cycle environmental performance is achieved by reduction of energy use through reduction of steel content in the product, i.e. operational focus on product development. An improved environmental performance can also be obtained by in-house process development with a focus on energy efficiency in manufacturing, specifically when the electricity supply does not come from low-CO2 sources. For low CO2 electricity supply it shall though be considered that a reduction of energy use will be beneficial from a global perspective, as energy from renewable resources will be made available for other energy users. Increased added value of LCA’s within the studied company can be realised by a homogenisation of methodological choices for LCA’s. To ensure that performed studies result in a knowledge build-up, it would be valuable to document studies in a standardised way, and develop guidelines for methodological choices for performing LCA’s. The credibility and usability of LCA results can be increased by including factors that have been left out in previous studies. It is also crucial to update and validate datasets with dominant impact on the results, such as electricity mixes and steel production.
Miljöteknik , Environmental engineering