Life cycle assessment in green chemistry

Abstract

Background, Aims and Scope. Using renewable feedstock and introducing biocatalysts in the chemical industry have been suggested as the key strategies to reduce the environmental impact of chemicals. The Swedish interdisciplinary programme 'Greenchem', is aiming to develop these strategies. One target group of chemicals for Greenchem are wax esters which can be used in wood surface coatings for wood furniture, etc. The aim of this study was to conduct a life cycle assessment of four different wood surface coatings, two wax-based coatings and two lacquers using ultra violet light for hardening (UV lacquers). One of the two wax-based coatings is based on a renewable wax ester produced with biocatalysts from rapeseed oil, denoted 'green wax', while the other is based on fossil feedstock and is denoted 'fossil wax'. The two UV lacquers consist of one '100% UV' coating and one 'water-based UV coating. The scope was to compare the environmental performance of the new 'green' coating with the three coatings which are on the market today. Methods. The study has a cradle-to-grave perspective and the functional unit is decoration and protection of 1 m(2) wood table surface for 20 years'. Extensive data collection and calculations have been performed for the two wax-based coatings, whereas mainly existing LCI data have been used to characterise the production of the two UV lacquers. Results. For all impact categories studied, the '100% UV' lacquer is the most environmentally benign alternative. The 'waterbased UV is the second best alternative for all impact categories except EP, where the 'fossil wax' is slightly better. For GWP the 'fossil wax' has the highest contribution followed by the 'green wax'. For AP and EP it is the 'green wax' that makes the highest environmental impact due to the contribution from the cultivation of the rapeseed and the production of the rapeseed oil. For POCP the 'fossil wax' makes the highest contribution, slightly higher than the contribution from the 'green wax'. Also the energy requirements for the '100% U-V' lacquer is much lower than for the other coatings. The results from the toxicological evaluation conducted in this study, which was restricted to include only the UV lacquers, are inconclusive, giving different results depending on the model chosen, EDIP97 or USES. Discussion. The result in this study shows that the environmental benefits of using revewable feedstock and processes based on biocatalysis in the production of wax esters used in wood surface coatings are rather limited. This is due to the high environmental impact from other steps in the life cycle of the coating. Conclusions. Overall the '100% UV' lacquer seems to be the best alternative from an environmental point of view. This study shows that the hot spots of the life cycle of the coatings are the production of the ingredients, but also the application and drying of the coatings. The toxicity assessment shows the need for the development of a new model, a model which finds common ground in order to overcome the current situation of diverging results of toxicity assessments. The results in this study also point to the importance of investigating the environmental performance of a product based on fossil or renewable feedstock from a life cycle perspective. Recommendations and Perspectives. The results in this study show that an efficient way to improve the wood coating industry environmentally is to increase the utilization of UV lacquers that are 100% U-V-based. These coatings can also be even further improved by introducing biocatalytic processes and producing epoxides and diacrylates from renewable raw material instead of the fossil-based ones produced with conventional chemical methods in use today. In doing this, however, choosing a vegetable oil with good environmental performance is important. An alternative application of the 'green wax' analysed in this study may be as an ingredient in health care products, for example, which may result in greater environmental benefits than when the wax is used in wood coating products. The results in this study illustrate the importance of investigating the environmental performance of a product from cradle.-to-grave perspective and not consider it 'green' because it is based on renewable resources.