The environmental performance of biobased 1,3-propanediol production from glycerol compared to conventional production pathways - A Life Cycle Assessment
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Due to environmental concerns and the reliance on depleting fossil resources the conventional chemical industry is facing increasing pressure to alter their production methods towards a sustainable direction. Despite having also its disadvantages like the land-use issue, biomass is considered to have a major potential as a more sustainable feedstock for the future chemical production. Research in this area is increasing, but profitable business models for biobased products are still lacking. A good example for a biobased chemical product which already found its way to the markets is 1,3-propanediol (PDO), a platform-chemical with a wide range of possible uses and a rapidly growing market. It has been commercially implemented and environmentally assessed by DuPont, an American chemical company. While DuPont produces PDO from glucose based on corn, there is also the possibility to use glycerol as a biological feedstock. Glycerol is a by-product of the large biodiesel production and is thus currently facing an over-supply on the market which cannot be accommodated by the conventional uses of glycerol. As research has indicated, it could be an attractive solution to use it as a cheap feedstock for the production of PDO. However, so far no analysis of the environmental impacts of this production pathway has been conducted. This thesis therefore assesses what the environmental impacts of the glycerol-based PDO production are and indicates how they relate to impacts of other biobased and petrochemical alternatives of PDO-production. Hence, a cradle-to-gate Life Cycle Assessment was conducted, assessing the greenhouse gas emissions and the non-renewable energy use of the glycerol-based PDO production. This assessment includes a contributional analysis and an extensive sensitivity analysis which develops three scenarios. The results of those scenarios are compared to results of other studies assessing environmental aspects of alternative fossil- and biobased production pathways for PDO. This benchmarking between the different production pathways indicates that the glycerol-based production route is environmentally preferable compared to fossil alternatives and might be competitive with biobased PDO from glucose, if the production process is further optimized. The contributional analysis revealed that the process of PDO recovery and purification shows the biggest environmental impact, which is mainly due to its intensive steam use from fossil sources. Moreover, the study gave insight to the future development of the biodiesel market, which might negatively influence the prospects of a glycerol-based PDO production on long term.