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Anthropogenic greenhouse gas emissions are the main cause for global warming and climate change. Most of the greenhouse gas emissions (80%) originate from the burning of fossil fuels to generate heat and electricity. National policies such as the Dutch ‘Energieakkoord’ and other (inter)national agreements strive to reduce these emissions.

For the chemical industry, the use of renewable energy and -material feedstock could potentially be the most powerful part in the transition to a clean and sustainable economy. However, the switch to such alternative sources will take some decennia to be finalized. In the meantime the industry should search for intermediate solutions. Several approaches are possible, e.g. energy reduction or process intensification of commercial fossil based routes (more effective unit operations, reuse of wasted energy). Another possibility is using new, more advanced fossil fuel-based processes that require less fossil energy input, and therefore lead to  less environmental impact.

With the goal of a rigorous benchmark of these possibilities and therefore the identification of the best intermediate sustainable solution(s), it is of paramount importance to develop and apply reliable comparison methods. The current thesis describes a method to assess the sustainability of chemical manufacturing. The polyamide-6 (nylon) manufacturing industry is used as a study case.

Although the product (nylon) is the same, the studied manufacturing routes vary in the used raw materials. We have established five manufacturing routes to produce nylon from fossil raw materials or biomass. 

When looking at the nylon manufacturing process, we can conclude that

• fossil-fuel based nylon routes have the technological potential to surpass the biobased routes with respect to energy efficiency and primary energy use. 
• replacing fossil based feedstock by biomass in existing plants is not straightforward, since the use of a different starting material will often require an entirely new process and major changes in the plant layout. Moreover, the feasibility of replacing fossil based feedstock by biobased feedstock is questionable whenever a steady supply of similar biomass is not possible.
• from an energy efficiency perspective alone, it is questionable for the studied processes if the biobased process is preferred. When not accounting for end-of-life emissions, e.g. if they are compensated via carbon capture and storage or direct air capture, a shift to renewable energy sources in the existing process must be prioritized.  However, if only the total life-cycle greenhouse gas emissions are considered this result may change and favour the biobased route, though at the expense of increased energy use.