PhD Thesis Defence Presentations - ELENI MOUTOUSIDI

The heavy dependance of todays societies on the limited and depleting fossil resources has led to an unprecedented global crisis, facing serious consequences such as climate change. The effects of these devastating changes are present in our everyday life and intensify as time passes without taking serious actions and change our way of life. Scientific society and industry come up with innovative and sustainable solutions regarding the way products and services are provided to society. One of these solutions is moving towards a sustainable biobased economy. In a biobased economy, organic matter such as biomass is converted into materials (such as bio-based plastics, chemical building blocks, high value ingredients for pharmaceuticals or cosmetics, advanced biofuels) and energy by means of physical, chemical or biological treatment, limiting the reliance on nonrenewable resources.

The production of chemicals through microbial fermentation, using renewable resources, has gained significant attention and its development in the market is rapid. The need for more sustainable products has resulted in numerous experimental investigations on the potential of producing different products that can compare on even terms or substitute fossil-derived chemicals. However, despite the general public beliefs, biochemicals are not sustainable by default just because they are produced using renewable resources. For truly sustainable processes, comprehensive environmental assessments should be performed in the early stages of the development and planning of a specific product and cover all stages of the production chain. It is necessary to integrate the environmental performance of products in the decision-making tools that in most cases consider economic criteria to achieve sustainability. This also aims to expand the adoption of viable bioconversion technologies in the industry.

This thesis aims at presenting comprehensive technoeconomic and life cycle assessments of bioprocesses to produce selected platform chemicals, polymers and fuels using agricultural crops as feedstock. These two assessments will be the indicators of economic and environmental viability accordingly and they will assist with the identification of areas that need to be reconsidered or optimized. The overall objective is to develop a framework that incorporates technoeconomic and life cycle assessments in the development of bioprocesses.

This dissertation consists of six chapters. The first Chapter introduces the main challenges of todays societies and present the current developments of biobased products. Additionally, the focus and the aims of this PhD are presented.

In Chapter 2 the theoretical overview of the methods used in this thesis is presented. First, the fundamental principles of preliminary plant design necessary for the development of engineering tools to evaluate the technical and economic characteristics of biobased chemicals with sufficient accuracy are reviewed. Then the basic steps of a life cycle assessment are presented followed by a review of the basic environmental impact categories. Finally, an overview of the integration methods of TEA and LCA is presented.

Chapter 3 presents in detail the potential process flowsheets that describe the production of selected chemicals in large scale capacities from renewable raw materials. More specifically, the design of upstream and downstream processes, to produce 1,4-butanediol, ethanol, isobutanol, lactic acid, methyl-ethyl ketone, poly(3-hydroxybutyrate), poly(lactic acid) (deriving directly from chemical conversion of lactic acid), single cell oil and succinic acid, is presented. An extensive literature review is performed to obtain the essential design data and the specific operating conditions of each studied chemical.

Chapter 4 offers the comprehensive environmental assessment of the selected biochemicals across three different agricultural feedstocks using the LCA method. The impact categories examined in detail are the global warming potential, the acidification potential and the eutrophication potential and the main contributors to the total impacts are identified. Identifying the process or elementary flow that accounts for the most significant proportion of an impact is crucial when potential actions and optimizations are prioritized with the aim of improving the performance of biochemical processes. Other impact categories considered include abiotic depletion potential, freshwater aquatic ecotoxicity potential, terrestric ecotoxicity potential, human toxicity potential.

Chapter 5 first presents the monetization of the estimated environmental impacts across twelve different impact categories in an economic single score value. The monetized environmental impacts are compared with the minimum selling prices of the chosen chemicals as well as the selling prices revealing that TEA or LCA alone are not enough to assess the total sustainability of a product. Finally, the external costs are incorporated in the estimated minimum selling price, for each selected chemical, and their ranking is examined.

In Chapter 6 the main conclusions of this work are discussed followed by recommendations for future work with the aim to further improve the sustainability of the production of biobased chemicals, fuels and polymers.