Environmental assessment of a biorefinery concept for production of bulk and fine chemicals

Övrigt konferensbidrag, 2019

Moving from a fossil-based to a bio-based economy requires the development of new technologies and process concepts for the production of bio-based energy, chemicals and materials. Biorefinery concepts can be designed by integrating such technologies in order to provide environmentally and economically attractive alternatives to produce bulk and fine chemicals. This paper presents life cycle and techno-economic assessments of a novel biorefinery concept, in its early stages of development, for the combined production of adipic acid from forest residues and of lutein from micro-algae.

Adipic acid is a bulk chemical with a yearly production of approximately 2.3 million tonnes, and is primarily used for the production of nylon-6,6. Conventional adipic acid production from fossil resources causes significant emissions of N2O due to the use of nitric acid as an oxidizing agent. This conventional production can thus lead to a significant climate impact if these emissions are not sufficiently mitigated. Lutein is a high added-value chemical used in the food and pharmaceutical industries, and is conventionally produced from marigold flowers.

The biorefinery concept in this work consists of the pretreatment of forest residues, the separation of lignin (which is an important by-product), and the hydrolysis and fermentation of the pretreated forest residues to adipic acid which is then separated and purified. Water, nutrients and CO2 flows from the adipic acid production can be connected to the algae production. The lutein is extracted from the micro-algae using methanol. Anaerobic digestion is used in this concept to produce biogas (another important by-product) from waste streams. The biorefinery concept thus comprises technologies that are at different technology readiness levels (TRLs), from as low as a TRL of 2 for the fermentation process, to a TRL of 9 for the anaerobic digestion process.

Twelve design variants of the biorefinery concept were modelled and simulated based on experimental and literature data. These variants aimed at narrowing down uncertainties about, for instance, the performance of the fermentation process. The data and information resulting from the simulations of the design variants were used 1) to compile the life cycle inventories for the LCA of each of these variants, and to do the subsequent life cycle impact assessment, and 2) to determine the capital and operating costs in order to calculate the economic feasibility of the biorefinery design variants. The assessment of all variants provides a range for the environmental and economic performance of the biorefinery concept based on design choices and process conditions. Furthermore, scenarios for future energy systems were considered in order to assess the influence of the background system on the performance of the biorefinery concept.

The results show that there is a large variation in the performance among the different design variants, where some designs can significantly improve the prospects for the bio-based adipic acid production. However, the results are strongly dependent on the foreground and background energy systems. The results provide valuable insights to industry and policy decision makers in order to guarantee an environmentally benign and economically feasible production of bulk and fine chemicals in a biorefinery.