Biomass to Chemicals

Lignocellulosic biomass is an abundant and sustainable feedstock that can be used to produce biofuels and bioproducts. However, the low price of crude oil and the challenges in applying biorefinery technologies at scale hamper the commercial production of biofuels from biomass. Another option for biorefineries to become more profitable is to produce high value commodity chemicals. Towards this goal, we study two questions.

Identification of Promising Renewable Chemicals

Chemicals that are expensive to produce from fossil fuel feedstocks today, would have an advantage if produced cheaply from alternate feedstocks. Recent progress in metabolic engineering enables the use of microorganisms for the production of ‘bio-based chemicals’ (bioproducts). We study which of these bioproducts have the highest economic prospect (Figure 1), following the three steps: 1) we identify a candidate pool of 209 high volume chemicals from KEGG and MetaCyc databases, 2) we design screening criteria based on profit margin, market volume and market size, and 3) based on the screening criteria we identify the products which will be economically promising if their maximum yields or maximum productivity can be achieved (Wu et al., 2018).

Product Identification Framework — Figure 1. Economically promising products identification framework, including the compilation of HPV chemicals, identification of the candidate pool, and development of the screening criteria. E. coli: Escherichia coli; HPV: high‐production‐volume; res.: residence time; S. cerevisiae: Saccharomyces cerevisiae Reproduced from (Wu *et al.,* 2018), with permission from John Wiley and Sons

Figure 2. Proposed metric for evaluating bio-based production efﬁciency of various chemicals Reproduced from (Wu, 2019), licensed under CC BY-NC-ND 4.0

We also identify the characteristics of promising bio-based replacement chemicals (Figure 2) that are relatively easy to obtain through bioconversions (Wu and Maravelias, 2019).

Biorefineries for High Value Chemicals

Several studies have highlighted the potential of lignocellulosic biomass as a feedstock for building blocks and platform chemicals as alternatives to the conventional monomers and products obtained from fossil resources. We use process systems engineering methods to design biorefineries producing high value chemicals, identify critical blocks in the production process, and synthesize potential alternative approaches (Alonso et al., 2017).

Figure 3. Sankey diagram for the integrated process to produce furfural, lignin, and dissolving pulp from lignocellulosic biomass. LA, levulinic acid. Reproduced from (Alonso *et al.,* 2017), with permission from AAAS

To further increase the economic value of lignocellulosic biomass, conversion of lignin and waste streams (e.g. carbon-rich residues) to valuable co-products are necessary. We develop a superstructure based optimization model to generate and compare different strategies in terms of economic and energy performance and investigate the impact of a number of parameters thereby providing insights into critical areas of improvement for viable lignin and stillage valorization (Huang et al.,2019; Ng et al., 2019).

Superstructure — Figure 4. The superstructure of corn stover-to-ethanol. Abbreviations – AFEX: ammonia fiber expansion, AHP: copper-catalyzed alkaline hydrogen peroxide, CB: combustor and boiler, COFER: co-fermentation, DA: dilute acid, EA: extractive ammonia, GVL: γ-valerolactone, HYD: hydrolysis, LV: lignin valorization, SEP: separation, SSCF: simultaneous saccharification and co-fermentation, SV: stillage valorization, TBG: turbogenerator, WWT: wastewater treatment. Reproduced from (Ng *et al.,* 2019), licensed under CC BY-NC-ND 4.0

References

Huang K, Fasahati P, Maravelias CT. System-level Analysis of Lignin Valorization in Lignocellulosic Biorefineries. iScience, 23, 1, 100751, 2020.

Martin Alonso D, Hakim S, Zhou S, Won W, Hosseinaei O, Tao J, Garcia-Negron V, Motagamwala AH, Mellmer MA, Huang K, Houtman CJ, Labbé N, Harper DP, Maravelias CT, Runge T, Dumesic JA. Increasing the Revenue from Lignocellulosic Biomass: Maximizing Feedstock Utilization. Science Advances, 3 (5), e1603301, 2017.

Ng RTL, Fasahati P, Huang K, Maravelias CT. Utilizing Stillage in the Biorefinery: Economic, Technological, and Energetic Analysis. Applied Energy, 241, 491-503, 2019.

Wu W, Maravelias CT. Identifying the Characteristics of Promising Renewable Replacement Chemicals. iScience, 15, 136-146, 2019.

Wu W, Long MR, Zhang X, Reed JL, Maravelias CT. A Framework for the Identification of Promising Bio-based Chemicals. Biotechnology and Bioengineering, 2328-2340, 115, 2018.