Performing Department
Biological & Agr Engineering
Non Technical Summary
To meet the stringent climate targets set forth by the Intergovernmental Panel on Climate Change (IPCC), the United States is expected to sequester 1 Gt-CO2 per year in 2050 and 3 Gt-CO2 per year in 2100 (1 Gt = 1 billion metric tons).1 To meet such ambitious targets, research, development, and demonstration of CO2 capture, utilization, and sequestration (CCUS) technologies must rapidly accelerate.2-4 CCUS technologies can generally be classified as biotic or abiotic. Biotic, or biological, CO2 fixation occurs naturally through photosynthesis and other autotrophic mechanisms, with the majority of the fixed carbon releasing back into the atmosphere as CO2 or CH4 upon aerobic or anaerobic degradation within a relatively short time frame (0.5 - 20 years). Biological CCUS (bio-CCUS) technologies utilize and subsequently sequester biogenic carbon, thereby resulting in a net reduction of atmospheric CO2. In the US, the "bioeconomy", which refers to the production, sale, consumption, and disposal of bioproducts, is responsible for greater than 500 Mt of CO2 fixation, the vast majority of which is released back to the atmosphere upon degradation at end-of-life. The US Department of Energy estimates the bioeconomy could fix an additional 1 to 2 Gt-CO2 per year through growth, cultivation, and processing of sustainable, non-food biomass feedstocks. Thus, the US has the potential to meet its entire obligation for CO2 sequestration through biotic CCUS technologies.For the US to realize this potential, it must transition from a circular bioeconomy to a "carbon-negative" bioeconomy, wherein bioprocesses and bioproducts result in a net reduction of atmospheric CO2. For such a transition to happen in the narrow window of time allotted by the IPCC, highly ambitious and innovative projects must be carried out by talented, interdisciplinary teams. At present, the driving incentives for CO2 utilization and sequestration in the US are in the form of two policies: the state level Low Carbon Fuel Standard in California and the federal level 45Q Carbon Oxide Utilization and Sequestration tax credit. In addition, corporate commitments by multiple fortune 500 companies, including Microsoft, Apple, and Shell, to name a few, are motivating the development of CCUS technologies. Experts agree that incentives for CCUS will only grow in the near future. Thus, the time is ripe for aggressive R&D in bio-CCUS technology development.The primary goal of this project is to develop carbon-negative bioprocesses of relatively high technology-readiness-level (TRL) that integrate with existing industrial and agricultural operations, thereby providing near-term, low-risk, and large-scale bio-CCUS opportunities. Experts in synthetic biology, chemical catalysis, soil science, bioprocess engineering, techno-economic analysis, life cycle assessment, and environmental policy will work together to design, develop, experiment, model, and assess four bio-CCUS technologies. The technologies include multiple avenues for biogenic CO2 utilization and sequestration, including mineralization, geologic storage, graphite synthesis, and microbial fixation.
Animal Health Component
80%
Research Effort Categories
Basic
10%
Applied
80%
Developmental
10%
Goals / Objectives
The primary goal of this project is to develop carbon-negative bioprocesses of relatively high technology-readiness-level (TRL) that integrate with existing industrial and agricultural operations, thereby providing near-term, low-risk, and large-scale bio-CCUS opportunities. Experts in synthetic biology, chemical catalysis, soil science, bioprocess engineering, techno-economic analysis, life cycle assessment, and environmental policy will work together to design, develop, experiment, model, and assess four bio-CCUS technologies. The technologies include multiple avenues for biogenic CO2 utilization and sequestration, including mineralization, geologic storage, graphite synthesis, and microbial fixation. Experimental and modeling data will be used to answer the following general research questions for each bio-CCUS technology:What existing industry can this particular technology integrate into?What is the techno-economic feasibility of the integrated technology?What is the potential for carbon sequestration?For each bio-CCUS technology, these general research questions will be addressed through rigorous applied engineering and technology-to-market analysis.The four bio-CCUS technologies selected for development have undergone intensive preliminary assessment using strategies learned by PI Sagues during his time working at the US Department of Energy's Advanced Research Projects Agency (ARPA-E) as a Technology-to-Market Analyst. Each bio-CCUS technology is given a TRL to demonstrate the level of technical maturity, with low numbers (1 - 5) indicating relatively early-stage and high-risk and high numbers (6 - 9) indicating relatively mature and low-risk technologies.
Project Methods
Bio-CCUS Technology 1: Integrating CO2 Utilization and Sequestration in Chemical Pulping and Cotton Farming (TRL: 6)CO2 will be utilized by converting three pulp mill residues, namely dregs, grits, and lime mud (DGLM) to mineral carbonate fertilizer. The carbon in the mineral carbonates is derived from CO2 generated in the recovery boiler and lime kiln. Excess CO2 that is not utilized as fertilizer will be pumped deep underground into suitable geological reservoirs for permanent sequestration. Retrofitting the lime kiln to oxy-fuel will enable low-cost generation of high purity CO2. We will achieve the project goal, increase the technology-readiness-level (TRL), and reduce technology risk through a comprehensive multi-disciplinary approach that will involve numerical modeling, experimental work, chemical process simulation, techno-economic analysis, life cycle assessment, and policy consideration.The recently revised 45Q tax credit could enable low-cost CCUS at pulp mills, particularly for the 32 mills in southeastern states co-located with suitable geology for permanent CO2 sequestration and in close proximity to agricultural and forestry areas that demand carbonate fertilizer. The novel concepts of in situ and ex situ CO2 capture, as shown in Figure 1, will be thoroughly investigated to understand the eligibility of the mineral carbonate fertilizer co-product for the 45Q utilization tax credit. Given that the market price for carbonate fertilizer (limestone) is ~$115 per tonne CO2-equivalent and that pulp mills have to dispose of the DGLM residues in landfills at cost, the 45Q utilization tax credit of $35 per tonne CO2 utilized in year 2026 (when this technology is expected to scale) could enable a very low-cost and competitive carbonate fertilizer. In addition, the 45Q sequestration tax credit of $50 per tonne CO2 in year 2026 could enable low-cost CO2 sequestration if retro-fitting lime kilns to oxy-fuel proves to be techno-economically feasible.Bio-CCUS Technology 2: Catalytic Graphitization of Biomass for Carbon-Negative Lithium-Ion Battery Anodes (TRL: 5)The pine biographite generated in our preliminary work demonstrates exceptional electrochemical performance as anode material in a Li-ion cell, as shown in Figure 6. Figure 6A shows the characteristic capacity loss attributed to the reduction of electrolyte and the formation of a stable solid-electrolyte interphase (SEI) layer.57,58 Figure 6B shows an initial capacity of 335 mAh/g, capacity retention of 89% over 100 cycles at 0.5C, and Coulombic efficiency of greater than 99%. To be commercially competitive, we will increase capacity retention greater than 95% over 100 cycles by reducing electrolyte reactivity and irreversible capacity loss. Our preliminary economic assessment indicates a levelized cost of production of less than less than $10,000 per tonne is possible, which would be highly competitive with commercially available graphite anode products, which sell for prices between $10,000 and $20,000 per tonne.31-34 Based on the challenges with reported processes for catalytic graphitization of lignocellulosics, and our robust preliminary evidence, we believe the proposed research will make significant advancements in converting lignocellulose into commercially-viable graphite anode materials.The primary goal is to demonstrate the techno-economic feasibility of converting pine and switchgrass to graphitic Li-ion anode material. To accomplish this goal, research methods will involve the characterization of biomass, catalytic conversion of biomass to graphite using a tube furnace, catalyst recovery via mechano-magnetic separation, catalyst characterization, catalyst oxidation and recycling, performance testing of graphite in lithium-ion coin cells, and techno-economic-life cycle analysis.Bio-CCUS Technology 3: Microbial Conversion of CO2 and CRISPR-Edited Poplar into Bioplastic and Nanocellulose (TRL: 4)To be effective at CNC production, an enzymatic system must selectively hydrolyze the hemicellulose and amorphous cellulose into soluble sugars, while leaving the crystalline cellulose in solid form. Endo-(1,4)--D-glucanses and-glucosidases are known to be effective at selectively hydrolyzing amorphous regions of cellulose, but there are gaps in knowledge regarding the optimal bioprocess conditions needed for CNC isolation.68 Thus, there is potential to optimize an enzymatic bioprocess for selective hydrolysis of amorphous cellulose through variation in temperature, pH, and retention time. Up until recently, bioprocess scientists and engineers have mostly focused on optimization for complete hemicellulose and cellulose hydrolysis for sugar production, and thus there are gaps in knowledge pertaining to optimized bioprocesses for nanocellulose production. We will fill the aforementioned gaps in knowledge by developing and demonstrating an innovative process (Figure 8) that converts two biomass feedstocks of high cellulose content to CNCs and SA while largely avoiding the aforementioned techno-economic hurdles and environmental impacts. Poplar-derived market pulp from a commercial mill will be used as the baseline feedstock for statistical optimization. Dr. Wang's (Co-PI) CRISPR edited poplar has shown incredible potential as a feedstock for biochemical production.72,73 Specifically, the lignocellulose composition and structural conformation allow for direct enzymatic conversion to free sugars without pretreatment or lignin removal.72Bio-CCUS Technology 4: Bioelectrochemical Conversion of CO2 to Butanol (TRL: 3)The metabolic pathways involved in C1 assimilation by C. beijerinckii involve partial Wood-Ljungdahl (WL) and reversed-pyruvate ferredoxin oxidoreductase/pyruvate-formate-lyase-dependent (rPFOR/Pfl) pathways.80,81 C. beijerinckii's genome codes for many of the same genes present in C . ljungdahlii as part of the WL pathway, with the major exception being genes for acetyl-CoA-synthase. However, C. beijerinckii is capable of assimilating C1 gases into acetyl-CoA via rPFOR/Pfl pathways.80,81 New transcriptomic data indicate expression of C. beijerinckii's genome encodes cytochromes, flavoproteins, and Rnf-complexes which act as redox mediators to shuttle electrons and build up pools of NADH and subsequently acetyl-CoA.80,81 Thus, improvements in electron transfer to cytochromes, flavoproteins, and Rnf-complexes should allow for an increased rate of C1 assimilation. Interestingly, cytochromes, flavoproteins, and Rnf-complexes are capable of accepting electrons from externally supplied artificial redox mediators (RMs).79,88 The ferrodoxin NAD+ reductase present in the Rnf-complex can be substituted entirely by externally supplied artificial RMs.87 Prior studies have shown an increase in butanol yield and selectivity by using externally supplied artificial RMs in heterotrophic fermentation of C. beijerinckii.85-87 Notably, there has been no study in which artificial RMs are assessed for mixotrophic fermentation of C. beijerinckii - a gap in knowledge we will address. We propose a bioelectrochemical mixotrophic fermentation process wherein Clostridium beijerinckii converts hexose sugars and CO2 to butanol at high yields without exogenous H2 gas supply. As shown in Figure 10, an innovative annular bioelectrochemical reactor utilizes renewable electricity to drive cathodic transfer of electrons to redox mediators (RMs) which act as external reducing equivalents for butanol synthesis. Preliminary data demonstrate C. beijerinckii's ability to mixotrophically utilize hexose sugars and CO2 to synthesize butanol with high carbon efficiency (greater than 0.45 C-mol/C-mol), yields (greater than 0.27 g/g), and titers (greater than 16 g/L).80-82For the first time, a bioprocess for microbial electrosynthesis of butanol via mixotrophic fermentation with C. beijerinckii will be developed, optimized, scaled, and modeled to demonstrate economic viability and environmental benefits.