While Renewable Natural Gas (RNG) and Hydrogen have dominated the headlines recently, ethanol fermentation is still making the news. Corn processors have been lobbying regulators to modify Advanced Biofuel rules for valuable RIN credits. However, there may be a different approach to appease regulators. In this blog post, I describe four opportunities that use corn fermentation waste CO2, purchased Hydrogen, and novel alcohologens for biofuel production.
Biofuel Alcohols
Biologically derived alcohols for transportation are biofuels. Ethanol is the only gasoline additive in the USA. Corn fermentation is the primary source of ethanol. Longer chain alcohols, such as propanol and butanol, are interesting due to higher energy content relative to ethanol.
Methanol
Methanol is a single carbon alcohol not widely used as a biofuel, but an industrial chemical. Syngas derived from natural gas and coal generates the bulk of methanol. There is interest in bioMethanol and eMethanol.
Ethanol
Corn processors are the major source of ethanol used as a biofuel. Yeast fermentation of corn-derived glucose generates equimolar amounts of ethanol and waste CO2.
Propanol and Butanol
The production of longer chain alcohols, such as Propanol and Butanol, is possible in rare fermentation pathways. These pathways have low yields of these alcohols and the microbes suffer from end product inhibition. Researchers modify the genome of E. coli to overcome these barriers. There is interest in BioButanol production. With the review of relevant molecules and biomolecules for green alcohol complete, let us focus on the new opportunities.
Known Versus Predicted Autotrophic Microbes
Most readers with an interest in green energy are familiar with autotrophic methanogens, which are responsible for the production of methane derived from biomass. Are there other autotrophic microbes of interest, such as novel alcohologens for advanced biofuel production?
Autotrophic microbes use CO2 as their carbon source for cell growth. Some also use CO2 as reactant for energy production. Other autotrophic microbes of general interest include: sulfate reducing bacteria (SRB), homoacetogens, nitrifying bacteria, and anammox.
Key Insight #1
All autotrophic microbes share an unusual growth sensitivity to CO2. Elevated CO2 concentration inhibits the growth of autotrophic microbes. A tight band of low CO2 concentration provides optimal growth conditions for autotrophic microbes.
Key Insight #2
Thermodynamic analysis predicts multiple groups of novel autotrophs including Alcohologens. This thermodynamic analysis predicted Anammox. It took microbiologists about 10 years to isolate the first Anammox strain, but inhibitory concentration of CO2 was to blame. Isolation and characterization of these novel autotrophic microbes will be much faster with the ideal CO2 concentration.
Predicted Alcohologens for Biofuels
My original analysis (USPTO application US 20140011185 A1) used identical non-standard conditions to evaluate the potential for alcohologens. Methanologen metabolism was not favorable for those conditions However, the analysis for the Methanologen with different non-standard conditions (1% CO2 and >5% H2) suggests favorable grown conditions. The table below shows the five predicted novel alcohologens for biofuel production. Note that there are two different Ethanologens. The first Ethanologen utilizes methanol as a substrate in a single step -CH2– addition. The second Ethanologen generates ethanol solely from CO2 and H2. Homoacetogens are autotrophs capable of a similar 2-step end product formation, so this may be a possibility. The Propanologen and Butanologen carryout out single step -CH2– additions.
BioAlcohol Opportunities for Biofuel Production
Four different BioAlcohol opportunities are described below. All four utilize ethanol fermentation waste CO2 and Hydrogen. The final two opportunities use ethanol as a reactant to generate longer chain alcohols.
Case 1: BioMethanol
The first opportunity utilizes a BioMethanol Reactor to convert waste CO2 from the Ethanol Fermenter and external Hydrogen into BioMethanol. Biomethanologen waste will need to be separated from the reactor effluent prior to distillation for BioMethanol recovery. Inactive biomethanologen waste may be attractive as a feed additive. It is unclear whether the existing Ethanol recover (distillation) system could be used to recover BioMethanol.
Case 2a: BioEthanol – 2 Step Bioreactors
The second opportunity generates additional ethanol with two bioreactors. The first bioreactor generates BioMethanol as shown in the first opportunity described above. A second bioreactor converts the BioMethanol to BioEthanol using the first ethanologen. This configuration has the advantage of using the same ethanol recovery system. Inactive ethanologen waste may be attractive as a feed additive.
Case 2b: BioEthanol – 1 Step Bioreactor
The third opportunity generates additional ethanol with a single reactor utilizing the second ethanologen. This ethanologen would convert two molecules of CO2 into ethanol. Similarly, the acetogen has the ability to convert two CO2 molecules into acetate. This configuration is simpler than the previous opportunity with lower capital costs (single reactor vs. two reactors). Inactive ethanologen waste may be attractive as a feed additive.
Case 3: BioPropanol
The third opportunity deploys a bioreactor to convert ethanol to BioPropanol. A propanologen converts ethanol to propanol with one molecule of CO2. All of the available ethanol is converted into BioProponal with the available CO2 waste gas. The current ethanol recovery system may be modified to recover propanol. Inactive ethanologen waste may be attractive as a feed additive.
Case 4: BioBuatanol
The final opportunity deploys two bioreactors to convert ethanol to BioButanol with two separate alcohol recovery systems, as shown below. The current ethanol recovery system could recover both ethanol and butanol. Only half of the available ethanol is converted to BioButanol, since BioButanol production requires 2 molecules of CO2 for each molecule of ethanol. Inactive butanologen waste may be attractive as a feed additive.
Profitability of Novel Alcohologens
The following table shows the profitability of using novel alcohologens in biofuel production. I used current (August 2023) wholesale prices for alcohols and assumed costs of $0.10 and $1.80 per kg of CO2 and H2, respectively. My analysis includes the costs ($0.20/gallon) of alcohol production and recovery. I compared the Net Dollar Value for each opportunity to the existing value of the ethanol fermenter. The Base calculation includes the sale of CO2 generated from ethanol fermentation.
With the given cost assumptions, it is clear that Methanol production is not favorable, while the other three opportunities look promising. BioButanol production looks very promising with a 1.39 ratio. At a lower hydrogen cost of $1.00, all four cases improve, but Methanol is still lagging. With the potential of D5 RIN credits, all four opportunities look very promising. With fluctuating prices, a battery of several alcohologenic bioreactors could be deployed to maximize profitability.
Commercialization Pathway for Novel Alcohologens
If there’s interest in this approach to generating BioAlcohols for biofuel production, then follow the four step plan for commercialization.
Isolate and Characterize Novel Alcohologens for Biofuel Production
This BioAlcohol commercialization plan requires one or more novel alcohologens: methanologens, ethanologens, propanologens, and butanologens. Thermodynamic analysis predicts these alcohologens and other novel autotrophic microbes. The combination of a proper anaerobic, autotrophic microbiology laboratory and a skilled microbiologist should suffice. The laboratory will require gas chromatography for gas characterization. Growth rate information for isolates will be necessary for bioreactor design. I’m available to assist in this effort.
Demonstrate Alcohologenic Bioreactors System for Biofuel Production
With the alcohologens properly characterized, design a simple bioreactor system for a simple demonstration using CO2, H2, and Ethanol. A successful demonstration provides a good estimate of the potential profitability of the bioreactor system for biofuel production.
Petition US EPA for Advanced BioFuel Pathway
In order to qualify for the valuable D5 RIN credits, the US EPA requires a petition describing the approach using novel alcohologens for Advanced Biofuel production.
Secure License for Patents
License the patents for the Novel Alcohologen bioreactor system from the University of South Florida (USF). Send me an email for USF contact information.
More Information Available
I provided a video that describes multiple business opportunities that could impact Agriculture, Environmental Remediation, Water and Wastewater Treatment, Metals Recovery, BioEnergy, and Health markets. In the future, I’ll provide new blog posts that describe opportunities for novel autotrophic probiotics for ruminants that reduce methane emissions.
Send Me Your Questions About Biofuel Alcohols
Send me your questions about using novel alcohologens for biofuel production to pete@glixin.com.
