Rationale for Biobased Chemicals ProductionThe production of chemicals from biomass, also known as bio-based chemicals, plays a critical role in creating a sustainable and environmentally friendly future, particularly as the world strives to reduce dependence on fossil fuels. Some of the advantages of biobased chemicals are listed below:
Approaches for the Production of Biobased ChemicalsThere are two main ways in which biobased chemicals can be obtained from biomass feedstocks:
How Celignis Can HelpAt Celignis our multidisciplinary team has strong understanding of: biomass chemistry, bioprocessing technologies, and the mechanisms and challenges involved in producing a wide variety of biobased chemicals. We are ready to work with you on developing a suitable bioprocess to either obtain your targeted biobased chemical from biomass or to obtain the most appropriate biobased chemicals from a given feedstock.
Ethanol Chemistry and ApplicationsChemically, ethanol is a simple compound with the molecular formula C2H5OH. It consists of a two-carbon chain (ethane), with one of the hydrogens replaced by a hydroxyl (OH) group, which makes it an alcohol. It is this hydroxyl group that gives ethanol its characteristic properties, such as its ability to dissolve in water and to act as a solvent for many organic compounds. Biobased ethanol is typically referred to as bioethanol.
History of Ethanol ProductionIt is possible for ethanol to be produced from fossil fuels, specifically from petroleum or natural gas, through a process known as hydration of ethylene. In the chemical industry, ethylene is typically produced through steam cracking of hydrocarbons derived from petroleum or natural gas. In the steam cracking process, hydrocarbon molecules are broken down into smaller molecules, one of which is ethylene. The ethylene can then be converted into ethanol through a process called acid-catalyzed hydration. In this process, ethylene (C2H4) is reacted with water (H2O) in the presence of an acid catalyst to produce ethanol (C2H5OH).
Biomass HydrolysisThe current focus of bioprocess development on bioethanol production concerns utilising lignocellulosic feedstocks. These feedstocks contain sugars, like many 1st generation bioethanol feedstocks, that can be used as substrates for the production of bioethanol via fermentation. However, the difference is that these sugars are part of the structural polysaccharides cellulose and hemicellulose, rather than the easier to process sucrose and starch.
Fermentation of Biomass-Derived SugarsIn bioethanol fermentation, a primary target is a high concentration of fermentable sugars. This will then lead to higher concentrations of ethanol in the beer and, hence, in lower product recovery costs. However, the pretreatment and hydrolysis stages may also release other compounds into the liquid phase, for example components of the extractives and some sugar degradation products. These compounds can complicate the downstream fermentation, hence it is important that either robust microorganisms are used for the fermentation or that the concentrations of such fermentation inhibitors are minimised. Achieving these aims requires careful work in the bioprocess development.
Recovery of Bioethanol after FermentationThe conventional method for recovering bioethanol from fermentation broths is distillation, which separates the ethanol from water and other components based on differences in boiling points. However, distillation is energy-intensive, particularly when dealing with dilute solutions. Ethanol forms an azeotrope with water at about 95% ethanol concentration, meaning they boil at the same temperature at this composition. To break the azeotrope and obtain anhydrous ethanol (nearly 100% ethanol), an additional dehydration step is needed, often involving the use of a molecular sieve, which adsorbs water but not ethanol. This adds to the energy cost and complexity of the process.
Valorisation of Other Biomass ComponentsLignocellulosic biomass feedstocks vary greatly in their compositions, however they all contain cellulose, hemicellulose, and lignin. In addition, some lignocellulosic biomass can contain significant amounts of extractives as well as ash and protein.
GasificationAn alternative route for producing bioethanol from lignocellulosic feedstocks is via the catalytic or biological reforming of the gases produced from the thermal processing of the biomass, with gasification considered to be the most suitable thermal treatment.
C6H12O6 + 3⁄2O2 -> 6CO + 3H2 + 3H2O
CO + H2O -> CO2 + H2
Syngas to Ethanol (Catalytic Approach)The conversion of syngas into ethanol is a complex process that involves a series of chemical catalytic reactions. One common approach is to first convert the syngas into methanol or dimethyl ether (DME) using a methanol or DME synthesis catalyst. For instance, copper-based catalysts, often supported on zinc oxide and alumina, are typically used for methanol synthesis. The reaction proceeds as follows:
CO + 2H2 -> CH3O
2CH3OH -> CH3CH2OH + H2O
CO + 3H2 -> CH3CH2OH + H2O
Syngas FermentationSyngas fermentation, also known as gas fermentation or syngas bioconversion, is an alternative, biological, route for the production of products (such as bioethanol) from syngas. The process employs a group of microorganisms known as acetogens, a type of anaerobic bacteria capable of using carbon monoxide (CO), carbon dioxide (CO2), and hydrogen (H2) - the primary constituents of syngas - to grow and produce various chemicals. These organisms follow a metabolic pathway known as the Wood-Ljungdahl pathway or Acetyl-CoA pathway.
Syngas Ethanol vs. Hydrolysis EthanolAdvantages of bioethanol production via gasification:
1. Understanding Your Requirements
2. Detailed Feedstock Analysis
3. Pretreatment Optimisation (Lab-Scale)
4. Hydrolysis & Fermentation Optimisation
5. Bioethanol Recovery
6. Valorisation of Remaining Biomass
7. Validation at Higher TRLs
8. Technoeconomic Analysis (TEA)
Bioethanol from Palm ResiduesCelignis undertook a bioprocess development project for a client, based in the Middle East, that was targeting the production of bioethanol from the residues of local palm trees. This was a lab-scale vertically-integrated project covering pretreatment, hydrolysis, and fermentation.