Chemical effects enhanced by charging N2 or CO2 during pretreatment

During biomass pretreatment, introduction of N2 or CO2 into the reactor will enhance the chemical changes of cell wall components due to the mechanical effect.

Uronic acids and metals in biomass

Uronic acids and metals in biomass will cause some problems in acid hydrolyzates.

Don't panic when your mass great than 100% for biomass composition analysis

When we do biomass chemical composition analysis, it often turns out the mass add-up of all the chemical components great than or less than 100%, which is very common.
1. Different chemical components are analyzed by different methods and instrument, which cause the errors
2. For sugar analysis, each sugar has different optimal post-hydrolysis conditions, which cause both under and over hydrolysis of the sugars
3. Klason lignin includes some ash and proteins, which are accounted for twice
4. Uronic acid and acid lignin should be included when doing mass balance.
5. The standard solution composition should be as close as possible the real samples

Mechanism of furfural inhibition

• Furfural is metabolized by S. cerevisae under aerobic, oxygen-limited, and anareobic conditions to furfural alcohol.
  –Furfural reduce the specific growth rate, the cell-mass yield on ATP, the volumetric, and specific ethanol production
  –NADH-dependent yeast alcohol dehydrogenase (ADH) is believe to be responsible for furfural reduction.
  –Under anaerobic conditions, glycerol is normally produced to regenerate excess NADH formed in biosynthesis. Glycerol production reduction during furfural reduction suggests that furfural reduction regenerates NAD+.
  –Elevated concentrations of acetaldehyde excreted in the beginning of the fermentation, which was suggested to be due to a decreased NADH concentration in the cell during furfural reduction.
  –Furfural inhibition of glycolytic enzymes in vitro and the direct inhibition of ADH might have contributed to acetaldehyde excretion.
  –Intracellular acetaldehyde acumination suggested to be the reason for lag-phase in growth in the presence of furfural.
  –The model
  »i) furfural reduction to furfural alcohol by NADH dependent dehydrogenases had a higher priority than reduction of dihydroxyacetone phosphate to glycerol
  »ii) furfural caused inactivation of cell replication.

Mechanism of acidic acid inhibition

Uncoupling and intracellular anion acumination
–The drop in intracellular pH resulting from inflow of weak acids is neutralized by the action of plasma membrane ATPase, which pumps protons out of the cell at the expense of ATP hydrolysis. At high acid concentration, the proton pumping capacity of the cell is exhausted, resulting depletion of the ATP content, dissipation of the proton motive force, and acidification of the cytoplasm.
–However, the anionic forms of acetic, formic acid, are lipophobic and do not traverse the plasma membrane in both dissociated and undissociated form, causing a high rate of proton impart. The extent of intracellular anion accumination will be a function of the pH gradient over the plasma membrane.

The Effect of Lignin on Enzyme Hydrolysis and Fermentation

• Barrier to cellulase enzymes
  – limit the efficacy of hydrolysis
• Adsorb cellulases
  –Increase enzyme loading and therefore the cost
• Phenloc compounds partition into biological membrances cause loss of integrity, therefore affecting their ability to serve selective barriers and enzyme matrices.

Less heavily substituted phenolics are the most inhibitory compounds
–Phenols
–Vanillin
–Hydroxylbenzaldehyde

Pulp Mill: A Natural Home for the Forest Product Biorefinery

It is costly to start a greenfield biorefinery plant. When we closely look at pulp and paper industry, it will not hard to find:

• this industry is the largest handler of forest residues (lignocellusics)
• $Millions investment has been completed in infrastructure, which will allow to save ~ 35% of capital cost versus a greenfield plant and utilize the boiler house, generators, control rooms, pipe bridges, water and effluent stations, warehouses, woodyards, wood procurement, storage tanks etc
• Hundreds of highly trained technical professionals are available for cellulosic biorefineries
• Co-production and process integration reduce allocated production cost for both pulp mill and biorefinery plant
• Bioethanol adds additional revenue to pulp and paper mills

There, when we borrow the ideas from paper industry to treat biomass , somehow we should not turn our attention away from this industry. More we can take advantge of them.

Purification of Crude Glycerol for Omega-3 Fatty Acids Production

According to Biodiesel Magazine, a technology was developed by Wen at Virginia Tech that uses glycerin to aid in the production of algae that produce omega-3 fatty acids. For this purpose,the soap and methanol present in crude glycerin must be removed before it can be used to aid in the algae growth.

When adjusting pH of the medium containing crude glycerol for algae to grow, the soap contained in the glycerol will be precipitated out of the medium, i.e. the process used to adjust the pH of the solution causes the soap to solidify and settle out of the glycerin.

Next when the glycerin is sterilized at 120 C before used to cultivate algae, the residual methanol will be evaporated and collected.

Biofuels or biochemicals: Are you ready to get in? (2)

According to the report from Ethanol Producer Magazine, the cellulosic ethanol project with $30 million DOE fund was suspended by Lignol and Suncor. The reasons disclosed are instable energy prices, capital market uncertainty and general market malaise. However, although the technology was not listed as a reason, I guess at least a cost-effective well-developed technology is not ready yet since Suncor will continue to monitor the progress of Lignol's technology.

I feel that it is very wise for both partners to make such a decision at an early stage in the project’s development and no significant costs have been incurred. They are serious about cellulosic biorefining.

My question is: what will happen if they continue to proceed the project with the government funding, or with misleading information? What about other players?

These days, biorefining has been driving by a lot of aggressive and ambitious objectives. The good news is that it can attract more attention and investment;on the other side, technology can not be well developed overnight. A gap often occurs between the ambitous goals and the timeline of available technology development. As a result, if unrealistic goals have been set with significant investment, the risk is not far or near around no matter how we are aggressive or smart or very supportive. In the process, realistic and objective evalution must be provided.

It is great lesson for us to learn from this wise decision.

Biofuels or biochemicals: Are you ready to get in? (1)

According to AE report, although many alternative energy investors suffered huge losses in 2008 when several prominent stocks fell by 70% or more, they have not lost hope in alternative energy stocks and their future. The measured optimism from financial community is also a stimulus to alternative energy under the current deeply challenging business climate. So does the government support!

For biofeuls and biochemicals industry, it is still uncertain when the great potential become reality. To use biomass as feedstocks, the utilization of hemicelluloses is the key because it accounts 20-28% of the chemical components in biomass and will have significant impact on the production cost. However the available cost effective technology for commercialization is not ready yet: the scalable microorganisms to ferment C5 sugars under toxic environment, the process to achieve high sugar recovery yield from biomass….

So it is the time for scientist and engineers to get in. It is also great time for investors to jump in if the opportunity has a solid fundamental support. Certainly, a detailed and solid technical evaluation before jumping in is very critical.

A recommendation for biomass pretreatment reactor

The most widely used lab pressurized reactors for biomass pretreatment are autoclaves, steam guns, etc, which is hard to scale up.

A reactor like M&K lab digester has been widely used for lab study on pulping. The rapid liquor circulation provides excellent chemical/biomass interactions or mixing. The two-vessel design allow us to use steam for rapid heat-up and the cooling pipe line allows us to cool down fast after treatment. Such a kind of design has been scaled up for pulp and paper industry and should be easily done for the biorefinery.

Extractives: Easily negligible chemical compounds from detoxification

When talking about detoxification of biomass hydrolyzate, almost all the research and studies focus on these compounds such acetic acid, sugar degraded products (furfural, HMF etc). However, small amount of extractives exist in the hydrolyzate, which is often ignored. Actually, some of these extractives, naturally exist in biomass for coloration and as insectcides, which are also toxic to miroorganisms. For example, stilbenes are generally very toxic! So, it is not enough to remove just furfural and acetic acid.

Typical extractives in tree:

- Resin acids (no or little in hardwood)
- Fatty acids
- Monoterpenes (turpentine)
- Phenolics (Gallic acid, vanillin, Stilbenes, Flavonoids, Lignans)

- Others (Alkanes, Proteins, Monosaccharides and derivatives)

Extractive components are “small” molecules that can be extracted with a solvent from wood, bark, or foliage.
-Generally, extractives are present in small amounts.
-Extractives vary tremendously within species, between species, and within trees.
-There are thousands of different extractives present in wood.

Enzyme torwards breakdown lingin in biomass hydrolysis

The traditional enzymatic hydrolysis of biomass is to hydrolyze pretreated biomass to release monomer sugars for further processing. A new different approach has been reported recently on the research at MSU: it focused the white-rot fungus that is often found on rotting wood and used for biopulping. The fungus contains the peroxidase enzyme that initiates lignin breakdown. After isolation from the fungus, the enzyme-producing gene was reproduced by introducing it into E. coli. The idea was to to isolate the gene, slice out the DNA and basically have the bacteria eat the lignin.

Efficient ethanol fuel cells could be practical soon

A new catalyst cable of breaking ethanol's bonds and generating electricity could soon result in practical portable fuel cells powered by ethanol, according to Technology Review.

"NEW KIDS ON THE BLOCK"

According to ICSI.com, "There is currently a limited talent pool of experienced sustainability executives...".

"The chemical industry, however, is a different animal when it comes to looking for CSOs. Aside from the required tree hugger and company-conscience roles, sustainability leaders of chemical companies need to be technically and financially savvy, understand how the industry operates from top to bottom, and be a long-term strategic thinker."

Actually, there is a great need of real professionals who has solid technical background and experience in these areas. However, we can not build up the Rome city overnight. It takes time and need more patience... Otherwise, the fake experts will cause more problem than the fresh learners.

Detoxification of hydrolyzate by activated carbon

Activated carbon is known to have high affinities for colored impurities in hydrolyzate of sugar mixtures, and its unit cost is relatively lower and it can be reactivated and reused.

It has been found that the affinities of acetic acid and furfural (and HMF) are much higher than that of the sugars. The key parameters include activated carbon particle size (surface areas), the ratio of activated carbon to hydrolyzate, temperature, and adsorption time, etc.

The activated carbon can be packed into a column and the hydrolyzate will be pumped into the column. The residence time will be determined by the flow rate and the length of the column.

A inline IR or UV detector can be used to monitor the compounds in the eluent.

Integration of pretreatment and enzymatic hydrolysis of biomass

This a new concept: The biomass is first pretreated with water only or with other chemicals. After pretreatment, the treated biomass and slurry is enzymatically hydrolyzed without separating the solid and liquid.

Here is one of the research projects conducted at The BioEnergy Science Center.