Is Algae and Bacteria the Perfect Combination for Biodiesel Production?

[Ivan Seeking]

A number of strains of microalgae are known to produce relatively high yields of energy as fuel stock [pre-biodiesel] in the form of plant oils, as a function of area and time - typically as BTU/acre-year, or MJ/hectare-day, etc.

From a review of the literature, it is my perception that microalgae have the highest solar conversion efficiency [in producing sugars and oil] of any plant option due to not only the simplicity of the organism, but also because its small size and geometry allows for approximately 100% utilization of the available sunlight. So, for starters, is my information correct?

Next, one of the biggest challenges in making biodiesel from algae is the extraction of the oils. That, combined with the fact that algae consists of sugars, oil, and fiber, suggests to me that bacterial processing of algae could be an ideal approach to fuel production.

How does it work? A special type of genetically altered bacteria are fed plant material: basically, any type of sugar. They digest it and excrete the equivalent of diesel fuel.

Humans have used bacteria and yeast for centuries to do similar work, creating beer, moonshine and, more recently, ethanol. But scientists' recent strides in genetic engineering now allow them to control the end product. Watch the fuel-making process at work »...

http://www.cnn.com/2008/TECH/science/08/12/bug.diesel/index.html

It seems to me that while producing fuel from the available sugars, the bacteria would consequentially release the oil stored in pockets, in the algae. So we get not only the oils already stored in the algae, but also the oils converted from sugars by the bacteria. This would seem to solve many problems with algae processing while increasing the yields. Also, if algae has the highest conversion efficiency [sunlight to hydrocarbons] of any plant - as a function of area and time - then it would seem to be the ideal choice for fuel production using engineered bacteria.

Thoughts?

 

[alxm]

From a review of the literature, it is my perception that microalgae have the highest solar conversion efficiency [in producing sugars and oil] of any plant option due to not only the simplicity of the organism, but also because its small size and geometry allows for approximately 100% utilization of the available sunlight. So, for starters, is my information correct?

Algae don't utilize anywhere near 100% of the available sunlight. More like 10% of the sunlight in the absorption range for that particular algae*.

Next, one of the biggest challenges in making biodiesel from algae is the extraction of the oils.

It isn't. Conventional extraction methods from chemical engineering work just fine**.
I'm not sure how you think bacteria could do the job. Do you happen to know of any bacteria that do that?

Anyway, the use of bacteria to perform an anaerobic digestion of the remaining biomass in order to produce biogas (and perhaps other useful products), which could provide the energy for the production and extraction processes, is already being proposed.

*Bolton, J.R. (1996) “Solar photoproduction of hydrogen.” Report to the Int. Energy Agency, IEA/H2/TR-96.
** Belarbi, et al, "A process for high yield and scaleable recovery of high purity eicosapentaenoic acid esters from microalgae and fish oil", Enzyme and Microbial Technology 26 (2000) 516 –529

 

[Ivan Seeking]

Algae don't utilize anywhere near 100% of the available sunlight. More like 10% of the sunlight in the absorption range for that particular algae*

That is the conversion efficiency - actually I think that is the typical par [photosynthetically active radiation]. But I am talking about geometry in addition to the efficiency in converting water and CO2 into sugars and other hydrocarbons.

It isn't. Conventional extraction methods from chemical engineering work just fine**

They are energy intensive [and/or expensive].

I'm not sure how you think bacteria could do the job. Do you happen to know of any bacteria that do that?

See the link.

Anyway, the use of bacteria to perform an anaerobic digestion of the remaining biomass in order to produce biogas (and perhaps other useful products), which could provide the energy for the production and extraction processes, is already being proposed.

That is also true. The bacteria linked in the report would convert this biomass directly into fuel, which is the point of the thread. In the process, it seems to me that pockets containing the oil would be degraded and release the oil.

The point is that it might maximize the oil production rate and efficiency by combining the two technologies.

 

[Ivan Seeking]

Centrifuges have always been a weak link in the algae process. They are energy intensive and problematic. If the oils could be released while the algae is in suspension, perhaps as a 10% solution, after a settling pool, the centifuges might be avoided altogether.

The original methods of releasing the oils involved presses and or chemicals. There are people using other technologies, such as ultrasound, and pressure based extraction methods. and I have even heard of microwaves being used to explode the oil pockets [I think], but in all cases the process is an energy negative and an expense. By using bacteria to do this job, the process becomes a net energy and financial positive.

Part of the point here is that while algae will readily produce plant oil, there is always a compeitition between oil production, and sugar production. There is actually a biological switch that selects for one or the other. The bacterial process would make this issue moot as both the sugars and oil are ultimately used as fuel stock.

 

[alxm]

Centrifuges have always been a weak link in the algae process. They are energy intensive and problematic. If the oils could be released while the algae is in suspension, perhaps as a 10% solution, after a settling pool, the centifuges might be avoided altogether.

Centrifuges are not used for oil extraction AFAIK, but simply to remove as much water as possible.
Not that I see the problem here, given that centrifuges/cyclones are used all the time in ordinary chemical engineering.

The original methods of releasing the oils involved presses and or chemicals.

Which doesn't make it expensive since the chemicals are not consumed in the process and can be reused. Liquid phase extraction is a quite common, cheap and mature tech.

There are people using other technologies, such as ultrasound, and pressure based extraction methods. and I have even heard of microwaves being used to explode the oil pockets

These are technologies to break up the cellular membranes. I don't know of any bacteria that can do that. In fact, with most microbacterial techniques, you still end up needing to do that job.

Part of the point here is that while algae will readily produce plant oil, there is always a compeitition between oil production, and sugar production. There is actually a biological switch that selects for one or the other. The bacterial process would make this issue moot as both the sugars and oil are ultimately used as fuel stock.

Well that's a fine idea, provided you can find some bacteria that will both break up algae and turn the resulting sugars into oil, and then break up themselves.

 

[Ivan Seeking]

Centrifuges are not used for oil extraction AFAIK, but simply to remove as much water as possible.
Not that I see the problem here, given that centrifuges/cyclones are used all the time in ordinary chemical engineering.

A review of the industry reveals that centrifuges are highly problematic. This goes all the way back to the Aquatic Species Program that first studied algae for fuel production. Right now there is an engineer at OSU working to resolve some of these problems. He gives it five years before the issues are all resolved [which means it could take much longer]. Also, it is an energy negative. The efficiency of the processing has a direct bearing on the viability of algae as a fuel source.

Which doesn't make it expensive since the chemicals are not consumed in the process and can be reused. Liquid phase extraction is a quite common, cheap and mature tech.

Are you talking about supercritical extraction methods?

These are technologies to break up the cellular membranes. I don't know of any bacteria that can do that. In fact, with most microbacterial techniques, you still end up needing to do that job.

Are you kidding here? Have you read the link? That was what motivated the thread in the first place.

Well that's a fine idea, provided you can find some bacteria that will both break up algae and turn the resulting sugars into oil, and then break up themselves.

Either read the link or please quit responding.

 

[Bob S]

Algae don't utilize anywhere near 100% of the available sunlight. More like 10% of the sunlight in the absorption range for that particular algae.

I think the best agriculture (vs. aquaculture) fuel conversion efficiency is about 2% (for miscanthus biofuel), so 10% is a big number. Food sugar (meaning saccharide- C₆ H₁₂ O₆) production in grains (wheat, rice, etc) is in the realm of 0.1%, which is why the World needs about 4 billion acres of cultivated land to produce food for 6.7 billion people.

All we have done in the last 10,000 years since we began farming is interbreeding crops for better yield, tolerance for drought, and resistance to disease etc. Crops are still using the old Calvin (or C4) photosynthesis cycle. How about having bacteria create food sugars with 10% efficiency?