Exploring Microalgae as Solutions to Global Fuel Issues

[Ivan Seeking]

Well it seems there are two goals with biomass to ethanol/diesel fuels that may or may not be independent, depending on other factors. One is to capture solar energy in a stored form as efficiently as possible, and the second is to provide liquid fuels for transportation. These goals may be independent if the transportation market remains combustion engine based for decades, but other energy sources besides fossil somehow become cheap. Say for instance that nuclear fission power actually does become plentiful and 'too cheap to meter', while transportation fuels remain costly. Then it very well might make sense to supplement algae growth with things like electric lights or chemically produced sugars, as the conversion efficiency would be less important, while the demand of the final product remained high.

True. However, assuming the remaining practical issues can be resolved, and until we remove the requirement for an energy source, for now the elegance of the algae solution is undeniable. As you pointed out, algae-derived fuels actually solve two problems as once...three if you include the CO2 problem.

Then there is the potential for the remediation of municipal, industrial, and agricultural waste... I don't recall ever seeing a solution to a serious problem that operates on so many different levels.

It would have been nice to get a piece of the action, but at least the big players are involved now.

 

[Ivan Seeking]

Based on this I would suspect a practical limit for algae oil of less than 10,000 gallons an acre. Even within these limits thew authors point out that that algae has far more potiental than other biofuels, such as corn or soy.

After many months of research, that is where I landed as well. In fact, if you go back to the Aquatic Species Program, you will find peak yields of about 5000 or 6000 gallons per acre-year. It was believed at the time that the yields could be improved significantly, but some evidence now suggests that these may have been practical limits [not to include strains produced through genetic engineering or hybridization]. Between various biological factors specific to the algae, water circulation rates, and the depth of the water, the energy input to the system is unavoidably reduced in any real system. After mulling over many different design concepts for bioreactors, my own impression is that probably comes out about right. Take your theoretical max yield and divide by two as a best case.

 

[Ivan Seeking]

Here is one more thought that is what actually drove me to get involved in the algae business: One can beat the divide-by-two rule that I was following, but to this end I saw people using high-tech approaches that utterly defeat the system through cost. No matter how efficient a system might be, $20 or $30/gallon fuel is nothing but a curiosity. Beyond that, upon considering the energy required to produce those costly materials, the lifetime energy efficiency of the entire system has to be reconsidered. I became convinced that the high tech solutions have their place only in the biology and processing of algae, but not in the farming of it. Due to the scale of the problem - the many millions of acres required to supply the world's energy needs - it is hard to imagine any practical algae farm that has a high cost per unit area. As I have mentioned before, in my efforts, given the constrains listed in the posts above, as a practical business model, the dictated cost per sq foot of bioreactor made it all but impossible to make [design and build] anything at all. I thought it was doable given those constraints, but just barely using a $3/gallon model, using low-tech but hopefully clever solutions, and only after many months of hard work and fixating on the problem almost entirely [ask Integral]. Even with the various and presumably vast improvements to the processing methods being tested, we are still on the order of dollars [maybe one digit only] per sq foot of bioreactor surface, per year, as an amortized cost. Beyond improved processing techniques, and assuming gas doesn't hit $20 per gallon, the only other variables that I can see here are the characteristics of the algae strain used. Algae can presumably be engineered so that much higher yields are possible. So that lands in the laps of biologists.

Improving yields by 50%, while increasing the amortized cost per unit area by 800%, makes no sense. It doesn't take rocket science to figure that one out. For perspective, recall that one acre is 43,560 sq ft.

 

[Ivan Seeking]

we are still on the order of dollars [maybe one digit only] per sq foot of bioreactor surface, per year, as an amortized cost.

Yikes! I'm glad I checked this. That should be in units of square meters, not square feet. A quick check of the math reveals that this cost is the most siginficant to any system even assuming the most optimistic yields. This also brings to mind the fact that ocean surface area comes for free, as compared to land. There is no purchase price or taxes. The cost of land is a major consideration.

 

[joelupchurch]

I think we should keep in mind that Biodiesel wouldn't be the only revenue stream for an algae farm. What remains after the oil is removed can be sold as animal feed. An algae farm can also be used to process sewage and capture CO₂ from power plants.

Some of the estimates I've seen for carbon capture, indicate that the cost per KWH would at least double for coal plants just for the carbon capture and not even calculating the sequestration charges. Using an algae farm would provide offsetting revenue and probably be cheaper to operate, since the energy to capture the CO₂ would come from the sun rather than using salable power from the plant.

Biodiesel using CO₂ from a power plant doesn't sequester the CO₂, but since it are displacing displacing conventional diesel, the effect can be similar.

 

[mheslep]

I think we should keep in mind that Biodiesel wouldn't be the only revenue stream for an algae farm. What remains after the oil is removed can be sold as animal feed. An algae farm can also be used to process sewage and capture CO₂ from power plants.

Some of the estimates I've seen for carbon capture, indicate that the cost per KWH would at least double for coal plants just for the carbon capture and not even calculating the sequestration charges. Using an algae farm would provide offsetting revenue and probably be cheaper to operate, since the energy to capture the CO₂ would come from the sun rather than using salable power from the plant.

Biodiesel using CO₂ from a power plant doesn't sequester the CO₂, but since it are displacing displacing conventional diesel, the effect can be similar.

The net effect is to allow the use the same carbon atom twice before it's released to the atmosphere, i.e. double the amount of useful energy produced per C. Helps, but does not completely cure the carbon problem.

 

[Ivan Seeking]

The net effect is to allow the use the same carbon atom twice before it's released to the atmosphere, i.e. double the amount of useful energy produced per C. Helps, but does not completely cure the carbon problem.

That is why, it seems to me, there is no reason to use the coal. If a closed CO2 capture system can produce a cost-competitive fuel, then replace the coal with algae biomass or an algae-derived fuel. Now we have a closed system that not only captures the carbon from a generating station, but also preserves the nutrients needed for the next batch of algae. The nitrogen, phosphorous, and CO2 problems all go away. The water is preserved as well. Algae takes the hydrogen from water in order to grow, and we get it back from the burner's exhaust stream.

We do have to be careful when considering byproducts. Everyone expected to recapture some costs from the production of biodiesel from soy, by selling the glycerin that reacts out of solution. However, as biodiesel production increased, the bottom fell out of the glycerin market.

Something else to be considered is the mind-numbing quantity of biomass that is left over after processing the fuel.

 

[mheslep]

That is why, it seems to me, there is no reason to use the coal. If a closed CO2 capture system can produce a cost-competitive fuel, then replace the coal with algae biomass or an algae-derived fuel. Now we have a closed system that not only captures the carbon from a generating station, but also preserves the nutrients needed for the next batch of algae. The nitrogen, phosphorous, and CO2 problems all go away. The water is preserved as well. Algae takes the hydrogen from water in order to grow, and we get it back from the burner's exhaust stream.

Hmm, yes that seems right. A closed system rules out using bio algae directly for transportation fuel, but then we've discussed before how it appears to be more efficient to burn algae derived fuel at the generating plant to make electricity for transportation.

I'm imaging a ~100megawatt plant, surrounded by algae tanks. So how much land for a ~100MW plant? 35% eff rankine cycle, 10,000 gal/acre-year, 140 MJ/gallon? Not accounting for energy to process to algae to BD, I get just ~100 acres for the algae tanks.
Edit: Interestingly, http://solar.coolerplanet.com/News/10130902-albiasa-concentrating-solar-power-back-on-mohave-county-arizona.aspx" concentrated solar plant wants 1800 acres for a 200MW facility.

 

[Ivan Seeking]

I get just ~100 acres for the algae tanks.

X 2 [divide by two rule] X 1.6 [energy required to operate]

hopeful approximations.

mheslep, IIRC, you were the one who posted Exxon's expectations of, I think, 3500 gallons per acre-year, as a net-net yield? If I read this correctly, it would be closely in line with the approximations suggested above.

 

[Ivan Seeking]

Doggonnit! You you all got me thinking about all of this again. There are still plenty of niche opportunities.

Funny! Algae-fed beef means that big fat juicy steaks are off the endangered species list.

Talk about elegance!

I just wanted to complete the one calculation in case anyone miseed it. If we want to sell fuel for $3 retail, we need to be around $1.5 wholesale [testing, taxes, resale, etc]. At 3500 gallons per acre-year, we gross $5250 per acre per year. So, at 43560 sq ft per acre, we gross 12 cents per sq ft per year. We have already paid for the energy to operate, but we still need to pay for labor, and the amortized cost of land, bioreactor hardware, and supporting hardware like pumps, pipes, and the processing equipment. Not to mention the interest on loans, insurance... donuts for board meetings...

Nitrogen, phosphorous, and CO2 supplies? Assume those are free. This is still a terribly difficult budget to balance, but I think it can be done, now. Obviously any rise in price of gas or diesel makes this easier.

Oh yes, we haven't made a profit yet. That's all just to break even,

 

[mheslep]

X 2 [divide by two rule] X 1.6 [energy required to operate]

hopeful approximations.

mheslep, IIRC, you were the one who posted Exxon's expectations of, I think, 3500 gallons per acre-year, as a net-net yield? If I read this correctly, it would be closely in line with the approximations suggested above.

2000 g/a-y, or so they said at the initial press release.
https://www.physicsforums.com/showpost.php?p=2271740&postcount=239

 

[mheslep]

Doggonnit! You you all got me thinking about all of this again. There are still plenty of niche opportunities.

Funny! Algae-fed beef means that big fat juicy steaks are off the endangered species list.

Talk about elegance!

I just wanted to complete the one calculation in case anyone miseed it. If we want to sell fuel for $3 retail, we need to be around $1.5 wholesale [testing, taxes, resale, etc]. At 3500 gallons per acre-year, we gross $5250 per acre per year. So, at 43560 sq ft per acre, we gross 12 cents per sq ft per year. We have already paid for the energy to operate, but we still need to pay for labor, and the amortized cost of land, bioreactor hardware, and supporting hardware like pumps, pipes, and the processing equipment. Not to mention the interest on loans, insurance... donuts for board meetings...

Nitrogen, phosphorous, and CO2 supplies? Assume those are free. This is still a terribly difficult budget to balance, but I think it can be done, now. Obviously any rise in price of gas or diesel makes this easier.

Oh yes, we haven't made a profit yet. That's all just to break even,

At 12 cents per sq ft I now see the problem w/ the cost of a making a bioreactor. What was the est. lifetime of your reactor? 10 yrs?

 

[Ivan Seeking]

At 12 cents per sq ft I now see the problem w/ the cost of a making a bioreactor. What was the est. lifetime of your reactor? 10 yrs?

Some components of the system I envisioned [and crudely tested], such as pvc pipe, were good for twenty years, but the killer is the plastic. It was a bit of a draw between UV resistant plastic good for 5 or 6 years [I think some might have been rated as good for ten years], or lower cost plastics that would only last 3 years. The life of the plastic is determined primarily by the optical properties of the material. Over time, even the highest quality greenhouse plastics will become cloudy and transmit significantly less light. It was also necessary to allow for incidental damage, as well as getting wiped out by a storm from time to time. The risk of damage from storms is what drove me to the lowest-cost materials having a relatively short life expectancy. That in turn drove up the cost of labor, but labor is relatively cheap. From there, it was critical to design for 9 out of 10 years of storms, for example. That, combined with planned maintenance rotations made it appear to be feasible. On any given year you plan to lose 33% of your plastic anyway.

I found myself landing about as far away from a high-tech solution as one can get. There is nothing like a budget to bring one back to earth.

The next logical step is to reduce the cost of the plastic by recycling it onsite.

 

[Ivan Seeking]

2000 g/a-y, or so they said at the initial press release.
https://www.physicsforums.com/showpost.php?p=2271740&postcount=239

Maybe it was DARPA who cited 3500. Anyway, I think the difficulty of this challenge is fairly obvious now. But apparently I [we?] am not alone in thinking it's doable.

Joel got scared and ran for the government money.

 

[OmCheeto]

I found myself landing about as far away from a high-tech solution as one can get. There is nothing like a budget to bring one back to earth.

The next logical step is to reduce the cost of the plastic by recycling it onsite.

I keep running across places that have problems with http://english.aljazeera.net/news/americas/2009/11/2009112219319226668.html" .

Seems like a skimmer like they use on oil spills could be used in some of these spots to harvest the algae. http://en.wikipedia.org/wiki/Lago_de_Atitl%C3%A1n" has an area of 32,000 acres. A low tech system that continuously removed the algae would both clean up the lake and create a nice profit, even with a low octane strain of natural algae.

Perhaps they could build a floating corral in the middle, ala fish farms, say 10,000 acres, pump their poo out there, let the algae eat it, harvest the algae, etc, etc. (I suppose the acreage would be based on local population size: poo/person/day/how much the buggers can eat.)

I think the Chinese might lend them a hand, as they have quite a bit of http://news.bbc.co.uk/2/hi/7482791.stm" !

Ivan, I think you need to learn Mandarin, and go have a talk with those folks.

 

[Ivan Seeking]

I keep running across places that have problems with http://english.aljazeera.net/news/americas/2009/11/2009112219319226668.html" .

Wild algae strains tend to be poor sources of oil for biodiesel, however it seems possible that it might be used as biomass for generating stations; in place of coal, for example. I have no idea what energy content is found or the maximum temp at which the algae would burn, but I haven't seen it ruled out as a viable option yet either.

By remediating agricultural and municipal waste streams with algae under controlled conditions, perhaps unwanted natural blooms can be avoided. One major cause of unwanted blooms is nitrogen, which the algae obviously love. In fact the cost of nitrogen is significant for algae farmers.

 

[Ivan Seeking]

The next logical step is to reduce the cost of the plastic by recycling it onsite.

Which hints at perhaps the most important realization of all, for me at least. This is not a scalable problem. I began with a willingness to manage $100K of cash expenses, or so, in order to get proof of concept using a few acres at most. From there, I hoped to gain access to some serious money, but still with 500 acre sites, and $millions in capital in mind. As we continued to work the nuts and bolts of doing this, it became more and more clear that, while it appears to be doable based on the cold hard facts and some best guesses, it depends on the economy of scale. Given the constaints assumed, I don't tend to see solid prospects for profitability until we are talking about thousands of acres of bioreactor surface per site. 50,000 acres looked to be quite profitable, in the right location.

Of course, at the time the price of fuel was skyrocketing. Also, with improved processing techniques and technolgies, as well as improved strains provided by biologists, the bottom-line numbers should improve for some time to come. Consider for example that even the best algae strains only use a small percentage of the available energy. So we could see dramatic improvements in the yields per a-y. However, my goal was to find a model that would be profitable today. In order to do that, it appeared that it was going to take many tens or hundreds of millions of dollars.

Enter, Exxon and BP.

 

[mheslep]

Maybe it was DARPA who cited 3500. Anyway, I think the difficulty of this challenge is fairly obvious now. But apparently I [we?] am not alone in thinking it's doable.

Yes we, at least I agree if any biofuel can pay off (without guvvament $) algae is it.

 

[Ivan Seeking]

For anyone interested, since at this point my effort is dead, here are some more specifics of what was learned and considered. By no means do I claim our approach would have worked [unless you are an investor : D]. We still had a long way to go before any real system would be built. But it does all address some of the practical concerns in doing this. There are still some very difficult issues to resolve.

One of the most difficult issues is that of purity. Strains will mutate from good producers to poor producers. Also, to maintain 50,000 acres of pure algae growth is a practical impossibility. This is a problem because the first thing a biologist wants to do is sterilize everything in an autoclave for 24 hours.

Firstly, there is the threat that invasive algae, bacteria, or viruses, will contaminate the system; significantly reducing yields. All that it takes for that to happen is for one contaminated bug to get into the system. Beyond that, it is difficult to imagine any system of a practical size that can be completely sealed. So, either we will have contamination or we have to farm the algae in sacrificial containers. But when we get back to our 12 cents per sq ft per year, and considering that we might expect to harvest each batch once a month or more, the idea of sacrificial containers does not seem viable. The question becomes one of how to manage the contamination.

My take was that contamination might be managed in a closed batch system, but any open or continuous-yield system is far too vulnerable. In fact, there is a local story about a couple of scientists who struck gold in a local lake. The indigenous strain choking the lake was very valuable in the health food world, so they started harvesting the stuff and were making a small fortune. The bloom suddenly died and they never knew why. Practically overnight they were out of business. So, with known vulnerabilities and those sorts of examples in mind, and also considering that a closed and controlled system can produce higher yields, it seemed that a closed batch process was the only viable option. From there the trick would be to balance contamination concerns with operating costs.

My solution was to maintain a three-tier system. First are the pure lab-grade cultures that are grown and maintained according the highest lab standards. This would be a small system with tens or hundreds of gallons [depending on the size of the farm] of pure culture maintained, and perhaps new cultures from UTEX continuously being used for starts. We use the pure cultures to charge a larger but less pure and closely monitored system, on the order of tens of thousands of gallons. The second stage is used to charge each field batch. Each field cell would be charged to such a level [ratio] that the desired algae was certain to dominate the batch cell. The reasoning being that with a relatively fast-growing algae and a strong enough charge, nothing else would have time to do significant damage before we harvest. Also, by doing this and periodically purifying the second stage system, we constantly introduce pure and healthy culture. This way we avoid the potential for mutations that could take to the entire system down for months. We have enough second stage solution to recover quickly [one batch cycle] should the entire system have a problem and we need to start from scratch. Field cells would have to be periodically sanitized using bleach, so at any time some number of batch cells are out of service for treatment.

.
As far as the design of the bioreactor, as one can probably tell by the budget, for a land-based system, we are effectively talking about tented lined ditches. From there it doesn’t take long to realize that land preparation is critical to make this possible. Very large and expensive custom equipment is needed. This is what quickly drives one to the 50,000 acre model. By the time things began to fall apart, - as this continued to go beyond our reach – we realized that much of the real work would be to develop the equipment needed to do this. And that shouldn’t be a surprise, really. The same is true for all large farms, but a food farmer has a much higher budget per unit area.

In order to make a system as I [eventually, we] envisioned, you need think in terms of miles and miles and miles of a very cleverly designed but dirt-cheap bioreactor. I even imagined a machine that produces the reactor as it lays it down in the field, but by that time it was clear that this was getting more and more expensive.

The reactor has to be drained and filled for each batch of algae, and it all has to be serviceable for cleaning in some fashion. It must survive rain, wind, and hail storms. To a certain extent, temperature control is required, esp depending on the location. Aeration is also required, as is circulation. As the algae flocculates out of solution, it tends to stick to the bottom of the bioreactor, so that needs to be addressed when draining a cell.

I won’t go into all of the details, but I think we had a way to manage all of it. Nonetheless, this is probably the most difficult practical problem I have ever considered. Many of the problems are not sophisticated, just terribly difficult from a practical point of view.

It is hard to deny the advantage of doing this in large lakes, or in the ocean. This seemingly voids the cost of land and the problem of temperature regulation, both of which are critical issues. You quickly start to imagine what amounts to giant water-filled baggies floating in the ocean. My tested solution to temperature control for heat was to capture and redirect evaporated water, rather than allow it do go right back into the algae water. After the water has cooled overnight, put it back into the system. It is also possible to some extent to manage temp as a function of the season. By anticipating the position of the sun and the relative orientation of the bioreactors, something as simple as white stripe of paint in the right place can shield the algae from the direct and damaging light of a summer sun, while allowing for all light to be captured in the winters months when the sun is at lower angles. This idea was also tested and seemed to work very well. After a couple of crops started to die off from heat and light, through the use of a white stripe of paint and evaporation control, I was able drop the temp siginficantly, by up to ~ten degrees, and was able to maintain good growth even during the warmest days of the year. Seemingly difficult problems can sometimes be resolved with very simple solutions. You just have to think about it for a few hundred hours, nonstop.

It also becomes obvious that one wants to run probably several different strains of algae, depending on the season. That is another reason why a batch system is the best choice, imo. This allows one to vary the strain according to conditions.

 

[Ivan Seeking]

late edits - a few more critical thoughts that I wanted to pass along.

 

[Ivan Seeking]

By using a shaped ditch as a form for the bioreactor, the cost of the bioreactor is greatly reduced. Nearly all of the structural integrity issues go away less for the top surface. This also helps with temperature regulation. Based on drainage concerns - the need to be completely emptied - it appeared that the best shape for the “ditches” was a simple or slightly modified V. The shape of the ditch also plays a role in aeration and circulation. Unfortunately, it does not appear to be possible to provide enough slope for the algae to settle completely at the vertex for easy drainage. Some algae will be left stuck to the side walls. This is true even for vertical walls made of glass.

It appeared that it was possible to use a single pipe with carefully spaced and sized holes, to fill, drain, and aerate each cell. This reduces the cost of materials significantly by using one pipe in place of three. By playing games with the size and spacing of the holes, one can achieve approximately uniform aeration over a finite length of pipe. One even finds that water pressure allows the end of the pipe to be left open, which is helpful when the pipe is acting as a drain. This is also likely what best determines the length of any given batch cell. Beyond a certain length, it is not possible to do this using only one pipe. Balancing the system for uniform aeration is no small challenge. Even slight changes in the depth of the pipe over its length created relatively siginficant variations in backpressure.

The depth of the aeration pipe, as well as the length of run between an air source and a given cell, largely determines the energy required for aeration. So, deeper water means that we need more power to run the farm. This tends to drive the design to shallow ditches. Next, the length of run – backpressure - for water and air pumps is a concern that interestingly is made more difficult by scale: A larger farm means longer air and water pipe runs, hence more energy per unit land area is required for pumps than is required than for a smaller farm. So, the geometry and topology of the entire farm is driven by energy considerations. In order to make a farm most efficient, a great deal of effort should be made to first select a good site, and then modify the land as is required. In principle, you only have to move the dirt once and it pays back for the life of the site. I assumed that these costs could be amortized over thirty years.

Another set of variables driving the depth of the ditches is temperature regulation. My approach was to assume max and min ambient temps, and then to consider the energy input to the system through solar radiation, and energy lost and gained through heat conduction to or from air and land. From there, ideal max and min water temps were selected. By using the heat capacity of the water and the assumed range of acceptable temps, the minimum acceptable water depths [volumes] were calculated. Obviously we want deep water for the greatest temp regulation, but recall that this means that we use more energy for aeration. One also finds that water circulation is required in order to maximize the rate of the algae growth. This in turn wants to drive the system to a minimum volume. Beyond that, the cost of land preparation is minimized with shallow ditches. In the end, my best efforts suggested that we want an ~ V having a depth of something around 8 inches, and about a 45 degree slope for each wall. I would have to dig into my notes to give you the precise numbers calculated but that is close, just for perspective. Initial testing suggested that the depth of the water combined with other solutions mentioned in the previous post, were sufficient to maintain the desired temperature buffer to ambient extremes. But I was only able to test the design for about six months ~ June through December.

 

[mheslep]

By using a shaped ditch as a form for the bioreactor, ...

Using just soil for support, no other improvement? How would you maintain that through rain, and prevent erosion or flooding of the ditch?

 

[Ivan Seeking]

Using just soil for support, no other improvement? How would you maintain that through rain, and prevent erosion or flooding of the ditch?

Here is the basic idea:

There would be no exposed soil. Land preparation requires the use of high compression [many tons, very big machines] in forming the ditches. Anchor rods are driven into the ground at specific intervals, which in turn would allow the bioreactor to be secured later by design. This is all something done only once over the life of the farm.

The liner considered was a relatively heavy plastic good for at least ten years or more, in theory. For the most part it covers the entire field. This cost seemed to be manageable. In the end this must all be made to fit. So there we have more specialized machines.

The roof of the reactor is sloped as a low A-frame and designed for easy replacement [3 year UV rating]. This also allows a cell to be opened for servicing if needed. I never did decide if it made more sense to use a less expensive support structure – a simple spring-wire system, for example - to cover each ditch independently, or if it made more sense to cover several ditches with a single canopy. Obviously the least amount of height is required if each ditch has its own top. This means that we suffer the minimum lateral forces from wind. A taller roof required stronger materials but could cover several ditches, making things more accessible. This may need to be as much as 24 inches in height. So this becomes a bit of a practical question. In either case, one plastic pipe running the length of a group of cells, with evenly spaced vertical supports secured to the attachments points, seemingly makes it possible to stay within the budget while providing a suitable structure. The plastic for the roof uses a tension in order to maintain its shape, as is done for the Denver airport, for example – much the same idea principle that is used for tents for camping. The tension for any canopy can be adjusted as it stretches and ages. This is all done with nickel and dime hardware having a long lifespan. It is also integral to the design of the reactor and its top. It takes some thought to manage all of this.

Integral to each group of cells, perhaps in groups of four, is a drainage system that doubles as a walk space. Basically it is just a deeper and wider ditch inserted periodically between groups of cells. Ultimately this all ties into a standard system at the nearest branch point, but the point is that the majority of the field can be drained without using any pipe. .

Water costs money and we need tons of the stuff. It makes sense to capture and use all of the water possible. While we did have a land-use expert attending our official startup meeting, I never got so far as to discuss the proper land management in this regard. Presumably we may need to allow for a certain amount of rain water to go back into the soil. But water costs money, so it makes sense to keep all that you can catch. Plus, we really want the soil rock-hard in order to maintain its shape, which I assume means that we want to keep it dry. To whatever extend excess water presents a problem, my hope was that we could always dump to standard leach lines located well below the bioreactors. Also, ideally, perimeter control – redirecting runoff - would provide additional protection against flooding.

 

[Ivan Seeking]

I should also mention that wrt the roof or lid for each cell [and the liner for that matter], it may be that a hard plastic shell could be made having the required design characterstics - the proper shape and function, as for evaporation control, and the ability to withstand hailstorms and UV - without creating too much cost per unit area per year. My concern here was the ability resist impacts. By using the sheet plastic under tension, the system can be designed to flex in response to severe conditions. Whether hard or soft plastic is the best option is not known, but for testing purposes the soft plastic allowed for easy modifications and was immediately functional - no custom hardware required. It was also known that soft plastics would likely satisfy the budget.

 

[Ivan Seeking]

That covers the basics, but I will continue to post anything that seems particularly relevant. I am working from memory here so bits and pieces keep occurring to me.

When I first presented the idea of using a compressed dirt surface as a base, our land expert and our chemical engineer [a bit of a big shot] looked at each other and immediately suggested that rather than using a liner, the surface could be sprayed with a waterproof compound that would be extremely cheap. I never did learn more about the specific compound they had in mind, but apparently this is environmentally friendly and lasts for many years. It would make repairs incredibly simple - just point and spray. My impression was that this is something used by the road department.

Note that since at least 40% of the energy harvested is needed to run the farm, onsite generators are needed. This is another aspect of the problem of scale. Only when we get into very large generators are acceptable efficiences achieved. But there is a bonus: The generator exhaust can also be used to enrich the air supply to the field cells, in turn helping to increase the yields. The chemistry of doing this was only briefly discussed but our chemist seemed to feel it was manageable. A 40% return on the carbon is significant. This assumes that we lose the other 60% to fuel production. In the case of a closed system used for a commercial generating staion, we intend to capture all carbon by design.

The energy required for aeration can be a killer. In order to stay within the energy budget, I found it necessary to not only minimize the required system pressure for aeration, but also to evaluate the required duty cycle and mixture for any cell. Firstly, we need no aeration when the sun goes down. Next, the mass ratio of algae to water immediately after innoculating a cell, may be as low as 0.001%, at which time a minimum of CO2 is needed. At harvest time we expect to have ~ a 1% solution by weight, so we might require 1000 times the CO2 for growth at the end of the batch cycle as we do in the beginning. This allows one to throttle the energy consumption for any cell as a function of the batch cycle time. This is also where the exhaust stream from the generators becomes critical. We can run a very rich mixture using a high duty cycle only for the cells with a high CO2 demand. This minimizes the mass of air that must be moved for each batch of algae.

Since I was using aeration to assist with circulation, the duty cycle was considered rather than throttling the rate of flow. A blast of aeration helps to keep things in suspension.

 

[chemisttree]

Something else to be considered is the mind-numbing quantity of biomass that is left over after processing the fuel.

You mean the fish food? Seems an adjacent menhaden fish oil facility might be in order.

 

[turbo]

The liner considered was a relatively heavy plastic good for at least ten years or more, in theory. For the most part it covers the entire field. This cost seemed to be manageable. In the end this must all be made to fit. So there we have more specialized machines.

You don't need to buy those machines or source the materials, though. Your liner-contractor can save you lots of money in materials (they buy by the truck-load or rail-car load) and save you from having to pay for the purchase/maintenance of expensive specialty tools and the training to install the liners properly. Until he tired of the constant travel, my little brother was foreman for a large company that specialized in lining ponds and storage pits and capping landfills. The liner material is cut and laid out to conform to the contours of the substrate, then the seams are "welded" with special machines. If the job was planned properly, they could pretty much keep with the earth-movers and line your reactor-ditches as they were created.

Note: Proper siting could save you a TON of money. If you could get your mitts on nice level acreage underlain by blue marine clays, you could scrape off the topsoil with pan-bellies (sell the loam for $$$), cut the trenches into that nice impermeable clay, and line them.

 

[Ivan Seeking]

You mean the fish food? Seems an adjacent menhaden fish oil facility might be in order.

Hmmmm ,and fish are already being co-farmed with algae for the nitrogen from the fish poop.

Something else about the energy for aeration: Ideally, the energy losses could be buried in the existing losses in the generator exhaust system. A large engine of any sort would have an exhaust system pressure of at least 3 psi, which should be more than enough pressure for the aeration system. By eliminating the need for a muffler we have some free pressure with a high volumetric flow. I would imagine that the rest of the exhaust system could be further modified to minimize losses.

Beyond providing a free source of air pressure, the generator also acts as an air purifier. This eliminates the need for filters and the associated energy losses for an air intake system. I remember doing volume calculations for this but frankly don't remember the exact results. I do recall that the idea seemed to be workable and the energy savings significant. Surprisingly, the heat energy from the generator is insignificant as compared to the solar energy input to the system each day. I initially assumed that we could use the engine heat for the algae beds during the winter months, but the bed temperature gains would be a drop in the bucket. More likely the generator's heat could be best used during the transesterification process in the production of biodiesel.

In a completely closed system, oxygen-rich air from the algae beds could help to improve the generator's fuel efficiency. In my own design, the long pipe used to support the ditch cover could double as an air return line. I was opting for a positive-pressure system [no air return line] in order to reduce contamination concerns.

Recall that the depth of the ditches helps to determine the temperature stability of the system. If we assume that we are not dealing with temperature extremes, which would be most of hte year, the water level in the ditches might also be throttled as a function of the batch cycle time. There is an ideal ratio of algae to water based on the optical density of the solution. Ideally, we start a batch cycle with a minimum of water in a ditch; say one inch of water, for example. As the optical density of the solution increases, we slowly add water in order to maintain our optical setpoint, thus helping to maximize growth. This also greatly reduces the mechanical work required for aeration during that period of the batch cycle. In the beginning, we only need one inch of water of pressure, instead of eight inches or water. By maintaining our optical setpoint we also help to ensure that the desired algae dominates the batch cell.

 

[Ivan Seeking]

You don't need to buy those machines or source the materials, though. Your liner-contractor can save you lots of money in materials (they buy by the truck-load or rail-car load) and save you from having to pay for the purchase/maintenance of expensive specialty tools and the training to install the liners properly. Until he tired of the constant travel, my little brother was foreman for a large company that specialized in lining ponds and storage pits and capping landfills. The liner material is cut and laid out to conform to the contours of the substrate, then the seams are "welded" with special machines. If the job was planned properly, they could pretty much keep with the earth-movers and line your reactor-ditches as they were created.

The cost per sq foot would worry me, but I'm guessing this would probably be good for thirty to fifty years.

Note: Proper siting could save you a TON of money. If you could get your mitts on nice level acreage underlain by blue marine clays, you could scrape off the topsoil with pan-bellies (sell the loam for $$$), cut the trenches into that nice impermeable clay, and line them.

A dry lake bed comes to mind as well. It seemed pretty clear to me that that clay is ideal. Anyone who has been around construction sites knows that compressed clay, when kept dry, is like concrete. What about burrowing rodents? Do you know if the liners are impervious to pests? I have to admit that this issue had me worried. The only solution that came to mind was rather ugly. As is done with dams, a layer of broken glass would have to be spread over the entire site during the inital land preparations. Everything else would go on top of that.

A few more thoughts about production: In the literature there exists some discussion about nitrogen starvation during the last stage of growth, as a means to boost oil production. This seems to be a siginficant issue to consider. On one hand the stated claim is made. By starving the algae for nitrogen just before harvesting, growth slows with more energy directed to the production of hydrocarbons. Others claim that that while true, if fed sufficient quatities of nitrogen, the increased growth rate compensates for the lesser yields by weight - in the end we have about the same amount of oil. Assuming that is true, do we see any siginficant energy savings by processing less algae having higher yields? Superficially I would expect that we prefer have the algae with twice the yield per unit mass, but this issue was never resolved. Clearly there is the potential for reduced operating costs here.

Strain selection is a huge issue. The fact is that we don't have a lot of good information in the public domain. There are some strains known to be good producers, both fresh and salt-water strains, but there are only a handful discussed in great detail. Some strains of algae may have doubling rate [mass] of twice a day, while other strains only double in mass every three or four days. It seems that faster growing strains have relatively lower yields of oil per unit mass of harvested algae. Yields can range from single digits for wild strains, to 15-40% oil by dry weight, as a practical range. Claims as high as 80% oil by dry weight can be found for Botrycoccus braunii, a slow-growing, green, fresh-water algae considered to be the beginner's strain. If one wishes to be optimistic, perhaps something over 50% yields could be achieved under the right conditions, but it seems reasonable to expect that the ultra-high yields mentioned would be impractical at production levels. Still, one quickly gets into numbers games with yields, doubling times, temperature range, light preferences, nitrogen and CO2 levels, processing efficiencies, and even considerations such as the PAR [photosynthetically active radiation], which is different for each strain.

I was told by two of our experts that since algal oils tend to be low in saturated fats, alga oil fuels burn more cleanly than do fuels produced using soy beans or corn oil. However, it is also my understanding that not all algal oils contain glycerides [eh... chemistry may not quite be right there, but not all can be made into biodiesel] so the reaction would not occur. Additionally, some algal oils may be appropriate for some applications without the need for the change to biodiesel. I never could be sure about this, but from what I gather, the Boeing 737 flight test was done with an algae oil mix, not biodiesel.

It would seem to be ideal to fuel the generators on an algae farm with raw algae oil; or better yet perhaps, use biomass burners to power steam turbines. Given that we know a high-yield algae biomass has the required energy density, biomass burners seem a promising option.

 

[Ivan Seeking]

Here is one of the crazier ideas that came to mind. I have no idea if this is feasible, but the beauty of this is too tempting to avoid mention. My thought was that maybe some fancy catalytic chemistry would make this doable if its not implicity functional.

We have an algae system that is hungry for nitrogen. Diesel engines could operate more efficiently if they used higher compression ratios, but compression is limited in order to reduce NOx emissions. Since we need diesel engines, and since we want to direct the exhaust stream to the algae beds for the carbon capture, would it be beneficial to maximize NOx production due to combustion, in order to allow the generator to act as a nitrogen fixer? This would allow for higher compression ratios making the generators more efficient. How high can we go? Would enough oxidized nitrogen be generated to be significant, and could be this easily be made useful for the algae?

 

[mheslep]

Here is one of the crazier ideas that came to mind. I have no idea if this is feasible, but the beauty of this is too tempting to avoid mention. My thought was that maybe some fancy catalytic chemistry would make this doable if its not implicity functional.

We have an algae system that is hungry for nitrogen. Diesel engines could operate more efficiently if they used higher compression ratios, but compression is limited in order to reduce NOx emissions. Since we need diesel engines, and since we want to direct the exhaust stream to the algae beds for the carbon capture, would it be beneficial to maximize NOx production due to combustion, in order to allow the generator to act as a nitrogen fixer? This would allow for higher compression ratios making the generators more efficient. How high can we go? Would enough oxidized nitrogen be generated to be significant, and could be this easily be made useful for the algae?

How do envision connecting the two? Just have high compression diesels dumping NOx into the air?

 

[joelupchurch]

Here is one of the crazier ideas that came to mind. I have no idea if this is feasible, but the beauty of this is too tempting to avoid mention. My thought was that maybe some fancy catalytic chemistry would make this doable if its not implicity functional.

We have an algae system that is hungry for nitrogen. Diesel engines could operate more efficiently if they used higher compression ratios, but compression is limited in order to reduce NOx emissions. Since we need diesel engines, and since we want to direct the exhaust stream to the algae beds for the carbon capture, would it be beneficial to maximize NOx production due to combustion, in order to allow the generator to act as a nitrogen fixer? This would allow for higher compression ratios making the generators more efficient. How high can we go? Would enough oxidized nitrogen be generated to be significant, and could be this easily be made useful for the algae?

Isn't this kind of circular, since the purpose of the system is to generate Biodiesel? I would prefer to use a coal power plant for a CO₂ and NOx source. Of course, you would still need a SO₂ scrubber, unless someone develops a sulfur tolerant Algae strain.

 

[Ivan Seeking]

Isn't this kind of circular, since the purpose of the system is to generate Biodiesel? I would prefer to use a coal power plant for a CO₂ and NOx source. Of course, you would still need a SO₂ scrubber, unless someone develops a sulfur tolerant Algae strain.

As you mention, with coal we have to worry about sulfur. Biodiesel has no sulfur.

If we power the farm using coal power, we are only recycling the carbon from the coal. If we power the plant using biodiesel or biomass, we are using the carbon captured from the atmosphere. Note that the coal plant would have to increase production in order to supply the farm with electrical power. Biodiesel is ~ carbon neutral. If we can effectively capture CO2 from a coal plant to make a cost-competitive fuel, why bother with the coal?

 

[Ivan Seeking]

How do envision connecting the two? Just have high compression diesels dumping NOx into the air?

I don't know. I spoke at length with our chemist a few times but we never got that far. Same is true even for the carbon capture. Presumably people have been looking at the practical aspects of carbon capture, so I assume that this is addressed in the literature somewhere - the practical considerations and the chemistry of carbon capture were never specifically addressed. We only touched on the subject.

I do know that plants want to see NO3. I also know that we have an energetic system that make makes nitrogen available for additional reactions. It is hard to believe that we can't get there from here. As mentioned, perhaps it would be a matter of using catalysis. Also, I know that some NOxs react with water to form nitric acid, so that might be another route to pursue.

In any case, just to be clear, the exhaust stream is directed to the algae beds. I don't understand your reference to dumping NOx into the air. The point wouild be to make the nitrogen available to the algae, which means reacting the NOxs in some fashion to form NO3. Ideally this could solve the nitrogen problem.

Also, earlier I made the comment about the generator engine acting as an air purifier. Note that I was referencing to the pressures and temperatures found in the combustion chamber of the engine. I would expect this to eliminate any concerns about biological agents entering the system through the air intake system. Otherwise we would need biological grade HEPA filters that come with significant energy losses. Remember that we are moving a lot of air.

 

[Ivan Seeking]

I also know that we have an energetic system that make makes nitrogen available for additional reactions.

That is to say that the generator's exhaust gases are in highly energetic state. Energy has already been added to the system through the inefficiencies in the generator. That being the case, my hope is that we already have the chemical or heat energy required to get from NOx to NO3. It wouldn't be a free lunch because we have already paid the energy price. That makes me suspect it is doable. It could eliminate a siginficant operating cost. A ready supply of nitrogen is a costly aspect of algae farming.