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.
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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.