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I very recently tried and failed to commercialise a novel bioreactor system for microalgae [0]. You are correct that surface area is an important factor in considering algal growth characteristics.

In my opinion, microalgae production for bulk purposes (i.e. biofuels rather than current pharma usages) has thus far failed because the existing cultivation systems are very energy intensive (pumps), labour intensive (cleaning), and inconsistent (cell growth and lipid concentrations are more or less non-deterministic). This all means that the cost of production is higher than what you can sell the raw output for in most cases.

Our novel approach was to engineer growth media aerosols (100 micron diameter microdroplets), and suspend microalage cells inside each microdroplet. Then we made a literal cloud (microdroplet air suspension) inside an environmentally controlled greenhouse volume. Doing this enables an extremely large surface area contact between the growth media and atmosphere (also CO2 enriched atmosphere), as well as energy efficient mixing and circulation processes. Our calculations showed that orders of magnitude energy efficiency improvements are possible compared to existing cultivation systems (raceways, tubular PBRs), and additionally scaling is inherently possible due to the ease of building out larger and larger volumes to contain such microdroplet atmospheric suspensions.

Existing systems cannot be effectively scaled due to e.g. pressure limitations associated with tall water volumes, risks of culture contamination, light penetration etc.

[0] https://skyfarmclimate.tech/

Thanks for sharing your experience. Can you talk about the business aspect? Like I assume up to now you're having trouble getting additional funding? What worked and didn't work? What's the current direction?

Currently we have ceased all work due to lack of funds - there are multiple reasons behind this, but we are still bullish on the tech. Our university partners may develop it further, or I may come back to it in a few years when my situation changes.

A core takeaway from our investors is that we should have tried harder to demonstrate strong market pull for our reactors, or the microalgae itself. In this respect it was a kind of chicken and egg problem, in that microalgae can be used for many different things, but no one is doing it because it is too expensive, and the existing markets are supply saturated.

So why did it fail?

Ultimately because I made too many mistakes / not good enough as a founder. I will probably try again in a few years

> A few people would admit that the challenge was going from algae growing in the pipes to algae growing on the pipes, where it could not be harvested.

I'm not an expert here but I've done a lot of reading on this.

My understanding is that people really don't have a hard time growing algae, it's just that algae doesn't make very good fuel.

This is evidenced, IMHO, by the vast number of companies that started as algae fuel producers and then pivot to algae supplement companies.

This article goes more in depth on the topic [0].

"One of the biggest challenges was that wild strains of algae couldn’t deliver the high levels of lipids needed to produce large quantities of fuel, said Todd Peterson, the former CTO of Viridos, Exxon’s longstanding and now former algae research partner."

[0] https://www.theguardian.com/environment/2023/mar/17/big-oil-...

Algae isn't hard to grow and makes great fuel, it's just very difficult to harvest (and depending on what you're doing, biofouling may make it difficult to maintain a system long term). Things like corn and soybeans work okay to create fuel, but they're easy to harvest. (Note that we aren't using wild types of vascular plants either, except in eg wood stoves.)

Food supplements are a much higher ticket item than fuel. It's a lot easier to make money that way. But you're right, pivoting to some kind of food product is a cliche.

I suppose it makes sense to pivot, if you can find someone who’ll pay you $100 for a gallon of dried algae, versus $4 for a gallon of algae lipids catalyzed into fuel. And how many gallons of algae does that take?

The dream would be to efficiently fractionate your algae, and separate out lipids, proteins, carbohydrates, and specific high value stuff like phycocyanin or astaxanthin. Then you could sell into these high margin markets to supplement your fuel production.

Or you could not do any of that and press your dry algae into a pill and sell it at a high margin. As far as the profit motive goes, it just doesn't add up. So the dream dies on the vine.

I'd love to see the government pour money into this and build a plant that operated this way at a loss, on a sort of Apollo project basis; it wouldn't necessarily make financial sense, but we'd generate a bunch of great technology which would be applicable in many areas, and eventually it just might work. I think it's worth a shot to see if we can sustainably meet our food and fuel needs, maybe even in a carbon negative manner. But sadly I think we're going in a different direction.

I bet even as an animal feed supplement it makes more sense than making fuel. We have connected the dots between feed and healthiness of fish and eggs. For ungulates I understand you have to beware of high protein. Unrestricted access to clover (which is one of the most palatable things they can eat) can make them quite sick. An algae/clover blend could probably still be palatable, and if you selected for high fat to protein ratio in the algae it might actually be safer.

As someone once put it, “oil is so plentiful we can afford to set it on fire”. Finding something else we can set on fire will be difficult, but it might be better to pyrolyze it directly and feed electricity into the power grid. The waste heat from the heat engine could be used in a heat exchanger to dry the algae before firing.

Speaking of power, the cooling effect of photosynthesis is also an underexplored areas.

Why grow fuel, and not a fertilizer/top-soil additive for agriculture or soil remediation? If you've got a product which contains that much carbon, covering fields with it is a great way to take CO2 from the air and put it in the ground while also improving the soil.

Cover millions of acres of marginal/desert soil with sheets of algal mesh built for moisture retention. Plant trees or crops into it.

That it can't be burnt and turned back into CO2 seems like a positive, not a negative.

Oh, it doesn't make money? I guess that's the rub.

Couldn't you get carbon credits or whatever for this?

No idea how reliable or good that revenue source is now, or in the long term.

I wonder how hard it would be to make such an "algal mat". I would use something like this around here on my little farm/vineyard even as a kind of weed block, alternative to "plastic mulch": rolls of algal-produced fibrous mats, 2" or so thick. Permeable so water and air can get through, but thick and tight enough that weeds get blocked out. Would just degrade or be tilled into soil over time.

There's already equipment out there for laying "plastic mulch" but the stuff itself is fairly controversial because even the biodegradable stuff is still a plastic. If one could economically produce such a thing made out of algae, and compete with plastics on cost, that would be pretty damned nifty.

That and just some kind of bulk powder that can be soil incorporated as a carbon amendment. Pay farmers to lay the stuff down in huge quantities as a way of improving soil while getting CO2 out of the atmosphere.

Even better if a bioreactor and related equipment to make this stuff could be made to operate locally on site.

For what it's worth, I worked for a company making an algal soil amendment, and we would distribute it as a suspended biomass (green water).

Harvesting the algae is one of the problems, but the more pertinent problem that breaks the economics is that the energy density at the generation point just isn't good enough. Going from sunlight to biodiesel via algae seems to have single-digit efficiency.

Ya.

I was also very bullish on cellulosic biofuels from switchgrass. Just mow the prairies (don't disturb the soil).

I'd love to know why I was wrong. Too soon? Like GM's EV1? Little potential for Wright's Law (learning curve) to drive down costs?

> corrugated material

Very interesting. I hope someone tries this.

The reason is that if you mow the prairie, you will get droughts and floods. The grass captures water and reduces evaportation, and makes it a soil rather than dirt. Plus you are still left with the problem of replanting it.

The proposals were literally mowing. Like a lawn. Leaving the soil undisturbed. An improvement over every other crop, esp corn.

That said, all the (huge scale) biofuel options will likely be mooted by green hydrogen. Fingers crossed.

Why algae? An alternative could be power to X with carbon capture for sugars' synthesis.

This is more land efficient than growing plants.

I don't recall exactly why. Algae on nutrient effluent, then harvest the lipids.

Some people used carbon capture to carbonate the water.

[ES: Educational and professional experience. All this comes with caveats because many parts of working with algae are unsolved, you probably won't get all of these properties at once.]

Algae are much more efficient for various reasons. Or rather, the efficiency ceiling is higher, whether it is realized is a separate question.

They make better use of space (your culture may vary).

They can have a higher proportion of their mass as oil or protein (relevant if you're harvesting them for food).

They are highly adaptable, they can acclimate themselves to new environments readily.

They are simpler and lack the "overhead" of vascular plants.

Relatedly, on paper at least it's a very nice system to engineer. You've got a logistic growth curve (a sigmoid) for biomass in suspension, and you're harvesting when you get to the flat part of the curve to "rewind" to the exponential part of the curve, so you're staying in the part which is very productive. Biomass is difficult to measure, but there are good proxies for it (such as pH, optical density, or conductivity).

You can get many harvests in a year, you may be able to harvest them every day or every week depending on conditions (I've worked in an algae farm that harvested every day during the summer and occasionally in the off season [though technically it was cyanobacteria, which some don't count as algae, it's kind of a Pluto situation]). Vascular plants I think are usually harvested 1 to 3 times a year (though I won't discount someone clever being able to get more harvests by harvesting sap or something like that).

One of the important bits about use of space is that you can do it so you're not taking land use away from food growth, because you can grow algae in places you can't grow crops.

I don't see that as a very strong reason, you can cultivate algae for food (spirulina, chlorella) and you can use adjacent technologies (controlled environment agriculture) to grow vascular plants in harsh environments.