Can Microalgae Solve Global Fuel and Environmental Challenges?

[turbo]

The other things to keep in mind are the scale of a large algae farm, and the supply and demand cost curve. What is the nitrate requirement for several million acres of algae, which is what we need before we begin to make a dent in the fuel market? I was caught several times by seemingly good source solutions that were dwarfed by the demand for a real operation.

Obviously, for this to work, the algae production facilities need to be diffuse (spread all over the place) in order to have access to cheap nitrate-rich waste. You'd also need to site the facilities near major cities, to get the best bang for the buck, which would increase the cost of the land - suburban property tends to be expensive. Of course, if the government got involved and subsidized the transport and use of the sludge, that could change, but you'd have to have some pretty impressive pilot programs running to convince Congress to cough up the bucks.

Over 20 years back, I did a plant evaluation for an ethanol plant in Iowa prior to bidding on the creation of a system analysis and training materials. I expressed my skepticism about the economic viability of the operation, and was told by a manager that without Federal subsidies, the plant would never even break even. There is was - a small chemical plant in the middle of corn country that was designed, built, and operated entirely on subsidies based on the premise that diverting valuable food from human consumption and animal feed could fuel our vehicles.

 

[Ivan Seeking]

I do think it is important to remember that should it be practical, generating pure nitrate onsite is likely the ideal solution to the nitrogen problem. One way or another we produce tons of the stuff. We can also increase in our generator efficiency. Otherwise, the only practical option that I could see TODAY was to buy sodium nitrate for $550 a ton.

The use of fish, sludge, waste water, fowl and cattle manure, agricultural runoff, or other waste products, introduces a whole new set of problems. I would expect that those sorts of applications could differ significantly from a high-yield farm aimed at fuel production. Again, the first thing a biologist wants to do is to put everything in an autoclave for 24 hours. That was not an exaggeration.

 

[turbo]

I do think it is important to remember that should it be practical, generating pure nitrate onsite is likely the ideal solution to the nitrogen problem. One way or another we produce tons of the stuff. We also increase in our generator efficiency.

The use of fish, sludge, waste water, fowl and cattle manure, agricultural runoff, or other waste products, introduces a whole new set of problems. I would expect that those sorts of applications could differ significantly from a high-yield farm aimed at fuel production.

That being the case, it should be a solid case for NOx scrubbers. They are already in wide usage, and your major costs would be in buying the scrubbers, running the water-showers, and pumping out the sumps to the trenches. Not real high-tech, but I just don't know if your generating facilities (diesels) could generate enough nitrates to feed the algae.

 

[mheslep]

The other things to keep in mind are the scale of a large algae farm, and the supply and demand cost curve. What is the nitrate requirement for several million acres of algae, which is what we need before we begin to make a dent in the fuel market? I was caught several times by seemingly good source solutions that were dwarfed by the demand for a real operation.

Well for this to work at large scale, algae biodiesel has to start displacing corn ethanol. So demand for nitrates should simply shift from corn to algae.

 

[mheslep]

I do think it is important to remember that should it be practical, generating pure nitrate onsite is likely the ideal solution to the nitrogen problem. One way or another we produce tons of the stuff. We can also increase in our generator efficiency. Otherwise, the only practical option that I could see TODAY was to buy sodium nitrate for $550 a ton. ..

At full scale, full replacement of petroleum scale, I assert you have no choice but to recycle most of that nitrogen. It has to be mostly a closed cycle over 20 million acres.

 

[Ivan Seeking]

Well for this to work at large scale, algae biodiesel has to start displacing corn ethanol. So demand for nitrates should simply shift from corn to algae.

I have no idea how agricultural demands compare to algae farming on a tons/acre-year basis, but I see algae as an entirely new demand for nitrates. It would be interesting to go back to global demands for fuel and the required acreage of algae, and see if the nitrate supply for this even exists.

I seem to recall that we once estimated that it would take 40,000 sq miles of algae to entirely replace the US petro supply. That would be something over 25 million acres, so we might expect a need for something like 30 million metric tons of nitrate per year.

The chemistry of nutrient recovery does seem to be a critical consideration. This would especially be true for a farm designed to produce electrical power using a completely closed system.

 

[Ivan Seeking]

That being the case, it should be a solid case for NOx scrubbers. They are already in wide usage, and your major costs would be in buying the scrubbers, running the water-showers, and pumping out the sumps to the trenches. Not real high-tech, but I just don't know if your generating facilities (diesels) could generate enough nitrates to feed the algae.

Considering the baseline estimates, I am encouraged. This goes back many years for me but I do believe NOX production is easy to increase significantly - maybe even double or triple. It would require that engines be modified or special builds, but it is fairly easy to do. There may even be a brand of marine engines or generators that are exempt from emissions standards and still use the higher compression ratios. For example, I could easily see the military using something like this.

 

[chemisttree]

Solar energy could be used to convert N2 into nitrate. I have a bit of information if anyone is interested.

 

[mheslep]

I have no idea how agricultural demands compare to algae farming on a tons/acre-year basis, but I see algae as an entirely new demand for nitrates. ...

I can't see how. For algae biofuel to work, it must eventually become more cost effective than corn biofuel. At at ~40X higher yield per acre for algae this is surely possible. Edit: main point is that at full scale one has to keep track of where your nitrogen molecules go. You can't just throw them away. Thus while the nitrate requirements probably are right for start up, later they should decrease as the recycling takes place, somehow.

 

[mheslep]

[...]
I seem to recall that we once estimated that it would take 40,000 sq miles of algae to entirely replace the US petro supply. That would be something over 25 million acres, so we might expect a need for something like 30 million metric tons of nitrate per year.

I reran the numbers for an internal energy group the other day - 29m acres / 45k sq miles at 10,000 g/a-y, for 2009 US petro total all sinks. Edit: 5x that using Exxon 2000 g/a-y numbers. Compares to 93 million US acres planted just for corn.

 

[Ivan Seeking]

I reran the numbers for an internal energy group the other day - 29m acres / 45k sq miles at 10,000 g/a-y, for 2009 US petro total all sinks. Edit: 5x that using Exxon 2000 g/a-y numbers.

Hopefully they were being unduly conservative. I am hoping for a multiplier no worse than 3. But given your check of the information, I would bet that we need a minimum of 100 million acres, with a little over one mt of nitrate required per acre-year.

Compares to 93 million US acres planted just for corn.

This acreage is currently dedicated to corn?

 

[Ivan Seeking]

Did you include efficiency gains for gasoline use? Note that we get something like a 0.75 multiplier on the energy demand by converting gasoline use to biodiesel use - i.e., the efficiency of diesel compared to gasoline engines.

 

[Ivan Seeking]

Solar energy could be used to convert N2 into nitrate. I have a bit of information if anyone is interested.

Those nitrates are a little hard to scoop-up, aren't they?

Can you offer any thoughts as to the reaction time required and the efficiency [completeness] of the reaction, going from NO or NO2, to HNO3, in a scrubber?

We also high high concentrations of CO and CO2 to in the exhaust stream. Carbonic acid is good. In fact, one typically adjusts the pH level of the water by increasing the available CO2 through aeration. But I have no idea what potential interactions there might be with CO, CO2, NO, and NO2 reacting in unison with water.

As an aside, note that we also recapture 40% of our water lost to hydrocarbon production.

 

[chemisttree]

Those nitrates are a little hard to scoop-up, aren't they?

Can you offer any thoughts as to the reaction time required and the efficiency [completeness] of the reaction, going from NO or NO2, to HNO3, in a scrubber?

The "nitrates" are soluble. In the process air is pumped through a silica substrate doped with some transition metals. In the sun it produces ammonia, not nitrates. Sorry for that.

I don't have any information about reaction rates for NO to nitrate. I imagine that would be pretty straightforward to find though.

Nitric acid is produced by bubbling NO2 into water. NO is produced in this process and is rapidly oxidized to NO2 which is then captured by water. It seems that the scrubbing/aeration processes already in use for HNO3 could be adapted for scrubbing NOx but I'm not sure how the process would be affected for ppm levels of NOx compounds.

 

[mheslep]

..This acreage is currently dedicated to corn?

Yes just to corn, 2007 peak. It's down a bit now.
http://www.nass.usda.gov/Charts_and_Maps/Field_Crops/cornac.asp
From the chart spike one can guess 10-15 million acres is dedicated to ethanol.

 

[mheslep]

Did you include efficiency gains for gasoline use? Note that we get something like a 0.75 multiplier on the energy demand by converting gasoline use to biodiesel use - i.e., the efficiency of diesel compared to gasoline engines.

No I did not include that. I used current US consumption 291 billion gallons per year, 2009, that's unrefined petroleum. Imports are ~60% of that.

 

[Ivan Seeking]

The "nitrates" are soluble. In the process air is pumped through a silica substrate doped with some transition metals. In the sun it produces ammonia, not nitrates. Sorry for that.

Ah, actually, I thought you were joking. My mistake.

 

[Ivan Seeking]

Yes just to corn, 2007 peak. It's down a bit now.
http://www.nass.usda.gov/Charts_and_Maps/Field_Crops/cornac.asp

That's a great point of reference. We need about as much algae acreage as we already have dedicated to corn.

 

[Ivan Seeking]

Here is an interesting doc that I found by chance. It provides a very practical baseline for comparing the economics of algae farming [based on the discussion here] to food crop farming.
http://www.cias.wisc.edu/curriculum/modV/secd/Costs and Returns worksheet.doc

I noticed a few specific numbers in the examples, that were interesting.

 

[chemisttree]

Ah, actually, I thought you were joking. My mistake.

No joke, really!

http://www.pnas.org/content/80/12/3873.full.pdf

 

[Ivan Seeking]

The design tends to migrate towards the notion that the heart of the bioreactor is really the generator. Note again that if we only want to generate electrical power, the system might be closed with all water and nutrients preserved, though one always expects that there are some practical limitations and losses.

One business strategy considered was that agreements could be made with power companies to sell power to the grid, esp during peak demand periods, in order to help offset fluctuations in fuel prices. In the limit this could be accomplished by over-sizing the generating capacity of the farm by 250%. Assuming 6000 gallons per acre-year with a net yield of 60%, we get 3600 gpay. At 125KBTUs per gallon, 40% efficiency for the diesel, 90% efficiency for the generator, we get 162 MBTUs, or 47,500 KW-Hrs per acre-year. Given this and our assumed maximum operating cost of $5400 per acre-yr, we can break even about 11 or 12 cents per KW-Hr. With this in mind, it might make sense to locate a farm near a area with a growing demand for relatively expensive electrical power. By accepting the up-front equipment costs, we can help to at least recover operating costs should the price of fuel drop significantly below 3 or $3.5 a gallon. It was a risk management strategy. It is also a way to recover costs if you have millions of gallons of oil that for some reason don't meet the fuel standards. But it is also interesting to know when we might begin to sell electrical power.

Given Exxon’s numbers we would seem to be in the range of 20 cents per KW-Hr.

Another observed advantage in using a simple or modified V ditch having a 45 degree or similar slope, is that algae growth might be maximized during periods of low light levels, as follows: As I understand all of this, by increasing the volume of water according to an ideal optical set point, we maximize the number of algae cells optically active at any time. The only active cells are those at the surface of the water, so the density of the cells at the surface determines the rate of photosynthesis for the system. If the optical density is too great, the cells in effect begin to shade each other, which is what happens as the system approaches equilibrium. If the density is too low, we aren’t maximizing the exposed area of the reactor. By using a V shape and adjusting the water volume, we reduce the surface area of the water, rather than the time spent at the surface by any particular algae cell - we reduce our energy input to the system either way. This is reasonably compatible with our cause because have less algae [mass per unit area] to “power” in the early stages of growth. However, if we use a white or even a clear plastic liner, and if the reactors are oriented properly wrt the sun, we get reflected sunlight from the walls of the reactor into the water. Much of this is due to semi-specular reflection. This can be true for much of the day and year, again, depending on the orientation of the reactor, the latitude, and the slope of the walls. If for example we only have one inch of water in an eight inch reactor using a 45 degree slope, we have one-eighth of the exposed area as compared to the total possible. But we might hope to get an average adder of [8 x 0.1 or 0.2], or an 80-160% gain, for example, for the total incident light acting on the algae.

Likewise, it would seem that during the summer months, simple shading tricks like that mentioned earlier could be used to provide a surprising degree of control over the amount of light incident on the algae. This would need to be targeted according to the strain or strains of algae selected and the associated light preferences and limits.

 

[turbo]

Regarding shading - if you are introducing nitrogen-rich water from scrubber-sumps via perforated pipes lying on the bottom of the trenches, you may get enough up-welling to mix the algae and optimize light exposure. Of course, if you've got thick mats of algae at the surface of the water in the trenches, that might not hold true.

 

[mheslep]

The design tends to migrate towards the notion that the heart of the bioreactor is really the generator. Note again that if we only want to generate electrical power, the system might be closed with all water and nutrients preserved, though one always expects that there are some practical limitations and losses.

One business strategy considered was that agreements could be made with power companies to sell power to the grid, esp during peak demand periods, in order to help offset fluctuations in fuel prices. In the limit this could be accomplished by over-sizing the generating capacity of the farm by 250%. Assuming 6000 gallons per acre-year with a net yield of 60%, we get 3600 gpay. At 125KBTUs per gallon, 40% efficiency for the diesel, 90% efficiency for the generator, we get 162 MBTUs, or 47,500 KW-Hrs per acre-year. Given this and our assumed maximum operating cost of $5400 per acre-yr, we can break even about 11 or 12 cents per KW-Hr. With this in mind, it might make sense to locate a farm near a area with a growing demand for relatively expensive electrical power. By accepting the up-front equipment costs, we can help to at least recover operating costs should the price of fuel drop significantly below 3 or $3.5 a gallon. It was a risk management strategy. But it is interesting to know when we might begin to sell electrical power. ...

11-12 c / kWh sounds overly optimistic, but I don't see anything wrong with your figures. Note that's the bus-bar, or wholesale price of electricity. Even large industrial customers would pay an extra 20%, double for residential daytime.

We discussed this before - there was that Science paper showing more useful energy delivered if biofuels went directly to electricity generation, and they (Science) didn't even address the increased efficiencies you identify in such a closed system. One problem, however, is that direct solar thermal generation plants will necessarily always beat algae in efficiency per acre. Algae is a great organism for photosynthesis (the best?) but it can not match man made solar collection per acre.

At the same time algae has the advantage of providing a direct method to store the solar energy indefinitely as diesel, where as solar arrays catch a week of snow or clouds and shut down. That is, algae can 'do baseload', solar concentrators not, not more than ~24 hours. Given these pros and cons, its not clear to me whether algae biofuel works better economically as a transportation fuel or for electric generation.

 

[Ivan Seeking]

11-12 c / kWh sounds overly optimistic, but I don't see anything wrong with your figures. Note that's the bus-bar, or wholesale price of electricity. Even large industrial customers would pay an extra 20%, double for residential daytime.

The key assumptions are $5400 per a-y [12 cents per sq-ft per year] total operating costs, including all amortized costs, and 3600 gallons per a-y net yields.

We discussed this before - there was that Science paper showing more useful energy delivered if biofuels went directly to electricity generation, and they (Science) didn't even address the increased efficiencies you identify in such a closed system. One problem, however, is that direct solar thermal generation plants will necessarily always beat algae in efficiency per acre. Algae is a great organism for photosynthesis (the best?) but it can not match man made solar collection per acre.

In large part it comes down to the cost per KW-Hr. Algae likely can't compete with the $10k per sq-meter solar cells on the Mars rovers either.

At the same time algae has the advantage of providing a direct method to store the solar energy indefinitely as diesel, where as solar arrays catch a week of snow or clouds and shut down. That is, algae can 'do baseload', solar concentrators not, not more than ~24 hours. Given these pros and cons, its not clear to me whether algae biofuel works better economically as a transportation fuel or for electric generation.

The two goals do not appear to be mutually exclusive. In fact it would seem that any algae farm is a hybrid of both. Looking at the economics of things, especially until this is a proven technology, one expects to produce substandard fuels from time to time. Having the ability to recover those losses by selling electrical power is pretty easy to justify. So the ideal generating capacity of any farm is an interesting issue to explore.

 

[Ivan Seeking]

Regarding shading - if you are introducing nitrogen-rich water from scrubber-sumps via perforated pipes lying on the bottom of the trenches, you may get enough up-welling to mix the algae and optimize light exposure. Of course, if you've got thick mats of algae at the surface of the water in the trenches, that might not hold true.

That's where it gets a little tricky. It is easy to kill the energy budget with aeration. I was landing on a compromise between aeration duty cycles and volumetric flow rates, and mechanical circulation - a simple rotating cylinder [pipe], perhaps one inch in diameter with simple paddles extrusions, that rests in the bottom of the V just above the aeration pipe, and turns very slowly, or at least with a very small average demand for energy.

It seems most efficient to use aeration only to the extent that required CO2 is delivered to the system, and to satisfy the circulation requirements mechanically. But this issue was never resolved to my satisfaction. It is a very difficult practical problem. One has to count the watt-minutes very carefully.

 

[Ivan Seeking]

In order to maximize the effective area of the reactor, perhaps the ideal cycle would be to drain one-half of the volume of water from given cell once every doubling period That is, if the algae doubles in mass every two days, then every two days we harvest half of a 1% solution and replace the water. There are any number of variations that one can imagine here, and which is best might be debated. However, perpetual systems are prone to contamination concerns and mutations that reduce yields. Based on this information and a number of discussions with algae biologists supporting those views, it was decided that a hybrid batch system was the best approach. Cells will need to be drained and sterilized periodically, so cell recovery time is a critical concern. It takes a long time, perhaps 20 doubling periods, to get from even hundreds of gallons of algae water, to many million of gallons. To me it seemed imperative to ensure that a ready supply of innoculant is avaiable and and a clear strategy in place that minimizes the recovery time for any cell taken out of service. However, this could be treated as a perpetual system to the extent that the yields and resident biologist allow.

 

[Ivan Seeking]

11-12 c / kWh sounds overly optimistic, but I don't see anything wrong with your figures. Note that's the bus-bar, or wholesale price of electricity. Even large industrial customers would pay an extra 20%, double for residential daytime.

Consider that our assumptions were based loosely on the wholesale price of fuel. That in turn drove the budget plans. So I guess it isn't surprising that the two numbers would agree.

We paid the price for this in part when our bioreactor was reduced to lined, covered ditches, in a pressed clay form. What is the amortized equipment cost and operating cost for the solar farm mentioned, on a per sq-ft per year basis? Do they come anywhere close to 12 cents? I would bet that just the cost of the reflectors kills any chance of meeting that budget requirement.

At the same time algae has the advantage of providing a direct method to store the solar energy indefinitely as diesel, where as solar arrays catch a week of snow or clouds and shut down. That is, algae can 'do baseload', solar concentrators not, not more than ~24 hours. Given these pros and cons, its not clear to me whether algae biofuel works better economically as a transportation fuel or for electric generation.

I couldn't get this out of my head and had to make a quick post. This had never occurred to me before. Using the business strategy discussed, the algae farm itself becomes a transition technology that supplies carbon-neutral fuel for more efficient diesel technologies in today's hydrocarbon world, while having the ability to transition to electrical power generation as plug-in hybrids and all-electrics increase the load on the grid. In any event, any site might be planned with future additional generating capacity implicit to the design. After considering the equipment costs for processing the fuel, the cost of additional generating capacity is relatively minor.

Should algae produce fuels for less than $5 or so, and assuming that traditional fuels are similarly priced, I don't tend to think people will want to give up the power of diesel for batteries. So unless electric vehicles gain a siginficant market-price advantage, I don't tend to expect a large swing to electric-powered transporation.

 

[Ivan Seeking]

... i.e 47500 KW-Hrs per a-y and assuming a %100 duty cycle --> 5.5 KW per acre. Using a price est of $50 per KW for the generator, we can amortize a cost of about 0.6 cents per sq-ft over ten years min... at scale, perhaps 30 years. This assumes a 100% generating capacity - a 1:1 ratio of fuel produced to fuel that can be used to sell power.

 

[mheslep]

In any event, any site might be planned with future additional generating capacity implicit to the design. After considering the equipment costs for processing the fuel, the cost of additional generating capacity is relatively minor.

Yes, ok, so the tanks need (or growth is greatly enhanced by?) the CO2 from some fosile burning electric plant and is collocated. An appealing economic plan might be that the a. farm sells diesel to transportation nominally, but the generation plant is dual fuel - say coal boiler or diesel engine? If the price of transportation fuel falls for some reason, the a. farm diverts to electric generation.

Should algae produce fuels for less than $5 or so, and assuming that traditional fuels are similarly priced, I don't tend to think people will want to give up the power of diesel for batteries. So unless electric vehicles gain a siginficant market-price advantage, I don't tend to expect a large swing to electric-powered transporation.

Not power, range is the EV limitation, that and turn around time at depletion.
On a cost per mile basis, including battery cost and electricity cost versus petroleum cost per gallon, EVs are cheaper now: battery cost ($800/kWh or lower) + US electric energy cost = diesel at $3.5/gal.

It turns out interestingly, it's nearly always been this way: EV's were a better deal economically but didn't have the range. I just finished B. Schiffer's https://www.amazon.com/dp/1588340767/?tag=pfamazon01-20, fascinating story about EVs running all over America from 1900 to ~1920:

o Edison's involvement, developed the Nickel Iron battery just the EV.
o Edison and Henry Ford attempted together an electric version of the model T
o New York to Chicago 1000mile long distance demonstration trips
o 70mph stunt EV that lost control and killed some gawkers.
o Some three dozen US EV makers at the peak.
o EVs were more reliable, lasted longer than the gasoline cars.
o Women loved them as they didn't need a hand crank.
o City-local EV truck fleets all over, i.e., the milk truck was often an EV.
o EV taxicabs with charging stations in front of all the big north east city hotels where they charged and waited for fairs.
o Price of electricity dropping while the price of gasoline was rising (!).
o Towards the end a few hybrids were made.
o "MIT performed a study" (!) demonstrating better economics per mile in EVs.​

Seems this whole thing already happened 90 years ago.

In the end, people wanted to dash long distances and "enjoy with his family the blessings of happy hours spent in God's great open spaces." - Ford. America was just too big, and at that time, had too little electrification.

 

[mheslep]

One the better known EV manufacturers, closely tied to Edison, was Baker Electric. 1912 model:

Edison in an early Baker EV

Walker Vehicles Electric Truck 1918. Made in Chicago.
Top speed 14 mph, range <40 mi

1923 Advertisement for the Walker:
"Marshall Field & Co. operate 276 Walker Electric Trucks -- the largest store fleet of electrics in the world."
http://www.megawattmotorworks.com/classifieds/filelist_download_poster.asp?id=745