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Arizona Public Service and GreenFuel Technologies Recycle Power Plant Flue Gases into Transportation-Grade Biodiesel and Ethanol

Arizona Public Service Company (APS) and GreenFuel Technologies Corporation have successfully recycled the carbon dioxide (CO2) from the stack gases of a power plant into transportation grade biofuels.

Using GreenFuel’s Emissions-to-Biofuels algae bioreactor system (earlier post) connected to APS’ 1,040 MW Redhawk power plant in Arlington, Ariz., GreenFuel was able to create a carbon-rich algal biomass with sufficient quality and concentration of oils and starch content to be converted into transportation-grade biodiesel and ethanol.

This is the first time ever that algae biomass created on-site by direct connection to a commercial power plant has been successfully converted to both these biofuels. The conversion and certification of the fuels were conducted by respected, independent laboratories.

—Isaac Berzin, GreenFuel founder and Chief Technology Officer

GreenFuel’s Emissions-to-Biofuels technology uses algae to recycle carbon dioxide from the stack gases of power plants and other commercial sources of continuous CO2 emissions. At the Redhawk Power Plant, specially designed pipes captured and transported the CO2 emissions coming out of the stack. The gas was then transferred to specialized containers holding algae, which consume CO2 in the presence of sunlight.

A portion of the media is withdrawn continuously from the bioreactor and sent to dewatering to harvest the algae. The dewatering operation uses two stages of conventional processing. Primary dewatering increases the algae concentration by a factor of 10-30. Secondary dewatering further increases the algal solids concentration to yield a cake suitable for downstream processing.

Water removed from the dewatering steps is returned to the bioreactor, with a small purge stream to prevent precipitation of salts. Make-up water is added to maintain the media volume. A blower pulls the flue gas through the bioreactor. Using an induced draft fan provides several operating advantages, including ensuring minimal disruption to power plant operations, simplifying retrofits to existing facilities.

Downstream processing of the algae cakes is based on conventional processes.

We estimate that this process can absorb as much as 80 percent of CO2 emissions during the daytime at a natural gas fired power plant. Unlike typical agricultural biofuel feedstocks such as soybeans or corn which have a limited harvest window, algae multiply every hour can be harvested every day.

—Cary Bullock, GreenFuel CEO

GreenFuel and APS have been conducting a field assessment program over the past 18 months, and have moved into the next phase of study with the construction of an Engineering Scale Unit that will be completed in first quarter of 2007.

APS is Arizona’s largest and longest-serving electricity utility and serves about 1 million customers in 11 of the state’s 15 counties.

(A hat-tip to Cervus!)

Comments

jgray

This is indeed very good news! I look forward to reading about the next phase. Any word on how much biodiesel and ethanol was created?

Brad

Now why can't we get stuff like this in canada? As far as i know we can't even buy biodiesel here. Almost makes me wish i lived down south.

Steve

This is the future, good to see it have some success.

Neil

I wonder what the cost of storing night time emisions for doubling the daytime production would do to the economics. What is the cost of the resulting bio diesel even under regular processing?

doofusgumby

That looks like a good way to perform carbon sequestration when we have to start reducing CO2 output...but what do we do with the algae if we're using it to store carbon?

Brad

Process it and turn it into bio-fuels.

Cervus

doofusgumby:

This is not carbon sequestration. It's a method for using the carbon in the coal/natural gas twice before they are actually put into the atmosphere. This displaces the oil that would otherwise be burned, resulting in a net reduction in CO2 emissions. Since we will likely be using natural gas and coal for electricity production for decades to come, this is a good way to make the most of the situation.

allen_Z

Neil,
You could intall this at peak plants, ones that primarily operate during daytime. There are some nightime peaks, of which are during hottest summer (>80F 26C), and coldest winter (<0F -18C) nights.

Tom

I think that algae to biofuel seems to have great potential, however, I wonder if the algae is actually being "hyper ventelated" with flue gas CO2 or does it convert atmospheric CO2 at the same rate.

Andy

I've spoken with these guys. They have a good buisness plan. Accordibg to an artile on PBS 2 days ago if every powerplant in the U.S. were to install this device they would produce twice as much diesel fuel as is being consumed now. For algae or any plant to grow they need CO2 for the carbon to absorb for hydrocarbon growth. The higher the CO2 levels the faster the growth. These reactors would work in a atmospheric setting but with much lower output. Powerplants have enormous reserves of CO2 to guve up. If the 1040MW plant were to fully implement it would produce 90 million gallons of Biodiesel and Ethanol combined yearly. That is big.

Cervus

Andy:

I love this technology since it has vast, vast potential to solve so many problems. On the global warming side, there's the net reduction in CO2 emissions. On the energy independence side, we could stop importing oil from places like Saudi Arabia and Venezuela. It's a win-win, as far as I'm concerned.

I dream of seeing algae farms like this next to the local powerplants.

Everything I've read about this company indicates they're going about this the right way, by touting the economic benefits first. If it's simple for powerplant operators to add it and start to generate additional revenue from biofuel sales, GreenFuel won't be able to sell them fast enough. In effect, it turns the waste CO2 that would normally just go out of their smokestacks into a valuable feedstock.

The question in my mind right now is how fast the tech can be adopted, and if the power companies will do so without Kyoto-style restrictions. Considering we're talking a potential for 80% CO2 reduction, I'm surprised that Europeans aren't in negotiations.

Thomas Pedersen

By removing algae from the "soup" they are not just removing hydrocarbons but also salts, minerals vitamins, all the things that make living things grow. How are these materials replaced? Hopefully by returning by-products from the biodiesel refining process... Otherwise it is the whole story about natural gas for fertilizer in ethanol farming all over again.

I seriously hope the "depleted" algae carcasses are not just dumped, but at least used as feedstock for other processes if not returned to the power plant.

Does anyone have any info about this?

Still a great concept, though!

er

"I'm surprised that Europeans aren't in negotiations."

Me too. I would be surprised if some European energy companies weren't already negotiating with these guys. They should, this seems to be just what is needed. I guess as the technology matures it will become more known also among energy companies here. Sure hope so. In the mean time we need to spread the word...

A Spanish company is starting to build a plant in the Mediterranean sea to make fuel out of aquatic algae. The plant will use athmospheric CO2, but still the company claims a barrel of their algae "crude" will be cheaper than a barrel of crude oil. Google BFS, or Bio Fuel Systems SA.

Paul Dietz

I wonder what the cost of storing night time emisions for doubling the daytime production would do to the economics. What is the cost of the resulting bio diesel even under regular processing?

I suspect the cost would not be acceptable for a conventional powerplant. For a powerplant designed for CO2 sequestration, storing liquified CO2 overnight for use the next day would be much easier.

But perhaps if they can make the algae grow in alkaline conditions they can charge up the solution with CO2 at night, forming bicarbonate and lowering the pH, then allowing photosynthesis the next day to raise the pH again.

Rafael Seidl

Any biofuel created using intensive algae farming replaces petroleum-based fuel. Ergo, the setup reduces the volume of crude oil that needs to be brought to the surface to produce automotive fuels. In terms of climate change mitigation, that's an inspired bit of lateral thinking, since the carbon from the fuel is put to good use twice by virtue of the sunlight captured. This can be expressed in terms of a "virtual" thermodynamic efficiency as described below.

Note that APS Redhawk is a natural gas co-gen plant.

Assumptions:
gravimetric energy density natural gas ~39MJ/kg
approx. gas composition: 90% methane, 8% propane, 2% inert (no COx)
carbon emitted: 0.90*12/16 + 0.08*42/50 = 0.74kg/kg NG

thermodyn. efficiency co-gen plant ~55%
electric power 19.8MJ/kg NG = 5.5 kWh/kg NG

daytime fraction of total electricity produced: ~2/3
fraction of daytime CO2 convertible to biodiesel: 80%
repr. for biodiesel(1): CH3(CH2)14COOCH3
carbon available for triglyceride production: 2/3*0.8*0.74=0.51kg/kg NG
carbon converted into biodiesel(2): 0.51/1.026 = ~0.5kg/kg NG
carbon content: 0.76kg/kg biodiesel
biodiesel yield: 0.5/0.76=0.66kg/kg NG
gravimetric energy density biodiesel: ~42MJ/kg
avg. thermodyn. efficiency HDV diesel(3): ~25%
mechanical power 0.66*42.2*0.25 = 7MJ/kg NG = 1.9 kWh/kg NG

1kg NG + sunlight -> 5.5kWh el. + 1.9kWh mech.

Put another way:

39MJ fossil energy -> 19.8 + 7 = 26.8MJ useful energy
virtual therm. efficiency(4): 26.1/39 = ~69%

---

(1) actually a mix of oils, also varies by algal species. This is just a quick & dirty approximation.

(2) transesterification requires 0.026kg/kg NG methanol, which is itself typically produced from additional natural gas. The specific biodiesel yield given here refers to the gas burnt at the power plant.

(3) in the US, diesel is used mostly for HDVs. The engines of the total HDV fleet are typically operated at high but not optimal load.

(4) in practice, the algaculture, methanol production, transesterification and distribution of the biodiesel all consume a small fraction of the input energy. This has been neglected here, as have useful applications of the glycerol by-product.

Rafael Seidl

CORRECTION:

I stand by the methodology for my calculation but I just noticed I made one mistake in following it. Here is the corrected calculation:

Assumptions:
gravimetric energy density natural gas ~39MJ/kg
approx. gas composition: 90% methane, 8% propane, 2% inert (no COx)
carbon emitted: 0.90*12/16 + 0.08*42/50 = 0.74kg/kg NG

thermodyn. efficiency co-gen plant ~55%
electric power 19.8MJ/kg NG = 5.5 kWh/kg NG

daytime fraction of total electricity produced: ~2/3
fraction of daytime CO2 convertible to biodiesel: 80%
repr. for biodiesel(1): CH3(CH2)14COOCH3
carbon available for triglyceride production: 2/3*0.8*0.74=0.39kg/kg NG
^^^^

carbon converted into biodiesel(2): 0.39/1.026 = ~0.38kg/kg NG
carbon content: 0.76kg/kg biodiesel
biodiesel yield: 0.38/0.76=0.51kg/kg NG
gravimetric energy density biodiesel: ~42MJ/kg
avg. thermodyn. efficiency HDV diesel(3): ~25%
mechanical power 0.51*42.2*0.25 = 6.3MJ/kg NG = 1.75 kWh/kg NG

1kg NG + sunlight -> 5.5kWh el. + 1.75kWh mech.

Put another way:

39MJ fossil energy -> 19.8 + 6.3 = 26.1MJ useful energy
virtual therm. efficiency(4): 26.1/39 = ~67%

---

(1) actually a mix of oils, also varies by algal species. This is just a quick & dirty approximation.

(2) transesterification requires 0.026kg/kg NG methanol, which is itself typically produced from additional natural gas. The specific biodiesel yield given here refers to the gas burnt at the power plant.

(3) in the US, diesel is used mostly for HDVs. The engines of the total HDV fleet are typically operated at high but not optimal load.

(4) in practice, the algaculture, methanol production, transesterification and distribution of the biodiesel all consume a small fraction of the input energy. This has been neglected here, as have useful applications of the glycerol by-product.

Sid Hoffman

"virtual therm. efficiency(4): 26.1/39 = ~67%"

Correct me if I'm wrong, but there's not a power plant on Earth that matches this efficiency, is there? I know car engines are extremely inefficient, like 25% or so peak, diesel around 35% and most stationary power generation is something like 45-55%, correct? To get a boost up to 67% efficiency is amazing.

Harvey D.

Using unwanted GHG (CO2) + sun energy to produce algae and further produce biofuel and ethanol is a great idea.

One input (good sunshine)is restricted to an average of about 6 hrs/day and a substitute is difficult to find.

Using the end products in very inefficent ICE vehicles (gas guzzlers) will still produce huge amount of CO2, COV and fine particles.

Wouldn't it be more appropriate to transform CO2 and sunlight into easily transportable electricity for PHEVs and EVs, instead of liquid fuels for inefficient polluting ICE machines?

Neil

If you used the algae in a combined cycle electrical generator you could then take the CO2 exhaust and feed it back into yet another (slightly smaller) set of algae tanks in a 80% (CO2 utilization) efficient loop.

Neil

Then repeat until the remaining CO2 is too depleated to be usefull. Thats effectively a large solar array. How does the efficiency of algae compare to mirrors and a sterling machine? Dry the algae with solar and burn whenever you need the power.

Cervus

Harvey:

I'm afraid the ICE is going to be dominant for a long time to come. Tesla and Altairnano may finally come up with a practical EV, but even if they do it will take decades to replace the millions of ICE vehicles on the road. Given that reality, GreenFuel's flue gas CO2 recycling is the way to go. It's a stepping stone to using atmospheric CO2.

Roger Pham

Thanks, Rafael, for the calculation. Incidentally, this calculation reflects the glaring inefficiency of HDV at only 25% thermal efficiency. And once that carbon is incorporated into biodiesel fuel for HDV, the carbon is released to the atmosphere that will contribute to global warming.

Therefore, I hereby propose research grants into developing electric hybrid HDV capable of running on Hydrogen using current ICE-HEV technology at tank-to-wheel efficiency of 45%, almost double today's HDV's efficiency. How is the Hydrogen produced? by local gasification of the algae biomass into H2 and CO, and further water addition to the CO at high heat will produce more H2 and CO2. Ah ha, separate the H2 for transportation fuel, and feed the CO2 back into growing more algae using solar energy. Thus, the CO2 will never get released into the atmosphere. The ash product of gasification or pyrolysis will contain valuable minerals important for algae growth that will again be fed back into the algae farm.

Now then, if you have a big enough algae farm, you can produce enough H2 to power your utility power plants' gas turbines as well, and forget about using NG altogether! Now, you have a closed-cycle CO2 photosynthetic cycle that is completely renewable, using solely solar energy, yet not affected by the unconstant nature of solar availability due to rainy or cloudy day, since the H2 can be stored in a limited fashion for rainy days.

Now, what if all the vehicles will run on H2, with H2 produced cheaply from CO2-fed algae farms? Is this a strong enough argument for further development into the Hydrogen Economy?

Roger Pham

Oh, one more observation: the 18-wheeler tractor trailers have huge amount of empty space below the trailers that would be perfect for compressed H2 tanks at 350 bars. Look at the diesel fuel tanks on each side of the cab, and multiply this volume by eight, and you will have arrive at the volume required for compressed H2 at equal range. Perfectly doable!

Rafael Seidl

Sid Hoffman -

power plants delivering district heating (and possibly, district cooling via a central absorption chiller) can aggregate achieve efficiencies of over 80%. It's all a question of what you consider useful energy. In economic terms, electricity and shaft work are more valuable, because the efficiency of the processes required to produce them are <<1. The aggregate efficiency of straight co-gen plants (electricity only) is currently limited by the high-temperature fatigue strength of the turbine vanes in the secondary steam cycle, but designs currently in development feature go as high as 60-62%.

Of course, you could still attach an algal oil process to those, as well. Even more valuable, from a GHG mitigation point of view, would be attaching them to coal-fired plants. However, you'd have to do a very thorough job of scrubbing the flue gases of particulate matter and sulfur compounds and probably use hardier algae species. Perhaps we will see this happen as algal biodiesel technology matures.

Roger Pham -

powering HDVs with H2 to improve efficiency is an interesting idea, but it only works if those HDVs are powered by fuel cells rather than an adapted spark ignition ICE (cp. BMW 760h). Right now, the feasible power of a PEM is limited by the size of the radiator that can be fitted given the frontal area of the vehicle. Higher power ratings will depend on increasing the operating temperature of the stacks and/or switching to alternate fuel cell types (MCFC, SOFC) - but those are not considered viable for mobile applications today. Current HDV engines are rated at around 300kW to ensure they can haul their gross weight rating of ~80,000lbs up steep inclines in a low gear.

On a separate note, the economics of hydrogen production, distribution, on-board storage and PEM fuel cells manufacturing are nowhere near competitive with diesel engines at this point. My 25% average HDV fleet efficiency number was just a conservative guesstimate, btw. In the optimum point in the engine map, an HDV diesel will achieve more like 42%, but not every HDV is operated there at all times.

allen_Z

If the temperatures fall enough, during the winter, some of the waste heat could be used to keep the algae from freezing, and at optimal conditions.
_PHEV/EV and electrified rail would be customers if the the biomass went to electricity instead of BTL. Accounting for electrical transmission/transformer losses(7-9%), varying storage/discharge(70-90%), and motor/generator(50-90%) efficiencies, 32-76% raw material to end use ratings can be achieved.

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