Typical yields from algal biofuel technologies

This is an examination of yields of "primary product" (algal oil/ethanol/biodiesel), expressed as barrels of oil equivalent/hectare of land area/year, from various algal (algae) biofuel technologies. I used data from company websites and press releases and converted the algal oil/ethanol production to a BOE/ha/year basis.
From the above figure, typical "yields" range from 100-1000 BOE/ha/yr. Compare this to Dr. Benemann's recent statement that the maximum algal yield without using genetically modified algae would be ~2000 gal algal oil/acre/year (101 BOE/ha/year).

Disclaimer: This is not meant to be a comparison of various processes or an endorsement/critique of a specific process. Utilization of and the value for the algal biomass and the biofuel determines the overall process economics. My assumptions and data are given below:

1. Algenol: 6000 gal EtOH/acre/year
2. Solix data from here.
3. GreenFuel, from a previous post
4. PetroAlgae: Assumed 200x current soybean oil yields (200x50 gal oil/acre/year).
5. GSPI: Link here
6. Theoretical maximum: from CircleBio's website, assuming 20,000 gal biodiesel worthy plant oil/acre/year.
7. I further assumed that 1 T of algae oil gives 1 T of biodiesel, unless mentioned otherwise on the company's website (the ratio is ~0.96 for soy oil).
8. Calorific value of 33MJ/L for biodiesel and 20 MJ/L for ethanol.

Related posts:
Analysis: Algae for CO2 capture - II
Analysis: Algae for carbon dioxide (CO₂) capture

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Analysis: Algae for CO2 capture - II

I evaluate the process economics of algal CO2 capture from cement plant, using the GreenFuel Holcim facility mentioned in a previous post. Internal rates of return (IRR) and payback periods for various scenarios are presented. As shown in the above figure, both increased yields as well as higher oil prices significantly influence the economics of algal CO2 capture.

Base case
Capital expenditure: 92 million $, CO2 fixed: 50,000 T/year (2011).
Algal oil production: 1.3 million gal/year.
Cost algal oil: 4 $/gal.
Price of CO2 offsets: 20 $/T CO2.
Timeline considered for IRR calculations: 10 years.

The rest of the scenarios are explained in the figure. Doubling the yields (and CO2 captured) does increase the IRR and lower the payback periods more than doubling the oil prices (mentioned in my last post). Moreover, CO2 trading plays only a minor role by itself, but results in higher IRRs and lower payback periods when considered along with other possibilities. The highest IRR and lowest payback occur when both yields as well as the oil prices are significantly higher than in the base case scenario.

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CO2 to fuels processes - II

Recently Carbon Sciences, featured in an earlier article on this blog revealed the source of hydrogen for their CO₂ to fuels process.
"Dr. Naveed Aslam, inventor of the company's technology and chief technology advisor, commented: "Unlike other CO2 to fuel approaches, Carbon Sciences' technology does not use molecular hydrogen (H2) because the creation and reaction of H₂ is very energy intensive. Rather, the company's approach is based on a low energy biocatalytic hydrolysis process where water molecules (H₂O) are split into hydrogen atoms (H) and hydroxide ions (OH) using a biocatalyst. The hydrogen atoms (H) are immediately used in the production of hydrocarbons and the free electrons in OH are used to power the various biocatalytic processes." "Our technology is not based on photosynthetic plants where sun light is used to drive biofuel production reactions, such as in algae. Instead, it is based on natural organic chemistry processes that occur in all living organisms where carbon atoms, extracted from CO₂, and hydrogen atoms extracted from H₂O, are combined to create hydrocarbon molecules using biocatalysts and small amounts of energy. Our innovative technology allows this process to occur on a very large industrial scale through advance nano-engineering of the biocatalysts and highly efficient process design," concluded Dr. Aslam."
My opinions given below:
Understandably Carbon Sciences is justified in not fully revealing the details . However, the splitting of water to produce protons (H⁺) and hydroxide ions (OH^-) still consumes energy. All the biocatalyst does is to speed up this transformation. It cannot influence the thermodynamics (feasibility) of this reaction. Judging by what the release says, I think that there is a sacrificial oxidant (something which gets oxidized, ex: simple sugars, providing the energy to drive the splitting of water) involved.

Related links:
Opinion: CO2 to fuels processes
Carbon Sciences Announces Prototype Plan for CO2-to-Fuel Technology

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Analysis: Algae for carbon dioxide (CO2) capture

Summary
This post describes a simplified economic analysis of an algal biofuel technology that converts carbon dioxide (CO₂) from cement plants into (potentially) useful algal oil. I examined various key factors such as CO₂ offset price, price of algal oil, and productivity that affect the profitability of such a process.

Based on my analysis I conclude that the single most important factor that affects the economics of CO₂ capture is the algal biomass yield (mass produced/unit area). Doubling the productivity (and the CO₂ offset) per hectare decreases the payback time by 50 % (15 years to 7 years).

Disclaimer: This is not a critique of the specific algal biofuels process proposed. CO₂ mitigation using algae is one of the answers to our grand energy challenges, and we must continue to address these issues.

Assumptions:
The Holcim plant in Jerez likely produces a fraction of the total 5.1 million tonnes of cement per annum (5.1 MTPA). (A cement plant in India I worked at produced 2.6 MTPA, and it was the largest in Asia at that time. Not having first-hand data for this specific facility, lets assume that this plant is 1 MTPA, for the sake of comparison. The exact production does not alter the results significantly).

Cost of algal oil: 4 $/gal
Price of carbon offsets: 15 Euros/T CO₂ (20 USD/T CO₂)
(A high-cost scenario for algal oil and carbon offsets would be 6$/gal, 50 $/T CO₂. This is also addressed in the analysis.)

Data:
Each lb of cement produces 1.0 lb of CO₂ (U.S. average, pg.10).
Total CO₂ to be mitigated annually by 2011: 50,000 T in 100 ha (0.05 MTPA CO₂ in 100 ha) .
Algal biofuel production: 1.3 million gallons/year

Calculations:
Total CO₂ production: 1 MTPA
By 2011, the 100 ha. facility would mitigate 50,000 T of CO₂ (0.05 MTPA CO₂). This would be 5% of the CO₂ emissions (if the Jarez facility production is 1 MTPA)
Average CO₂ use of algae: 0.0005 MTPA/ha.
Revenues from algal biofuel: 5.2 million $/year
Revenues from carbon offsets: 1 million $/year
Total revenues: ~6 million $/year

Results
Capital cost of algal facility: $ 92 million/0.05 MTPA CO₂.
Area needed for 5% of the cement plant's CO₂ output (assuming 1 MTPA production): 543 U.S. football fields (5.4 football fields = 1 ha.)

Payback on investment: 92/6 =~ 15 years. In comparison, typical payback for a new chemical plant is ~ 7 years.

Higher CO₂ prices (50 $/T CO₂), decrease the payback period by ~ 3 years. Higher algal oil prices (6 $/gal) and 20 $/T CO₂ prices will result in a payback period of approximately 11 years.

Higher oil and higher CO₂ prices will lower this period (11 yrs) by an additional ~2 years. However, doubling the productivity (and the CO₂ offset) per hectare decreases the payback time by 50 % (15 years to 7 years).

The revenues from algal biodiesel + carbon offsets will be partly offset by the parasitic losses from the power plant to run the system. I don't have a feel for how much these utility costs would be. Any comments, anybody?

Bottomline The single most important factor that affects the economics is the productivity of algal biomass/unit area. Doubling the productivity (and the CO₂ offset) per hectare decreases the payback time by 50 % (15 years to 7 years).

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Opinion: CO2 to fuels processes

The Green Car Congress blog has an article on a CO2 to fuels process by a company called Carbon Sciences.

Important features of this process are:
1) The use of biocatalysts (enzymes?) to effect the transformations under mild conditions.
2) The use of relatively “dilute” CO2 streams, which could lower the costs for CO2 separation from power plant-flue-gas streams.
My graduate research is in a closely related area, the photocatalytic conversion of CO2 to fuels in which CO2 and water react upon light-induced electron transfer to/from a suitable photosensitizer. This reaction is not very efficient. On the other hand, the heterogeneous hydrogenation of CO2 with H2 is fairly effective (but involves high temperatures), a Japanese company, Mitsui Chemicals will begin the construction of a pilot plant this year to produce 100 T/year of methanol (CH3OH) from CO2 and solar-produced hydrogen.

My opinion:
The conversion of CO2 to fuels is a hydrogenation reaction (add hydrogen, remove oxygen). However, I could not find information on the Carbon Sciences website about their hydrogen source.
One wonders how effective the scale up of this biocatalytic process will be. The main questions for me here are the source of hydrogen, enzyme stability and costs, and the product separation and purification costs. These factors would determine if this process indeed is cheaper than the heterogeneous catalytic process (using Cu/ZnO-like catalysts).
Hat tip: Green Car Congress blog.

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