Algae Reactors - Another way to fuel vehicles

Algae are the fastest-growing plants in the world. Like other plants, they use photosynthesis to harness sunlight and carbon dioxide, creating high-value compounds in the process. Energy is stored inside the cell as lipids and carbohydrates, and can be converted into fuels such as biodiesel and ethanol. Proteins produced by algae make them valuable ingredients for animal feed.

GreenNRG uses a portfolio of technologies to profitably recycle CO
2 from smokestack, fermentation, and geothermal gases via naturally occurring species of algae. Algae can be converted to transportation fuels and feed ingredients or recycled back to a combustion source as biomass for power generation. Industrial facilities need no internal modifications to host a GreenNRG algae farm. In addition, the system does not require fertile land or potable water.

What does GreenNRG do?

GreenNRG uses a portfolio of technologies to profitably recycle CO2 from smokestack, fermentation, and geothermal gases via naturally occurring species of algae. Algae can be converted to transportation fuels and feed ingredients or recycled back to a combustion source as biomass for power generation.

When was GreenNRG founded?

GreenNRG, a privately held, venture-backed firm, was founded in 2001 as a subsidiary of Global NRG Ltd.

Why is Global NRG focusing on algae instead of other energy crops like corn?

Algae have some advantages to other energy crops*, specifically:

·          Algae are the fastest growing plants in the world and can be grown year round, unlike seasonal crops.

·          Algae farming does not require agricultural land or clean water, so it does not compete with food crops for these resources. 

·          While it is difficult to compare one energy crop to another, per hectare of land algae is more productive than corn, soy or palm.

·          Unlike other energy crops, the entire biomass produced from algae can be used in end products.

·          Lastly, the algae produced by GreenNRG can be used to produce renewable biofuels needed to reduce dependence on non-renewable fuel sources such as coal, oil and natural gas.


 What are algae?

Algae are simple organisms that range from very small, single-celled microalgae to macroalgae that group into very large organisms such as kelp. There are more than 300,000 species of algae in the Smithsonian Institution collection. The vast majority of algae are photosynthetic, deriving energy from the sun to produce energy and biomass.

 Are algae currently a commercial crop?

Yes. Algae are grown commercially around the world, primarily for nutritional, feed, and specialty product use.

What is required to grow algae?

The primary requirements for growing algae are sunlight, water, and carbon dioxide (CO2). Algae also require nutrients and environmental conditions appropriate to the specific algal species. Algae are known to grow in environments as diverse as the arctic and hot springs.

Does GreenNRG grow algae using the CO2 in our atmosphere?

No. GreenNRG’s technology consumes high concentrations of CO2 (between 5-30%) as it is emitted from power, cement and chemical plants before it is absorbed into the atmosphere. Atmospheric CO2, at less than 0.04%, is not concentrated enough to deliver the productivities we are seeking.

Does GreenNRG grow algae in open ponds?

No. GreenNRG algae farms are enclosed systems resembling greenhouses. They are often called algae-solar bioreactors.

What kind of algae does GreenNRG use?

GreenNRG selects microalgae based on a number of factors, most notably high innate growth rates, favorable overall composition (lipids, carbohydrates, and proteins), and ability to grow in specific climatic conditions.


How much algae does a GreenNRG algae farm grow?

There are a number of variables including innate growth rate per species and seasonal availability of sunlight. GreenNRG anticipates that a commercial algae farm will grow an average of 80 grams of algae per square meter growing footprint per day.*


*See Appendix Photosynthesis at the bottom of the page


Do algae accumulate heavy metals or other harmful substances that may be present in the CO2 source?

No. GreenNRG only selects algae species that do not accumulate metals or other harmful substances. In addition, Global NRG has established analytical methods to confirm the lack of bioaccumulation in initial studies at each host facility and throughout commercial operations.



Does GreenNRG use algae that have been genetically modified?

No. Global NRG does not use any algae species that are genetically modified organisms (GMOs). 


What products does an algae crop yield?


A GreenNRG algae farm is designed to produce a number of products including algal oil, delipidated algal meal (DAM) and dried whole algae (DWA). The algal oil is suitable for conversion to biodiesel and can be substituted for any other vegetable oil (soy, palm, jatropha) in a commercial biodiesel production plant. The DAM and DWA are suitable for a wide variety of animal feed applications.


How much oil can be made from algae?

Different species of algae generate different amounts of oil. Global NRG has focused on several algae species that contain approximately 25% of their weight as oil.


How does GreenNRG algal meal compare to other meal products?


The algae meal from a GreenNRG algae farm has a high protein content compared to other animal feed product such as dried distiller’s grains from ethanol production or soy meal after oil removal.


Energy Crop Comparisons          


Are there any accurate measures to compare algae to other energy crops?

Due to a large number of variables, it is difficult to accurately compare one energy crop to another. Global NRG recommends comparing energy crops based on the final products produced, and the resources required to produce those products. 


How are algae different from other energy crops?

Algae are different from other energy crops in one significant way--the entire biomass produced from an algae farm can be used in end products that are economically valuable. Unlike comparable crops (corn, sugar cane, rapeseed/canola, palm, soybeans, sunflower, jatropha, etc.) which typically contain a substantial amount of wasted biomass, 100% of algal biomass can be used to create new products.


How does algae productivity compare to other energy crops?

Unlike seasonal crops, algae can be grown year round. Since an algae crop does not result in wasted biomass, algae are generally considered to be more productive than comparable energy crops.


How does algae fuel production compare to other liquid fuel crops including corn ethanol?

Under our base design, oil production from the algae farm is estimated at over 5,500 gallons per acre per year. This compares to palm oil at 500, soy at 90, and corn (in the form of ethanol) at 350 gallons per acre per year.


Impact of Algae on CO2, Water and Other Resources  


How much CO2 can algae consume?

CO2 consumption is based on the overall lipid/protein/carbohydrates balance of the final algae. Lipids are typically about 75% carbon by weight, with carbohydrates approximately 40% carbon by weight, and proteins between the two.


GreenNRG algae is approximately 50-55% carbon by weight; about 1.9 times the biomass weight in CO2 is required to generate algae with this composition. If algae with a higher lipid content is produced, that ratio will be higher; the higher the carbohydrate composition, the lower this ratio.


What is the maximum CO2 consumption per acre of a GreenNRG algae farm? **


A GreenNRG algae farm will consume approximately 500 metric tons of CO2 per hectare per year based on current algae composition and growth rates.


How much of the CO2 from an industrial facility can a GreenNRG algae farm consume?


The current design of a GreenNRG farm can mitigate a maximum of 40% of the emissions from a round-the-clock operation. 


How large must an algae farm be to mitigate emissions from a typical power plant? **


Based on information in the US Energy Information Administration 2006 power plant database, for the approximately 500 power plants in the US that generate and sell electricity as their primary business and use coal as the primary power source, the average facility nameplate size is 655 megawatts. For this 'average' plant, when both the power plant and algae farm are in full operation, approximately 3400 hectares of algae growing area is required to consume 40% of CO2 emissions. To achieve a 5.2% reduction in CO2 emissions, which is comparable to the 2008-2012 Kyoto Protocol overall goal, 420 hectares of algae growing area would be required for the same 655 megawatt plant.


How much water does a GreenNRG algae farm require?

Because GreenNRG’s algae farm is a closed system, overall water use is minimal and evaporation losses are limited. Some water is required for the photosynthesis reaction, and some is lost in the creation of algal products. Where available, water may also be used for system cooling based on site-specific dependencies. 


Does GreenNRG’s system produce agricultural (nutrient) runoff?

No. GreenNRG’s algae farms are enclosed and nutrients are recycled to make the most efficient use of resources.


Can the GreenNRG system use feed water streams that are high in nutrients such as phosphorous and nitrogen?

Global NRG is actively pursuing several opportunities where nutrient-rich water feed streams will be used to provide some or all of the nutrients needs of the algae farm. Streams which have a potential to be used in this way include runoff from animal facilities and treated wastewater.



Photosynthesis is the process by which plants utilize the energy in the sun’s rays to produce energy and new plant matter (biomass). Photosynthesis is the base reaction supplying the vast majority of energy used by plants and animals on earth. In photosynthesis, energy (photons) from the sun’s rays converts carbon dioxide and water to carbohydrate plus oxygen. The carbohydrate can be converted to protein or fat.


Solar energy is spread along a wide range of wavelengths, of which only a portion is useable for photosynthesis. The wavelengths useable by plants are known as photosynthetically active radiation (PAR), and include about 45-50% of the total solar energy. Energy requirements of the photosynthesis reaction reduce the usability of that 45-50% by another factor of 4, making the theoretical energy use roughly 11% of the overall solar energy.


This photosynthetic efficiency is translated into biomass including fats, proteins, complex carbohydrates (cellulose, lignin, etc.) and simple carbohydrates. Also, most crops contain water. To eliminate the effect of water, we present values based on dry biomass. We also need to understand that production of other compounds from simple carbohydrates requires some of the energy.


We have grown algae at a photosynthetic efficiency of approximately 5.4% under natural sunlight. General crops grow at a photosynthetic efficiency of approximately 1%. Algae can be grown much more efficiently because of the nature of the bioreactor and the removal of factors that might limit growth such as lack of nutrients or CO2.


You can also improve algae growth by using artificial lighting. Algae will grow 24 hours per day if there is sufficient light. However, due to the energy losses inherent in each step from generating electricity to create light and using the light for photosynthesis, this is not economical for anything other than studies, unless the value of the final product is very high (as it is for some commercial algae farms where artificial light is used).

Arizona example:

Based on actual meteorological data from the ‘Typical Meteorological Year’ data (TMY) for Phoenix, Arizona, the average hour by hour Global Horizontal Direct and Diffuse solar radiation is 242 W/m2 (across 24 hours, 365 days), which converts to 5.81 kWh/m2-day (242 * 24 hours * 1000 kW/W). From the NREL solar database the average is 5.7 kWh/m2-day.

Using the lower value of 5.7 kWh/m2-day, the total energy on a yearly basis is 2080.5 kWh/m2-yr. At 1 kWh = 3.6 million Joules, and 1 Joule = 0.002388 kCal, this is equivalent to 2080.5 * 3.6 * 10^6 * 0.0002388 = 1.79 * 10^6 kCal/m2-yr

At 11% maximum theoretical photosynthetic efficiency, 1.97 * 10^5 kCal/m2-yr is available for photosynthesis, which is sufficient to create 51.6 kg/m2 glucose.

The energy required to fix 1 mole of CO2 via photosynthesis is 114 kCal, or 686 kCal per mole of glucose created. 1 mole of glucose is 180 grams, so 1 Kg of glucose (as biomass) requires 3811 kCal of solar energy. Our proven productivity of 98 g/m2-day dry biomass at our Arizona facility in 2007 is equivalent to 36 kg/m2-yr productivity, which is 70% of the theoretical maximum, or a photosynthetic efficiency of approximately 7.7%. Since these results were achieved during the summer, when peak solar radiation is experienced, we would expect the annual average productivity to be somewhat lower. In fact, using the average monthly solar radiation of 8.0 for June and July in Phoenix, compared to the annual average of 5.7, leads to an expected annual average productivity of 70 g/m2-day based on our experimental data which is 25.5 kg/m2-yr, about 50% of the maximum photosynthetic efficiency.

**Facility Size

We generally assume that the growing areas of the algae farm will be available for growing algae 85% of the year. Similarly, the annual average productivity is estimated at 80 gm/m2-day for our highest productivity system. Thus the overall system productivity is about 25 kilograms per square meter per year (55 pounds).

The overall biomass is expected to be slightly over 50% carbon by weight. Since carbon is 27.3% of the weight of CO2, it requires approximately 1.9 times the weight of produced biomass in CO2. Thus for every 1 ton of biomass produced, 1.9 tons of CO2 are consumed.

Multiplying 55 * 1.9 = 104.5 pounds CO2 consumed per square meter growing area per year.

Our standard commercial algae farm includes 100 hectares (247 acres) of algae growing area, which will consume over 52,000 US tons of CO2 per year.

The algae farms are expected to be built in multiple units of the 100 hectare standard for facilities where more CO2 is available.


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