3rd generation biofuels: algae

Posted by Stella

Quick facts

1. There are more than 100,000 different species of plantlike organisms belong the algae family, from microscopic protozoa to seaweed.
2. Algae require only water, sunlight and CO2.
3. Various algae contain different levels of oil. Of all the algae out there, it seems that pond scum is best suited for biodiesel.
4. The algae have chlorophyll and can manufacture their own food through the process of photosynthesis, converting atmospheric CO2 into O2.
5. They produce more oxygen than all the plants in the world, put together! 
6. They form an important food source for many animals such as little shrimps and huge whales. Thus, they are at the bottom of the food chain with many living things depending upon them.
7. Biodiesel makers claim they'll be able to produce more than 100,000 gallons of algae oil per acre per year depending on:

• The type of algae being used
• The way the algae is grown
• The method of oil extraction

Extracting oil from algae
Algae are grown in either open-pond or closed-pond systems. Once the algae are harvested, the lipids, or oils, are extracted from the walls of the algae cells.

• The oil press. Extracts 75% of oil from pressed algae.
• Supercritical fluids method: extracts up to 100 percent of the oil from algae. Carbon dioxide acts as the supercritical fluid - when a substance is pressurized and heated to change its composition into a liquid as well as a gas. At this point, carbon dioxide is mixed with the algae. When they're combined, the carbon dioxide turns the algae completely into oil. The additional equipment and work make this method a less popular option.

Once the oil's extracted, it's refined using fatty acid chains in a process called transesterification. Here, a catalyst such as sodium hydroxide is mixed in with an alcohol such as methanol. This creates a biodiesel fuel combined with a glycerol. The mixture is refined to remove the glycerol. The final product is algae biodiesel fuel.

Growing algae for biodiesel use

1. Open-pond growing: Using open ponds, we can grow algae in hot, sunny areas of the world to get maximum production. While this is the least invasive of all the growing techniques, it has some drawbacks. Bad weather can stunt algae growth, as can contamination from strains of bacteria or other outside organisms. The water in which the algae grow also has to be kept at a certain temperature, which can be difficult to maintain.
2. Vertical growth/closed loop production has been developed by biofuel companies to produce algae faster and more efficiently than open pond growth. With vertical growing, algae are placed in clear plastic bags, so they can be exposed to sunlight on two sides. The bags are stacked high and protected from the rain by a cover. The extra sun exposure increases the productivity rate of the algae, which in turn increases oil production. The algae are also protected from contamination.
3. Closed-tank bioreactor plants help increase oil rates even further. Instead of growing algae outside, indoor plants are built with large, round drums that grow algae under ideal conditions. The algae are manipulated into growing at maximum levels and can be harvested every day. This yields a very high output of algae, which in turn yields large amounts of oil for biodiesel. Closed bioreactor plants can also be strategically placed near energy plants to capture excess carbon dioxide that would otherwise pollute the air.
4. Fermentation. Algae are cultivated in closed containers and fed sugar to promote growth. This method eliminates all margin of error since it allows growers to control all environmental factors. The benefit of this process is that it allows the algae biodiesel to be produced anywhere in the world. But, researchers are trying to figure out where to get enough sugar without creating problems. 

Advantages
Algae produce oil, and because of their growth rate and yields, they could produce a lot more than other energy crops. Some estimates suggest that microalgae are capable of producing up to 15,000 gallons of oil per Hectare a year. This could be converted into fuels, chemicals and more.
Microalgae, specifically, possess several attractive characteristics in the context of energy and biofuels:

1. Select species of algae produce bio-oils through the natural process of photosynthesis — requiring only sunlight, water, minerals and carbon dioxide. 
2. They can be grown under conditions which are unsuitable for conventional crop production, unlike some other first- and second-generation biofuel feedstocks.
3. Microalgae are capable of fixing CO2 in the atmosphere, thus facilitating the reduction of increasing atmospheric CO2 levels. This provides greenhouse gas mitigation benefits.
4. Algae biofuel is non-toxic, contains no sulfur, and is highly biodegradable.
5. They can be cultivated in marine water and waste water, deserts, etc, etc.
6. They can be cultivated under difficult agro-climatic conditions and are able to produce a wide range of commercially interesting byproducts such as fats, oils, sugars and functional bioactive compounds.
7. Bio-oil produced by photosynthetic algae and the resultant biofuel will have molecular structures that are similar to the petroleum and refined products we use today. 
8. They provide much higher yields of biomass and fuels, 10-100 times higher than comparable energy crops. Algae could yield more than 2000 gallons of fuel per acre per year of production. Approximate yields for other fuel sources are far lower:
   - Palm — 650 gallons per acre per year
   - Sugar cane — 450 gallons per acre per year
   - Corn — 250 gallons per acre per year
   - Soy — 50 gallons per acre per year
9. Algae used to produce biofuels are highly productive.  As a result, large quantities of algae can be grown quickly, and the process of testing different strains of algae for their fuel-making potential can proceed more rapidly than for other crops with longer life cycles. 
10. If successful, bio-oils from photosynthetic algae could be used to manufacture a full range of fuels including gasoline, diesel fuel and jet fuel that meet the same specifications as today’s products.

Disadvantages

1. Open pond growing is extremely exact in temperature. Carbon dioxide has to be pumped into the ponds, and there is a high risk of contamination. (However the closed bioreactor system can counteract these issues.)
2. Photobioreactors - capital cost is very high. This is one of the most important bottlenecks that is hindering the progress of algae fuel industry. No cheap source of sterile CO2.
3. Still in test phase for algae biodiesel and actual cars. (See Mercedes Benz E320 diesel, Sundance Film Festival. However, no statistics were released on the car's gas mileage or what kind of emissions it produced. Also see Boeing and airlines looking to use algae as a biofuel.) 
4. Performance of algal-based biodiesel is lower than other alternatives like biodiesel extracted from rapeseed and soybean??
5. The production of biodiesel from algae also results in several other unstable compounds??

Other uses
Apart from its form of biodiesel, bioethanol, biobutanol and vegetable oil), algae can also be used as biomass that can be burned to produce heat and electricity.

Food stabilizer, food supplement, fertilizer, pollution control...

Summary:

• 60 percent of algae biomass can be converted into biofuel
• 100,000 gallons of algae oil per acre per year??
• much higher yields of biomass and fuels, 10-100 times higher than comparable energy crops
• highly productive: large quantities of algae can be grown quickly 
• very exact conditions required
• photobioreactors - capital cost is very high
• still in test phase
• amount of carbon emission after using algal biofuel is lower than those of fossil fuels??

More to follow...
References
Oilgae

Exxon Mobil.com

How stuff works.com