Biofuel algae :

  

Biofuel algae :

Algal biofuel is an alternative to fossil fuel, which is generated by specific algae species from carbon dioxide. These algae species are primarily unicellular or diatom microalgae that produce high carbohydrate compositions suitable for ethanol production, high lipid compositions suitable for biodiesel production or high hydrocarbon compositions that are suitable for producing renewable distillates.

Increase in fuel costs and consumption, and depletion of natural fuel resources have created a demand for research into alternative forms of fuels in the last decade. Several companies and government agencies are funding research to try and make algae fuel production commercially viable.

The optimum selection of the algal species for biofuel production is based on the ability to sustain the culture, growth rate of the species, the biomass specific contents of proteins, carbohydrates, and lipids, and the overall supporting photosynthesis environment.

Algae Facts:

Algae are tiny biological factories that use photosynthesis to convert CO2 and sunlight into energy-rich chemicals.

There are more than 30,000 freshwater and saltwater species of algae.

Nearly 1000 algae species that have been studied so far exhibit the potential for producing biofuel.

Fuels from Algae:

The lipid (oily) part of the algae biomass can be extracted and converted into biodiesel by a process similar to that used for any other vegetable oil.

Butanol can be made from algae or diatoms using a solar-powered biorefinery. This fuel was found to have an energy density 10% less than gasoline, and greater than that of either methanol or ethanol.

The green waste left over from the algae oil extraction can be used to produce butanol.

Additionally, it was found that macroalgae can be fermented by Clostridria to form butanol and other solvents.

Biogasoline produced from algae biomass can be used in internal combustion engines. Methane, which is the chief component of natural gas, can be produced from algae using several methods - pyrolysis, gasification or anaerobic digestion.

Algae can also be used to produce green diesel, also known as renewable diesel through a hydrocracking refinery process that breaks down molecules into shorter hydrocarbon chains used in diesel engines.

Algae Cultivation:

Algae can produce up to 300 times more oil per unit area than conventional crops such as palms, soybeans, rapeseed or jatoba. The following three primary ways to grow algae for biofuel production have been identified:

Opend pond system :

The open pond system is one of the easiest methods for the cultivation of algae with high oil content. In this method, algae are grown in open ponds under very warm and sunny environments.

Although it is the simplest form of algae production, it also has some major drawbacks. Open systems using a monoculture are also vulnerable to viral infection. To enhance algae production using this method, water temperature needs to be controlled.

Closed-Loop System:

The closed-loop system was adapted to produce algae more quickly and efficiently than the open pond system. In this method, algae are placed in clear, plastic bags to allow them to be exposed to sunlight.

These bags are stacked high and protected from external elements using a cover. The clear plastic bag provides enough exposure to sunlight to increase the rate of algae production.

The greater the algae production, the greater the amount of oil will be extracted. Unlike the open pond method, this method prevents algal contamination.

Photobioreactors:

Most of the companies that use algae as a source of biofuels employ borosilicate glass tubes known as bioreactors that are exposed to sunlight. Within these tubes, the algae can be grown at maximum levels, even to the point they can be harvested every day.

This method results in a very high output of algae and oil for producing biofuels. However, running a photobioreactor is more expensive and difficult than using the open pond system, but may provide a high level of control.

Benefits of Algae Fuel:

Algae require much less land to grow when compared to other traditional row crops, such as corn. Also, algae can be grown on non-arable, nutrient-poor land that does not support conventional agriculture.

Algae farms for producing biofuel can thrive without petroleum-based fertilizers, freshwater for irrigation of arable land.

Rebirth of Algae Biofuel and Subsequent Setbacks:

Promoted as an answer to the negative financial and environmental impacts of traditional oil production, algae biofuel development had substantial amounts of money invested by large companies.

These companies ran into a fair amount of limitations once it came time to retain productivity at a large scale, mainly due to the high expenses of providing enough light and nutrients to keep the farms healthy. Paired with yet another decrease in oil prices, most companies chose to cut their losses and pull the plug on algae biofuel research.

Today, the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy Bioenergy Technologies Office supports technologies to produce biofuels. Specifically, the Advanced Algal Systems program performs research and development to lower the costs associated with producing biofuels from algae.

So far, the program’s Pacific Northwest National Laboratory has developed a process to turn algae into bio-crude oil in just minutes, while participating researchers at the Scripps Institute of Oceanography have made breakthroughs in the metabolic engineering of algae to improve yields of energy-storing fat molecules used in biofuel production.

Although major corporations like Shell and Chevron had previously invested in algae biofuel research and development, pretty much all of them (with the exception of ExxonMobil) have stopped actively pursuing it in recent years.

How Efficient Are Algae Biofuels?

Studies testing different ratios of traditional diesel fuel mixed with algae biodiesel have shown that blends of 30% biofuel are slightly more efficient compared to diesel fuel.5

In a 2017 study published in Renewable and Sustainable Energy Reviews, engine exhaust gas (nitrogen oxide) showed no significant difference between fuels, though carbon monoxide was reduced by 10% when the algae biofuels were used.5

Algae biofuel can be used by most diesel cars without major changes to the engines or infrastructure—the issue lies in the ability to produce algae biodiesel at a commercial scale.

Algae Biofuel Pros and Cons:

Algae are a fast-growing, easy-to-cultivate, renewable resource, and they also have multiple uses outside of biofuel. Hydrocarbons from algae biomass can be used in different varieties of products such as fertilizers and industrial cleaners. Plus, cultivated proteins can be used for both human and animal feed.

Perhaps most importantly, algae absorb CO2 from the atmosphere.

On the other hand, research is still lacking when it comes to algae biofuel, and there are some concerns over human exposure to algae-derived toxins, allergens, and carcinogens from GMOs, since algae are commonly genetically modified.67

Algae also have a large water demand, often necessitate fertilizers, and can have high costs.

Still, many of the barriers keeping algae biofuel from the mainstream are being addressed by top minds and researchers. 

How to Extract Oil From Algae:

Not surprisingly, there are numerous ways to remove the lipids, or oils, from the walls of algae cells. But you may be surprised to learn that none of them are particularly earth-shaking methods. For example, ever hear of an olive press? One of the ways for extracting oil from algae works very much like the technique used in an oil press. This is the simplest and most common method for extracting oil from algae and yields about 75% of the total available oil from the algae plant.

Another common method is the hexane solvent method. When combined with the oil press method, this step can yield up to 95% of available oil from algae. It utilizes a two-step process. The first is to utilize the oil press method. Then, instead of stopping there, the leftover algae is mixed with hexane, filtered and cleaned to remove all traces of the chemical in the oil.

Used less frequently, the supercritical fluid method can extract up to 100% of available oil from the algae. 10Carbon dioxide is pressurized and heated to change its composition into both a liquid as well as a gas. It is then mixed with the algae, which turns completely into oil. Though it can yield 100% of available oil, the plentiful supply of algae, plus the additional equipment and work required, make this one of the least popular options.

Growing Algae for Biodiesel:

The methods used for promoting algae growth in a particular way to yield the most oil are more diversified than the extraction processes. Unlike practically universal extraction methods, growing algae for biodiesel varies greatly in the process and method used. It is possible to identify three primary ways to grow algae, and biodiesel manufacturers have worked hard to tweak these processes to customize and perfect the growing process.

Open-Pond Growing:

One of the easiest processes to understand, open-pond growing is also the most natural way to cultivate algae for biodiesel production. As its name implies, algae are grown on open ponds in this method, particularly in very warm and sunny parts of the globe, with the hope of maximizing production. Though this is the simplest form of production, it has serious drawbacks, like comparatively high potential for contamination. To truly maximize algae production this way, water temperature needs to be controlled, which can prove very difficult. This method is also more dependent on weather than others are, which is another impossible to control variable.

Vertical Growth:

Another method for growing algae is a vertical growth or closed-loop production system. This process came about as biofuel companies sought to produce algae faster and more efficiently than they could with pond growth. Vertical growing places algae in clear plastic bags, which are stacked high and covered as protection from the elements.

Summary:

Algae-based biofuel is a promising energy source that is in the late stages of development. Although producing biofuel with algae is not yet a cost-equivalent solution to the replacement of gasoline, further optimization of current methodologies and economies of scale may change this for some markets in the future.

References:

Algae to biofuels – the process – Algae.tec Ltd

Algae: Biofuel of the Future? – 

University of Virginia

Economic Benefits of Algae – UC SanDiego

Making Biodiesel from Algae – About.com

Algae Biofuels – Stoel Rives.