Producing crude oil from algae

Biofuels are an alternative to fossil fuels that are produced from fats derived from living organisms. One source of biofuel that is being explored more thoroughly in recent years is microalgae. The bio substance can be turned into crude oil, which can then be used to create biodiesel, biobutanol, biogasoline, methane, ethanol, or jet fuel.

History

In 1942, European scientists Richard Harder and Hans von Witsch proposed the mass cultivation of diatoms to produce fat, which was urgently needed because of World War II. Government researchers began exploring algae as a source of fuel in 1978 and continued experiments through 1996.

Process

Algae cultivation

Algae can be grown under multiple conditions, including those unfavorable to other plants. It can bloom in places where salty water, excessive sun exposure, and lack of vital nutrients inhibit growth of other crops. But the higher the concentration of algae cells, the lower the ability to absorb light. In heterotrophic conditions, the algae can use sugars, organic acids, and other organic carbons as carbon sources, replacing the need for light.

Converting the algae into crude

Fuel production

Converting wet algal biomass into combustible fuel is a challenge. After the algae is harvested, the biomass is typically processed in a series of steps, which differs based on the species and desired end product. Often, the algae is dehydrated and then a solvent, like hexane, is used to extract energy-rich compounds, like triglycerides, from the dried material. Once extracted, the compounds can then be processed into fuel using standard industrial procedures. For example, the extracted triglycerides are reacted with methanol to create biodiesel via transesterification. Each species contains a unique composition of fatty acids that influences the quality of the resulting biodiesel and thus must be taken into account when selecting algal species for feedstock.

High temperature and pressure

An alternative approach employs a continuous process that subjects harvested wet algae to high temperatures and pressures—350 °C (662 °F) and 3,000 pounds per square inch (21,000 kPa).

Products include crude oil, which can be further refined into aviation fuel, gasoline, or diesel fuel. The test process converted between 50 and 70 percent of the algae’s carbon into fuel. Other outputs include clean water, fuel gas and nutrients such as nitrogen, phosphorus, and potassium.

Advantages

Versus fossil fuels

Algae fuel’s carbon footprint is smaller than that of fossil fuels and it is renewable, making it more eco-friendly. Additionally, wastewater is a possible nutrient source for algae, making the use of freshwater less necessary and decreasing, rather than increasing, pollution.

Versus other biofuels

When compared to other biofuels, algae has a higher productivity rate, and does not compete with food sources because it does not need arable land to grow and is not a food crop. Microalgae can harvest radiant energy from the sun into valuable products at the expense of inexpensive natural resources like CO2, contributing to global CO2 reduction.

Disadvantages

Commercial Viability

Algae biodiesel is still a fairly new technology. Though United States government-funded research began over 30 years ago, it was put on hold during the mid-1990s, mainly due to a lapse in funding and a relatively low petroleum cost. For the next few years, algae biofuel saw little attention; it was not until the gas peak of the early 2000s that it eventually had revitalization in the search for alternative fuel sources. While the technology exists to harvest and convert algae into a usable source of biodiesel, it still hasn't been implemented into a large enough scale to support the current energy needs. Further research will be required to make the production of algae biofuels more efficient.

Stability

The biodiesel produced from the processing of microalgae differs from other forms of biodiesel in the content of polyunsaturated fats. Polyunsaturated fats are known for their ability to retain fluidity at lower temperatures. While this can be an advantage in production during the colder temperatures of the winter, the polyunsaturated fats result in lower stability during regular seasonal temperatures.

Noteworthy papers in OnePetro

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See also

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