## Column

## Potential of Microalgae

Microalgae are known as organisms that have produced oil shale. Algae have many species that produce significant amounts of fat and hydrocarbons, and the utilization of algae as biomass energy material has been under research mainly in the United States since right after the oil crisis in 1970s. Oil production capacity of algae is estimated at about 47 to 400 tons/ha, 25 to 120 times the capacity of oil-producing plants such as corn, soybeans, safflower, sunflower, oilseed rape and oil palm.

For example, if half of the amount of oil used in transportation in the United States is to be covered by algae oil, an area of a pool needed to cultivate algae is about 1.9 million to 5.6 million hectares, only one-seventh to one-twentieth of the area of the State of Colorado. Since energy consumption by the transportation sector accounts for about 70% of the total energy consumption in the United States, a project to develop a technology to produce diesel oil from algae in the country's vast deserts has been drawing keen attention.

Botryococcus braunii (hereinafter referred to as just "botryococcus") is known to produce hydrocarbons equivalent to 20-70% of heavy oil per alga body dry weight. Botryococcus is characterized by its capability of "producing oil components in both cells and colonies," and thus, it is possible to extract only oil without destroying cells. Generally speaking, oil of vegetable origin oxidizes metals and residual oil gets solidified. But hydrocarbons produced by microalgae can be refined and utilized just as fossil fuels using existing systems. The University of Tsukuba has obtained this promising botryococcus strain, and is proceeding with research and development through the large-scale use in open system for its cost advantages.

The University of Tsukuba’s research and development goal for the moment is to “improve the oil production efficiency by one digit (1,000 tons/ha in terms of yield).” It plans to demonstrate the development by a full-scale production plant by 2020.

## Conclusion

In this chapter, we discussed the damage caused by global warming and the economic benefits of measures to cope with the problem, and then introduced various global warming countermeasures being implemented in Japan and overseas. There are various options as to how to proceed with global warming countermeasures, but in any case, solutions to the global warming problem should not

and hopes to apply it to society by 2025.

In recent years in Japan, the depredation of abandoned agricultural land has become a serious issue. If we install microalgae cultivation tanks on all abandoned agricultural land totaling 220,000 hectares, there is the possibility that we can produce 220 million tons of oil, which is equivalent to Japan's annual oil imports, and also can reduce carbon dioxide emissions by about 657 million tons-CO $ _{2} $ /year. While there may be competition for land from photovoltaic power generation, it is possible that “needs for fire power of oil” still exist in a low-carbon society in the future for manufacturing of industrial materials and as fuel for aircraft.

Oil-producing microalgal strain established as cultivated strain from selective culture sample

A. Botryococcus cultivated strain selected under the 20mM NaHCO $ _{3} $ condition

B. Monocellular green alga strain selected under the 0.35% seawater condition

C. Chlorococcum-like green alga selected under the 20mM NaHCO $ _{3} $ condition

References and photos: "Prospects of Algal Biomass Energy," Prof. Shin Watanabe, Graduate School of Life and Environmental Sciences, University of Tsukuba

sacrifice our cultures and affluence of our life. Everything in our daily activities is related to the progress in global warming. And its adverse impacts not only affect us but also continue to haunt children in the future. We will immediately stand up to fight the problem and aim to create a sustainable economic society with reduced emissions of greenhouse gases, a new Japan.