McDonnell Scholar Wins Three Minute Thesis Competition2018 McDonnell International Symposium, Beijing
Next Generation Biofuels—Are Algae the Answer?
Fossil fuels are indispensable natural resources for human beings. They are formed by the decomposition of dead organisms subjected to heat and pressure for millions of years. Petroleum is refined into gasoline, which powers combustion engines in aircrafts and vehicles. If we look at the history of the oil industry in the past 200 years, we will find that we are at the peak of oil production. Although new technologies have been developed to extract unconventional oil like shale oil to increase supply, the high production cost and environmental impact of the shale oil industry raises concerns. Furthermore, cheap fossil fuels are predicted to be depleted in the next few decades.
Burning fossil fuels emits greenhouse gases such as carbon dioxide (CO2), increasing the temperature on earth. Climate change will create a comprehensive impact, including rising seas, increased risk of drought and floods, stronger storms, biodiversity crisis, and economic losses. Concerns over climate change and energy shortage have triggered research and development of biofuels in an attempt to displace fossil fuel energies.
Current biofuels are mainly derived from crops, such as corn and sugarcane. In the U.S., corn is the major source for biofuel production. The grains are fermented into ethanol, which is blended with gasoline for use in vehicles. In 2013, the U.S. produced over 13 billion gallons of ethanol fuel, which accounts for 10% of total gasoline based fuel.
Making fuels from corn has provoked considerable debate in the U.S. It has been criticized by environmentalists because large-scale biofuel production creates environmental problems and threatens human food supplies and livestock feeds. It has become a moral issue of using food as a source to produce fuels. In 2000, over 90% of corn in the U.S. was used for food and feeding livestock. Less than 5% was used for ethanol production. In 2013, however, 40% of corn was used to produce ethanol. The world’s population is estimated to reach 9 billion by 2050. How to feed 9 billion people with sufficient food is a huge challenge. We should consider other resources for sustainable fuel production that do not compete with the food supply.
Another concern of corn ethanol is the low yield. The corn used for making 25 gallons of ethanol can feed one person for one year. If all of the corn produced in the U.S. were used for ethanol production, it would only supply 25% of gasoline. Such low productivity is unable to meet the increasing demand of transportation fuels. A new generation of biofuel must be developed in order to produce economically viable fuels.
In recent years, microalgae have become potential sources for biofuel production. Microalgae are photosynthetic organisms that utilize sun light as energy to convert CO2 into lipids, which can be processed into biodiesel. It has been shown that several algal strains can produce a considerable amount of lipids (over 50% of their dried weight) under certain environmental conditions. Compared to terrestrial plants, microalgae have higher growth rates and require less water and nutrients for cultivation. They can be grown on non-arable land, which will not compete with land use for food crops. Moreover, certain algal strains can be cultivated by wastewater or seawater, thus eliminating the impact on freshwater resources.
The estimated yield of algal biofuels is 5 times higher than corn ethanol, reaching 2,400 gallons per acre in one year. Moreover, lipids produced by microalgae are 10 to 20 times higher than other fuel crops such as palm and coconut oil. These features indicate that microalgae are promising for fuel production.
But current algal fuel prices are too expansive for commercialization. In 2012, the estimated cost of fuels from algae was around $8 per gallon, which is still higher than petroleum-based fuels. However, as technologies improve and production scale increases, the price will go down in the future. The cost of algal biofuels is expected to be competitive with fossil fuels around 2020, and that is the time to use the biofuels to power our engines.
Although algae seem to be promising as a source for fuel production, a recent study estimates that in order to displace 30% of oil consumption in the U.S., half of the non-arable land is required for algae cultivation. Such analysis suggests that we are unable to completely replace fossil fuels with biofuels. To reduce reliance on fossil fuels, algae will not be the only answer. Various types of renewable energies such as solar, wind, and hydropower are required to be utilized in order to achieve sustainable development.
There is only one earth. We are consuming natural resources at a rate faster than what is needed to be replenished. If everyone on earth lived the lifestyle of an American, we would need five planet Earths to support us. The way we are currently living is borrowing resources from our children. It is our responsibility to think about how to achieve sustainability, and conserve the environment for the next generation.