The world is currently on track to miss its target of limiting global warming to 1.5°C relative to pre-industrial levels, a goal set in the December 2015 Paris Climate Accord. To avoid catastrophic global climate change, society must start to significantly cut its greenhouse gas emissions. World population numbers are expected to jump from today’s 7.3 billion to 11.2 billion by 2100, and many scientists believe that climate mitigation will have to include capturing and storing atmospheric carbon. Either way, no sufficient technologies nor cost-effective, safe approaches exist to address the vast scale of the problem. “We have about ten to fifteen years to figure it out,” says Charles Greene, Professor of Earth and Atmospheric Sciences at Cornell University, New York. “That gives us two to three decades to implement whatever solutions we come up with. After that, it’s too late.”
Greene is a member of the Marine Algae Industrialization Consortium (MAGIC), led by Duke University in North Carolina. On November 7, 2016, the journal Oceanography released a Consortium paper on line that will be published in its December issue and presents the large-scale industrial cultivation of marine microalgae (ICMM) as an answer (Link to Publication DOI: https://doi.org/10.5670/oceanog.2016.91). The team had begun with algae as an option for biofuel. “But in making that work, we discovered an integrated approach that solves other critical issues and can make the effort viable,” says Greene, the paper’s lead author. “Fuel is only part of the story. The algae can have an enormous impact.” Underpinned by numerous prior research papers through MAGIC’s predecessor, the Cornell Marine Algae Biofuels Consortium, the ICMM approach delivers a series of co-products: liquid hydrocarbon fuels to power heavy-vehicles, ships and aircraft, proteins and other essential nutrients to feed the planet’s population, and biopetroleum products to store carbon for the long-term.
How does it work? Marine microalgae grow at least ten times faster than the planet’s most productive land crops, so they can produce the same amount of bioenergy or food on less than one tenth of the land area. This speed and efficiency are important. Each time we destroy a forest to create agricultural land, carbon that was locked up in the forest’s ecosystem enters the atmosphere. “Currently, about 20% of all carbon emissions are caused by changing forested lands for agricultural use,” says Greene. “If we can reduce the amount of land that we are changing, that makes a big difference.” The Consortium researchers point out that cultivating marine microalgae for biofuel and food not only results in less deforestation, hence less carbon emissions, but agricultural lands reserved for large-scale land crops can be reforested, providing new carbon storage. Marine microalgae grow in seawater, so cultivation facilities could even be located in coastal deserts.
If these algae were grown to the scale of current global fuel needs, they themselves would capture about 28 gigatons of carbon per year. This is substantial, since annual anthropogenic carbon dioxide emissions currently measure 40 gigatons globally. True, if all the algae were burned as fuel or metabolized by animals (including people), then all of that captured carbon would return to the atmosphere.However, the consequential land-use changes, including reforestation and forests saved by using the algae instead of land plants, can compensate. Furthermore, there is the possibility to manufacture algae-based biopetroleum products, like plastics. “They could lock up some of the carbon for a long time,” says Greene, “and could be used in the human-built infrastructure that we’ll need in the future.”
Growing enough algae to provide the current global demand for liquid fuel would require an area of 1.92 million km² (slightly less than three times the size of Texas). The residual or remaining algae biomass could deliver 2.40 gigatons of protein, which corresponds to about ten times the global annual production of soy protein. The algal proteins, which are high quality, could serve human nutrition, replace soy in animal feed, and substitute for aquaculture fishmeal. Even environmental problems associated with crop fertilizers can take a solution-oriented turn with marine microalgae. Algae do need substantial amounts of nutrients to grow, but they take up nutrients with minimal loss. Further, the MAGIC team offers that the algae could use nutrient-concentrated wastewater instead of fertilizer.
The potential of ICMM is clear and realistic. “But we need people to step in and invest in the technologies required to solve our climate, energy, and food security problems during the narrow window of time that we have,” says Greene, adding that a 10-km² commercial facility would cost $400-500 million. “That may seem like a lot of money, but integrated solutions to the world’s greatest challenges will pay for themselves many times over during the remainder of this century. The costs of inaction are too steep to even contemplate.”
~ Sophia V. Schweitzer