According to the Intergovernmental Panel on Climate Change (IPCC), reducing carbon emissions from our food sector is absolutely essential to combat climate change. The most recent report of the expert group was devoted to land and agriculture, but there was no question of how oceans in general could contribute to this struggle.
Algae, perceived by some as little more than marine debris on the beach, could be a new player in the effort to mitigate climate change. That's what UC Santa Barbara researchers say, who have studied the carbon offset potential of algae aquaculture.
"This is not a quick fix, nor an industry that still exists," said Halley Froehlich, assistant professor in the department of environmental studies and the department of ecology, evolution and marine biology. "But he has huge potential." Froehlich is the lead author of the world's first global scale assessment of the carbon sequestration scale potential of marine algae aquaculture, found in Current Biology.
According to Froehlich and his co-authors Jamie Afferbach, Melanie Frazier and Benjamin Halpern of the National Center for Ecological Analysis and Synthesis, who synthesized various datasets from the scientific literature, seaweed aquaculture could be a powerful new way to sequester carbon. The process would involve cultivating and harvesting algae to sink the algae into the depths of the ocean, where the carbon stored in its tissues would remain "buried".
"We really wanted to know if this could be beneficial, but also be realistic about its potential," said Froehlich about the research, which she has limited by such constraints as nutrients, temperature and energy. 39 geographical adequacy, as well as an assessment of growth and cost of production. Researchers also looked at the potential for mitigation at different scales with a focus on the food sector – a major source of greenhouse gases and a major obstacle to tackling climate change.
According to the study, there is a large favorable area – about 48 million square kilometers – in which algae could be grown. A relatively small proportion (0.001%) would be enough to make the entire global carbon-neutral aquaculture sector.
However, the benefits are not commensurate with the global greenhouse gas emitting sector, which is much higher, partly because of cost and growth constraints, Froehlich said. Marine algae cultivation will not be enough to offset emissions from global food production, but could be a useful new tool in a suite that includes other carbon reduction and offsetting measures such as cleaner energy sources , reforestation and protection of carbon sinks.
Research has shown that growing seaweeds that reduce greenhouse gases could have the greatest potential for achieving local and regional carbon neutrality goals. California is particularly well-prepared to take advantage of the alleviating benefits of seaweed aquaculture, given its state's aggressive policy to combat climate change and its long, nutrient-rich coastline. Only 3.8% of the West Coast Exclusive Economic Zone (a marine area not exceeding 200 nautical miles from the coast) would be sufficient to offset the carbon produced by the state's agricultural sector.
Compared to the rest of the world, seaweed aquaculture in the United States is still in its infancy.
"The vast majority of marine algae aquaculture occurs in Southeast Asia," Froehlich said. Although there was no measurable algal breeding in the United States in 2016 – the last period of the study – small algae farms are beginning to appear in the United States, although act primarily on food and other commercial purposes, and not on carbon sequestration.
Mr Froehlich pointed out that the United States is the world's second largest emitter of greenhouse gases, stressing the need to find solutions such as growing algae to mitigate millions of tons of carbon dioxide equivalent that the country issues each year. Fortunately, the cultivation of algae has other beneficial effects on the environment, she noted.
"We like to call it" charismatic carbon "because it has additional benefits, such as potentially providing habitat for fish and marine life, reducing ocean acidification and oxygen depletion, and absorbing excess nutrients in local areas.
The beneficial effects on climate of seaweed cultivation far outweigh the fact that it can not completely offset the greenhouse gas emissions from the country's food production. In fact, according to co-author Halpern, there is not and will never be a unique tool for dealing with climate change.
"The problem has become too important for simple solutions," he said. "We need everyone on the bridge." Although solutions to climate change are not easy, he added, the more strategies there are, the better.
"The big advantage is that if we can deploy many different strategies, from seaweed cultivation to renewable energy to energy efficiency, the solution is more resilient," said Halpern.
To make it a real option in the United States, the policy should allow and accelerate the cultivation of algae for carbon sequestration, farmers should react by significantly increasing production and the carbon market should expand to offer higher prices .
In the meantime, research will continue to explore the potential of algae culture to mitigate the effects of climate change.
"My colleagues and I are evaluating alternative ways with algae to find the best value for money for reducing carbon emissions," said Froehlich. Since algae are also subject to the effects of climate change, a better understanding of how they could be affected would greatly inform how they could be grown and managed in the long term.