[Global] Scientists hoping to meet the Paris climate accord goal of limiting global temperature rise to less than two degrees Celsius think they might have a new solution: marine microalgae.
Not only can these fast-growing single-celled plants provide biomass for carbon-neutral fuels, they can provide animal feeds and high-quality protein supplements for a human population that looks to be headed for a peak of about 9.5 to 10 billion, says Charles Greene, an environmental scientist from Cornell University, New York, US.
It might even be possible to convert algae into bioplastics for building materials that permanently remove carbon dioxide from the air, he adds.
Greene recently presented his arguments at the American Geophysical Union’s biannual ocean sciences meeting, in Portland, Oregon.
The plan starts with cultivating the algae on land, where there is no risk to marine ecosystems. The same could be done with fresh-water algae, but that would compete with other needs in an increasingly water-strapped world.
“Freshwater is in such high demand,” Greene says. “There’s a lot of seawater out there.”
The idea has been kicked around since the early 1970s, but had run into a problem: algae is food for a lot of organisms, and if we start growing it in large outdoor ponds, it isn’t going to take them long to start chowing down, destroying the crop. That can be prevented by growing it in sealed bioreactors, but those are expensive. For years, the whole idea looked like a dead end.
Then, Greene says, scientists realised it was possible to split the difference. Algae cultivation could be started in bioreactors, then moved to outdoor ponds. Algae-eating organisms would still get into the mix once the process moved outdoors, but the algae would by then have such an enormous head start it would no longer matter.
But the process also needs a large source of carbon dioxide. “You need to add CO2 because the algae take it up so rapidly it can’t diffuse through the air-water interface fast enough to keep up,” Greene says.
Originally, he says, the algae cultivation was suggested as a way of abating CO2 emissions from fossil fuel power plants. But then a company called Global Thermostat found a way to use heat to capture carbon dioxide directly from the air — heat that could come from solar collectors used to provide electrical power to run pumps and other algae-farm equipment.
The whole process, Greene says, is extraordinarily productive — one to two orders of magnitude more so than other biofuel crops such as soy, rapeseed, palm oil, and biodiesel focus, Jatropha. Not to mention that it produces a protein-rich byproduct more nutritious than soy protein. In fact, Greene says, market analysts estimate that within five years, the global market for algae-derived food ingredients could reach $400 billion.
Ramping up to produce enough algae to solve the climate problem would take a tremendous amount of land — about 1.92 million square kilometres, Greene says – about three times the size of Texas.
Still, that’s only 8% the size of Australia and a tiny fraction of the land already used for conventional cultivation and grazing. “The land is available,” Greene says.
Australian coastal deserts, he adds, are among the best locations, along with those in the Middle East, Africa, and South America. In these places, he says, “we envision ribbons of algae farms as far as the eye can see. We’re talking with people in Peru about doing one of our first commercial enterprises there.”
Like all grand schemes to save the planet, it has some drawbacks. What if an algae plague kicked off something akin to the Irish potato famine of the 1840s? “This is a huge monoculture,” one questioner asked at Greene’s conference presentation. “What if you get an infective agent?”
Greene admitted this was a concern, but noted that the plan is to work with a variety of local strains that would be “basically adapted” to whatever infectious agents might exist in their parts of the world. “And we are not working with gene modified organisms,” he said.
What of the ecological damage to the deserts in which these giant algal farms would be sited? “There’s a huge land footprint on a desert ecosystem,” another questioner said.
Greene noted that, so far, nothing has been done on a large scale, though a pilot plant has been constructed in Kona, Hawaii. But, he said, “my general philosophy is that anything humans do is going to have an environmental impact. What we have to decide is what kind of environmental impacts we’re willing to accept.”
A more general comment comes from Sally Jewell, who was President Obama’s Secretary of the Interior. When it comes to solving climate change, she tells Cosmos, “we are absolutely going to need geoengineering” — whether in the form of carbon capture and sequestration, large-scale reforestation, reflecting sunlight back into space, or algae farming.
But she’s not a fan of one-size-fits-all approaches. “I don’t think there is a single solution,” she said. “We need to experiment.”
She also doesn’t think the Trump Administration’s planned withdrawal from the Paris accord is fatal to global efforts to control climate. Even within the US, she says, there is dissent at the local level, ranging from the giant economy of California, which under Governor Jerry Brown remains committed to climate-change abatement, to smaller-scale movements by other states or cities.
“It’s not all about the federal government,” she says. “I think there is an embarrassment that a lot of us Americans feel about the words and actions coming out of this Administration and we’re not going to step back and not take action. There will continue to be progress in the US; it’s just not going to be led by the federal government.”
Photo: Tubular bioreactors filled with green algae fixing CO₂ to help reduce climate change, in Andalusia, Spain. Similar set-ups would be needed to kickstart food production. SANTIAGO URQUIJO/GETTY IMAGES
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