In the struggle to slow down the runaway freight train of humanity’s destructive impact on Earth, scientists are increasingly looking at the role our oceans can play.
Joining the industry, scientists at the University of Southern California have discovered an “algae-growing” technique that produces ample algae, potentially providing a high-yield biofuel to help us move away from fossil fuels.
Many terrestrial biofuels capable of fueling cars, planes, ships and trucks now come from mass-produced crops such as corn, soybeans and replacement grass. There are several problems with these options, including the use of limited land space for food supply, the devouring of massive amounts of water, pollution of pesticides and fertilizers and the violation of rare biodiversity habitats.
Not only does it rely on giant seaweed, such as seaweed, it avoids these problems, but the algae biology is better suited to be used as a biofuel.
Giant seaweed (Macrocystis pyrifera) can grow at an impressive rate of up to 35 cm (14 inches) per day under ideal conditions. They constantly form new leaves, allowing the harvest of mature leaves, which can reach 30 meters in length and otherwise would deteriorate and die, without affecting the growth of algae.
Because algae are more of a protist than a plant, their molecular composition lacks the plant’s robust lignin, which complicates the process of turning terrestrial crops into fuel. Moreover, growing algae also capture carbon dioxide, which in turn raises pH levels and oxygen supply in the immediate area – helping to mitigate the local effects of ocean acidification.
But questions remain as to whether we can grow enough seaweed to feed our future in an ecological way. Now, researchers may have found a way to produce algae efficiently – by raising and lowering the depth of the algae in the water.
“We found that deep-cycled cabbage grew much faster than the cabbage control group, producing four times the biomass production,” said Diane Young Kim, an environmental scientist at the University of Southern California.
Cycling the depth of the algae throughout the day, the team found that it took nutrients from the depths of the water that were missing closer to the surface at night, feeding the extra growth, while still receiving enough access to sunlight at deeper depths. small during the day.
The team found that algae exposed to greater depths underwent some physiological changes that made them better equipped to cope with the increased pressure. Their pneumatocysts – the air-filled structures that help algae leaves float closer to the sun – have become thicker and more fluid.
The researchers built a summer elevator off the coast of California made of fiberglass and stainless steel, with horizontal beams on which they could “plant” juvenile cabbage. The entire structure was cycled through the water column using an automatic winch, powered by solar energy.
“The good news is that the agricultural system can be assembled from products available without new technology,” said one of the team members, Marine BioEnergy chief engineer Brian Wilcox. “Once implemented, deep-cycle cycling farms could lead to a new way to produce affordable, carbon-free fuel throughout the year.”
This technique could open up to the cultivation of huge nutrient-poor regions of the ocean, where algae would not normally grow, which would also allow us to protect the vital carbon sinks of natural summer forests over time. what we still use brown algae.
The team called for further research in this area, and much remains to be done before seeing if this idea is really as good as it seems, including the costs and energy requirements involved in growing, transporting and converting summer biomass into liquid fuels. .
But other scientists, such as Woods Hole Oceanographic Institution biologist Scott Lindell, are also working on the selective breeding of more resistant and larger summer species, which would be even more suitable for use as biofuel.
“In a hotter and drier world of the future,” Lindell said in 2019, “it will be difficult to find a better resource for biofuels than farm algae that does not require arable land, fresh water, or fertilizer. fossil fuels unlike modern land cultures. “
This research was published in Renewable and sustainable energy reviews.