In the fight to slow the runaway freight train from humanity’s devastating impact on Earth, scientists are increasingly looking at the role our oceans can play.
In collaboration with industry, scientists at the University of Southern California have discovered a ‘kelp-lift’ technique that produces enough seaweed and potentially provides a high-efficiency biofuel to help wean us off fossil fuels.
Many terrestrial biofuels that can power cars, planes, ships and trucks currently come from mass-produced agricultural crops such as corn, soybeans and switchgrass. There are several problems with these options, including using up the limited food supply on land, slurping huge amounts of water, pollution from pesticides and fertilizers, and invading rare biodiverse habitats.
Relying on giant marine algae such as seaweed not only prevents these problems, but the biology of seaweed is also more suitable for use as a biofuel.
Giant kelp (Macrocystis pyrifera) can grow at an impressive rate of up to 35 cm (14 in) per day under ideal conditions. They constantly form new leaves, allowing for the harvesting of the adult leaves, which can reach 100 feet in length and otherwise simply spoil and die, without affecting the growth of the kelp.
Because kelp is a protist rather than a plant, its molecular composition lacks the solid plant lignin that complicates the process of converting land crops into fuel. In addition, growing kelp also traps carbon dioxide, which in turn increases the pH levels and oxygen supply in the immediate environment, reducing the local effects of ocean acidification.
But the question remains whether we can grow enough seaweed to fuel our future in an environmentally friendly way. Now researchers may have discovered a way to produce kelp effectively – by increasing and decreasing the depth of kelp in the water.
“We found that depth circle kelp grew much faster than the control group kelp, producing four times the biomass production,” said environmentalist Diane Young Kim of the University of Southern California.
By cycling the depth of the kelp over a day, the team found that it took nutrients from deeper in the water that were missing closer to the surface at night, fueling the extra growth, while still giving it plenty of access to sunlight in it. shallower depths during the day.
The team found that when exposed to greater depths, the kelp underwent some physiological changes that made them better equipped to deal with the increased pressure. Their pneumatocysts – the air-filled structures that help drift kelp leaves closer to the sun – thickened and filled more with fluid.
The researchers built a kelplift off the coast of California from fiberglass and stainless steel, with horizontal beams on which to “plant” young kelp. The entire structure was cycled through the water column using an automated solar powered winch.
“The good news is that the agricultural system can be assembled from ready-to-use products without new technology,” explains Brian Wilcox, Marine BioEnergy Chief Engineer. “Once implemented, deep circulation farms can lead to a new way to produce affordable, carbon neutral fuel year-round.”
This technique could open up huge areas of nutrient-poor ocean where kelp would not normally grow, also protecting vital carbon stores of naturally occurring kelp forests while still taking advantage of the brown algae.
The team urged further research in this area as much remains to be worked out before we can see if this idea is really as good as it sounds, including the costs and energy needs involved in growing, transporting and converting the kelp biomass in liquid fuels.
But other scientists, such as Woods Hole Oceanographic Institution biologist Scott Lindell, are also working to selectively breed stronger and larger kelp species that are even more suitable for use as biofuels.
“In a warmer and drier world of the future,” Lindell said in 2019, “it will be difficult to find a better source of biofuels than farmed seaweed that requires no arable land, no fresh water, and no fossil-fuel fertilizers. as opposed to modern land crops. “
This research is published in Renewable and sustainable energy assessments.