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In the fight to slow the fleeing freight train of humanity’s destructive impact on Earth, scientists are increasingly interested in the role our oceans can play.
Teaming up with industry, scientists at the University of Southern California have discovered a ‘kelp elevator’ technique that produces enough algae, potentially providing a high-yielding biofuel to help us wean ourselves off. fossil fuels.
Many land-based biofuels capable of powering cars, planes, ships and trucks currently come from mass-produced agricultural crops like corn, soybeans and switchgrass. There are several issues with these options, including the use of limited land space to provide food, consumption of huge amounts of water, pollution from pesticides and fertilizers, and encroachment on land. rare habitats rich in biodiversity.
Not only does relying on giant marine algae like algae avoid these problems, but the biology of algae is also more suitable for use as a biofuel.
Giant kelp (Macrocystis pyrifera) can grow at an impressive speed of up to 35 cm (14 inches) per day, under ideal conditions. They are constantly forming new fronds, allowing the harvest of mature fronds, which can reach 30 meters (98 feet) in length and which would otherwise deteriorate and die, without affecting the growth of the kelp.
Since kelp is a protist, rather than a plant, its molecular makeup lacks the robust plant lignin that complicates the process of converting land crops into fuel. In addition, growing kelp also captures carbon dioxide, which in turn raises pH levels and oxygen supplies in immediate areas, helping to mitigate the local effects of ocean acidification.
But questions remain as to whether we can grow enough algae to fuel our future in an environmentally friendly way. Now, researchers may have discovered a way to mass-produce kelp efficiently – by raising and lowering the depth of kelp in the water.
“We found that the deep cycled kelp grew much faster than the kelp control group, producing four times the biomass production,” said University of Southern California environmental scientist Diane Young Kim.
Walking through the depth of the kelp over a day, the team found that it was taking in nutrients deeper in the water that were lacking closer to the surface at night, fueling its additional growth, while still having sufficient access. in sunlight in shallower depths during the day.
The team found that kelp exposed to greater depths had undergone physiological changes that made them better equipped to deal with the increased pressure. Their pneumatocysts – the air-filled structures that help kelp fronds float closer to the sun – have become thicker and more filled with fluid.
The researchers built a kelp elevator off the coast of California out of fiberglass and stainless steel, with horizontal beams on which they could “plant” juvenile kelp. The entire structure was cycled through the water column using an automated solar powered winch.
“The good news is that the farming system can be assembled from off-the-shelf products without new technology,” said one of the team, Marine BioEnergy Chief Engineer Brian Wilcox. “Once implemented, deep cycle farms could lead to a new way of producing affordable, carbon neutral fuel year round.”
This technique could open up huge, nutrient-poor regions of the ocean where kelp would not typically grow for cultivation, which would also allow us to protect vital carbon sinks in natural kelp forests while using brown algae.
The team called for further investigation into this area, as there is still a long way to go before we see if this idea is really as good as it looks, including the costs and energy requirements associated with it. the cultivation, transport and conversion of kelp biomass into liquid fuels.
But other scientists, like Woods Hole Oceanographic Institution biologist Scott Lindell, are also working on the selective breeding of tougher and larger kelp species that would be even more suited for use as a biofuel.
“In a hotter, drier world of the future,” Lindell said in 2019, “it will be difficult to find a better resource for biofuels than cultivated algae that does not require arable land, fresh water, and fertilizer derived from fossil fuels, unlike modern land crops. “
This research was published in Renewable and sustainable energy reviews.
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