Seaweed farming has the potential to offset CO2. A research paper looks at the potential for seaweed farming to offset global agriculture. Directly, agriculture (excluding GHG flux from land use and forestry) has consistently contributed about 12% of global emissions annually for the past 30 years (5.1 billion tonnes of CO2eq per year; ca. 50% of the agricultural total). To mitigate this fraction of emissions by the end of the century, seaweed farming would need to ramp up from the current 1,900 square km to 7,300,000 square km, representing 15% of the ocean that is possibly suitable for seaweed aquaculture or approximately two times the area of wild species. Note: using 100% of the ocean suitable for seaweed aquaculture would be 80% of annual global emissions. Nextbigfuture notes that there are plans to use ocean drones to grow seaweed over any part of the ocean.
The 8% per year growth of seaweed aquaculture expansion is clearly not enough. currently, the world produces about 30 million tons per year of seaweed. We need to scale this up by about 10,000 to 20,000 times.
Seaweed for Animal Feed to Reduce 2 Billion Tons of CO2 equivalent Methane
Adding seaweed to livestock feed can reduce potent methane emissions from the burps of cows and other grazing livestock—a significant source of global greenhouse gases—by as much as 70 percent. Experiments in sheep showed that if dried Asparagopsis taxiformis seaweed made up just 2 percent of total feed, methane emissions drop by 70 percent.
Globally, livestock consumed ∼4.7 billion tons of feed biomass in 2000, with ruminants consuming the bulk of feed (3.7 billion tons compared with 1 billion tons by pigs and poultry). Overall, grasses comprise some 48% (2.3 billion tons) of the biomass used by livestock, followed by grains (1.3 billion tons, 28%).
If we made livestock feed 2% seaweed then we would need 50 million tons of seaweed per year. Over the past 50 years, global meat production has almost quadrupled from 84 million tons in 1965 to more than 330 million tons in 2017. The IAASTD predicts that this trend will continue, especially because the growing urban middle classes in China and other emerging economies will adapt to the so-called western diet of people in North America and Europe with its taste for burgers and steaks.
Adding seaweed quickly would reduce methane from farm animals for a few decades and then the growth of meat consumption will get us back to where we are today if the modified feed reduced methane by 70% from animals. There is the possibility of finding the right feed additive mix to reduce methane by 99%.
Seaweed buffer some of the other impacts of anthropogenic pollution, including ocean acidification and low-oxygen events (hypoxia).
Based on average nutrient levels and temperature suitability for a suite of seaweed species researchers find a total area of approximately 48 million km2 ecologically available for seaweed production.
Limited evidence suggests that current seaweed farming costs (seaweed farm median = $543, minimum = $71 USD per tonne of CO2) may be at the higher end of equivalent land-based offsetting, with some terrestrial estimates of $31.84–$383.62 per tonne of CO2. Exact costs will depend on species grown, oceanographic conditions, and available technology. For instance, one of the fastest growing species in the world, Macrocystis pyrifera, could contribute approximately 27% more production per hectare than the average species, and maximizing seaweed carbon content could potentially reduce costs by 38%.
Research and experiments are needed to drastically reduce the costs for seaweed production and maximized offsetting.
Primary Ocean participates as ‘Technology to Market’ Subcontractor to ARPAE Mariner Project, MacroSystems, for the development of large scale, open ocean, seaweed cultivation systems.
Australia Sized Ocean Kelp Farm Would Offset All Human CO2
Kelp can grow at 2 feet per day. This is 30 times faster than the growth of trees and plant on land.
A kelp farm that is four and half times the size of Australia would produce sufficient biomethane to replace all of today’s needs in fossil fuel energy and removing 53 billion tons of CO2 per year from the atmosphere. This would offset current emissions.
The kelp would provide a home for fish and would feed 10 billion people with 200 kilograms of fish per year. It would also reduce ocean acidification and increase ocean primary productivity and biodiversity.
Growing Kelp in the Open Ocean
Giant kelp does not grow naturally in the open ocean because kelp normally needs an attachment at about 10-20 meters of depth. Key nutrients are not at the surface in the open ocean and would have to be supplied for an open ocean kelp farm.
Marine Bioenergy received a $2.1 million ARPA-E grant to develop an ocean kelp farm system.
Kelp Forests Need Help
A 2016 global analysis revealed that 38% of the world’s kelp forests have been in decline over the past five decades.
Marauder Robotics is working on robots to clear purple urchins from Kelp Forests. The Northern California coast experienced a sudden surge of purple urchins. The pest ate 93 percent of the coastline’s kelp forest. Similar urchin outbreaks are occurring all over the world, from California to Maine to Australia.
The robot can dive down to a maximum of 120 feet and is approximately the size of a large dog, has computer vision to identify the different types of urchins. The pilot will help them validate their navigation assumptions and how to facilitate interactions with the urchins.
Once collected, the team will distribute the urchins through appropriate channels for use in food, animal feed or construction materials.
SOURCES- Balanced Oceans, Primary Ocean, Current Biology, ARPA-E, GlobalAgriculture.org
Written By Brian Wang, Nextbigfuture.com