Seaweed to Offset Emissions Will Mainly Be Reducing Methane from Farm Animals

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.

Total non-CO2 GHG emissions from the livestock sector in 2000 was 2.45 Gt CO2 eq. Cattle accounted for 77% of emissions.

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%.

Current Biology – Blue Growth Potential to Mitigate Climate Change through Seaweed Offsetting

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

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,
Written By Brian Wang,

13 thoughts on “Seaweed to Offset Emissions Will Mainly Be Reducing Methane from Farm Animals”

  1. With growing kelp for farm animals, it reduces methane and making the animals larger. The reason why is probably because it inhibits bacterial enzymes in the gut from metabolising the feed. Therefore, the animal can use those nutrients instead. My money would be on development of either 1) new factory produced antibiotics/enzyme inhibitors to fulfil this role instead – so avoiding the kelp farms. Or, 2) efforts are made to control the gut flora of our herd animals, so that they don’t have these unwanted microbes.

  2. About the 4.7 billion tons: A study (Alltech Global Feed Survey) from 2018 claims it’s almost exactly 1 billion tons.

    The grass-based fodder isn’t the issue. The burping largely stems from the use of inappropriate fodder (corn) that the animals did not evolve with.

    Less than 2 % additive may suffice.

    So we’re down to less than 20 million tons. Now assume a doubled content of the relevant component by optimising the seaweed variety (10x should be possible) and we’re down to 10 million tons.

    An old FAO report indicates a dry weight production of 178,500 tons of Kappaphycus alvarezii (Cottonii) and Eucheuma denticulatum (Spinosum) in 2010.

    China produces 250kt dry Saccharina Japonia on 200k acres a year.

    Now assuming this yield for the seaweed needed, I end up at less than 33,000 sq km or 330 x 100 km.
    This appears to be very feasible on a global scale, though there would no doubt be monoculture-related issues.

    I suppose we can eliminate 90% of farm animal methane emissions by 2040 without any such scheme, though. Port production and even much of cattle livestock will become superfluous and economically unviable through the rise of cultured meat. We might make do with 10,000 sq km, or even less if the seaweed optimisation is done well.

  3. If you’re ever bored and want to waste a lot of your time, read Pournelle’s blog lamenting everything from climate change to “insane experiment in ‘equality'”.

  4. If it’s the full scale 4.5Oz program then you would have to (BEFORE you start) come up with some approach to get rid of the stuff (without letting it rot, which just produces more methane).

    Given it floats, I think you’d have trouble sinking it int the deep ocean. So I don’t know what they’re thinking of doing with the stuff.

    Breeding huge quantities of Japanese? I know they eat it… nah, you want to sequester the carbon after all. I just can’t think of what you could do with billions of tonnes of kelp every year that would sequester it.

  5. They said 4 1/2 times the size of Australia. In the animal feed, the sea weed is just 1-3%. That means you have thousands of times as much as you need for the animals. Humans and animals would be getting the good fresh stuff, the stuff floating hundreds of miles rotting is what you would get at the beach.

    You would have millions of tons of this stuff just clogging the first few miles of water not just the beach itself. There would be no waves.

    It is possible the sea urchins would eat the stuff pretty much as it arrived but then you probably still could not enter the water as there would be trillions of very sharp sea urchins to step on everywhere. And many would get washed up die and stink.

    I know this is very negative, but we are talking 4 1/2 times the size of Australia. This stuff is going to be everywhere. The scale proposed is simply untenable.

  6. If we’ve developed markets for all the kelp, then wouldn’t a vast mass of kelp washed up on the beach be just the arrival of a bunch of animal feed? Send a couple of bulldozers with winch rakes down, fill up a fleet of trucks, and sell it to the local farms for cash?

  7. I am all for kelp…the kelp (and other varieties of sea weed) for cows, other rudiments, fish food, iodine production, and modest human consumption (you can’t eat this stuff frequently it has very very high concentrations of iodine. some have several hundred times daily optimums for 3 oz). But, no, this is not a panacea. We need ocean fertilization so a wide variety of phytoplankton proliferate rather than an immense monoculture. It would be extremely vulnerable to some blight or some creature (the purple urchin obliterated our kelp beds) that proliferates dramatically and eats most of it…burp!

    I don’t think you can just breed a bunch of sea otters to protect the kelp, as they need to eat more than just sea urchins. Unless you grew the other things they eat. They don’t naturally live far from shore. They also need access to rocks to crush their food.

    We have giant kelp growing close by. You end up with parts ripped off (they are designed to do that to spread out and find other places they can grow) and deposited on the beach. Tons of this stuff washes up. It is very alien looking stuff…something like rubbery silicone. Anyway, times 10,000,000 and we would not even have a beach we would have a rotting mat stretching out miles covered with nasty flies. It would smell like horrendous low tide at every beach on the planet. No one is thinking very deep. Even shipping would be effected.

  8. There is frozen methane on the bottom of the ocean. It has and will continue to thaw releasing methane into the ocean. Global warming may be due to the planet heating up from within and the atmospheric result is heating. Farm animals are not the cause.

  9. Re: Urchins
    IINM sea otters eat the sea urchins which eat kelp, so it was the reduction of sea otter numbers by hunting for the fur a few centuries ago, which reduced the amount of kelp in the oceans.

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