About 37 percent of Earth’s land area is used for agricultural land. About one-third of this area, or 11 percent of Earth’s total land, is used for crops. The balance, roughly one-fourth of Earth’s land area, is pastureland, which includes cultivated or wild forage crops for animals and open land used for grazing.
There is a proposal to use about 9% of the oceans surface for massive kelp farms. The Ocean surface area is about 36 billion hectares. This would offset all CO2 production and provide 0.5 kg of fish and sea vegetables per person per day for 10 billion people as an “incidental” by-product. Nine per cent of the world’s oceans would be equivalent to about four and a half times the area of Australia.
Fiant of the kelp forest grows faster than tropical bamboo—about 10 to 12 inches in the bay and under ideal conditions, giant kelp can grow an astonishing two feet each day.
In the last decade, seaweed cultivation has been expanding rapidly thanks to growing demand for its use in pharmaceuticals, nutraceuticals and antimicrobial products, as well as biotechnological applications. Seaweed today is used in some toothpastes, skin care products and cosmetics, paints and several industrial products, including adhesives, dyes and gels. Seaweed is also used in landscaping or to combat beach erosion.
In 2016, seaweed farms produce more than 25 million metric tonnes annually. The global value of the crop, US$6.4 billion (2014), exceeds that of the world’s lemons and limes.
A 2016 report from the World Bank estimates that the annual global seaweed production could reach 500 million dry tons by 2050 if the market is able to increase its harvest 14% per year. Hitting that 500 million mark would boost the world’s food supply by 10% from the current level, create 50 million direct jobs in the process and, as a biofuel, replace about 1.5% of the fossil fuels used to run vehicles. The Ocean forest plan would be to accelerate growth of seaweed farming to 25-50% per year growth and reach about 20-60 billion tons per year of production. The world currently produces about 4 billion tons per year of agricultural product.
Ocean Afforestation (aka Ocean Macroalgal Afforestation (OMA)), has the potential to reduce atmospheric carbon dioxide concentrations through expanding natural populations of macroalgae, which absorb carbon dioxide, then are harvested to produce biomethane and biocarbon dioxidevia anaerobic digestion. The plant nutrients remaining after digestion are recycled to expand the algal forest and increase fish populations. A mass balance has been calculated from known data and applied to produce a life cycle assessment and economic analysis. This analysis shows the potential of Ocean Afforestation to produce 12 billion tons per year of biomethane while storing 19 billion tons of CO2 per year directly from biogas production, plus up to 34 billion tons per year from carbon capture of the biomethane combustion exhaust. These rates are based on macro-algae forests covering 9% of the world’s ocean surface, which could produce sufficient biomethane to replace all of today’s needs in fossil fuel energy, while removing 53 billion tons of CO2 per year from the atmosphere, restoring pre-industrial levels. This amount of biomass could also increase sustainable fish production to potentially provide 200 kg/yr/person for 10 billion people. Additional benefits are reduction in ocean acidification and increased ocean primary productivity and biodiversity.
The proposed model includes the materials and energy to use all three of the following mechanisms to ensure maximum local recycling of the plant nutrients:
a) The dissolved nutrients are distributed evenly through a grid of floating hose. Because this is mostly ammonia at perhaps 800 mg/L of nitrogen, it may have to be distributed only during daylight hours when the algae are providing high dissolved oxygen concentrations so that aerobic microbes can quickly convert the ammonia to nitrate.
b) The undigested solids from digestion float in “tea-bags” through the forest providing a slow-release fertilizer. When the aerobic bacteria of the ocean surface have extracted most of the remaining plant nutrients, the remaining solids would be released to sink.
c) The nutrients from dying plants that are not harvested are pumped back up from the water or seafloor beneath the forest.
Store the bio-CO2: Ocean Afforestation concentrates CO2 from air that can be then be stored as pure gas or liquid CO2 with a variety of carbon storage technologies:
a) Deep geologic storage where the CO2 is either a gas, a supercritical fluid, or dissolved in saline aquifers several kilometers below the surface of the earth or the seafloor;
b) Shallow sub-seafloor storage, proposed by House, et al. (2006) where the CO2is either a liquid or a hydrate perhaps 100 meters below the seafloor for a combined depth in excess of 3 kilometers;
c) Solid snow, proposed by Agee, et al. (2012) where the CO2is a frozen solid “landfill” in Antarctica;
d) Artificial geologic seafloor storage where the CO2is hydrate or denser-than-seawater liquid embedded in geosynthetic and other artificial geologic layers; or
e) Other future technology
Replacing fossil fuels will require so many macroalgal forests that the production of fish sufficient to provide 0.5 kg of fish and sea vegetables per person per day for 10 billion people could be almost an “incidental” by-product. In actuality, seafood production is likely to be a higher fraction of OMA products initially because food is generally a higher unit value than renewable energy. However, food uses can remove nutrients from an OMA ecosystem. We project that this would mean less than 2% of the annual forest nutrient requirement, in the 2050 scenario (OMA over 6% of world oceans) actually leaving the forests in the form of fish and other edible food stocks (based on data from Ramseyer, 2002).We have not included fish and other food products in our calculated energy balance.Potential other products include liquid fuels, agar, carrageenans, algin, etc
Ocean forests project proposed taking five years to get initial demonstration 10,000 hectare forest operating economically in a near-shore sheltered water environment (involving an investment of about $20 million). This forest may be located where there are sufficient existing nutrients that nutrient recycling needs would be minimal and inexpensive.
It could take another ten years (o get many sheltered water 10,000-hectare forests operating. Initial forests may be located where there are sufficient existing nutrients that nutrient recycling needs would be minimal and inexpensive. The sheltered water approach could involve as much as 0.3% of the ocean’s surface (1 million km2). In this case, ‘sheltered water’ may be the entire Mediterranean Sea, the Gulf of California, and other such bodies of water where tropical storms are rare or enclosed, perhaps 4 million km2. Sheltered water can be any depth. Occupying a quarter of the available sheltered water may be a challenge, but all the sheltered water operations will put only a small dent in humanity’s CO2 debts. Open ocean operations are needed.
The reason OMA expansion can be so rapid is that the basic technology involves low-tech components, such as harvesting nets, large geosynthetic (plastic) bags, and pipes, with the methane feeding into existing natural gas and diesel power plants. Also, many sheltered waters suffer from an over-abundance of anthropomorphic nutrients.
The first open-ocean 10,000-hectare forest could be developed with an investment of perhaps $100 million. But it could take another seven years to get many open-ocean 10,000-hectare forests operating.
What might a kelp farming facility of the future look like? Dr Brian von Hertzen of the Climate Foundation has outlined one vision: a frame structure, most likely composed of a carbon polymer, up to a square kilometre in extent and sunk far enough below the surface (about 25 metres) to avoid being a shipping hazard. Planted with kelp, the frame would be interspersed with containers for shellfish and other kinds of fish as well. There would be no netting, but a kind of free-range aquaculture based on providing habitat to keep fish on location. Robotic removal of encrusting organisms would probably also be part of the facility. The marine permaculture would be designed to clip the bottom of the waves during heavy seas. Below it, a pipe reaching down to 200–500 metres would bring cool, nutrient-rich water to the frame, where it would be reticulated over the growing kelp.
Von Herzen’s objective is to create what he calls “permaculture arrays” – marine permaculture at a scale that will have an impact on the climate by growing kelp and bringing cooler ocean water to the surface. His vision also entails providing habitat for fish, generating food, feedstocks for animals, fertiliser and biofuels. He also hopes to help exploited fish populations rebound and to create jobs. “Given the transformative effect that marine permaculture can have on the ocean, there is much reason for hope that permaculture arrays can play a major part in globally balancing carbon,” he says.
The addition of a floating platform supporting solar panels, facilities such as accommodation (if the farms are not fully automated), refrigeration and processing equipment tethered to the floating framework would enhance the efficiency and viability of the permaculture arrays, as well as a dock for ships carrying produce to market.
Given its phenomenal growth rate, the kelp could be cut on a 90-day rotation basis.
The seaweed could be converted to biochar to produce energy and the char pelletised and discarded overboard. Char, having a mineralised carbon structure, is likely to last well on the seafloor. Likewise, shells and any encrusting organisms could be sunk as a carbon store.
Once at the bottom of the sea three or more kilometres below, it’s likely that raw kelp, and possibly even to some extent biochar, would be utilised as a food source by bottom-dwelling bacteria and larger organisms such as sea cucumbers. Provided that the decomposing material did not float, this would not matter, because once sunk below about one kilometre from the surface, the carbon in these materials would effectively be removed from the atmosphere for at least 1,000 years. If present in large volumes, however, decomposing matter may reduce oxygen levels in the surrounding seawater.
Large volumes of kelp already reach the ocean floor. Storms in the North Atlantic may deliver enormous volumes of kelp – by some estimates as much as 7 gigatonnes at a time – to the 1.8km-deep ocean floor off the Bahamian Shelf.