Friday, August 15, 2014

Seven Ocean Fertilization Strategies

by William S. Clarke

Buoyant, long-­lasting flakes can release nutrients slowly, avoiding nutrients waste and allowing balanced marine ecosystems to develop over a period of about one year. The flakes can be blown from ships’ holds to cover large ocean surfaces.

Global biosphere—the ocean's long-term average phytoplankton chlorophyll concentration between September 1997 and August 2000 combined with the SeaWiFS-derived Normalized Difference Vegetation Index over land during July 2000.

Seven different strategies have been identified that use these flakes.

1. Phosphate-­rich, but iron- and silica-deficient areas of the global oceans south of 42° South, together with some Arctic and sub-­Arctic waters, can be addressed with buoyant flakes carrying ultra-­slow-­release iron and silica minerals to generate albedo increase, marine biomass and carbon biosequestration.

2. The highly stratified and nutrient-­impoverished seas of the Caribbean and many tropical waters may be addressed using flakes bearing a mix of nutrients, chief of which are phosphate wastes (from Florida, Morocco and Australia), iron, silica and trace elements. Whilst this provision should help to transport dissolved inorganic carbon (DIC) somewhat deeper into the highly stratified sea by the oceanic carbon pump, its main functions will be to generate increased albedo (reflectiveness) of both the ocean surface and of the marine clouds above it;  to generate additional marine biomass; and to make some contribution to reducing ocean acidification, ocean surface temperature and consequently hurricane strength.

3. Some favorable tropical locations, where there are frigid currents running beneath the surface, may use Ocean Thermal Energy Conversion (OTEC) pumping mechanisms to generate power, potable water and the uplifted, nutrient-rich waters needed to fertilize mariculture operations.

4. The temperature/nutrient/salinity stratified waters of the Gulf of Mexico, with their excessively-­‐nutriated benthic waters (from the Mississippi) and often impoverished surface waters, together with other oceans where the needed nutrients can be found in deeper water, are probably best addressed by wave or wind powered pumping mechanisms. These bring nutrients to the nutrient-­‐deficient surface where they can be used by phytoplankton and in cultivated macrophyta (kelp and sargassum) forests. The process also tends to cool the warm surface water by mixing it with cooler water from the depths and by increased solar reflection.

5. Fertilizing polar waters with buoyant flakes, that include in the fertilizer mix minerals containing tungsten, cobalt, nickel and molybdenum (Glass et al. 2013) plus possibly gypsum (calcium sulfate) and seed methanotrophs (methane eaters), could play a vital part in converting huge and potentially catastrophic methane emissions occurring there into less hazardous CO2 which may itself then be converted into biomass by fertilized phytoplankton. These trace elements, but the tungsten in particular, are necessary for the production of metalloenzymes that catalyze the anaerobic oxidation of methane. Other methanotrophs would oxidize more methane aerobically in the water column above the anaerobic sediments.

6. Temperate oceans will each need to be treated differentially, depending on the mix of the nutrient concentrations already in their water columns and what can be used there near the surface by phytoplankton and macrophyta.

7. Productive ocean areas, coral reefs, seagrass meadows, and most inshore waters should typically not be treated at all, except conceivably when there are seasonal or otherwise temporary nutrient deficiencies that might beneficially be offset by the use of nutritive flakes. In many ocean regions, different combinations of these methods will be optimal.

Strategy 5. is described in more detail below.

Biological Control of Arctic Methane Emissions

Methane bubbles from: Sauter et al. 

As the Arctic Ocean seabed, tundra, and the frozen methane clathrates they contain warm, increasingly large clouds of methane bubbles have been observed ascending in pools and seawater. If these cannot be contained or converted, they are likely to cause catastrophic global warming within the expected lifetime of our children.

Reducing our carbon dioxide and methane emissions dramatically is no longer sufficient to avoid this from happening. Our two best chances are either to have the issuing methane captured and converted into something more benign, or to cool the Arctic quickly. Both appear to be daunting tasks. However, both may still be feasible. This paper focuses upon using biological means to convert the issuing methane into biomass.

Methanotrophic (methane eating) bacteria can do this using one of two metabolic pathways, aerobic or anaerobic. The aerobic route oxidises methane into methanol or formaldehyde that is then transformed into biomass. In the anaerobic route typically used by bacteria resident in ocean sediments, consortia of archaea and nitrite- or sulphate-reducing bacteria produce both biomass and carbon dioxide from methane (source: Wikipedia ‘Methanotroph’). Both routes use enzymes that contain essential metal atoms that are typically in short supply there. The metals include tungsten, copper, nickel, cobalt and molybdenum (Glass et al. 2013).

It is proposed that there be modelling, and subsequent testing, to establish optimal parameters for buoyant flakes carrying slow-release minerals that provide a balanced ‘diet’ of these essential metals, to allow the methanotrophs to proliferate and consume most of the newly emitted methane, before it can cause excessive global warming. Where a targeted site does not contain sufficient sulphate for the sulphate-reducing bacteria, cheap and plentiful calcium sulphate (gypsum) may be added to the powdered mineral mix.

Biological solutions typically have three major advantages. First, they are a natural form of control. Second, they modulate themselves to the extent of the problem. And third, they are typically both economical and fast-acting.

It is surmised that methanotrophs cannot metabolise methane when it is in frozen form in clathrates. Similarly, the methanotrophs in water, sediment, or soil must be in intimate, and preferably prolonged, contact with their gaseous or dissolved methane food source in order for them to be able to metabolise it effectively. This is not the case when the methane has been given time to aggregate into large bubbles or to issue directly into the atmosphere via vents, fissures or eruptions. It is therefore important that the metals be sufficiently available to methanotrophs both continuously and along the entire and diverse pathways of their emission and pre-atmospheric movement. Hence, the minerals should preferably: permeate the entire water column (albeit at low concentration); be present in at least the upper layers of sediments and soils; coat the surfaces of fissures and vents; and lie on the sea ice, tundra or swamp surface, ready to be elevated to a commanding position with the water surface. The surface may be either that of the sea, or of puddles, ponds, lakes and streams that form from rainfall or from thawing ice and permafrost.

The minerals should also be able to be economically distributed to all these environments. Small, benign and buoyant flakes can do this best, as they are readily disseminated pneumatically from ship or plane, with acceptable evenness and cost, to the most inaccessible areas. As the flakes slowly release their mineral payloads into the water, dissolution, assimilation and mineral particle sinking take the needed enzymatic metals to where the methanotrophs are present and can metabolise them so that they can proliferate enough to consume the varying amounts of emitted methane.

The buoyant flakes may be formed from a suitable mixture of low-grade mineral powders and the powdered lignin ‘thermoplastic glue’ left over from the extraction of sugars from straw or woody waste that glues the mineral mix in layers, and with tiny voids, onto cereal husks. These three materials have typically been regarded as waste products, or ones of little or no commercial value – though new uses are being found for lignin. All can be regarded as renewable resources. All are available in more than sufficient quantity to fertilise the Arctic many times over. It is surmised that the flakes will last approximately a year on the ocean surface, and possibly much longer in soil and sediment.

Most of the nutrients from the flakes will presumably enter the biosphere, where they will typically recycle many times before becoming buried deep in sediment, along with the lignin. Of course, some of this newly laid down, organically-rich sediment will be re-metabolised into methane or carbon dioxide. However, these in turn will readily be converted back into biomass by the aforesaid processes.

The flakes disseminated over the Arctic Ocean may also incorporate other lacking nutrients necessary for the growth of phytoplankton, such as iron, silica and phosphate. These will have the additional benefit of cooling the Arctic by increasing its albedo (reflectiveness) by ocean surface and marine cloud brightening. The increase in phytoplankton concentrations may be necessary to ensure that any additional carbon dioxide resulting from predation upon the methanotrophs, or that from other causes of methane oxidation, is also converted into benign biomass.

For more details, contact Sev Clarke at the address below.

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