Patent Publication Number: US-9888628-B2

Title: Apparatus and method for harvesting plankton and other biomass from a dead zone

Description:
This is a Continuation-In-Part of PCT/US15/61822, filed Nov. 20, 2015 (designating the US), which is a continuation of U.S. application Ser. No. 14/551,561, filed Nov. 24, 2014, now U.S. Pat. No. 9,155,248, issued Oct. 13, 2015. 
    
    
     BACKGROUND 
     Technical Field 
     The present invention relates to system, method and apparatus for harvesting plankton and other biomass, preferably from dead zones in lakes and oceans. Such harvesting of biomass leads to reductions in dissolved and atmospheric CO 2  and CH 4 , ocean acidity and acid rain. 
     Overview 
     A 2008 study (“Spreading Dead Zones and Consequences for Marine Ecosystems”, Diaz, Robert J. and Rosenberg, Rutgers, Science 15 Aug. 2008: Vol. 321 no. 5891 pp. 926-929, DOI: 10.1126/science.1156401) counted 405 seasonal dead zones encompassing more than 97,000 square miles in coastal waters worldwide. By 2014 there were over 550 dead zones. The plankton in these dead zones contain billions of tons of carbon. Most plankton are destined to release their carbon as CO 2  and/or CH 4  when they die. The aim of this invention is to interrupt the carbon cycle in about half of each dead zone and sequester its carbon. Some can be sequestered directly, some indirectly by processing the biomass into methane and fertilizer to replace fossil fuels and chemical fertilizers. See also “A Look Back at the U.S. Department of Energy&#39;s Aquatic Species Program: Biodiesel from Algae: Close-Out Report”, NREL/TP-580-24190, John Sheehan, et al., July 1998. They found that microalgae can “achieve very efficient (&gt;90%) utilization of CO 2 ”, considerably better than terrestrial plants. 
     Harvesting and processing a billion tons of biomass might take a million qualified boats and 10 million workers. For this to work it should be profitable: the value of the end products should exceed the cost of harvesting, processing, transport, etc. Most of the harvesting is passive, taking advantage of the shortened life cycle of microalgae in a dead zone, and using gravity and wave motion to speed the capture. The energy required for harvesting is minimal, and the energy for processing and transport need not be from fossil fuel; it can be replaced by methane (CH 4 ) produced from the biomass itself. Profits can be used to acquire deforested land and re-plant native trees, fertilized with harvested biomass. These trees will sequester CO 2  for centuries. The following concepts are helpful to understand and to responsibly use this invention. 
     1. The Aquatic Carbon Cycle. 
     In a healthy aquatic ecosystem phytoplankton (microalgae) absorb dissolved CO 2  and emit O 2  by photosynthesis. They are the base of the food chain for aquatic animals and microbes that reverse the carbon exchange by absorbing O 2  and emitting CO 2 . A small fraction of the carbon remains at the bottom, as evidenced by the abundance of coral reefs, carbonate rock, fossil fuels and methane ice. 
     2. The Diurnal Cycle of Microalgae. 
     In the photic zone, where there is enough daylight for photosynthesis, microalgae metabolize dissolved CO 2  into glucose and other carbohydrates. These are heavier than sea water allowing the algae to drift downward to escape predation and to where minerals are more concentrated. Like all plants, microalgae need some O 2  at night to process nutrients. They get this O 2  from the water and from what they internally stored. Leftover carbohydrates are stored as high energy lipids (bio-oils). These lipids are lighter than water and allow the microalgae to drift back up in time for daylight. Blue green algae produce an internal gas to allow them to rise. Before reaching the surface the specific gravity of microalgae is indistinguishable from that of the surrounding water. Then the cycle of descent and rise begins again. 
     3. Algal Blooms. 
     Algal blooms in lakes and oceans are caused by an excess of vital nutrients, without which microalgae cannot exist. They include salts of nitrogen, potassium, phosphorous and other trace minerals. Crucial among the vital nutrients are CO 2  and, of course, H 2 O. Carbohydrates including glucose and cellulose are made exclusively from C, H and O. Carbon constitutes 40% of these compounds. Excessive dissolved CO 2  was once so rare that large algal blooms were seldom seen. An excess of nutrients can come from natural events such as forest fires and floods washing topsoil into waterways, but more often from man-made sources such as:
         Farming practices. During rainy seasons, eroded soil, soluble fertilizers, cattle, pig, and poultry farm runoff may reach rivers and flow into lakes and oceans.   Burning fossil fuels. This raises dissolved CO 2  levels in lakes and oceans. Dissolved CO 2  forms carbonic acid that dissolves coral reefs, shells, carbonate rock, eggs, etc. The released calcium is also a vital nutrient for some microalgae.   Acidification. Sulfuric acid rain also dissolves minerals. It is formed as a noxious byproduct from burning coal and making coke for steel mills.       

     4. Methane and Methane Ice. 
     Methane, the main ingredient of natural gas, has the chemical formula CH 4 . If burned with enough O 2  it produces CO 2  and water vapor, both greenhouse gases. But unburned methane in the atmosphere is a much more potent greenhouse gas than CO 2 . It is reported that molecule for molecule the CH 4  radiative value is 72 times that of CO 2 . Therefore systemic leakage of methane should be prevented. 
     In deep water where the pressure is great enough and/or the water is cold enough, methane gets into the crystalline structure of water and forms methane hydrate, otherwise known as methane ice. Pressure-temperature tables for the formation of methane ice are available. According to the Lawrence Livermore National Labs, “ . . . the energy locked up in [underwater] methane hydrate deposits is more than twice the global reserves of all conventional gas, oil, and coal deposits combined.” Fortunately for life on earth, methane ice is heavier than water. 
     5. Dead Zones. 
     In the 1970&#39;s large algal blooms started appearing around the mouths of certain rivers during warm months. They are called “dead zones” if the deeper waters have too little dissolved oxygen (hypoxia), or no dissolved oxygen (anoxia). Few living things can survive under these conditions. In 2002 the dead zone in the Gulf of Mexico alone covered 8,500 square miles. 
     6. Causes of Dead Zones. 
     Lakes and oceans tend to be stratified by the weight of the water. Highly oxygenated surface water mixes only slightly with the heavier, colder and more saline bottom water. Surface currents range from 0 to 5.6 mph, but it barely helps mixing because these speeds reduce exponentially with depth. It is especially true in a dead zone where there are neither schools of fish, nor filter feeders to stir things up. As phytoplankton, dead zooplankton, zooplankton excreta and other biomass fall to the bottom, aerobic bacteria metabolize it, and in doing so deplete the dissolved O 2 . If the region becomes anoxic, Methanogenic Archaeons take over. The domain Archaea, discovered in 1977, contains the first life forms on earth some 3.6 billion years ago. They cannot function in oxygen but thrive in swamps, manure piles and the anaerobic colons of animals including zooplankton. They emit neither O 2  nor CO 2 , but methane (CH 4 ) and often hydrogen sulfide (H 2 S). In water H 2 S forms hydrosulfuric acid that raises water acidity. In high enough concentrations both of these emissions kill plants and animals and spread hypoxia upward. 
     Algal blooms cloud the water, limiting the depth of the photic zone. Algae have evolved to descend a certain distance during their night cycle before they drift back upwards. To do this they should have enough O 2  to produce lipids or gases, without which they continue to sink to the bottom and worsen hypoxia. Dead zones have very little ecology, but they have some. For example there are reports of a microbe that can metabolize CH 4 , probably emitting CO 2  and 2H 2 O. Whatever these microbes are, they should be thriving in dead zones. Any un-metabolized CH 4  may evaporate into the atmosphere and accelerate climate change. 
     7. Uses for Harvested Biomass. 
     Most chemical fertilizers consist of ammonium nitrate, phosphate and potash (N—P—K). Over time crops grown with only N—P—K fertilizers leach other needed micro-nutrients out of the soil. The process of making ammonium nitrate consumes 1% to 2% of the world&#39;s annual energy supply (see “The Haber Process” at http://en.wikipedia.org/wiki/Haber_process). It is therefore a major contributor to climate change. Phosphates and potash are mined adding to the energy budget, and phosphates are increasingly expensive. On the other hand fresh water biomass can be processed into fertilizer and CH 4  simply by composting it in an anaerobic digester. Digesters are commercially available and are used in communities and farms to profit from these products. (Oceanic biomass should be desalinated before it can be used as fertilizer). 
     Since aquatic biomass stems from phytoplankton, it contains all the nutrients needed to grow plants. These “marine derived nutrients” or MDNs build topsoil. Researchers at the University of Washington have shown that Sitka spruce grow over three times faster in watersheds fertilized by migratory salmon (via bears, eagles, otters, and whatever else eats dying salmon) than in watersheds without salmon. Everything that is in the MDN, salmon, had to be also in microalgae, the base of the marine food chain. Pyrolysis can be used to sequester carbon directly, as well as producing methane and other flammable gases. It involves heating biomass in an airtight container. Solar concentrators are the logical choice of heat source. A film that reflects sunlight with 95% efficiency has been developed with help from the National Reusable Energy Laboratories (NREL). Biomass is transformed into char, bio-oil, methane, syngas and ash. The relative amounts of each substance depend on the temperature of the pyrolysis. The ash contains minerals that could be used as fertilizer, if it were desalinated. The char (carbon) can be compressed with a non-flammable binder into blocks and sequestered, perhaps in abandoned coal mines. By comparing the atomic weights of C=12 and CO 2 =44 one sees that for every ton of char (C) sequestered, 11/3 tons of CO 2  are kept out of the atmosphere. Thus algae take dissolved CO 2  out of the water and pyrolysis keeps it out. 
     8. Where not to Harvest Biomass. 
     It is well established that plants can produce toxins to combat predation. Species of dinoflagellates sometimes produce neurotoxins “red tide” that concentrate in shellfish. Some blue-green algae can produce toxins such as microcystin that attacks the liver, and anatoxin-a that can kill a person and other animals within five minutes. Fortunately tests exist for such harmful algal blooms (HABS). Excess CO 2  causes an abundance of microalgae and that causes an abundance of predators and that may well cause microalgae to produce protective toxins. This growing problem is yet another reason to lower CO 2  levels. It is dangerous to harvest bottom sediment because disturbing it could release methane, hydrogen sulfide, heavy metals, PCBs and other toxins. It should not be harvested in waters cold and deep enough to form methane ice because once the biomass is metabolized by methanogens the emitted CH 4  is sequestered as methane ice. This sequesters carbon and reduces CO 2 . In these regions the algal bloom tapers off partially from lack of CO2. It is unwise to harvest near the surface. It makes poor fertilizer as it generally lacks the trace minerals that are more concentrated at greater depths. Moreover separating such algae from water is difficult. Microalgae near the surface have a specific gravity indistinguishable from that of the surrounding water. Therefore it cannot be “spun-dried” in an ordinary centrifuge. A filtering centrifuge would use undue amounts of energy and the filter would quickly clog. Evaporation is possible but impractical. Algae harvested near the mouth of a polluted river may well contain persistent toxins, and should not be used. 
     9. Some Likely Outcomes. 
     Millions of people worldwide could be employed for months out of the year. MDNs could replace chemical fertilizers, un-mined “bio-methane” could become the standard fuel, oceans will be less acidic, atmospheric CO 2  will decrease, dead zones will eventually disappear, and using profits for reforestation will restore a more natural climate. 
     In alternative embodiments to be described below, surface devices and floats have been replaced with underwater devices, to avoid surface congestion and prevent surface collisions. 
     SUMMARY OF THE INVENTION 
     An underwater funnel trap is preferably assembled on shore and towed to the site on pontoons. Arrays of traps connected to one another are preferably seasonally deployed and removed at the end of the season. This can all be done from boats at the surface. A funnel trap passively directs falling plankton and other biomass into a canister within the funnel&#39;s neck. A float scale at the surface displays the dry weight of the biomass. (A cubic yard of dry biomass weighs over a ton). It is assumed that a crane or overhead winch will raise and lower the canisters during harvesting. Nevertheless, smaller boats may not be able to handle a canister weighing more than 1 ton. They might have to harvest the same funnels several times during their shift. Funnel traps are designed to withstand hurricanes, but an unattended canister can overflow with biomass and fill the funnel until it breaks or sinks the array. Therefore the design includes a “release float” (preferably with no moving parts) that releases any further biomass into the water. 
     The funnel trap preferably has a main funnel and a bottom funnel. All internal surfaces preferably have slick, non-stick surfaces. The main funnel is made of strong ultra-light film, such as Mylar™ or polypropylene. The mouth of the funnel is kept open by any suitable means, but in this preferred embodiment the rim is metal and heavier than water. A debris net attached to the rim keeps large objects from clogging the funnel. A funnel trap&#39;s mouth area of 10,000 ft 2  is expected to be standard for oceanic dead zones. Fresh water traps would be much smaller. The trap hangs in the hypoxic zone from 3 or more cables attached to floats. This depth prevents barnacles and insures that the plankton are heavy enough to “spin dry.” The light should be too dim for large shadows to matter, but to be cautious the film should be clear or translucent. Wave action on the floats jiggle the sides of the main funnel and help the biomass slide into the canister. A conical bottom funnel is made of two nested metal funnels that sandwich the bottom of the film and provide needed weight. The removable canister resides in the neck of the bottom funnel. 
     When trying to cover some 50,000 square miles it is important to minimize materials. The use of ultra-light thin film is preferred, and the stress on it should be minimal. This is done in several ways. The angle that the cone makes with the horizontal depends on the ease of the biomass&#39; slide. A slicker surface allows a smaller angle requiring less film. A wide mouth on the bottom funnel distributes the weight of the biomass over a greater area of film. A circular mouth on the main funnel uses the least rim material for a given area. Regular polygons (equilateral triangles, squares, etc.) use less rim material than irregular polygons do. Surprisingly, the area of the film depends only on the area of the main funnel&#39;s mouth and the angle of the funnel, whether the mouth be circular or a regular polygon. 
     A loaded canister on deck can be spun dried on its vertical axis to lighten its load. When the centrifuge reaches a certain RPM an aperture at the bottom of the canister starts opening. The biomass, being heavier than water, is pressed against the cylindrical wall while the water is allowed to drain out the bottom. When the water stops the aperture is closed and the motor is shut off. To keep the boat itself from spinning, canisters are preferably spun in pairs and in opposite directions. It is anticipated that large service ships or barges will swap empty canisters for loaded ones and bring them ashore for further processing. 
     According to a first aspect according to the present invention, apparatus for harvesting biomass (for example plankton, algae, phytoplankton, zooplankton, zooplankton excreta, cyanobacteria, and whatever else is small enough to get through the debris screen to be described below) includes at least one support float configured to float on a surface of a body of water. At least one support structure is coupled to the at least one support float and is configured to support a substantially rigid frame within a dead zone (for example, a hypoxic zone) below the surface in the body of water. A main funnel is coupled to the at least one support structure within the dead zone, and is configured to collect descending biomass and funnel it toward a lower funnel that is coupled to the bottom of the main funnel. A collection canister is coupled to the lower funnel, and is configured to store the descending biomass. A guide float is configured to float on the surface of the body of water, and a hauling structure is coupled to the guide float, and is configured to haul the collection canister from the lower funnel to the surface. 
     According to a second aspect according to the present invention, biomass harvesting apparatus includes a plurality of support floats configured to float on the surface of a body of water. A plurality of support lines is provided, each being coupled to a respective one of the plurality of floats and configured to extend downward from the surface into a hypoxic zone of the body of water. A rigid frame is coupled to the plurality of support lines, and a main funnel is coupled to the rigid frame and configured to catch descending algae. A lower funnel is coupled to a bottom of the main funnel, and is configured to guide the algae descending in the main funnel into a capture device. 
     According to a third aspect according to the present invention, a method of harvesting biomass includes the steps of: (i) deploying a plurality of support floats configured to float on the surface of a body of water; (ii) deploying a plurality of support lines each coupled to a respective one of the plurality of floats and extending downward from the surface into a hypoxic zone of the body of water; (iii) deploying a rigid frame coupled to the plurality of support lines; (iv) deploying a main funnel coupled to the rigid frame; (v) harvesting descending biomass with the main funnel; and (vi) guide the harvested descending biomass with a lower funnel coupled to a bottom of the main funnel. 
     According to a first aspect of alternative embodiments, biomass harvesting apparatus has at least one guide float configured to float below a surface of a body of water. At least one support structure is configured to be coupled to a bottom beneath the body of water, and is configured to support a substantially rigid frame within a dead zone below the surface in the body of water. A main funnel is coupled to (i) the at least one guide float and (ii) the substantially rigid frame within the dead zone, and is configured to collect descending biomass and funnel it toward a lower funnel that is coupled to the bottom of the main funnel. A collection canister is disposed adjacent the lower funnel and configured to store the descending biomass. A hauling structure is coupled to the guide float, and is configured to haul the collection canister from the lower funnel to the surface. 
     According to a second aspect of alternative embodiments, biomass harvesting apparatus has at least one guide float configured to float beneath the surface of a body of water. At least one vertical support is coupled beneath the at least one guide float and is configured to extend downward into a dead zone of the body of water. A rigid frame is coupled to the at least one vertical support in the dead zone. A main funnel is coupled to the rigid frame and is configured to catch descending biomass. A lower funnel is coupled to a bottom of the main funnel, and is configured to guide the biomass descending in the main funnel into a capture device. Bottom support structure is affixed to a bottom beneath the body of water and is configured to support the lower funnel. 
     According to a third aspect of alternative embodiments, a method of harvesting biomass includes deploying a guide float configured to float below the surface of a body of water. A support line is coupled below the guide float and extends downward into a dead zone of the body of water. A rigid frame is coupled to the support line, and a main funnel is coupled to the rigid frame. Biomass descending within the main funnel is thus collected. The descending biomass is guided into a collection device in a lower funnel coupled to a bottom of the main funnel. The collection device is hauled to the surface to harvest the biomass. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic side view of a funnel trap suspended in a dead zone. 
         FIG. 2  shows a release float connected to a canister in the bottom funnel&#39;s neck. 
         FIG. 3  shows an overweight canister that has been released from the funnel. 
         FIGS. 4 a , 4 b , and 4 c    are top views of three arrays of underwater funnel traps. 
         FIG. 5  shows how funnel traps in an array can be coupled and uncoupled from the surface. 
         FIG. 6  shows a type-2 canister with its overflow. 
         FIG. 7 a    shows a side view of a type-2 bottom funnel, and  FIG. 7 b    shows a cutaway of its neck. 
         FIGS. 8 a  and 8 b    show a heavy tripod-anchor with a self-leveling upper plate. 
         FIG. 9  shows a type-2 bottom funnel attached to the tripod with one or more springs. 
         FIGS. 10 a  and 10 b    show how a snagging mast attaches to a type-2 canister and how it holds down the underwater guide float. 
         FIGS. 11 a  and 11 b    depict the type-2 telescoping guide tube and the method to snag the mast in order to raise the canister. 
         FIGS. 12 a  and 12 b    depict a tool to help deploy and recover type-2 funnel traps. 
     
    
    
     DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EXEMPLARY EMBODIMENTS 
       FIG. 1  is a schematic side view of a funnel trap  10  suspended in the hypoxic region  210  of a dead zone, above the anoxic zone  212  and the bottom  214 , but below the photic zone  216  and the surface  218 . In this preferred embodiment the top rim  25  that forms the mouth of a main funnel  26  should be heavier than water. If the mouth is circular, the top rim  25  could be a flexible metal rod or band bowed into a circle under tension. Preferably, three equal-length cables  18  are attached to three equally-spaced rings  12  along the top rim  25 . Each cable  18  extends upward, respectively, to three floats  11  that carry the weight of rim  25 , ultra-light film  27 , and its contents. The funnel  26  preferably comprises a film  27 , attached to the rim  25 , and narrows conically downward to the bottom funnel  34 , where the film is preferably sandwiched between two tightly nested metal cones  261  and  262  ( FIG. 2 ), forming the mouth portion of the bottom funnel  34 . The sandwiching of the film  27  between the nested metal cones  261  and  262  better distributes the weight of the biomass where it is most concentrated. Preferably, the floats  11  transmit wave motion to the top ring  25  via the cables  18 , which helps the biomass slide into the bottom funnel  34 . If the top rim  25  is a polygon, three or more cables  18  are attached equally-spaced to the polygonal rim  25 . A horizontal cross section of film  27  preferably changes smoothly from a polygon into a circle to form the conical main funnel  26 . Preferably, the buoyancy of floats  11  is such that they are pulled beneath the water in high waves, thereby relieving the tension on the film  27 . 
     Preferably, a guide float  19  is disposed at the surface  218  and is attached to a vertical guide tube  20  preferably made of nylon netting or other suitable material. The guide float  19  may have lettering or other identifier(s) for the harvesting boat that lowers and raises the canister  36  ( FIG. 2 ). The guide float  19  and the guide tube  20  preferably guide the canister  36  into and out of the neck  263  of the bottom funnel  34 , and hold the weight of the bottom funnel  34  with three chains  204 . Chains are preferably used instead of lines when accurate distances are required, as their length is relatively constant when fully extended, and can hold the bottom funnel  34  substantially horizontal. Preferably, the bottom funnel  34  is supported by the guide float  19  only. A bottom ring  202  helps to keep the guide tube  20  straight. The chains  204  preferably begin at the guide float  19  and attach to the bottom ring  202 , from where they extend downward to the mouth of the relatively heavy bottom funnel  34 . When the chains  204  are fully extended, the film  27  is preferably mildly taut. The film&#39;s only load is preferably that of the sliding biomass  39 , not the bottom funnel  34  or its contents, which are preferably supported by the chains  204 . The chains  204  preferably do not, however, hold all of the weight of the canister  36  residing in the neck of the bottom funnel  34 . The loaded canister may weigh several tons, and is preferably supported by a single line or chain  30  hung from a scale float  16  at the surface. That is, the self-contained scale float  16  and the canister  36  are preferably free floating and separate from the rest of the funnel structure (except for the O-rings  362  and  364  to be described below). 
     Also preferably, a conical debris net  24 , made of nylon or other suitable lightweight yet sturdy material, is affixed to the guide tube  20  at connector  22 , sloping downward and outward to the top rim  25 . The net  24  preferably keeps the bottom funnel  34  from being clogged with debris, and its slope helps to shake off the debris. 
       FIG. 2  shows the guide float  19 , a release float  17 , and a canister apparatus  36  in greater detail. The release float  17  is preferably attached to a hauling chain  30  that holds the canister  36 . The canister apparatus resides in the funnel trap, but is not attached to it. It is free floating and preferably adds little or no weight to the trap. The guide float  19  and its attached chains  204  can easily handle the frictional forces that the canister apparatus imparts to the  263  neck of the bottom funnel  34 . The proximity of the guide float  19  and the release float  17  minimizes the wave differential therebetween. That reduces wear on O-rings  362  and  364  by canister  36 . 
     The release float  17  preferably has a rod  15 , a hauling ring (or chain)  13 , and a release stop float  14  on the top of rod  15  that keeps a released canister from sinking. An adjustable scale stop  152  is preferably used during initial deployment to adjust the length between itself and an empty canister within the neck of bottom funnel  34 , as shown in  FIG. 2 . The float scale  16  is free to move along rod  15  between the float scale stop  152  and the stop washer  154 , but in use it is pushed upward by water pressure against scale stop  152 . The lower end of the rod  15  is preferably connected to a carefully measured chain  30 . The adjustable scale float  16  is preferably scaled to measure the dry weight of the biomass in the canister  36 . It also releases the canister when it is full, so that biomass will fall through the bottom funnel and not accumulate within the main funnel. The depth of the canister can be adjusted from the surface during the initial deployment. The numerals on the float scale can also be slid up or down and locked in place during initial employment. 
     The canister apparatus preferably includes an upper cage  31  that attaches the chain  30  to the canister  36 , and allows the flow of biomass  39  therethrough, while filtering out larger objects and debris which may come through the guide float, thus avoiding the debris screen. The hemispherical shape of cage  31  helps canister  36  to be pulled smoothly upward from its released state below the bottom funnel  34 . O-rings  362  and  364  keep the bottom funnel&#39;s neck relatively free of plankton. The O-rings can be made of soft substances such as silicone and/or lubricated felt, and/or hard substances such as carbon fiber and/or split bamboo. A baffle funnel  35  within the canister  36  keeps most plankton from drifting upward and out. One or more small holes (not shown) in the upper rim of the baffle funnel  35  vents trapped air and sometimes methane. After the canister  36  is hauled up, it is preferably placed upright in a centrifuge and “spun dried” around its vertical axis. As it reaches a certain RPM, an aperture  37  starts opening to release water. The lower cage  312  protects aperture  37  and helps lower fresh canisters into the bottom funnel. Preferably, the canisters  36  can be spun in pairs and in opposite directions. 
     As biomass  39  displaces the water in the canister  36 , the readings on float scale  16  effectively weigh the biomass minus the original weight of the water and the equipment—in other words, the dry weight of the biomass. The increasing weight lowers release float  17  attached to chain  30 . By Archimedes&#39; Principle, the upward force of release float  17  equals the weight of the water it displaces. The wider the release float&#39;s diameter the slower the canister descends as it fills. If a canister is ever allowed to fill to the point where the water level  218  reaches the upper rod  15 , it preferably drops the canister  36  out of the bottom funnel  34 , as shown in  FIG. 3 . At this point, the stop float  14  stops the canister  36  from falling any further. The released canister  36  could be capped to keep more weight out, but it is believed that slightly bobbing waves or a mild current is enough to shake off any excess accumulation of biomass. Preferably, the bottom funnel  34  is relatively heavy, so the friction of the canister&#39;s O-rings  362  and  364  will not let it get stuck when being raised. 
     It may happen that the guide float  19  is momentarily in the trough of a wave while one or more of the floats  11  are at the peak of the waves. Thus, large waves could put tremendous stress on film  27  and tear it. Therefore, the buoyancy of floats  11  are preferably pre-calibrated to be pulled underwater when under too much stress. Then, the film  27  becomes taut but not enough to cause damage. Thus, a lighter film can be used. 
       FIG. 3  shows the canister  36  in its released state. The canister has dropped far enough below bottom funnel  34  to avoid it accumulating significant further amounts biomass. 
     With an invention potentially covering a huge part of our planet, the cardinal rule is “First, do no harm.”  FIGS. 4 a , 4 b , and 4 c    addresses a potential ecological problem. Notice that these huge funnels and their connectors form a horizontal underwater net. If a migratory school of fish, marine mammals or another life forms happen to wander into the dead zone under the net, they may become disoriented and try to escape, perhaps in all directions. Dead zone floors are littered with carcasses. Some may be guided upward by the funnel toward the oxygen rich photic zone and escape, but some may be trapped under it because the space between funnels may be too small. Marine mammals don&#39;t breathe dissolved oxygen and, though their eyes might burn from the water acidity, they should know how to come up for air. If they happen to get lost under the array looking for an opening large enough, they may suffer cruel deaths. Endangered blue whales are said to grow 100 feet long or longer, no one knows for sure, and they should have a wide turning radius. Two simple rules preferably should be followed:
     1. Connect polygonal mouthed funnels only at their corners, as in the checkerboard pattern of array  42  in  FIG. 4 b   . If any were joined along adjacent sides, an animal swimming upward to where the sides join might not know which way to turn and die of asphyxiation.   2. In a body of water, each funnel should have a space around it that can accommodate the largest creature in that body of water. In an oceanic dead zone, distances  41 ,  43  and  45  in  FIGS. 4 a , 4 b , and 4 c    should be a hundred feet or more. In fresh water they might be ten to thirty feet.   

       FIGS. 4 a , 4 b , and 4 c    are top views of three arrays designed for underwater funnel traps  10  held in place by one or more anchored buoys (not shown). The funnels are connected by their underwater top rims  25 . Array  40  preferably includes round-mouth funnel traps connected by cables equal to the diameter of the funnels giving 25.3% coverage. Array  42  preferably comprises square mouth funnel traps in a checker board pattern giving 50% coverage. Array  44  preferably includes round mouth funnels with the horizontal and vertical openings between them the size if their diameters, giving 58.9% coverage. 
       FIG. 5  shows one way for boats at the surface to couple and uncouple funnel traps  10 . It is preferred that each trap can move vertically in the waves independent of one another. Deploying traps and removing them are preferably done only at the start and end of a dead zone season. Preferably, two strong upright connector tubes  50  are rigidly attached to top rims  25  of adjoining funnel. Openable shackles  52  are preferably attached to each other with a rod or a chain  321 . As depicted in  FIG. 5 , they fit loosely around connector tubes  50  and conjoin two or more funnel traps. Cords  54  emanating from within the connector tubes and are attached to floats  56  at the surface  218 . Another cord  55 , preferably tied to the rod (or chain)  321  conjoining shackles  52 , is attached to float  57  at the surface  218 . These cords are preferably left slack to reduce wear on the tubes  50  and the cords themselves. To decouple the funnel traps, the cord  55  is hauled up, the shackles  52  are opened, and they are removed from the cords  54 . To couple the funnel traps again, bring them together by slowly pulling cords  54  from their floats  56 , close the shackles around cords  54 , and let them slide down onto the connector tubes. 
     It is conservatively expected that a funnel with a mouth area of 10,000 ft 2  will capture more than one dry ton of biomass/day. If a work boat harvests a canister every 20 minutes they will harvest over 24 tons/8-hour shift. It is also expected that the biomass will contain about 25% carbon, which can produce about 6 tons of methane and perhaps 18 tons of fertilizer/8-hour shift. Of course the boat may opt to run  3  shifts per day. The biomass should be desalinated if it is to be sold as fertilizer. 
     In alternative embodiments if  FIGS. 6-12 , so-called “type-2” funnel traps preferably have no floats on the surface, except when actively harvesting. Preferably, the main funnel  26  in  FIG. 1  is unchanged except for the bottom funnel  34 . Type-2 funnel traps are preferably not connected to one another. Instead, they are preferably anchored on heavy, self-leveling tripods at the bottom of the lake or ocean. Without surface floats, these embodiments do not use wave action to help slide the biomass down the main funnel into the canister, but another kind of “shake down” is provided below in the description of  FIG. 9 . 
       FIG. 6  depicts a type-2 canister  60 . Hauling ring  601  attaches line  30  (see  FIG. 10 ) to an underwater guide float  19  above it. Line  30  is sufficiently strong to raise a canister full of biomass  60 . Cage  602  allows the falling biomass to pass through into cylindrical tube  612 . The streamlined shape of cage  602  allows it to be pulled through guide tube  720  smoothly without damaging the material. Cage  602  is affixed to the canister&#39;s strong upper rim  604 , which, in turn, is attached to cylinder  612  and to internal baffle funnel  606  at join  605 . Items  601 - 607  may be removed for maintenance preferably by unscrewing join  605 . Join  605  should have one or more very small vent holes to release any air trapped between baffle funnel  606  and cylinder  612 . A gasket (not shown) is affixed to the bottom of rim  604  to seal the conical seat  628  in bottom funnel  7   a  (in  FIG. 7 a   ). The diameter of the baffle funnel&#39;s vent  607  should be larger than the largest hole in the debris net to keep it from clogging. The biomass overflow release system is shown in  608 - 611 . A truncated cone with open top  608  and an open bottom  609  that is attached to cylinder  612 . There is no egress below open top  608 , except through  608  itself. Since biomass is substantially heavier than water it will gradually displace the water and become compacted from the bottom of cylinder  612  upward. As it reaches the “full” level,  608 , more and more dead plankton, etc., will escape to the outside of  608 , fall through an escape hatch  610  and out of canister  60  as shown in  611 . The simplicity of having no moving parts is worth more than the small amount biomass that may be lost during normal collection. Cylinder  612  is weighted at its bottom  614  for greater stability and speed of lowering when empty. Weighted bottom  614  can be removed via nut  616  along with cage  618  for emptying and cleaning. 
       FIG. 7 a    shows a cutaway of a bottom funnel, and  FIG. 7 b    shows a side view of its open neck  646 . Referring to  FIG. 1  the bottom of the thin film  27  that forms the sides of the main funnel  26  is preferably sandwiched between two cones  624  and  626 . That spreads and reduces the forces on thin film  27  as the canister gets heavier. Upper rims of  624  and  626  are preferably rounded  629  to keep them from cutting the film. Three or more equal-spaced hooks  623  are preferably used to hold down bottom ring  202  as shown in  FIG. 1 . The lowest conical area  628  just above cylindrical neck  632  preferably houses the upper rim  604  of the canister  60 . The reinforcement ring/neck  634  is preferably used to attach rods  644  that make up bottom funnel&#39;s neck  70   b , and to strengthen it enough to deploy when the dead zone begins and to remove when the dead zone ends (see  FIG. 12 ). The open cage formed by rods  644  allows biomass overflow to escape the neck  70   b . The deliberately heavy base  649  and flange  648  help to hold the main funnel rim  25  horizontal. Base  649  is filled with concrete and/or metal to keep the base stable. 
       FIGS. 8 a  and 8 b    depict a tripod-anchor with a self-leveling upper plate. The main function of the tripod-anchor is to hold the funnel trap in place at the bottom so that the harvesting boat can locate their assigned traps, preferably with a GPS, and to deploy and recover the traps themselves. The feet  662  can be added, removed, or modified (e.g., with spikes) as appropriate for the bottom conditions. The legs  666  of the tripod  66  are strong, heavy rods attached to plate  672 , which plate preferably houses a central ball joint  674 . The leveling mechanism comprises a heavy weight  668  held by rod  670  that pierces the ball joint  674  and continues upward and is rigidly attached to plate  676 . Notice that plate  676  is substantially horizontal despite irregular heights of the feet as shown in  80   b . The flange  648  and/or the base  649  may be coupled to the plate  676 . 
     In  FIG. 9 , the bottom funnel  70   b  is preferably attached to the tripod anchor  666 . The bottom funnel&#39;s weighted flange  648  is preferably attached to and seated upon a biasing structure, e.g., compression spring  680 , which is preferably mounted atop of and attached to plate a  676 . The flange  648  and the plate  676  are preferably connected with two or more spacer bolts  678 , as shown. Under enough force, the flange  648  can move downward as far as the compression spring  680  will allow, limited by the non-threaded portion  675  of the bolts  678  and the nuts  679 . 
     With the arrangement of  FIG. 9 , a harvester (e.g., boat/ship) can periodically raise the canister  60  and then drop it back onto spring  680  to produce vibration/shock/force waves in film  27  that can help biomass  391  ( FIG. 1 ) slide down the sides  27  of main funnel  26 . Spacer bolts  678  also serve as a safety feature that keeps the bottom funnel  70   b  and tripod anchor  666  connected if the spring  680  breaks loose. 
       FIGS. 10 a  and 10 b    show a type-2 harvesting apparatus  100 , including a snagging mast ( 702 - 710 ) preferably attached to an underwater guide float  19 , a guide tube  720 , and the canister  60 . The weight of an empty canister  60  should be more than the net upward buoyancy of everything above it: i.e., the float  702 , the snagging mast  706 , the hold-down disk  708 , and the guide float  19 , so that the canister  60  is not pulled up until it needs to be. In this preferred embodiment, four carabiners  704  are preferably rigidly attached to a smooth light-weight mast  706 . Since the funnel trap is preferably delivered in kit form, the mast  706  should be seamlessly joined together from shorter pieces. Any one of carabiners  704  should be able to hold a full canister  60 . The hold-down disk  708  is preferably rigidly affixed to the bottom of the mast  706 , with a line  30  extending from a connector  710  coupled to the bottom of the plate  708 . Connectors  710  are preferably used to couple to the guide float  19 . Line  30  preferably has a length that holds the guide float  19  down so that a float  702  is at a desired depth (perhaps 65′ more or less) for capture by the harvester. When the canister  60  is being raised and the carabiner  710  reaches the surface, it is preferably removed from the bottom of the hold-down disk  708  and is re-attached to a line on the hauling winch that continues to raise canister  60  through the telescoping guide tube  720  and the guide float  19 , both now at the surface. Guide tube  720  is preferably covered by a strong thin material  722  that stretches somewhat, e.g. nylon stocking material. 
       FIGS. 11 a  and 11 b    show a method to snag the mast  708 , and to raise and lower the canister  60 . One or more harvesting boats  750  pull a line attached to outrigger booms  751 . Weights  754  form a U-shape in the line. The bottom of the U is a line  752  that should be between depths  748  and  749  (e.g., depth  748  may be from about 20 feet to about 200 feet; depth  749  may be from about 25 feet to about 225 feet). It is important that bottom line  752  should be above the guide float  19 . As the boat  751  moves forward, the line  752  catches the mast  708  bending it forward and downward so that horizontal line  752  slides up the mast  708  and cannot escape and is trapped by snagging one or more of the carabiners  706 . The harvesting boat  751  then hauls up the retrieval mechanism shown in  FIG. 11 a   . The guide tube  720  is preferably made slack enough to stretch to the surface even during the highest tides and moderate waves. Harvesting should not be performed when storm waves are too high to have the line  752  to remain between depths  748  and  749 . When the connection between the bottom of the mast  708  and the guide float  19  reaches the surface, the mast  708  is preferably unhooked and the harvesters preferably re-hook the upper end of the line  30  and haul up the canister  60 . At this point, the guide float  19  preferably remains on the surface by its own buoyancy, stretching out the guide tube  720  to receive the same or another empty canister. 
     The above-described process may be reversed by re-attaching empty canister  60  to the bottom of the line  30  and lowering it into the guide tube  720  until the upper end of the line  30  reaches the guide float. Then, the carabiners  706  are re-attached to the mast  708  and guide float  19 . The canister will then pull both of these down into place. 
     The best time to deploy a trap accurately is at slack tide on a calm day. One way to deploy the trap may be visualized in  FIGS. 12 a  and 12 b   , which comprise a side view of a specialized tool  120   a  and an inside view  120   b  that helps to deploy a type-2 trap in a dead zone and remove it after the dead zone season is over. Referring to the funnel trap in  FIG. 1  it is clear that the easiest way to lower and raise the funnel trap is to go through the guide float  19 , the telescoping guide tube  720 , and then into the bottom funnel  70   b  ( FIG. 11 b   ). Ring  802  is an attachment ring for a line to lower and raise a type-2 funnel trap. A smooth outer shell  804  allows the tool  120  to take that route without tearing the material  722 . 
     Referring to  FIG. 11 b   , when removing a type-2 funnel trap the canister should first be retrieved and guide float  19  will still be at the surface. Then with arms  810  outspread as shown in  FIG. 12 b    lower tool  120  as far as it can go, which would be bottom  649  of bottom funnel  7   b . When raising tool  120  the outspread arms will hook under reinforced ring  634  ( FIG. 7 ) and the entire funnel trap can be lifted on deck where it can be disassembled. For deploying or moving, tool  120  is again hooked under reinforced ring, but after it is placed tool  120  is lowered until arms latch inside the shell. The smooth outer shell  804  has no sharp points or edges that could tear the material  722  in the guide tube  720 . Affixed to the inside of shell  804  are opposing bushings  811  that hold the ends of an axle  808  so that the arms  810  are aligned with a two-pronged fork  812 . If not thus-constrained, the arms  810  will fall open by gravity; but, when they are being lowered through the guide tube  720  or the bottom funnel neck  632 , the arms  810  are easily pushed up along path  806 . The arms  810  preferably have a rectangular cross section that is rounded wherever it can rub against anything outside of shell  804 , to keep the guide tube material  722  unharmed. The open bottom  815  of the shell  804  is preferably rolled inward for the same reason. 
     Near the bottom of the shell  804  is a strong horizontal disk  814  preferably affixed to shell  804  with machine screws. One or more holes  816  allow water to move freely there through. At the center of disk  814  is a preferably square hole that keeps the handle  812 H of the two-pronged fork  812  from turning. It should be in the same plane as the arms  810 , and  812  should only move vertically. If the bottom of the flat, two-pronged fork is pushed up through the square hole (obscured) in disk  814 , it will raise the arms  810  along the path  806  until the arms  810  are pushed through the slots  828 . If the tool  120   a  is lowered to the base  649  of the bottom funnel  70   b , a “door latch”  818  will be pushed through the square hole and lock the arms inside the shell  804 . This allows the tool  80  to be raised after the type-2 trap is deployed. A simple switch under the shell  806  resets the latch  818 . Removing a type-2 funnel trap is a reversed process, but that simple switch is used to completely disable latch  818 . 
     The individual components shown in outline or designated by blocks in the attached Drawings are all well-known in the plankton harvesting arts, and their specific construction and operation are not critical to the operation or best mode for carrying out the invention. 
     While the present invention has been described with respect to what is presently considered to be the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, the invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.