Pulsating climate

This is a pure bit of speculation.  If true, climate change will result, at least for the transition period, in very cold winters in America, Canada and Eurasia and very hot summers.  First a few facts (or at least accepted theories).

The Gulf Stream which brings warm water along the surface of the ocean from Florida towards the North Atlantic is powered primarily by the freezing out of fresh water ice from sea water in the Arctic and North Atlantic oceans.  Left behind is cold, saltier water which sinks and flows south along the bottom of the ocean.  Water is pulled north to replace this water.

The water which is being pulled northward is saltier than deeper water because of evaporation in the tropics but doesn't sink because it is warmer.  As it flows north, it cools and at some point is heavy enough to sink.  This positive feedback adds more power to the Gulf Stream.

As sea ice (and land ice for that matter) melts, it freshens the surface water in Northern latitudes and so when freezing starts, it will take longer before the resulting water is salty enough to sink. A big influx of fresh water into the North Atlantic should weaken the push that powers the Gulf Stream.

Ice is and insulator.  If you have open water in contact with cooler air, the water gives up its heat to the air, sinks and warmer deeper water replaces it.  The heat exchange between open water and the air is large and heat is being replaced on the surface by convection.  Once you have a cover of ice this convective process is greatly slowed.  Heat has to pass through the ice into the air in order to cool the water in contact with the bottom of the ice.  The thicker the ice the greater the "R" value of the ice.  ie, the slower the flow of heat between water and air.

As climate change continues, the time of net melting becomes earlier* and the time at which freezing exceeds melting is later.    The freezing period shortens, the melting period lengthens.  Here is where the speculation starts.

*Oddly enough over the past few years, the date at which melting starts has been getting later.

I wonder how long the delay is between the start of freezing and hence the sinking of salty water and the increase in flow of the Gulf Stream.  There should be a couple of factors in play here.  First it is a huge body of water to get moving with huge inertia so there should be a delay between push and move.  Think of a huge weight on one of those frictionless pads when you start to push it.  At first the motion is barely perceptible but builds up as you continue pushing.  Similarly, stop pushing and it takes the weight a long time to stop moving.

Secondly, it takes time for the warm salty water from the Florida region to move far enough north on the weakened Gulf Stream where it can cool enough to sink and add it's power to the Gulf Stream.

What strikes me as possible, is as the period of freezing shortens and the period of melting lengthens, we could reach a point where the push (cold salty water sinking) and the result (the Gulf Stream getting up to speed) could be 6 months out of sinkronicity.  We would end up with  a fast flowing Gulf Stream in the summer bringing warm water to the North Atlantic along with warm temperatures and, probably, heavy rain followed by a stalled Gulf Stream in Winter giving us really harsh winters.  Harsh winters would result in lots of freezing of fresh water ice from sea water, giving a push to the Gulf Stream.  It's effect would be felt next summer.

For those who suggest that this will lead to another ice age, remember, it doesn't matter how much snow falls in the winter or how cold it is.  An ice age can only start if the snow last through the summer.  In the above scenario, no snow would last through the summer.  In fact, the remaining glaciers should melt away with all the bad consequences this would bring.

Does anyone know if the flow of the Gulf Stream pulsates in any sort of annual cycle at present.

Post script:   A thought just occurred to me.  During this period of transition to a warmer climate in which the Arctic becomes largely ice free in the fall but freezes during the winter, the push to the Gulf stream should be shorter but sharper.  Clearly the ice starts to freeze later than previously but without a thick cover of ice, the transfer of heat to the atmosphere and the radiation of heat into space is more rapid.  It is possible that the rate of freezing and hence the rate of production of cold, heavy, salty water would be greater than when there is already a thick layer of insulating ice covering the ocean.  The length of the push is shorter but more intense.  How would this effect the whole system??

carbon sinks

Glaciated periods (glacials) end with a sharp increase in Carbon dioxide.  It looks most likely, as odd as it seems, that the rise in CO2 is the result rather than the cause of the melting.  In a couple of former blogs, I suggested why this might happen.  The release of CO2 then accelerates melting, in a feed-back loop.  Over the subsequent  years of the interglacial, carbon sinks continually reduce the level of atmospheric Carbon dioxide.  When Carbon dioxide levels fall sufficiently, snow begins to accumulate at high latitudes and high altitudes in the summer and we edge into another glacial.  I'd like to try to catalog as many potential sinks as I can think of, regardless of their perceived importance.  Others can work on working out which ones are significant and which not on the road to the next glacial.

Note that you can reverse each of these arguments to see what we are doing to increase atmospheric Carbon dioxide.

Corals
Corals and all other marine organisms that have a Calcium carbonate shell are sinks for carbon dioxide.  Every molecule of CaCO3 contains one molecule of Carbon dioxide (60.6% by weight).   In addition to the building of reefs by oysters and corals, some phytoplankton have calcium carbonate shells.  There are globigerina, a type of foraminifera, pteropods, a swimming snail and so forth.  When these die, they sink to the bottom of the ocean and form calcareous oozes.

 Curiously, at great depth (below about 4500m) the calcium carbonate dissolves so these oozes only form in medium deep water.  The white cliffs of Dover are such deposits and give a visual indication of the extent of carbon sequestration in the form of calcium carbonate that phytoplankton can effect.

Note: In an item I just saw on Discovery Channel (Feb20,2012) it appears that corals are much more common in the deep ocean than previously believed and even form quite large "hills" of Calcium carbonate in some locations.   This sink would presumably stop if the ocean overturn ceased and the deep ocean became anaerobic but as long as the system is working, deep water corals are another significant sink.

Question:::  What happens when this water which is enriched in dissolved Calcium Carbonate upwells into  shallower water???


Of special interest with regard to corals in the photic zone is that they are limited in their growth by the surface of the oceans.  If you have visited coral reefs you may have seen some of the brain corals which show concentric rings on their tops.  These rings are caused by  very low tides which have killed off the top of the coral.  As the diameter increases a new ring is formed.  Rather than recording yearly growth, these rings record king tides.  Corals don't grow in air.  Following the end of the last (and every other) glacial (ice period), the sea rose.  At the maximum extent of the last glacial the sea was about 120m below its present level. The last glacial lasted for about 125,000 years since the end of the Eemian interglacial.  With various smallish ups and downs, the sea level steadily dropped to this lowest point of 120m below its present level.  Coral reefs, of course, died as they were exposed and then a hundred thousands  years of waves pounded on the shore, washing the corals away, leaving cuts into the land.  Around 20,000 years ago the ice began to melt but the melt only really got under way about 11,000 years ago.  Sea level rose  quickly (in geological terms) to its present level.   During part of the transition to our present Holothurian interglacial, sea level occasionally was rising as much as 56mm/year.  The over all rise during the melt was about 6mm per year, twice the present rise.  For reference, at present (2012), the rate of sea level rise is about 2.8mm.yr.   



In tropical areas, corals grew to fill this 120m gap up to the surface of the ocean, an over all growth rate of 6mm per year.  It is estimated that the total area of coral reefs, world wide is 284,300 Square Kilometers.  This figure times 1,000,000square meters per square km times 120 meters depth times 2.5sg (specific gravity) for limestone times 60.6% Carbon dioxide in limestone  divided by 1billion gives a figure of 5,174 gigatons of Carbon Dioxide sequestered in corals since the end of the last ice period. To put this into perspective the total Carbon dioxide in the atmosphere today is about 3000 gigatons.  Corals which have grown since the ice age have sequestered about 1.6 times as much carbon dioxide as the Carbon dioxide at present in the atmosphere.  As sea level rises, we have a potential carbon sink in corals as long as we don't kill them with acidification or thermal shock. massive coral bleaching could, of course,  shut down this carbon sink.

Ocean Overturn
At the poles, sea ice freezes out fresh water ice leaving salty brine behind.  This brine is heavier than open ocean sea water and hence sinks.  As it moves across the ocean bottom, it picks up nutrients from the mineralization of the constant rain of organic material from the surface.  Where wind conditions are suitable, surface water is pushed away from the shoreline to be replaced by this upwelling, nutrient rich water.  As this water comes into the photic zone, productivity is immense.  The ocean off Peru is an example and the Anchovi produced there provides a significant percent of the fish meal for world animal production.  The Atlantic overturn is another example with the Gulf Stream being the surface manifestation of this overturn.  The shut down of such ocean systems would cause Carbon dioxide to rise more quickly in the atmosphere

Swamps
If the water in a swamp is sufficiently stagnant and there is sufficient organic loading to make the bottom of the swamp anaerobic, then all cellulose that falls into it is preserved.  This includes all plant material and probably explains the formation of many of our coal measures.   If the area is sinking, the organic material is buried, heated, gives up its volatile fraction and what remains is mostly carbon with some mineral material which forms the ash when coal is burnt.  This process removes carbon from the atmosphere and also contributes to sending us toward another ice age.  

Growing Forests
A mature tropical forest, at first glance, would seem to be a huge sink for carbon dioxide.  After all, the rate of photosynthesis is huge.  This is an illusion.   Once a tropical forest has truly reached maturity, the rate at which vegetation dies and is oxidized equals photosynthesis.  Mature tropical forests, however, do represent a large sequestering of Carbon as long as they remain untouched but they have no net effect on removing more carbon from the atmosphere.

The carbon content of organic material, wood included, is about 50% of the dry weight of that material.  If an plant is 80% water, 20% dry matter, then it's carbon content is about 10% (of its wet weight). The cutting down of the forests of the world has released a large amount of carbon into the atmosphere and this carbon would be rapidly taken up by letting the forests grow again.  In this way, tropical forests could be a huge carbon sink if allowed to regrow.  The only way a mature tropical forest will continue to sequester carbon is if it contains swamps as detailed above.  Of course another way is to selectively log tropical forests (at a rate that doesn't imperil their survival) and to use the wood in long lasting buildings, furniture etc.  New trees grow where the old ones are harvested and a mature tropical forest then becomes a carbon sink.

New forests are a whole different ball game.  At the maximum extent of the last period of glaciation ('glacial' as opposed to 'interglacial'), ice, estimated to have reached a depth of 3km, covered most of Canada and a strip of America down to and extending beyond New York.  Much of Europe, Germany, Poland and  Russia and the UK were covered.  Smaller ice sheets were found on high land right down to the equator (Mt Kilimanjaro, for instance).  When the continental glaciers melted all the scraped-clean land was open for colonization (primary and secondary succession).  Much of this land ended up clad in forests of giant trees with their sequestered carbon.  As the tree line moves north with global warming, we have another potential carbon sink.

While we are at it, temperate forests are a different situation from tropical forests.  When Tropical forests are clear felled, it is found that the soil is thin and is exhausted very quickly.  This is due to the characteristics of humus.  Humus is the final break-down product of organic material and contains a lot of carbon.  Amongst it's other characteristics, it holds nutrients in a form that can be used by plants.  Above about 25 degrees C, Humus breaks down.  

In temperate forests, the humus builds and builds, depositing more and more organic material in the ground.  When temperate forests are clear felled, agriculture can carry on for far longer than in the tropics, before the soil is exhausted. Temperate forests can continue to sequester carbon even after they are mature (with respect to the total mass of live vegetation they contain). The re-establishment of temperate forests not only would sequester considerable carbon but continue to sequester carbon when the forest is mature.  It is a bit rich for northern hemisphere countries to complain about the destruction of tropical forest when they have decimated their own forests.

Permafrost
During the summer, the top foot or two of permafrost melts and a range of dwarf, ground hugging trees, lichens and mosses grow.  In the winter this freezes.  Each year another small layer is added and the layer of organic material deepens.  Permafrost areas are carbon sinks.  Of course, the flip side is that thawing them with global warming is a source of carbon. It is estimated that the carbon stored in permafrost today is greater than all the carbon of all living things and is twice the carbon in the atmosphere.     If the layer is deep enough (about 300m) the pressure is great enough that a portion of this carbon is in the form of methane clathrate which only needs a little warming to be released. In addition, any geological methane seeping up under permafrost can also be stored as clathrate as it comes into contact with moisture.  The depth of the frozen soil is not the only factor for the creation of methane clathrate.  The frozen permafrost can act as an impermeable layer, like the lid of a pressure cooker and clathrate can form at shallower depths.

It is interesting to note (and counter-intuitive) that by covering an area of permafrost with a deep layer of insulating  ice during a glacial, the permafrost will be melted by the heat coming up from the earth.  This deep organic soil would break down anaerobically giving up methane.  This would likely collect at the bottom of the ice sheet as a methane clathrate, ready to be suddenly released when the ice sheet melted.  Of course, the clathrate already stored in the permafrost would give up it's methane too which would seep up and be stored in the ice sheet. This may be part of the explanation of how Carbon dioxide rises so quickly at the end of glacials.  Released methane trapped under the ice oxidizes rapidly into Carbon dioxide and shows up in bubbles in the ice cores from Greenland and Antarctica as Carbon dioxide rather than as Methane.

Note that the Firn layer (permeable top of an ice sheet) is about 70m and gas can diffuse between this layer and the atmosphere so the signal of sudden methane or for that matter Carbon Dioxide would be smeared out throughout the layers.

Grasslands
Native grasslands have most of their biomass underground.  This is an evolutionary adaptation to fire.  Grass fires are intense but short and the heat doesn't penetrate far underground.  With the introduction of nutrients from wind-imported-dust, grasslands in their natural state continue to grow upward and add more and more organic material.  Organic material is ultimately stored in deep rich humus containing soil.  This rich accumulation of nutrients was mined by farmers planting wheat and other crops, especially in the great plains of America, and the carbon returned to the atmosphere.  In pre-agricultural times, grasslands were carbon sinks. Now they are sources of carbon.  If returned to their native state, they once more would sequester carbon.  Some research suggests that the north American Buffalo can produce more meat per hectare on native North American prairie than our much vaunted beef cattle.  At the same time they allow the sequestration of carbon to once more occur in the grasslands. Have a look at this TED talk on how to restore our grasslands.  Direct seed drilling without plowing has also been shown to increase the Carbon content of soils.

Calcareous Oozes 
Many plankton animals such as foramanifera have calcareous tests.  These sink  form layers of calcium rich deposits on the ocean bottom up to about 4500m.  Below this depth, calcium carbonate is soluble.  These oozes get buried and are carried toward subduction zones by the ocean bottom conveyor system.  Over geological time, these deposits of lime are recycled by volcanoes as Carbon dioxide. 60.6% of calcium carbonate is Carbon dioxide. When you think of deposits like the chalk cliffs of Dover it is apparent that calcareous deposits are a large sink for Carbon dioxide.

Silicate rocks
As erosion or volcanic activity exposes new silicate rocks to the atmosphere, they are attacked by Carbon dioxide, producing carbonates.  This is also a sink for Carbon dioxide but on a geological time scale.

Cement
As cement is produced a large amount of CO2 is released.  As it cures the Carbon dioxide is re-absorbed.  All cement structures around the world are slowly absorbing some of the Carbon dioxide that was released when they were produced.

 Carbon sinks are slow but inevitable.  As they proceed, the Carbon dioxide content of the air decreases, the climate cools until snow can begin to accumulate over the summer.  It would appear that with the amount of sequestered carbon we have introduced into the atmosphere by burning fossil fuels, the next descent into a glacial  will be much delayed.  It is interesting to think that we will have used up the world supply of sequestered carbon in the blink of an eye.  We would expect the present interglacial age to last another 10 or 20 thousand years.  With our Carbon output, let's say we have pushed the end of the present interglacial out to 30,000 years.  If we still exist then as a species, which seems unlikely, our descendants will be faced with the onset of a glacial age with no large resources of sequestered carbon left to counter it.  

By by Coral Atolls

There is much to-do in the press about the immanent drowning of coral atoll islands due to rising sea level.  While climate change could well destroy coral atolls, it  won't be primarily due to the rise in sea level.  Some background:

The present ice age, which we are in the middle of,  started roughly 2.5million years ago.  It has had numerous glaciated periods (glacials) and warm periods (interglacials).   The  interglacial before the one we are in now, we call the Eemian.    It was centered about 125,000 years ago.  That is 62 times as long as from now back to the Roman empire.  The present interglacial we are living in we call the Holocene.  As the previous (Eemian) interglacial, faded away sea level fell as more and more water was deposited as snow on the continental glaciers*.  At its greatest extent, sea level was 120m below its present level.  Of course the corals that were growing within 120 meters of the surface of the ocean during the Eemian interglacial, were killed as sea level dropped.  Without live corals to resist the effect of waves, these islands would have eroded.  They may well have eroded down to the level of the  low tide mark, 120 meters below present low tide.   A lot of erosion can occur in more than 100,000 years.

 

*In the western hemisphere, glaciers start to accumulate on the high lands of Baffin Island and spread out from there.  

 
As the ice started to melt, some 20,000 years ago and really got under way 15000 years ago, sea level rose quickly as the continental glaciers flowed into the oceans.  The main melt ended 7000 years ago with a slow rise since then of about one mm per year.  Today, coral reefs all over the world are at about the current low tide level and Atoll islands are a few meters above high tide.  Clearly, corals have grown as the ice melted and sea level rose.  The corals have filled in the 120 or so meters between the low tide level at the maximum extent of the recent 'glacial' to the present low tide level*. The lesson is, as sea level rises, the restraint on coral growth is removed and they grow up to the current low tide mark.  The average sea level rise was about 14mm per year during the rapid melt with isolated periods of as much as 56mm per year. (today sea level is rising at about 3.5mm per year)

* Incidentally, the Calcium carbonate of which coral skeletons are made are a tad over 60% Carbon dioxide!!which ultimately comes from the atmosphere. This, under natural (without humans) conditions would be contributing to sliding us into the next glaciation as Carbon dioxide was built into coral.

OK,,,,,, so if corals are limited by low tide, why are the coral atoll islands meters above the level of the growing corals.  This question pertains to the present fear that coral islands will be swamped as the sea rises.

The answer, to a large extent,  is Parrot fish.  Parrot fish eat corals and digest the polyps.  They poop out coral sand.  A parrot fish typically produces 90kg of sand per year.  A thousand parrot fish in a lagoon and you have a production of 90 tons of sand per year.  The sand is moved by wind, currents and waves, especially during hurricanes,  and collects where the total energy is low*.  As long as the seas are healthy for corals, new ones grow providing more food for Parrot fish and hence more sand.

 Now we come to the function of hurricanes.  In a hurricane waves are longer and higher*. so they pick up, not only coral sand but coral rubble and deposit it where the energy of wind, currents and waves is low.  It is a sort of  one way valve.  This keeps the atolls supplied with sand and rubble which keeps them growing upward.  As long as nothing kills the corals (or the Parrot fish) coral islands will keep up with sea level rise.

*For those of you with a mathematic bent, for every ninth of a wave length  you go down in the ocean, the circle of rotation of a wave halves.  For instance, if you have a wave length of 18m and a height of 1m, if you go down 4m, the circle of rotation will be 25cm.  A long wave has an effect much deeper than a short wave.
 
Once the sand forms a bit of land above sea level, bird transported seeds can germinate and the resulting plants will dampen the force of the wind crossing the island.  This results in an increased catch of wind-blown sand on the island and a root system to retain what sand there is.  Once there is a bit of an island above the high tide, rain will accumulate in the soil of the island, floating as a lens above the sea water.  Varieties of plants, which need fresh water can then grow. Bird poop (Guano) will add to the fertility of the soil created.


So under natural conditions, it is unlikely that sea level rise will destroy the Atolls.  In fact some satellite pictures show them growing.  The real problem that climate change will cause is primarily due the increase in Carbon dioxide.  Two effects are at play here.  As the sea becomes more acidic due to the absorption of CO2, it becomes harder and harder for Calcium carbonate depositing animals to extract the calcium from sea water.  A bit more acidic, and  shells and corals will start to dissolve.  

The second problem which could come from climate change is temperature rise*.  The lethal temperature for corals is only just above the temperature of maximum growth which is, in turn, only a few degrees above the present water temperature.  There are a number of reasons that tropical seas could warm.  A major one is the shut down of the ocean circulation which is powered by two phenomenon.  The first is  freezing of Arctic (and Antarctic) water.  Fresh ice crystallizes out of the sea water leaving the salt behind.  This forms brine which sinks down to the bottom of the Arctic ocean and flows out of the Arctic.  This out-flowing deep water causes surface water to be sucked toward the poles, bringing with it calories.  Heat is being pulled from warmer regions of the earth, toward the poles.  Stop the formation of deep salty ocean water and no longer will this flow of heat exist and tropical areas will warm.

The second effect that powers the Gulf stream is the cooling of the somewhat saltier water that flows up the East coast of North America.  It only stays on top because it is warmer than the underlying water.  As it flows north into cooler climes, it cools as it gives up it's heat to the atmosphere until it is dense enough to sink down through the colder water below.  If there is an outflow of fresh water from melting continental glaciers, the mix of the surface, salty water with the fresh water from the ice will no longer sink as it cools.  Once again you get a reduction of the formation of deep oceanic water, and hence the reduction of surface water being pulled northward and the heat remains in tropical waters.

If the arctic overturn is stopped by increased melting of Greenland ice sheets, and by a reduction in the formation of oceanic ice,  we will have very cold winters in Europe despite the general warming of the planet.  The corollary is that heat will not be removed from southern waters.  If either acidification or temperature rise occurs, there is nothing that the people of the coral atolls can do**.  Without live corals and parrot fish to provide a constant source of coral sand, the islands will erode.   

** (Added Jan 2017)Note that in 2016, toward the end of a very severe El Nino there was wide spread coral bleaching.  Overall, each bleaching event seems to be more severe than the previous one.


Jason Buchheim reports 
As reef building corals live near their upper thermal tolerance limits, small increases in sea temperature (.5 –1.5 degrees C) over several weeks or large increases (3-4 degrees C) over a few days will lead to coral dysfunction and death. Anomalously high sea temperatures have often been reported in the Caribbean-wide series of bleaching events that occurred during 1986-88, leading to hypothesis that global warming was having an effect on the coral reefs in this region.

*If climate change results in an ice free Arctic ocean, it becomes a massive solar panel and could rapidly melt the Greenland Ice Sheet.  If fresh water pours into the sea sufficiently fast, this could shut down the ocean circulation system.  This system, as it warms northern Europe, cools the tropics.  Stop this cooling and tropical waters could reach a lethal level for corals.


However, Short of global acidification or a rise in the temperature  of the tropical oceans, the health of the coral atolls is in the hands of the local people. 

The three basic principles to avoid your atoll being swamped by the sea are: 

 
A) do nothing that damages corals, 
B) never kill a parrot fish and 
C) make sure the islands are vegetated so that any wind born sand across the island will land on the island for the root system to hold there.  

More specifically:

*  Don't use fishing methods that damage coral reefs.  This includes dynamite.
*  Don't use chemical fertilizers on land.  They can damage corals when they seep into the sea.  If land sourced nutrients are sufficient they can lead to phytoplankton blooms that shade the zoozanthellae that are necessary for coral health.They can also fertilize sea weed growth which can smother reefs.
*  Don't allow sewage to flow into the sea or into the water table unless it is fully treated.  Primary or even secondary treatment is not sufficient.  The nutrients must be removed.
*  Don't use pesticides or herbicides as they can harm sea organisms.
*  Don't over utilize the fresh ground water.  The vegetative cover of the island 
depends on this fresh water
*  Never ever ever harm a parrot fish
*  Leave the rabbit fish (Siganid sp.) alone too.   They eat algae that can smother corals. (third fish down in the link)
*  Reintroduce the system of Tapu (taboo) in which large sections of the reef are off limits to utilization of any kind for a number of years.  Every decade or so the area is changed.  Fishing in  areas not under Tapu will be greatly improved as a bonus because of the recruitment of fish from the tapu area.

Short of a global situation that kills the corals, the fate of the atolls is in the hands of the local people.   The elephant in the room, of course is population control.  All the strains on coral atolls mentioned above are exacerbated by over-population.  Atolls are microcosms of the situation the whole world is in at present.  With stable or decreasing numbers of people on coral islands, all the bad effects decrease to manageable proportions.

By the by, an interesting experiment to try would be to plant some mangroves in shallow water by the land. If they grow, they will catch sand from the water currents which will further increase the available real estate and will protect the land during hurricanes.  Mangrove  areas are also apparently great breeding grounds for fish. They are also areas of low energy where sand will accumulate during hurricanes.  Just a thought.

Final conclusion 
The future existence of coral atolls depends on the health of the corals and the presence of fish which turn corals into sand.  The corals respond by growing upward and providing fresh material to be turned into sand.  Kill the reef and the supply of sand and coral rubble will dwindle and storms will no longer have material to keep pace with sea level rise.

Charcoal Production

   Abstract
Traditional methods of charcoal production are messy, often operate in batches,  produce variable yields and  only use the volatile fraction of the pyrolysis process  to create the heat to char the wood.  A higher yield, continuous system is suggested which utilizes the combustion of the volatile fraction of the pyrolysis process to protect already pyrolyzed wood (charcoal)  from further oxidation.  In a commercial operation based on this system, considerable heat energy will be available for drying the feed stock or for whatever other purpose is required.  Continuous production should be easily to mechanize.  

Background
Over the last few years biochar/charcoal has become a hot new research topic. A number of factors, some old and some new have led to this situation.

Archaeologists have long known that Charcoal is refractory (doesn't break down easily) since they often find charcoal in ancient sites where fire has been used.  This is fortunate for them since at a push, charcoal can be used for carbon dating extending back 50,000 years.

Global warming has come upon us with the villain in the piece being our burning of sequestered carbon in the form of coal and oil and gas.  The resulting CO2 is the main suspect.

Some countries, Notably New Zealand, have rushed to sign up to Kyoto and take on a financial obligation for her production of green house gases.  This will cost the tax payers of New Zealand considerable money for no gain what so ever.  If we can use biochar to sequester carbon, this will reduce this hemorrhage of money.


All of the above were necessary but not sufficient reasons to spark the present interest in biochar.  The critical final factor was the discovery of Terra Preta in jungle locations.  In an area of  very poor soils, these charcoal rich soils are very productive.

Research efforts are underway all over the world to understand biochar.  The efforts are concentrating on the effect of different production methods (mainly the temperature at which the charcoal is produced) on its value as a soil enhancer and on its longevity in the soil.  In the Appendix, some information is given on the questions being asked.

However, the use of biochar as a soil enhancer will never become commercial if it is expensive to produce.  A commercial system should be inexpensive enough to establish at each source of raw material such as lumber mills with their offcuts and sawdust,  at forests with large supplies of prunings and forest litter or at an abattoir with a supply of bones.  It should be a continuous system rather than a batch system and it should effectively char a wide variety of material from fine sawdust and leaves to large pieces of wood and bark.The advantage of producing biochar on site is that it is reduced in volume and weight and hence is less expensive to transport.

The Learning Curve
As soon as Terra Preta was heard of, we started experiments  to produce charcoal.  It was thought that if charcoal is a valuable addition to tropical soils which are too warm to retain humus, it couldn't hurt to add it to temperate soils, many of which are humus poor.  The hope is that biochar will have the same water retaining and ion exchange properties as humus. In addition it is likely to supply surfaces and internal nitches (charcoal is porous) for microfauna films.

Charcoal Mark 1 consisted of simply making a fire, using material from the branch pile (about 2 meters high) and covering it with dirt once the flames had died down.  Anywhere a smoker showed through the dirt, more dirt was added.  After a dozen tries, discouragement set in.  The morning after the charcoal making exercise, the fire would more often than not still be hot and there were sections of ash where the charcoal had been consumed.  The system was laborious, dirty, batch rather than continuous and ineffective.  A huge quantity of branches resulted in very little charcoal.

Carcoal Mark 2 consisted of stuffing a 45gal drum with prunings from the branch pile and lighting it.  When the flames had died down, the barrel was gently tipped on its side and then upended, open side down.   Some dirt was kicked around the rim to seal it.  Next morning (many next mornings) we had some charcoal, the material was cold but there was much unburnt material from the bottom of the barrel.  However this led to Mark 3.

Charcoal Mark 3 used the same 45 gal drum but this time, a flame was lit in the bottom of the barrel using shavings from the woodwork shop and then branches were fed in to the barrel from the ever growing branch pile.   Branches were added until the drum was about half full of charcoal and then for a few minutes, only very fine material was added to to give lots of flame which died down quickly but kept the barrel very hot.  This was done to ensure that any large pieces at the top of the charcoal were fully charred.  The fine material gave out gasses rapidly which combined with the oxygen and protected the charcoal.  The barrel was then upended as described above.

During the production of one batch, large branches were pushed down into the charcoal layer to avoid them toppling  the drum.  When the Charcoal was examined next morning, uncharred wood was  found.  The butts of the branches had been protected from the heat of the fire and from oxygen.   It is critical that  new material is introduced on or above the surface of the growing layer of charcoal.

In most batches, the next morning the charcoal was cool, no ash was to be seen and everything from leaves to 5cm diameter branches were charred. The only batch with uncharred material was the above one where the branches were pushed into the charcoal layer.  An easily identified gum leaf, placed in the palm and rubbed with the thumb disintegrated into powdered charcoal while large chunks of wood, rapped on the edge of the drum to break them were completely charred all the way through.  A modest supply of branches gave a good yield of charcoal.  An added step was to wet down the charcoal next morning to ensure no live coals were present.

Why Does It Work
What is apparently happening is that as new material is put in the burning drum, it pyrolyzes and give out flammable gases.  Nothing new in that.  The burning gases use up the oxygen, protecting the charcoal from further combustion.  As long as there is a reasonable amount of visible flame, charcoal is produced rather than being consumed.  Important is to have a continual feed of new material.

A Comercial Unit
As a first pilot plant, one could start with a cast iron or steel cylinder with the same proportions as a 45 gal drum.  For ease of fabrication it could probably be octagonal, hexagonal or even square.  A conveyor belt would bring feed stock to a feed in trough sticking out of the side (like the old trash burners had).  The critical part, though, is to turn this into a continuous rather than a batch system.  This could be done by having an augur at the bottom to extract the charcoal.  The charcoal extraction system would have to be  air tight to ensure that air did not enter the charcoal bed.  The charcoal would be dumped into steel carts with air tight tops and left sealed overnight to ensure that the charcoal was extinguished.  Alternately the collecting carts could be sprayed with water.

Combustion air could come from the top as in the simple home system or could be introduced through vents in the side of the retort, above the surface of the charcoal.  Having these vents adjustable would give an added measure of control to the operator.  The extraction of charcoal from the bottom of the retort would ensure that the top of the charcoal bed was always below the vents.  The air could  be introduced tangentially to ensure a whirling, well mixed flame.

For the use of biochar to catch on, charcoal production must be inexpensive.  It is best if it can be carried out where the feed material is available since turning wood into charcoal greatly reduces its shipping weight and somewhat reduces its volume.  Any system which is continuous will be far more productive per retort than a batch system of the same configuration and size and hence more cost effective.  Having to cool and harvest a system takes considerable time and greatly reduces the production of a system of a given size.  Considerable heat will be produced which can be utilized for whatever purpose needed.

ps.  Just for the home charcoal maker, it helps if side branches are cut off large branches so that they don't hang up on the rim of the 45gal drum.  In this way, the branches self feed into the drum as the bottoms break off and you don't have to tend the drum all the time.  An occasional visit and top up is sufficient.

Fine furniture and Global Cooling

Jungles and Global Warming
It is often stated cutting down tropical jungles is contributing to global warming; that jungle logging is destroying the lungs of the world which we need for turning atmospheric carbon dioxide back into oxygen. Sadly, a mature tropical forest doesn't produce any net oxygen and doesn't sequester any carbon. A mature forest, by one definition at least, is one which has reached equilibrium between photosynthesis and oxidation of waste materials. If biomass is being oxidized by rotting as fast as it is being produced by  photosynthesis, there is no net oxygen production and no net conversion of carbon dioxide into biomass.  The correct sort of logging could convert mature tropical jungles into very effective carbon sinks, enrichen tropical soils and displace/replace fossil fuels.

In temperate forests, by contrast, you may have a build up of dead organic material on the forest floor that goes on and on and the final product of the break down of this forest litter is humus which contains sequestered carbon in a fairly refractory form. In the limited sense in which we are defining 'mature', such a temperate forest is not mature and can stay immature for a very long time. Similarly up in the tundra, some of each year's growth of organic material may be frozen into the permafrost and so over the years accumulate more and more organic material. The layer of organic material in the tundra can be very deep. In the limited sense we are talking about, this ecosystem is also not mature. However in the continuously wet warm conditions of a tropical forest, and with its huge diversity of life, any organic material that falls on a tropical forest floor is soon mineralized and incorporated back into the biomass of the forest. Humus oxidises (breaks down) above about 25 degrees so there is no accumulation of carbon in the soils. A major reason that tropical forests exist is because of their ability to recycle nutrients with very little loss from the system. When decay balances photosynthesis, no net biomass is accumulating and no net oxygen is produced.

In the present type of jungle logging, the land is clear felled, removing anything of value and burning the remainder. Then either grass for cattle or oil palms are planted. The logs are sent to make furniture etc. and the waste from the saw mills and from the furniture factories is burnt. In so far as you produce fine, high quality, long lasting furniture, houses and so forth, you are sequestering some carbon although only a small proportion of the original amount which was logged. The land is left nutrient poor and most of the original biomass is returned to the atmosphere as carbon dioxide. This type of logging is clearly detrimental in terms of increasing the amount of carbon dioxide in the atmosphere not to mention the destruction of an environment of great beauty.

If you really wanted to use the forests only to sequester carbon dioxide, you would selectively cut down large trees and bury them in a swamp. Under anaerobic conditions, wood is very refractory (doesn't break down). As long as the swamp stays flooded, the sequestered carbon remains sequestered. Let's be realistic though. Such a plan would have all of the expenses of logging and then some, but none of the profit. It would be an non starter economically. To make a system work, there has to be profit. So what sort of system could work.

First of all, let's keep the idea of selective logging. We take out selected prime trees for wood and turn them into fine furniture etc. Manufacturing is done in the country where the trees are logged and preferably close to where the logging occurs. Why ship prime wood overseas and allow someone else make most of the profit. Quality is important. Cheap furniture which is not properly engineered will break down and will be burnt, releasing its carbon and new wood will have to be cut to make new furniture. It is important to build fine products that will last many many generations. In addition if you produce very long lasting furniture, as the markets are saturated the need for new logging will decrease

Back in the jungle, masses of seedlings are just waiting for a ray of sun to reach them, many of them from the felled tree itself. Following the fall of a jungle giant, growth activity is insane. Seedling reach up at phenomenal speed in a race to find their place in the sun. Of course, as they do this they are sucking Carbon dioxide from the air. This part of the jungle is now 'immature'. Even when they reach the canopy, they continue to increase in diameter, sequestering more and more carbon. Now the question is what to do with all the waste wood in the form of branches cut off the tree during logging, offcuts and sawdust produced during the production of lumber and offcuts produced during furniture manufacture. All this material can be burnt just to get rid of it but it can also be burnt to produce energy which can run, for instance, the saw mill. Vertical integration can ensure that milling and furniture production are all in the same location and close to the area being logged.

The use of offcuts for energy was once done when the saws of saw mills were run directly from steam driven belts using the waste wood from the mill. The waste wood, however, can also be used to generate electricity which is more convenient energy form to transmit to the saws. Electricity has the added benefit that the excess can be fed into the grid to earn profit. The grid forms the energy storage unit for the mill and any energy produced reduces the amount of new carbon (coal) that must be burnt somewhere else.

Another intriguing solution is to char the wood. Heating wood in the absence of oxygen produces a mix of gas and tar, similar to what comes out of an oil well and leaves behind charcoal. In traditional charcoal production, all the volatiles are used in a wasteful system to produce the heat to pyrolyze the wood and the carbon contained in the volatiles goes back into the air. The charcoal, which is light to transport and burns without smoke is sold, mainly to private users, to cook their food. In an efficient industrial process, there should be a considerable quantity of volatiles left over to either be used for electricity production or as raw materials for industry. Pyrolysis needs high temperature but doesn't take much heat energy*. The amount of volatiles left over for the production of electricity or as an industrial feed stock depends to a large extent on how well the pyrolysis vessel is insulated and how efficiently you introduce heat energy into the vessel. An interesting possibility is to use electricity to heat the pyrolysis vessel. And what about the charcoal produced.

As mentioned you can sell charcoal for home cooking and it will replace the use of fossil fuel. A special benefit of charcoal is that it doesn't produce smoke pollution and hence can be used in crowded conditions. It also isn't dangerous in the way that kerosene is. Every year thousands of women in India, for instance, are burnt and maimed by exploding kerosene burners. (Indian divorce) One danger of charcoal burners, though, is their use in confined areas, especially for heating at night. As the oxygen is exhausted, carbon monoxide is produced which is deadly. Charcoal can also be used for soil enhancement.
Charcoal itself doesn't contain much in the way of nutrients. However, just like humus in cooler climates, charcoal can hold nutrients and release them to plants. Very rich soils have been found along the Amazon river where Milena of people have charred their organic wastes and incorporated them into the soil. The soils are called Terra Preta. Humus breaks down in tropical temperatures charcoal does not. By using charcoal this way we strike three blows against carbon dioxide. First and most obvious, the carbon contained in the charcoal is sequestered for a very long time in the soil. Charcoal even in warm tropical soils is very refractory. Secondly, by holding nutrients that might otherwise wash out of the soil, it produces a nutrient store for tropical agriculture. Charcoal will have a market with farmers and hence the charcoal makers can sell it at a profit. During charcoal manufacture there are big chunks, idea for selling for fuel and lots of small to tiny charcoal which is ideal as a soil conditioner. Thirdly, If your fields are more productive because of nutrient retention, you don't need to cut down more jungle to maintain your production.

Farmers won't gain any nutrients by applying charcoal to their fields but if they practice good farm management by, for instance, returning manure from their cow sheds to their fields, the charcoal will hold the nutrients on the land. Without humus (only available in cool climates) or charcoal, the nutrients are washed down into the water table. This is especially so in high rainfall areas typical of jungle areas. In this way, charcoal in soils also helps to protect water quality.

The correct logging systems and subsequent handling of wood waste could turn the jungles in tropical parts of the world into valuable carbon sinks while displacing some fossil fuels and enriching tropical soils. Properly managed it could also preserve the most amazing environment on earth.