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Chapter 2   Constraints, Physical, Materialistic

                     and Energetic

 

 

2.1.  Constraints in Energy

 

     There is no exchange of material between the planet earth and its surrounding (the universe), except for those due to minor incidences such as space crafts ejected from the earth and comets/meteorites coming into.  That is, the earth is a closed system as far as material is concerned.  The only input to the earth comes in the form of energy, solar energy.  The energy is also created on and within the earth in the form of geothermal or tidal one.  The energy on the earth is constantly released to the universe in several forms of radiation energy.  As long as the input and output of energy between the earth and the surrounding (universe) is balanced, the surface temperature of the earth would be maintained more or less constant. 

     Humankind invented methods to obtain energy by combusting carbon containing material.  They have been using primarily plants (trees) as fuel for a long time, until a few centuries ago when the industrial revolution started to utilize mechanical devices dependent on fossil fuels.  The fossil fuels are obviously non-renewable, and will be exhausted sooner or later. 

     How do the organisms live? They live by eating energy (food).  More than half of all the living organisms on the earth can produce their own food from readily available carbon, oxygen and hydrogen sources (i.e., carbon dioxide and water) utilizing solar energy.  They are plants, both terrestrial and oceanic.  They produce carbohydrates (consisting only of carbon, oxygen and hydrogen), fat, proteins and other organic compounds.  They consume about half of what they produce when they sustain their lives without sunlight (at night), but leave the half intact.  This is what other organisms (animals, fungi and bacteria, etc.) eat for their sustenance.  Well, that is what organisms other than human do.  Humankind use plants for the purpose beyond sustenance.  Plants, being able to recreate themselves, are renewable resources for humankind. 

     Humankind consumes an enormous amount of energy in exceed of its necessity for sustenance.  That includes transportation, manufacturing, mechanical agriculture, adobe heating, etc.  The total amount of energy consumed by humankind as a whole was estimated to be 0.49 Zjoule(per year) in 2005.  (Zjoule=10²¹ joule). 

     The energy influx (from the Sun) on the entire surface of the earth is estimated to be 8.9 x 10¹⁶ joule/sec, and hence it will be 2800 Zjoule per year.  Hence the solar energy alone could amply provide all the energy mankind needs.  Wind power (driven ultimately by solar energy) available on the entire earth is estimated to be 2.3 Zjoule; theoretically wind power alone may be sufficient.  The problems associated with these freely available energy sources need to be technically overcome, but humankind should resort to these energies as far as feasible.

     In other words, we could be energy-sufficient, without using nonrenewable fossil fuel or nuclear power generation.  The latter is both economically and ecologically

 

 

 

2.2.  Materialistic Constraints 

 

2.2.1.  General Considerations-metals and others-

 

     Quantities of any material on the earth are limited, but a material would not be lost when it is used.  Even when petroleum is burned, the materials in petroleum only change chemical natures but would not be lost.  Petroleum is a type of compound called “hydrocarbon” made of carbon and hydrogen, and carbon and hydrogen turns to, respectively carbon dioxide and water upon combustion.  The quantities of carbon and hydrogen remain the same before and after combustion.  However, currently it is economically and technically nearly impossible to turn carbon dioxide and water back to petroleum.  In this sense petroleum is a non-renewable resource. 

     Another group of compounds called carbohydrates are made of carbon, hydrogen and oxygen; typical examples are glucose and sugar.  Mankind has not developed technically feasible methods to produce carbohydrates from carbon dioxide and water.   But plants produce carbohydrates from carbon dioxide and water, using the energy of sunlight; this is photosynthesis.  Hence, plants are a renewable resource.  And such a resource can be regarded as limitless as long as it is consumed at a rate less than its recovering rate.  Indeed, plants (and associated material) are the only truly renewable resources on the earth.

     Ethanol can be produced from carbohydrates (of plants), and be added to fossil fuel; this is the so-called biofuel and renewable.  However, plants that are food for human consumption should not be used for this purpose, as the food for human has already become insufficient for the human population (see section 3.1). 

     The total production of all vegetation (in terms of carbon) is estimated to be about 4.8 x 10¹³ kg/year.  Homo sapiens seems to consume about 1.2 x 10¹³ kg/year (in terms of carbon of plants).  This total includes food (direct), food (indirect: feed for cattle, fish, etc.), fiber, paper, material for construction, fuel and others.  That is, a single species, mankind, consumes as much as 25% of all the plant products.  We are only a species among several million species of living organisms on this earth.  The total mass of mankind (of 6.6 billion individuals) is about 1.6 x 10¹¹ kg.  The total mass of all the animals is about 2 x 10¹⁵ kg.  Hence, Homo sapiens occupies about 0.01 % of all animals, and yet, it consumes a disproportionately large portion 25 % of plants’ carbon.

     Human is considered to be an omnivorous animal, and eats animals as well as plants.  Domesticated animals may be considered to be a renewable resource, as they can be raised by human.  That is, the amount consumed can be replenished through human’s will.  On the other hands, most of fish cannot be replenished arbitrarily and hence can be exhausted if consumed at a rate higher than the natural renewal rate. For that matter, any renewable resource can be exhausted if consumed at higher rates than renewable.  

     That is, “renewable or not” depends on whether a material can be remade either naturally or artificially.  Some material, even if artificially reproducible, may not be renewable in the economic sense, if it is too expensive to do so.  On the other hands, we may not have to concern ourselves with such a material that is non-renewable but almost inexhaustible in the foreseeable future. 

     Rock minerals consisting of silicon, aluminum, magnesium and oxygen may be considered almost inexhaustible.  Hence the raw material for ceramics, cement and the like might be regarded renewable or ratherinexhaustible.  Environmental disruptions that might be caused by the process of producing these goods are another matter.  In other words, “renewable or not” is independent of whether use of such a material would cause or not environmental damages.

     Ores containing iron are among the most abundant on this earth, and hence iron can be regarded almost inexhaustible in the near future, though it will be depleted eventually.  Copper and other metals, particularly nickel, cobalt and molybdenum, are much less abundant than iron, and hence can become exhausted (at least in the economic sense) in the near future.  Metals are, however, relatively easily recoverable after use, and hence can be reused.  Hence, they can be used for long time if recycled efficiently.   If recycling and reuse is not done in an effective manner, they can be rapidly depleted. 

     A few elements are already nearly exhausted.  An example of phosphorus, which is not abundant on the earth, and ores of phosphorus readily extractable have been almost completely dug out.  Phosphorus is one of the three major ingredients of artificial fertilizers.  Nitrogen and potassium are the other major ingredients, and they are almost inexhaustible.  Nitrogen fertilizer, mostly in the form of ammonium compounds such as ammonium sulfate, is synthesized by factory in a large quantity, and considered to be inexhaustible.  Potassium can be obtained readily from ash of plants.  The geological quantities and their global cycling rates of many elements including metals and phosphorus have been estimated and depicted pictorially by this writer [1].

 

 

2.2.2. Water      

   

    Problems with water resource are quite different.  Water remains chemically as water even after man’s use.  It may be lost as it evaporates, but it returns to the surface of the earth as rain.  The total amount of water of the earth remains the same.  The problems are caused by not water itself, but what in water.  Another issue of water as a resource is people’s accessibility to it.

     Natural water may contain a number of substances including living organisms.  When water evaporates, the vapor is chemically pure water.  As rain drops form and come down to the surface of the earth, they come in contact with quite a few substances, and some of those substances would be incorporated into rain drops and rainwater as it travels on the surface of rocks and soil, then river and into a lake or ocean.  Some part of rain water also seep through rocks and soil into subterranean water reservoirs.  There is a large quantity of subterranean water trapped during geological processes.  The water in this segment may be replenished, but it takes a long time; hence it should be regarded “non-renewable”.

     Water in these natural settings contains a number of substances.  Water with little substances dissolved is called “fresh water”, which fits to drinking.  Drinking water is not pure water, but usually contain small amounts of such useful ingredient as calcium and others.  Water containing significant amounts of substances that coagulate soap and form scam is called “hard” water; those that does not contain significant amount of those substances are “soft”.  The water in today’s ocean is quite salty, containing high levels of sodium, potassium, magnesium and calcium, chloride, carbonate (and others).  Potassium and sodium (salts) would not form scam with soap, and so water with these salts alone is not “hard” water.

     Most of the water on the earth is in oceans, constituting 98%, 1.4 x 10 ²¹ kg, of all water, but it is unfit for human consumption.  The total amount of the terrestrial water including the subterranean is about 3.3 x 10¹⁹ kg.  The amounts of water are about 2.9 x 10¹⁹ in glaciers and snow, 4 x 10¹⁸ kg in the subterranean locations and 1.2 x 10¹² kg in lakes.  The annual rainfall amounts to about 1 x 10¹⁷ kg on the lands and 4 x 10¹⁷ kg on the oceans.  The total amount of water used by humankind in 2000 is estimated to be about 6.2 x10¹⁵ kg, out of which 80% was used for agriculture.  The renewable water (i.e., based on rain) was used in the amount of ca. 2.2 x 10¹⁵ kg, and the non-renewable water (i.e., subterranean) ca. 4 x 10¹⁵ kg.

 

 

2.2.3.   Food

 

     In today’s world, the amount of the natural food obtained by hunting and gathering is negligible as compared to those raised and planted by human.  Land, water and fertilizers (and seeds and other sources of plants) are necessary for agriculture.  The arable land is limited and most of it has been cultivated by now.  It has been reported that the arable land area had been increasing little by little by 1990 but stopped increasing; i.e., it has been capped at about 1.4 billion hectares.  Limitations in water availability is mentioned above.  The accessibility to water is a very complicated issue; it involves localization of rainfall, sharing of readily available water in river, lakes and the subterranean reservoirs, and hence is a quite political issue.

    The issue of fertilizers is mentioned earlier.  Synthetic nitrogen fertilizers are a renewable resources but their excessive use has had negative effects on the fertility of soil.  Farming that does not depend on the artificial fertilizers (and pesticides, etc.) is becoming more widespread, reducing somewhat the ecological impact of agriculture.  It is desirable but a question is whether such agriculture (organic farming) would be able to produce enough vegetation to feed adequately the ever-increasing human population.  How sufficient the food supply is today and would be in the near future will be discussed in chapter 3. 

 

 

 

2.3.    Physical Constraints including Climate Changes

 

     The global warming seems to be real and becoming more severe at an accelerated rate at the outset of 21^st century; it is likely that it will impact the human civilization.  During the whole history of the earth the surface temperature went up and down repeatedly.  In the last several million years, cold periods (ice age) and warm periods alternated several times.  Once the last ice age was over about 12-14,000 years ago, mankind began cultivating grains and others, and domesticating animals, i.e., human civilization began.  Even during the more recent history of the earth the temperature varied; the first cold period after the end of ice age is known as “Younger Dryas” (13,000-9,500 years ago), and impacted the human civilization at the time, almost wiping out the whole population in certain areas, but also brought out human ingenuity to device agriculture and animal husbandry.  In the more recent past there was a warm period during the medieval period, and a cold period (little ice age) during 17-19^th century.  That is, the earth’s surface temperature varies due to various natural causes, among which the activity on the Sun is one of the main factors.

     The level of CO₂ in the atmosphere is another factor; it is known that the surface temperature is quite high on planet Mercury because of the high CO₂ content in its atmosphere.  The widespread use of fossil fuel (coal=carbon and petroleum=hydro-carbon) since the industrial revolution (mid 18^th century) is causing the rise of CO₂ level in the earth’s atmosphere, particularly in the recent decades.  This is a fact, but whether this rise of CO₂ level is the major cause of the current global warming is controversial.  There are natural causes (such as variation of the Sun’s activity) and anthropological causes (such as emission of greenhouse gases); both contribute to the climate change.  What percentage of the global warming is due to the greenhouse gas emission is difficult to determine.  The natural causes cannot be changed by our effort, but our activities to emit green house gases can be regulated by our will.  Reduction of the use of fossil fuel as the energy source is desirable, in order to preserve it as a useful carbon source for future use, as well.

     Would we be able to avoid an undesirable climate change by reducing, say, by 50%, the fossil fuel use by 2050?  It cannot be predicted with a certainty.  How about a reduction by 80-90 %?  Even if we may not be able to stop the current trend of global warming, at least we would have attained our desirable result, i.e., use of renewable energy source as the alternative.  This is a necessary condition for sustainability.

     The global warming would give serious impacts on many aspects of the human civilization.  Some areas may submerge under seawater, and living organisms, both animals and plants, may become extinct as they will have a difficulty to adjust to the new climate.  The ecosystem as a whole will eventually adjust to the new environment; in the process some organisms will disappear and new organisms may emerge.  Homo sapiens, as a biological species, will be able to readjust to the new emerging environment but the conditions necessary to maintain its current civilization may be lost.  This effect of the climate change will be added to the already-deteriorating environment caused by the human activities.  It is hoped that such a profound change as described above may not materialize.

     Many cultures tend to consider that the human is the center of the universe and the nature should behave for the benefits of mankind.  If it did not, human is entitled to change the nature to suit to the human interest; i.e., anthropocentrism. The Nature of the earth and the universe, however, does not necessarily operate for the human’s interest.  It behaves according to the natural laws.  Natural laws cause, for example, earthquake, changes in the Sun’s activities, significant amount of cosmic debris thrown on the earth, climate change associated with the plate tectonic change, etc.  Human is powerless for these natural changes.    A well-known example is extinction of dinosaurs caused by the impact of a large meteorite about 65 million years ago, though this took place long before the mergence of Homo sapiens.  Let us assume that there will be no significant natural events including the current climate change to cause the extinction of Homo sapiens in the near future.

     The areas of arable land on the earth may not significantly be changed any more; this is one of the basic physical constraints.  Some people may dream that the humankind may be able to expand its abode to the outside of this planet so that such a constraint can be removed. It is hardly possible, though, for energetic, materialistic and economic reasons.

     The basic constraints are the physical (natural) laws; no science or technology can override such a law.  For example, no permanent operator is possible, without added energy. No element can be artificially converted to another element.  Well, theoretically it is possible, though not arbitrarily; but technically almost impossible. During the medieval time, many charlatans claimed that they tried and succeeded in converting a base metal, lead, into gold; they are called “alchemists”.  Today, it is known that an element (unstable isotope of the element) change spontaneously into another element; usually it is accompanied by radiation (radioactive decay).  But an element, iron, cannot be arbitrarily turned into another element, gold for example.  This is the constraint at the level of elements.

     Chemical compounds can be converted into another compound; this is technically feasible and the basis of living organisms and chemical industry.  Yet, there is a constraint, not technical but theoretical.  For example, one can convert carbohydrates (of corn, e.g.) into alcohol; i.e., biofuel.  But you cannot convert water to alcohol, though the Christian Bible tells us that Jesus did indeed conduct such a miracle.  Carbohydrates consist of carbon, hydrogen and oxygen, and alcohol consists of the same set of elements; hence it is possible to convert one into another.  But water is made of only hydrogen and oxygen, and hence alcohol cannot be created from water alone.

 

Reference

 
[1] Ochiai, Eiichiro, Biogeochemical Cycling of Macronutrients, Encyclopedia of Life Support System, 1.1.8.2., (2004, UNESCO); Ochiai, Eiichiro, Biogeochemical Cycling of Micronutrients and Other elements, Encyclopedia of Life Support System, 1.1.8.3., (2004, UNESCO)

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