Natural resources are the basis for life itself. Every animal has an inherent need for such resources. We refer here to real natural resources and not to industrial products such as electricity and steel. Natural resources are what nature produces, with or without human intervention. The sun, wind and wild plants exist without human involvement. Agriculture, fishing and ores are products of Nature that human action turns into resources.
The concept of accessibility is crucial, and will be referred to often. It isn’t enough to know that a resource exists, it also has to be accessible. This concept is a broad one, applicable to any type of resource. It can sometimes be confused with the notion of efficiency. For example, the accessibility of copper in a mine is contingent on the sophistication of the machines employed. The accessibility of deep offshore oil is contingent on the sophistication of the infrastructures installed. We will apply the same concept to agriculture, so that the efficiency of farm machinery and fertilizers will be treated in terms of accessibility.
Natural resources can be classified in three groups
and three types
Finite natural resources are characterized by the notion of depletion. When one has a stock of a product, if the stock is replenished faster than it is utilized, a surplus is created. If the stock is used up faster than it is renewed, it is depleted. For finite natural resources, the renewal of the stock means the discovery of new deposits.
Since they are finite, the day will come when discoveries gradually decrease and tend toward zero. The point where the stock consumption curve intersects the discovery curve marks the transition from surplus to depletion (see the oil curves).
Table of the natural resources
These are the sun, the wind and gravity, and are often inaccurately referred to as renewable energies.
Some of the sun’s mass dissipates as radiation is produced. Some of the radiation transmits heat, which can be easily captured through passive heat absorption. Water can be easily heated in this way, and the heat thus stored can be released later.
Other types of radiation, equally easy to capture, cause plants to grow. These can be consumed or harvested for other uses, and they grow again.
The use of certain types of radiation to generate electricity with photovoltaic cells cannot be classed as a natural resource, since the cells must be built and are the result of an industrial process. The only product is electricity, a form of energy whose transport and storage demand other types of energy and raw materials. In short, if humans did not capture solar energy earlier except on their skins, it is because they did not possess the highly sophisticated means that are required.
Wind is produced by the movement of air masses as a function of their exposure to the sun’s rays. The moving air mass generates a force that is proportional to the square of its speed. One of man’s earliest machines was the wind generator, designed to recover this force by converting the rectilinear movement of the wind into a rotary movement. The earliest ones had wooden gearing designed to rotate two stones against each other in order to crush grain. Today, we use wind energy to generate electricity. Here again, manufacturing and maintenancing a wind generator requires an industrial process, and the end product is electricity.
Gravity has been used from time immemorial to transport water through canal systems; in treadwheel cranes (“squirrel cages”) to lift loads; or in counterweights of all types, the latest being as a component of clocks. Gravity is used today in hydroelectric dams for generating electricity. Here again, the force generated by the displacement of a mass - in this case, water instead of air - is recovered. The only difference with wind power is that water is about 1 000 times denser than air, the force generated being directly proportional to the mass of the fluid.
These are primarily fossil fuels, produced by the decomposition of living organisms, and which are burned to generate heat and light. Other than fossil fuels, there is uranium, for which the main civil use is (once again) to generate electricity, although it also has a number of applications in propulsion systems for submarines and icebreakers, as well as in weapons.
Energy must be expended to exploit a natural energy resource. The exploitation limit of a natural energy resource occurs when the energy return on the energy invested (EROEI) approaches 1.0. Here are a number of approximate values of the energy ratio:
The above figures are approximate, and the values themselves are not very important. What counts is the significant drop in the values over the last 50 years.
These resources have been around for a long time, but were relatively inaccessible. Although it was used in Antiquity for lighting and for caulking boats, coal was not extensively mined before the pre-industrial era. After coal, came oil and gas. Here is the crux of the system: the accessibility of natural resources has developed exponentially because of the considerable energy contained in fossil fuels.
Until the 17th century, iron oxides were reduced with charcoal (see renewable resources below). The use of finite resources like coal and then coke allowed the industrial production of high-grade steel, and the steel was then used to construct the machines that replaced tools, marking the birth of the industrial era. The industrial era clearly has its roots in the exploitation of natural fossil energy resources, which exist in finite amounts.
Unlike the earlier fossil fuel resources, produced by the decomposition of living organisms, uranium is a metal present in the earth’s crust. Exploiting it requires a complicated industrial process, whose end purpose, once again, is to generate electricity (but also to make atom bombs).
These consist of different varieties of biomass, but wood is the principal one. It is the only natural resource that has been available to man ever since he learned to use fire. Fire from wood marks the major difference between man and animal. This is the natural resource on which we need to lavish our care. Many civilizations have disappeared because they failed to manage this bounty. In any case, it is all that will be left to us for heating, apart from the sun on our skin, once finite resources have all disappeared.
Since the resources described above are called energy resources, we can divide them into three classes as a function of the amount of energy they generate:
We can consider that, while the extraction of finite resources is certainly an industrial process, the product exploited has a natural energy content, whereas electric power generation is a human invention.
For our purposes, energy equals a mass accelerated over a distance, so the above values are expressed in terms of mass. For solar photovoltaic and wind energy, the mean annual values for France are given, and what really counts is the kilo oil equivalent.
Hydrogen has the highest energy content of all. The only problem is that although it is a natural element, it combines with oxygen to form water; separating the two elements is difficult and demands a huge energy input. A complicated industrial process is required to produce, store and use hydrogen as fuel. Therefore, it cannot be included with the natural resources because it is not directly accessible.
In terms of energy content, the fossil fuels come next. These are coal, oil and gas. While coal can be used directly, it has been “dethroned” by oil, which contains more energy and is easier to produce (excluding the use of coal in steel production, of course). Natural gas exploitation is more recent. This high-energy resource is more difficult to store and transport than oil.
After fossil fuels comes the natural renewable energy resource par excellence, wood, which contains half as much energy as coal.
Solar and wind energy are next. For comparison, we use the quantity of energy produced per square meter of solar collector or wind generator over a one-year period. Since solar thermal is roughly four times more efficient than solar photovoltaic, we can state that a square meter of solar thermal for one year is approximately equivalent to 32 kg of oil.
For uranium, the energy recovered on energy invested (EROEI) ratio is about 4. Since the energy invested is mainly fossil fuel (mining, yellow cake production, construction of nuclear power plants, electricity distribution), we can consider that uranium is an oil energy multiplier.
Last comes gravity via hydropower. Here, it is difficult to use a reference unit. In France, hydropower generation is equivalent to about one-tenth of nuclear electricity generation, hence it produces 2.5 times less energy than oil. It also results from an industrial process that produces only electricity.
If the important yardstick is the exploitability of natural energy resources, the unchallenged winner is oil.
If the yardstick is the absence of an industrial process, it is definitely wood.
If the yardstick is energy efficiency, solar and wind energy clearly come last.
As natural energy resources, we have the sun, fossil fuels and wood. The sun is not a very powerful factor unless you add an industrial process, and storing its heat is a problem. The energy capacity of fossil fuels is easily exploitable, but they are present only in finite quantities, and their end is in sight. This leaves only wood, a renewable resource, to heat our food tomorrow, unless humans burn it faster than it can grow.
Raw materials enable humans to manufacture tools, objects, clothing, housing. With the energy of fossil fuels, they can be used to build and operate machines that greatly increase the accessibility of natural resources.
Soil and stones are raw materials that are directly accessible. They can be considered as an inexhaustible resource because, even assuming a local shortage of clay or sand, there is enough to go around on a global scale. There will always be rocks to tumble down the mountains, enabling us to build shelters, and erosion will continue to supply clay for a long time to make a few pots.
The two major groups of finite raw-material resources are metal ores and fossil fuels. These can be used to produce synthetic compounds.
Some metals are found in nature in their natural state, e.g. copper, tin, gold and silver; others, like iron, are in oxide form. It is only normal that humans discovered and used the “natural” metals before the oxides, which require far more sophisticated treatment.
Iron, for example, is only present in nature in ferrous and ferric oxide form; in other words, the iron atom is bound to oxygen atoms. To extract the iron atoms, the ore must be heated with carbon atoms, which attract the oxygen atoms to form carbon dioxide, leaving the iron atoms. This process, which can be qualified as industrial long before the so-called industrial era, was carried out for thousands of years using charcoal, a skill that has virtually disappeared today.
Humans discovered all the exotic metals with names ending in -ium much later. The extraction of these is even more sophisticated than that of iron, requiring the use of complex products and processes.
The metal produced by mining metal ores is recyclable. Roughly speaking, various bits and pieces are placed in a kettle and melted down, other products are added, and the result is a “new” metal. This is no longer a natural resource, but the result of an energy-consuming industrial process.
Plants and animals are renewable resources. Plants supply the fibers required for weaving and for building materials. Animals supply leather, fur, fats and tendons (to produce glue). Unless these are used up faster than nature can replenish them, such resources can be renewed and maintained.
Salt and water are inexhaustible products. Drinking water shortages are not a global problem that affects the entire planet, but a local problem associated with urban sprawl and the concentrated pollution that this engenders. There will always be drinking water as long as it rains, and as long the rain penetrates into the ground. If it ever stops raining, life will very likely come to an end.
The other nutritional natural resources are renewable, just like raw materials, plants and animals. The same conclusion applies: these resources must not be consumed faster than they are replenished.