петък, 17 май 2013 г.

Gail Tverberg: Reaching Limits in a Finite World

Светът е краен и трябва да го разберем в един момент. Препечатвам поста на Gail Tverberg:

We don’t usually think about it, but we live in a finite world. In other words, in theory we can count precisely how many atoms make up the earth. We can also theoretically count how many humans live on earth and how many of any other species live on earth at a particular point in time.
At some point, in a finite world, we start reaching limits. There are now about seven billion people in the world. We could probably add some more, but how many? What is it that limits our ability to add more people to the world we live in today?
Too Much Population “Morphs” to an Energy and Financial Limit
One obvious guess as to what might limit world population is the amount of fresh water that is available. If we don’t have enough fresh water available, we can’t continue to expand population.
The amount of fresh water that is available can be changed, though, by adding desalination plants. There are many other ways of getting fresh water. To give an extreme example, the amount of fresh water available could be increased by melting ice in Antarctica and importing it by ship. Either of these solutions would require energy in an appropriate form—either to run the desalination plant, or to melt the ice and transport it by ship. Thus the fresh water shortage, at least for the foreseeable future, can be worked around if there is sufficient energy available of the right type.
The other not-so-minor detail is that the cost of desalination or of importing melted ice from Antarctica needs to be inexpensive enough that users of fresh water can afford it. In order for this to be the case, the cost of the appropriate type of energy must be extremely inexpensive.
We can think of other kinds of limits to population growth as well. For example, carbon dioxide limits. In theory, there are ways around carbon dioxide limits. For example, assuming current research projects are successful, we can build carbon capture and storage facilities and change our electricity generating plants so that the carbon dioxide that is emitted can be captured and stored underground.
Here, too, there are energy limits and cost limits. Carbon has a molecular weight of 12, while carbon dioxide has a molecular weight of 44. Because of this, if we create carbon dioxide from coal, the carbon dioxide we produce is much heavier and bulkier than the coal that we burned to make the electricity. It will take a lot of energy to store this gas underground in a suitable place. Thus, we have another problem that can be handled, if there is enough cheap energy of the right type available.
Almost any kind of obstacle to increased human population that we can think of has an energy-based work-around. Will people be so crowded that disease transmission will be a problem?  There are workarounds: better water treatment plants and sewer treatment plants, especially in the poorer parts of the world; more immunizations; more and better hospitals; antibiotics for all those who need them. These solutions also require energy, as well as other inputs (which indirectly require energy as well). The difficulty is making them affordable for the people who need them.
If the problem is not enough food, perhaps because of degraded soil, there are energy-based workarounds as well. Food can be imported from a distance. More fertilizers and soil amendments (either made using fossil fuels, or transported using fossil fuels) may be used. Irrigation, which uses either diesel fuel or electricity to pump water may be used to pump water to too dry areas, to increase food production per acre. In some cases, artificial soil can be created, and plants grown in a green house—again requiring much energy.  The issue again gets to be whether consumers can afford the food produced using this more energy-intensive procedure. /more/

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