In April 2013 an explosion happened in a fertilizer production plant in Texas which had huge impact. It looks like it was ammonium nitrate which exploded. This is used for producing fertilizer. But it is also quite explosive and can be used in pure form or mixed with other substances as explosive. The worst known accident with ammonium nitrate happened in 1921 in the Oppau-plant of BASF in Germany.
For feeding the current earth population the nitrogen holding compounds that are generated by natural processes and become available to the plants are not sufficient. Therefore it is necessary to rely at least for part of the agriculture on chemical fertilizers, implying the need of production, transport and storage of these substances, of which ammonium nitrate is an important example. So it should be better to make the plant working with ammonium nitrate safer than to refrain from working with this substance.
This is an English translation of the German article Aluminiumrecycling.
Why is aluminum recycling so important?
aluminum (or aluminium) is occurring on the earth surface in chemically bound forms and it is the third most frequent element in the crust of the earth, after oxygen and silicon. So other than the lanthanides it is not really rare. Aluminum ore can be found in large quantities and they are relatively cheap. Many minerals could be used, but bauxite is what is really used for obtaining metallic aluminum. The process of obtaining aluminum from bauxite is really expensive. Aluminum is very reactive and a lot of Energy is needed to gain it. Purely chemical and thermal processes do not work or are not competitive. Current aluminum production work with Electrolysis. Using electrolysis with an aluminum salt dissolved in water would yield hydrogen, so it is necessary to do it with molten salt. First Bauxite contains chemical compounds and salts of aluminum, silicon and iron, which are separated and split to obtain aluminum hydroxide, which is heated to gain aluminum oxide. This is molten and put into the oven. Which contains a cathode of graphite on the ground, near which liquid aluminum is collected. The Anode consists also of graphite and oxygen is gained there, which slowly burns the anode, so it has to be replaced frequently. The heat of this process is sufficient to keep the aluminum oxide liquid, once the process has been started. So the production of aluminum from bauxite uses much higher magnitudes of the energy then the process of aluminum recycling. Even the burning of aluminum that is thrown into the regular garbage does not even nearly compensate for the energy usage in the aluminum plant, considering the whole process and the fact that thermal power plants have a limited efficiency due to thermodynamic principles.
In the old days the problem could be solved by simply transporting bauxite to countries like Norway and Iceland, where water power is available in large quantities. These days powerful electrical power transmissions exist from Norway to Central Europe. So Norway can now sell electricity to other parts of Europe and contribute to reducing the usage of German coal power plants. Electricity in Norway has become more expensive and Norwegian aluminum plants have a harder time then some years ago.
In short, recycling of aluminum is a good thing for the environment. So I recommend that you think about it and try to take it serious, if there is a way to deliver aluminum separate from your garbage.
For a change I am writing this about a non-railroad issue. It is the English translation of the German article Entwässerung mit Osmose.
Osmosis is described quite well in Wikipedia. In short, mixing of salt solutions with different concentrations sets free some energy. For example when mixing fresh water with sea water, this energy is equivalent to a falling height of 270 m (not 2.8!!!). By using a semi-permeable membrane between the two salt solutions, water molecules will diffuse through the membrane until the sea water side is about 270 m higher than the fresh water side, if dilution of sea water during this process is neglected.
About 30 years ago I have heard about the idea of building osmotic power plants at the mouths of rivers to the sea. They seem to have built a prototype of this recently in Norway and intend to produce 10% of the electricity demand of Norway by osmotic power. This indicates that the concept might become mature soon, even though few countries have as much precipation per inhabitant as Norway, so the achievable percentage will be much lower in most countries.
Another interesting use case of this technology could be draining land areas that are below sea level, like part of the Netherlands or New Orleans. I am sure that there are more of these. Today draining is mostly done by using electric pumps, which consume quite a significant amount of energy. As long as the height difference against the lower tide is less than 270 meters, draining could actually be achieved by using some kind of osmotic pumps without using electricity. Since the height difference is less, it would even be possible to produce some surplus electricity.
I expect that we will see this implemented in areas where applicable within the next ten years, since the osmotic power plant shows that the technology needed for this is becoming mature.