Perhaps it would be useful to unpack some of the claims made in the earlier post More Snakes

The real issue is energy. Birkland-Eyde used hydro-electric power from remote Norwegian hydro facilities. They had plenty of electricity but no grid to get the power to population centers. Using it on site to make industrial chemicals which could be more easily shipped to town was smart. We have other such situations. Geothermal energy in Iceland is an example. They can make plenty of electricity but can't ship it to customers. They also have plenty of water and air so they could make nitrates if the price is right. In short, the energy issue and the nitrate issue are linked, as environmentalists claim in their muddled way, but fossil fuels are irrelevant except in an economic sense. A dearth of cheap and abundant fossil methane will not result in a decline in agricultural production, it will result in yet another change in industrial technologies for nitrate production.

The Birkland-Eyde process is also called the arc process. In simple terms, it's lightning in a bottle. About 15% of the earth's annual nitrate supply is generated in this way by real lightning. When a strong electric arc passes through air, which has nitrogen gas (N2) and oxygen gas (O2), nitric oxide (NO) is synthesized. It was last used commercially in the 1940s since it took a lot of power to make the electric arc, and fossil fuels were cheap. There is some renewed interest as the fossil era comes to an end, and there has been some recent work to develop more efficient methods, better arc engineering systems. We've learned a great deal since 1940. There has also been a lot of work on developing better catalysts, which also lower power requirements. I'm intrigued by some of the recent advances using nano-particles that seem to be very much more efficient catalysts.

But it isn't only the arc process that can be used to satisfy our nitrogen needs without fossil fuels. We can also continue to use the Haber process of ammonia synthesis, but get the hydrogen needed from water rather than methane. Rather than steam reforming methane to get free hydrogen, use electrolysis to free the hydrogen from water.

The electricity needed for either process can come from any source. Birkland-Eyde used hydro-electric power from remote Norwegian hydro facilities. I mentioned geothermal energy sources in Iceland. Remote wind and solar farms far from the power grid, even far out to sea, could do the same. Decoupling some power generation from the distribution system solves some problems, such as their intermittent nature, since their product is the synthesized chemicals rather than the power itself. The chemicals in effect store energy in more easily transportable form.

Ammonia is an intriguing way to store electricity. Or, if you prefer, it's an intriguing way to store hydrogen. Seventy-five percent of ammonia (NH3) is hydrogen. The idea of hydrogen fuels often stumbles on the difficulty of storing and transporting it. Gases are harder to transport. That's what the LNG (liquid natural gas) efforts are all about. Cooling and compressing gases to liquid state allows them to be transported like other liquids, such as oil. It's more expensive and requires special facilities at both ends of the trip, and harbors are understandably concerned about having them near other shipping activities.

Conversion of hydrogen to ammonia, which is also a gas, has some of the same issues, but less so since it doesn't need to be as cold or compressed to be liquid. The technology is commonplace. There's also some other interesting ammonia attributes. It is fuel for alkaline fuel cells, so it could be both a liquid fuel for transportation and fertilizer. It has many industrial uses too. It's used as catalyst, neutralizing agent or reactant in rubber, plastic and textile industry, ammonia-soda (Solvay) process, metallurgy etc. One gram of ammonia absorbs approximately 1.4 kJ of heat when vaporizing, therefore it is also frequently used as cooling agent in air-conditioning systems, ice skating rinks and refrigeration (especially in bigger ships, therefore many harbors are equipped with ammonia fueling stations).

Due to that wide use, the infrastructure as well as standards for the use of ammonia are well established. It is either transported in cylinders at -33 deg.C (~ -27 deg.F) at ambient pressure or at approx. 8 bar (120 psi) at ambient temperature. In addition, pipelines for ammonia exist all around the world.

Ammonia is flammable within a small range when mixed with air (15 to 34 vol.%). In contrast to methanol, ammonia is not an environmental poison, because it serves as nutrient source for plants and bacteria. It is lighter than air end evaporates fast. As being part of the natural nitrogen cycle, it is recycled naturally in the environment and therefore does not last long there. Once released to air, it is rapidly removed by rain or snow, or by reaction with other chemicals in the air, especially acids. To a certain extent ammonia is toxic. However, the lethal amount is more than one thousand times higher than the limit of perception . . . it stinks.

If used as a fuel for transportation, as mentioned above, it has many advantages over more flammable and explosive fuels which are environmental poisons. Accidents that spilled fuel, a common enough event on roads all over the world, would be less harmful and dangerous to all involved.

Alkaline fuel cells are being developed, but they aren't mature yet. Still, ammonia seems to me have a lot to recommend it as a liquid fuel replacement for fossil liquids for many applications, and it so useful in other ways that it will always be around. It's already the second most common chemical produced in the world.

As we can see, fertilizer is only one of its uses. The idea that the end of the fossil era will mean the end of fertilizer is pretty silly. We can make it in many ways, and need it for many things. As methane becomes more expensive and less available I suspect we will get ever better at making ammonia. Great work is being done with catalysts, for example, but we are also getting better at engineering production facilities, better at handling high temperatures and great pressures.

One of the more attractive ideas is the production of ammonia as a coproduct of producing biochar (aka agrichar).

A typical process starts with the plant material undergoing pyrolysis. It is heated in a closed chamber, in the absence of oxygen, breaking down the complex organic molecules into simpler compounds that are released as gases. . .

Under the right conditions, the pyrolysis produces hydrogen, which can be used in fuel cells, or used to create ethanol and biodiesel, two valuable alternative fuels. To get an idea of the energy potential of such processes, if (and it is a big "if") the waste from all world's agricultural processes were used in BioChar processes, the alternative fuels produced would be equivalent to the world's total consumption of diesel oil.

Some of the hydrogen is also fed into the Haber-Bosch Process which combines hydrogen with nitrogen from the atmosphere to produce ammonia. The ammonia is then combined with carbon dioxide (from flue gases or from the atmosphere) to produce ammonium bicarbonate, a widely used low-tech fertilizer, which is absorbed into the charcoal. (Note this capture of carbon dioxide is in addition to that already achieved by the plants). The activated charcoal is a good host for beneficial microbes such as mycorrhizal fungi adding to the nutritional value.

The conversion of ammonia to ammonium bicarbonate isn't required for all applications. There are a bewildering variety of possibilities for the use of the hydrogen and other gases produced by pyrolysis. And, you get biochar!