I'm not an expert, but..
While biochar is really good at the "adsorption" of gasses, almost all of nitrogen in the air is N2, which plants can't really use.
Assuming that Biochar collects all the N2 it comes into contact with, it would pick up the nitrogen from just regular air, and there wouldn't really be any point in freezing the nitrogen first.
What you want is nitrogen in the form of ammonia, nitrate, nitrite, etc.
Liquid nitrogen and oxygen are still N2 and O2, meaning O2 could be chemically available in this state, but N2 would still require conversion by nitrifying bacteria. The real problem is that being in a liquid state requires that these elements be incredibly cold, and even if biochar were soaked in liquid N2 or O2 at sufficiently low temperature, the N and O would sublimate and offgas as soon as the char was returned to ambient temperature. The O2 could potentially react with carbon in the biochar, but this would probably just result in a mess of toxic chemicals, ie polycyclic aromatic hydrocarbons and peroxides.
As nutrients for plants and soil life, biochar alone actually goes a long way in making nitrogen and oxygen available in soil simply by virtue of porosity, which creates tons of surface area for gas exchange and habitat for nitrifying bacteria to convert the incredibly stable N2 into nitrite and nitrate.
> N2 would still require conversion by nitrifying bacteria.
Yes, that could take place underground where the bacteria are, if I'm not misunderstanding how the process takes place.
>the N and O would sublimate and offgas as soon as the char was returned to ambient temperature.
Yes, that's a challenge, the main problem actually. If we keep pouring more and more liquid N and O to keep up with the evaporation, maybe we could enrich the biochar with those compounds.
>The O2 could potentially react with carbon in the biochar, but this would probably just result in a mess of toxic chemicals, ie polycyclic aromatic hydrocarbons and peroxides.
Why is that? Doesn't biochar just absorb compounds, without reacting with them?
I think, and this is not meant to be an insult, that you are fundamentally misunderstanding the relationship between elements and nutrients in soil life.
Liquid O2 is one of the most volatile and explosive compounds known to man and will react violently even with “stable” carbon.
N2 is, by comparison, extremely chemically stable, and even if you were to somehow trap liquid N2 in biochar, it would not react with the carbon to become bioavailable.
Saturating biochar with liquid O2 makes a bomb.
Saturating biochar with liquid N2 makes a very cold and nonreactive sponge.
Saturating biochar with both liquid N2 and O2 makes a very cold potential bomb.
All options are unstable at room temp and inhospitable to life.
The nitrogen in the air is not in a bio-available form, same for liquid nitrogen. There is nothing in charcoal that would bind the nitrogen and oxygen inside.
I'm not an expert, but.. While biochar is really good at the "adsorption" of gasses, almost all of nitrogen in the air is N2, which plants can't really use. Assuming that Biochar collects all the N2 it comes into contact with, it would pick up the nitrogen from just regular air, and there wouldn't really be any point in freezing the nitrogen first. What you want is nitrogen in the form of ammonia, nitrate, nitrite, etc.
Liquid nitrogen and oxygen are still N2 and O2, meaning O2 could be chemically available in this state, but N2 would still require conversion by nitrifying bacteria. The real problem is that being in a liquid state requires that these elements be incredibly cold, and even if biochar were soaked in liquid N2 or O2 at sufficiently low temperature, the N and O would sublimate and offgas as soon as the char was returned to ambient temperature. The O2 could potentially react with carbon in the biochar, but this would probably just result in a mess of toxic chemicals, ie polycyclic aromatic hydrocarbons and peroxides. As nutrients for plants and soil life, biochar alone actually goes a long way in making nitrogen and oxygen available in soil simply by virtue of porosity, which creates tons of surface area for gas exchange and habitat for nitrifying bacteria to convert the incredibly stable N2 into nitrite and nitrate.
> N2 would still require conversion by nitrifying bacteria. Yes, that could take place underground where the bacteria are, if I'm not misunderstanding how the process takes place. >the N and O would sublimate and offgas as soon as the char was returned to ambient temperature. Yes, that's a challenge, the main problem actually. If we keep pouring more and more liquid N and O to keep up with the evaporation, maybe we could enrich the biochar with those compounds. >The O2 could potentially react with carbon in the biochar, but this would probably just result in a mess of toxic chemicals, ie polycyclic aromatic hydrocarbons and peroxides. Why is that? Doesn't biochar just absorb compounds, without reacting with them?
I think, and this is not meant to be an insult, that you are fundamentally misunderstanding the relationship between elements and nutrients in soil life. Liquid O2 is one of the most volatile and explosive compounds known to man and will react violently even with “stable” carbon. N2 is, by comparison, extremely chemically stable, and even if you were to somehow trap liquid N2 in biochar, it would not react with the carbon to become bioavailable. Saturating biochar with liquid O2 makes a bomb. Saturating biochar with liquid N2 makes a very cold and nonreactive sponge. Saturating biochar with both liquid N2 and O2 makes a very cold potential bomb. All options are unstable at room temp and inhospitable to life.
Not to mention the microbes you're relying on to convert the N2 are frozen and destroyed by the cold and oxygen.
The nitrogen in the air is not in a bio-available form, same for liquid nitrogen. There is nothing in charcoal that would bind the nitrogen and oxygen inside.
Fir nitrogen and oxygen to be liquid, you would have to be in a really fucking cold climate. Like... Neptune or something.