Ok.. I have to say something... must comment..
Hot composting, cold composting are what is known as aerobic forms of decomposition. Basically, it means composting in an oxygenated system.
Anaerobic composting/ decay/ altering of matter is basically the breakdown of materials in an oxygen deprived system. Now I had to say "altering of matter" because it isn't quite composting.
One with oxygen and one without... but are they different? Yes, and as with everything, there are pros and cons to every option.
Now this is where I encounter the wrinkle.. it is the same old wrinkle that pops up every time someone tries to shortcut the system without usually having a clue about what they are doing in the first place. That sounded crabby.. but just because the pace of life has reached break neck speeds, does not mean that mother nature is on the same time schedule.
I've gone through a bit of cold composting and hot composting... right now I want to explain a little of anaerobic decay. Primarily because I seem to be encountering a fair bit of it in a trend, yet quite a few things are glossed over or failed to be mentioned in it's entirety.
What I have been seeing is layers of green matter, or even vegetative matter run through a blender and then dumped into a bucket to rot in water. One such related method has been brand named Bokashi (which this method has a bit more study on.. but even more commercial spin attached to the concept). Anaerobic type of decomposition commonly occurs in bogs, swamps, and stagnant bodies of water.
Composting in an anaerobic situation utilizes a different set of microbes, in particular Methanogens. They feed on nitrogen, phosphorus and trace elements.. they expel methane and as well hydrogen sulfide byproducts. (Methane, is odorless.. a potent greenhouse gas many times more damaging than carbon dioxide.. and Hydrogen sulfide, which is actually a poisonous gas and smells like rotten eggs.. both of which are also flammable.) As well a little carbon in the decaying matter is released as carbon dioxide. This process reduces nitrogen into the forms of ammonia (& nitrous oxide) and organic acids.
This form of processing does in fact release a few bound up nutrients from the matter relatively soon. However, unless it is processed long enough.. it isn't going to kill off pathogens.
In fact the beginning stages of this decay produce a fair amount of phytotoxins. (Phytotoxin byproducts is a naturally occurring part of the composting process. Leachate is another term for this when you have the stagnant liquids drain from vermicomposting bins or landfills.) The reason it needs to be diluted is because it still needs to go through a final step of aerobic decomposition which is done actually very quickly. To use it at full strength, you would kill your plants. Full strength it acts as an herbicide (due to auxin levels), a germination inhibitor.
Anaerobic composting process created an acidic environment. It is in essence, fermenting. This is not a compost tea. Plants and their root system are in an aerobic state in gardens.
Yes.. if dilute you do see some benefits to this "fertilizer" as it does contain trace elements that are usable to plants. However I have yet to encounter very many that are aware that this process takes months and oxygen exposure should be regulated to be under 30% saturation levels. It also needs several days after this process to oxidize. In the case of Bokashi, the medium is buried. There is a reason for it.. to fully saturate it with aerobic microbes to finish the materials.
Sorry if this is scattered.. I am writing this in a hurry. I just had to put that out there in hopes that someone can utilize this information before they wonder how and why their plants died off.
This form of "composting" is probably the least eco-friendly option.