zondag 13 september 2015

Rich in oxygen and oxygen poor.

Adapting to circumstances. Part 2.


Think of a candle burning. You put a bell jar over it and the flame will go out from lack of oxygen. When you lift up the bell the flame will flare. The oxygen is aspirated into the bell jar. This happens fairly quickly. Then, when the heat can escape to the environment, fresh air will be sucked in regularly.
Nature wants that there will always be a balance in the composition of air. So a lack of oxygen draws fresh oxygen in order to reestablish balance. Every possible opening, what ever small will serve this purpose.

Compare this with a pile of hay, that we want to compost...
In the stems of the hay is air. In the pile of hay is air.

We make the dry hay wet, by immersing it. The counter pressure of the air is large. We keep it under water level with a heavy weight. The air in the hay has to come out.
Then we let it drip. The air in the pile of wet hay is made good either aspirated.
The bacteria in the grafting fluid are the starter of the heating, which will soon follow. The moisture and the oxygen are the circumstance in which it takes place. In addition, the outside temperature plays a role.
It is the psychrophilic bacteria, which begins heating. Later, after about 30ºC, the mesophilic and thermotrophic bacteria take over and after a 50ºC the thermophilic.

If now we would aerate the hay, by turning it (time after time), the thermophilic groups of bacteria will bring the process to excessive heat, about 80ºC. Also temperatures of about 95ºC are measured. This until the organic matter, for the most part, is volatilized in CO2. And most of the organic matter is reduced (burned up), so the temperature can drop.

We are striving to close the pile of from oxygen when the thermotrophic bacteria have done their job. This will succeed only partially. But we manage to create a low-oxygen environment in which the hay goes on digesting without 'burning up' in CO2. So, with a minimal amount of oxygen. A proper digestion of the hay is not dependent on excessive heat. It can do with lower temperatures.

This bacterial composting process we call a biochemical process. At lower temperatures it indicates also a partial chemical process (where there is no bacterium involved), in the sense of 'weathering'. Hay gets 'tired', due to all the influences it has to endure. And this is what we want to achieve. Hay must become 'tired' so that it disintegrates into small usable fragments, making it into compost. In our post Microbiology for Dummies we explain this further.

A crucial conclusion.

Meanwhile, for us it is proven that a complete oxygen-free environment (an-aerobic) can not be created, for the air in the hay will always attract oxygen, because of the balance that air wants to achieve. Each option, which it can get, though still so small, air will use.
Hay in a big bag is fully exposed to its environment. We wrap up the big bags very well and yet...
In the description of the method for the production of 'Noble Manure' (a description we followed through out the years) of the German agricultural engineer mr. H. Krantz (in 1939 by dr. Ir. F.C.Gerretsen), we read the opposite. Here is referred to an an-aerobic conservation of manure indeed, by tamping the dung pile. A dung pile which is inside wooden partitions in the open air. This in itself we see not as an accurate indication of what actually happens...

Photo from dr. ir. F.C. Gerretsen (1939)

Adapting to circumstances.

In our post, "adapting to circumstances', we tell about the winter conditions, in where Hendrik had to make compost. He wanted to adapt his method to the cold weather and did so by allowing more air into the process. He wanted to heat up the pile, to give the composting process a warmer start. This would then endure a cold winter. A logical thought?

But it did not went like it was conceived. Again many other influences played a role. Nature goes its own way and we are sorry to say that this experiment has failed.

On the north side of the big bags it was cold and the process went its normal course, due to the wrappings around the big bags. So, there the material was consumed normally and after three months it was ready. On the south side the sun played a big role and did the moisture evaporate from the big bags, which dried up the materials.
Was it the quantity of the mass? Hendrik always has the same mass, always one m3. No, according to Hendrik it was due to 'the pumping action of the air pressure, through solar and wind':

Hendrik: 'When the air pressure is changing from high to low it creates a kind of respiratory situation. This means that the moisture in the pile present (locally) will evaporate. A clear role is always played by the low humidity of the environment in the Alentejo. Only a little needs to happen and the material dries instantly. The process needs any moisture sorely.
This has not happened to me before. This is the first time. And that in three big bags simultaneously. They all dried up on the south side. The entire principle of aeration, of the aggressive aerating of the materials is useless in these circumstances. Here you will be left with a dry pile.'

A new test does provide new insights.

Now Hendrik learned this all he had set up a new test this winter, which was fully in contrary to the last aeration experiment. He composted a quantity of hay in a container. In a barrel (300 liter), that before he used for storage only. This test has given a clear insight.
A setup that reminds us strongly of the process within the Beccari Cells, which was patented in 1920 by Beccari and initially was developed to process domestic waste.

Three months later...
It is winter and it is cold. Here, the conventional plastic container with a grid at the bottom and a lid on top. Therein grafted and drained hay, covered with extra plastic. This is left to decompose for three months. Occasionally the lid goes up to see how far the process has progressed... which means new air in brought into the process...

After three months, about 75% of the hay is composted. Fully ready to mature and to sieve. The lower part of the material (about 25%), on the bottom of the barrel lies in grafting fluid that had drained during the 3 months composting.

Hendrik: "In the test setup the moisture had nowhere to go and gathered at the bottom of the barrel. In a big bag the excess of moisture would evaporate and disappear into the ground. So, if the moisture can not go somewhere there will be air in its place. This means that there is always air present in the process. Though it is still so little.
My conclusion is therefore that there can not be an absolute an-aerobic composting, but rather a low-oxygen composting (microaerophile, or perhaps facultative anaerobic). This will include the reason why our compost never stinks, not lactic acid nor butyric acid. This due to the neutral pH of the manure and the manure-bacteria which I graft at the start of the process. This directs the whole process in the right direction, right at the start.

...So indeed, it is not about the amount of materials you want to compost. It lies in the circumstance in which is composted. So I can compost the hay in a 300-liter barrel very well, in a low-oxygen space. Then it is ready within 3 months as well.
This means that the conversion process will always get enough oxygen. Either because oxygen is still sufficiently present in the materials, either because the bacterial process manages to attract it from the surroundings. And that, I think, is important. I can therefore compost oxygen poor, just as I used to. So that the organic material is optimally used and not evaporated into CO2, ánd it will not stink.
Of course what had happened is not something new in its self. It is just now so that I can reason it out.
I also noticed that the hay, that was under the grafting fluid, did not smell likewise. There had only happened too little. So I could easily put it in a new process together with other materials.'

The learning experience?
  • The composting of materials can be done in small quantities, in a small enclosed space, so that it can result in a low-oxygen environment, where adequate (grafting)fluid is present.
  • A full an-aerobic environment can not be created, and it is also not useful, because of the danger of acidification.
  • The grafting with grafting fluid at the start of the process is a prerequisite.
  • The intensive aeration of the materials is counterproductive:
    It inflames the heating due to the constant supply of fresh air.
    It does dry out the materials.
    Most of the organic matter evaporates into CO2.



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