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Effect of Nitrogen in Air for Composting?

03/05/2015 2:41 PM

Composting happens naturally. Rotary In-vessel composting machines use an Aerobic composting process vs. Anaerobic as in digesters that recover methane for fuel.

To keep the process aerobic, air is very often blown into the vessel to help provide the ideal environment for the thermophilic bacteria to reproduce and thrive.

Part of the ideal environment also includes a Carbon:Nitrogen ratio of 25:1 - 30:1.

Since air contains 78.09% nitrogen, would the nitrogen in the air affect the C:N ratio?

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Guru

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#1

Re: Effect of Nitrogen in Air for Composting?

03/05/2015 3:25 PM

Wiki says yes.

Composition of Earth's atmosphere

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#2

Re: Effect of Nitrogen in Air for Composting?

03/05/2015 3:29 PM

You can speed the process by adding oxygen.....

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#3

Re: Effect of Nitrogen in Air for Composting?

03/05/2015 5:54 PM

Most of the Nitrogen is consumed during the composting process and the process will slow down and/or stop unless the pile is aerated by turning it over regularly.

I am sure the N2 content of air does affect the composting process.

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#4

Re: Effect of Nitrogen in Air for Composting?

03/05/2015 8:52 PM

Found this...

"The ideal C/N ratio for composting is generally considered to be around 30:1, or 30 parts carbon for each part nitrogen by weight. Why 30:1? At lower ratios, nitrogen will be supplied in excess and will be lost as ammonia gas, causing undesirable odors. Higher ratios mean that there is not sufficient nitrogen for optimal growth of the microbial populations, so the compost will remain relatively cool and degradation will proceed at a slow rate.

Typical C/N ratios for common compost materials can be looked up in published tables such as Appendix A, On-Farm Composting Handbook. In general, materials that are green and moist tend to be high in nitrogen, and those that are brown and dry are high in carbon. High nitrogen materials include grass clippings, plant cuttings, and fruit and vegetable scraps. Brown or woody materials such as autumn leaves, wood chips, sawdust, and shredded paper are high in carbon. You can calculate the C/N ratio of your compost mixture, or you can estimate optimal conditions simply by using a combination of materials that are high in carbon and others that are high in nitrogen."

Materials High in CarbonC/N*
autumn leaves30-80:1
straw40-100:1
wood chips or sawdust100-500:1
bark100-130:1
mixed paper150-200:1
newspaper or corrugated cardboard560:1
Materials High in NitrogenC:N*
vegetable scraps15-20:1
coffee grounds20:1
grass clippings15-25:1
manure5-25:1
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#5

Re: Effect of Nitrogen in Air for Composting?

03/06/2015 6:30 AM

Thanks all:

I am pretty familiar with the C:N ratio and C and N %s of various materials and animals.

What I was wondering was once someone calculates the correct volume to mix to achieve the desired ratio. If that can be upset or thrown off simply by adding air periodically during rotation and blowing in fresh air to rotary the in-vessel composter.

http://compost.css.cornell.edu/calc/cn_ratio.html

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#6

Re: Effect of Nitrogen in Air for Composting?

03/06/2015 6:59 AM

Unfortunately, mortality is one challenge CAFO operators have to deal with:

http://michigan.sierraclub.org/issues/greatlakes/articles/cafofacts.html

PEDV: http://nationalhogfarmer.com/porcine-epidemic-diarrhea-virus-pedv can cause a large % of mortality very quickly on a CAFO.

The operators have choices what to with the mortality among the choices are:

Incineration, Rendering, Burying, Anaerobic Digestion, Aerobic Composting.

Incineration is expensive and pollutes the atmosphere.

Rendering is becoming less common and it is a nasty job and then the contamination issue from the Rendering truck going from farm to farm perhaps spreading the disease unknowingly.

Burying is fine for small farms not so with CAFOs.

Anaerobic Digestion is a huge investment for anyone who undertakes it.

Aerobic Composting is growing in popularity because it can be done in open windrows if there is space available or it can be accelerated in a Rotary In-Vessel composter.

A fully grown dead hog can be put in a Rotary In-Vessel composting tube and if you add a carbon amendment in the form of wood chips or sawdust and get the C:N ratio close to correct, rotate the vessel a few times a day on a timer, blow in fresh air to keep the process Aerobic, that hog can be reduced to unfinished compost in five days. Another 30-60 days of "finishing" the compost makes it safe to bag and sell as good soil amendment or the farmer can put it back on his own fields.

I was just wondering if the Nitrogen in the air that is blown into the tube during rotations will affect the C:N ratio.

Thanks,

Temperatures inside a Rotary In-Vessel composter are generally 130┬░-160┬░ naturally generated by the thermophiles reproduction and metabolism. At those temperatures pathogens and even weed seeds are 'killed' if kept at those temps. for a minimum of 3 days. It is a pretty neat way to deal with agricultural mortalities as well as food waste from large food operations such as prisons, universities, communities and other sources.

Here are some examples for rotary in-vessel composters:

https://www.google.com/search?hl=en&site=imghp&tbm=isch&source=hp&biw=1347&bih=979&q=rotary+in-vessel+composters&oq=rotary+in-vessel+composters&gs_l=img.3...1648.8382.0.8499.27.9.0.18.1.0.70.502.9.9.0.msedr...0...1ac.1.62.img..18.9.463.5x5_R21CTag

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#7

Re: Effect of Nitrogen in Air for Composting?

03/06/2015 10:36 AM

atmospheriic oxygen will engage in an aerobic process

atmospheric nitrogen will not engage in any biological process without first becoming "fixed"

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#8
In reply to #7

Re: Effect of Nitrogen in Air for Composting?

03/06/2015 11:12 AM

Thanks zzorb, that is what I am looking for. So will any of the atmospheric nitrogen become "fixed" within the composting tube?

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#9
In reply to #8

Re: Effect of Nitrogen in Air for Composting?

03/06/2015 11:43 AM

I couldn't say if the biological processes going on in your composter replicates how nitrogen fixation occurs in nature or in fertilizer manufacture. You might get a good idea by searching "nitrogen fixing", or get the opinion of a biology expert.

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#10
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Re: Effect of Nitrogen in Air for Composting?

03/06/2015 11:55 AM

Composting organisms require four equally important things:

1. Carbon for energy; the microbial oxidation of carbon produces the heat, if included at suggested levels. High carbon materials tend to be brown and dry (like old leaves or a banana peel).

2. Nitrogen to grow and reproduce more organisms to oxidize the carbon. High nitrogen materials tend to be green (or colorful, such as fruits and vegetables) and wet.

3. Oxygen for oxidizing the carbon, the decomposition process.

4. Water in the right amounts to maintain activity without causing anaerobic conditions.

The process and conditions must be balanced ....

I wouldn't blow air additionally through the material....pure oxygen can speed the process though....as an aside...

http://www.soilandhealth.org/06clipfile/0602robic.cmpstng.chrt.html

http://www.urban-composting.com/composting-tutorial.html

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#11

Re: Effect of Nitrogen in Air for Composting?

03/06/2015 7:25 PM

Nitrogen in the air is pretty tightly bound to itself, i.e. diatomic N2.

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#12
In reply to #11

Re: Effect of Nitrogen in Air for Composting?

03/06/2015 7:37 PM

AKA inert

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#13

Re: Effect of Nitrogen in Air for Composting?

03/07/2015 9:23 PM

Nitrogen (N2) in air is not available for use by bacteria in composting, any more than it is available for animals and plants (apart from nitrogen fixating rhizomes- I think I got that part right-such as legumes etc.). The nitrogen consumed must be available as an amino acid, nitrate salt etc.

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