this belief, one I have been vainly battling against for years continues to raise is misconcepted head in compost understanding ..so here is an explaination of the true difference between green (fresh sappy material) and brown (dead woody material) material
One reads time and time again that greens are high in nitrogen and browns hign in carbon... actually the Carbon: Nitrogen ratios are virtually identical.....
greens are cellulose based materials whilst browns are lignious based. Chemically speaking the ratio of carbon to nitrogen in cellulose and lignin is the same. where they differ is structually.
Cellulose breaks down rapidly whereas lignin is more resistant. Where an excess of one occurs there is an inhibiting effect; that is too much cellulose and the structual integrity quickly disintegrates and the heap closes down and respiration is prevented and anaerobic conditions prevail. When the heap has an excess in lignin based feed stocks insufficient N is initially available so the heap fails to start.
this green brown thing being relevent to the C:N ratio is a classic example of "throwing the baby out with the bath water" or dumbing down to the point of changing the truth. It is the structural or physical properties of the two materials that is important, both in terms of mechanical and chemical integrity and not the C:N ratio's which are near identical.
regards
greenman-23
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Re: greens and browns; a common misconception
Sat, July 1, 2006 - 6:50 PMokaaaaay. In layman's terms please tell what makes the structures different? Are they different materials altogether or is the brown brown because it's dry? For example, green grass=green and dry,brown grass=brown? -
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Re: greens and browns; a common misconception
Tue, July 4, 2006 - 12:58 PMhi,
basically its the resistability to degredation of the material..
in short woody material is composed of lignin which is robust and resists being degraded.
whereas green, leafy material is composed of cellulose whic is not resistant and so breaksdown easily..
when an excess of lignin based compounds are introduced the process is halted due to the difficulty the micro-oganisms experience in releasing the N from the material...
when an excess of cellulose based materials are introduced the material whilst easily degradable has low structural integrity.. it slumps and prevents air permeating the heap and the process switches to being anaerobic...
the practice of mixing grrens (cellulose) with browns (lignin) is correct.. but chemically they are near identical... it's the degradability and hence the structural integrity that differs....
with regards to grass....... green grass is usually lawn clippings whilst brown grass is usually straw... apart from the fact that they are diifferent things (grass is leaves whilst straw is flower stem) if you were to dry out green grass clippings (turn them brown) then heap them up they would still behave as if they were green... form a slimy smelly mess.. only more slowly due to the lower moisture content
straw contains some lignin (I'm working off memory.. not sure of the precise chemical nature of straw and don't currently have the easily checkable resorces) .. you could build a heap out of straw and it would compost successfully as it contains lignin, hence it is errect.
the green brown thing has come about because lignin type compounds (woody)- are generally brown wheras cellulose componds (leafy) are generally green..
someone once realised that lignin (woody) material doesn't compost well on its own and assumed that access to nitrogen was the same as absence of nitrogen.. they assumed that the compound was low in nitrogen
someone else once tried to compost grass clippings and when it slumped and became smelly assumed that it had too much Nitrogen..
both were wrong but it got into the literature... and we are stuck with it...
trust that helps.....
regards
GM23
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Re: greens and browns; a common misconception
Tue, July 4, 2006 - 10:27 PMYes, well put. Thanx.
So, here's a side question, now that you bring up straw. We get a fair amount of greens with our fairly expansive lawn (ahem, mostly dandelions and clover). I have chickens who's bedding is straw. So, to layer the straw, layden with chicken manure, and the grass, is that well enough balanced? -
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Re: greens and browns; a common misconception
Wed, July 5, 2006 - 8:00 AMWhat role would lime powder play in the process? I have a lot of brown tree branches to break down. -
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Re: greens and browns; a common misconception
Thu, July 6, 2006 - 1:45 PMif you have got a lot of wood then it will probable need chipping and some celulose material or some other easily accessable source of nitrogen added...
lime is always a good thing to add to compost but becareful not to add too much (no more than about a pound a cubic yard) as this can cause the pH to rise too much
personally though I prefer to use gypsum (calcium sulphate) it provides the Ca but also Magnesium and Sulphur.. It also reacts with any ammonia (coverts it to ammonium sulphate) and prevents it gassing off (so stops smells as well as saving precious nitrogen) .. causes floculation (stops the heap going slimy) and you can add a lot more than a pound a cubic yard as it doesnt have such a strong effect on the pH (the sulphur ion opposes the calcium) .. I used to use about 2lb a cubic yard..
another thing that can help the process get going is seaweed (if you live near the coast) esp the bladder and oar (laminara) types... its a great fast food for microbes.... if you don't have seaweed you can use seaweed extracts sold as foliar and root feeds just double the dilution rates and water the heap...
these are all approx quantities.. compost is quite forgiving.. most important thing )IMHO) is to build the heap open (in layers starting out and working in) so as to promote good air flow and to build it sufficiently moist.. then cover a finished heap with carpet or plastic sheeting.
adding lime, gypsum, always helps both with the process and in the garden when the finished product is used..
similarly sprinkling soil between layers is good as it introduces the microbes but best of all is to sprinkle with some previously made compost.. you only need a dusting every 2nd or 3rd layer.
the best way to tell if the heapsgoing well is with your nose... a hot well built and balanced heapalways has a sweet smell...
regards
GM23
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Re: greens and browns; a common misconception
Thu, July 6, 2006 - 1:24 PMsounds like a good mix to me... couple of hopefully usefull tips though...
be careful not to put too thick a layer of grass between the layers of straw as this can act as a blanket cutting out the air flow.. one trick is to mix some straw with the grass layer...
the other thing is chicken litter is likely to be dry (unlike spent stable bedding which is high in urine) so you may need to soak the straw (as long as you build the heap open and in layers you can wet each straw layer down using a watering can and rose) .. dry heaps tend to switch to fungal digestion rather than actinomycete (ther'e the organisms responsible for the sweet earthy smell of nice compost) ..
regards
GM23 -
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Re: greens and browns; a common misconception
Thu, July 6, 2006 - 1:30 PMah, very good. Lots to do. Can hardly wait to get my big tank and pump over there to get it going. -
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Re: greens and browns; a common misconception
Tue, February 12, 2008 - 2:34 PMlaughs, i know.. i wanna run out into my housemates backyard and fixed her "compost pile" (they dont know anything about gardening... the compost pile is covering 10 sq ft and is one layer thick) but i'm too sick to be outside! it sucks! grrr!
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