Understanding Composting - The Basics (aka everything you never wanted to know).

I was thinking about doing up post on basic composting about a week ago, and kept putting it off because "hey, who's interested in that?".  But lately I've seen a couple of people both directly (to me) and indirectly (to a group) ask a lot of questions - so I guess I'll get a cup of coffee and try and put fingers to keyboard for an hour or so.  This will be twice in as many weeks that I've been wrong about 'what people want to read about'.

I'm hoping to just cover the basics for people starting out in this, but I'm also a firm believer is trying to 'know a thing'.  If I know a thing, how and why it works, then I can be free to 'create a thing' with what I have, to do what I need it to. So I'll try and cover the things I've researched so we can, hopefully, understand composting - what it is and how it works, so we can all leverage it to work for our own situation.  I don't want to write a novel, so this will be all about the theory.  Later I'll get into practical.

What is it? What can it do? Why do it?

In a nutshell, composting is just the decomposition of organic matter. Happens all around us all the time.  In a forest you see that floor of leaves, peel it back and you'll see fresh humus. Technically this could be said to be be 'mulching', we just take those same processes and make them optimal, and we have 'composting' - organic matter breaking down to make (strangely enough) compost.

It's a soil amendment, we can add it sandy soil to make it hold moisture. To clay soil it makes it retain water and increases porosity. It helps resist erosion and surface crusting. Attracts earthworms. Adds Nitrogen and Phosphorus. I could fill the pages - but in general 'it's good stuff'.

Why compost? If you're interested in taking your garden or yard to the next level, you're going to want to do it - Pretty much every question you can ask on 'how do I fix this?' in the top 3 answers someone will say 'add compost'.  I personally have another reason : reduces my household waste stream.

Sure it's nice to do things 'for the planet', and if you want to think of me as some kindly man doing his part, please do - but alas, my motivations aren't very altruistic. It costs about 30 bucks a month to add a second garbage can that I would only half fill - and I'm too lazy to want to travel to the dump.. I also like getting my fertilizer and soil conditioners for free.
I compost all my yard trimmings, nearly 100% of my paper goods, and my kitchen scraps - by the handy dandy 'waste stream graph' over half of my garbage waste never sees a landfill...

The point is, no matter what side of the fence you sit on - it's a good thing, and even if you're just thinking of your beer-money at the end of the month,  the end result is the same as if you're environmentally aware.

I'm not even going to do a subheader for usage: You make it, you put it in your soil, mulch your plants, sprinkle it on the yard. It's not rocket science.

That being said - the science behind composting I find amazing.... and if you know how it works, you can make it work for you.

The Nitty Gritty

My first attempt at composting I read up on a couple of forums and looked at many 'it's simple!' type articles (btw it IS simple... when you see the whole picture), and managed to produce a really nice pile of wet, stinky, sludge... meanwhile I saw people making great stuff and when I asked how they did it would say 'LOL! DUNNO MAN! DUNNO WHAT I'M DOING! JUST THROW CRAP IN!' - and ignorance truly is bliss - yet in their approach they did everything right,  and in the tradition of 'knowing just enough to be dangerous' - I did everything wrong.

Composting needs only 3 things:  Suitable material, oxygen, and water.  Like beer only needs Water, Barley, Hops, and Yeast.  But as anyone who has failed at home brew knows, it might only need that - but that alone isn't a guarantee for a blue ribbon at the 'fest.

Composting Material.

I've covered a lot of this on my vermicomposting posts - It's amazing that these 2 processes are so similar and yet so different. The base guidelines of 'what to use' are practically identical:

It's easier to say what you CAN'T compost than it is to make a comprehensive list of what you can:

• No Meat. No Bones.  Ok, technically you probably could, but you don't want to. This won't break down well and you're going to have flies, some god awful smells, and pests like rats and racoons.. It's just not worth even thinking about.
• No Oily Stuff. Same as worms, no grease, oils, butter, margarine, all that stuff.
• No Pet Waste. Won't break down promptly. Amonia. And to be honest, I do my best to keep the cat from crapping in my garden, do I REALLY want to pre-add cat turds?
• No Dairy. Ever smelt 4 day old milk left out of the refigerator? I have. It's not pretty.

 That about covers what you should just leave out.  Putting in? Lots of things.

• Yard Clippings
• Green Kitchen Scraps
• Pine Needles
• Coffee Grounds
• Egg Shells
• Fruit
• Paper Goods 
• Bread
• Sawdust
• Wood chips

 Pretty much anything that isn't a 'don't' - even sod.  There is just too much to make a decisive list.

So with all this good stuff, how could I have made such an epic fail?  Well the devil is in the details, or in this case 'how much of what'.

The Composting Process

My fail came from reading other people saying 'how much of what' and not understanding what was going on, how to tell if it was working, or how to fix it if I wasn't - so before I can give you some kind of 'recipe', I have to cover what's going on and why....

Composting is just 'stuff breaking down'. That's it.  We're manipulating how to make it efficient and faster.  It's a combination of inveterates (bugs, insects, worms, etc.) chomping stuff up, microorganisms (protozoa , fungi, bacteria) breaking stuff down creating heat which will kill pathogens and destroy seeds, till finally you end up with compost.

It's important to note that composting is an aerobic process. Which is simply 'with air' - as opposed to anaerobic. The microorganisms that love one environment are different from the ones that don't. A good example of anaerobic decomposition is fermentation.
When your compost doesn't have oxygen, instead of of carbon dioxide being a bi-product, we get hydrogen sulphide... which is known in chemistry circles as 'stinky egg fart smell'.

So.. Oxygen.. it's a big one. The microorganisms we want to attract like a minimum of 5% oxygen.. this is no big deal as fresh air contains about 20%.

Also, there isn't any one type of bug or one type of microbug that will do the process, but rather large ranges of them that like different substances and different heats.  The prime movers are  Psychrophilic bacteria that start the process at around 55 degrees, their very existence generates heat, giving way to Mesophilic at 70 to 100 degrees, and finally Thermophilic at 113 to 155 degrees.
Anyone who's made cheese will recognize the last two bacteria families, which is a nice way to think of them as 'good' rather than 'yucky' when we say 'bacteria'.
Of these, the second type, Mesophilic, is the most active. It's this surge of activity that generates the heat for Thermophilic - who at that point generates so much heat a lot of decomposers are killed and go dormant - it's responsible for raising your compost to around 160 degrees - killing pathogens, destroying seeds, and ultimately itself..
So you have this surge of activity that goes up the scale, peaks, then decends - and you can monitor it just with a thermometer - who needs Lord of The Rings huh? It's all pretty epic when you think about it.  When you see fungi in your composter (I see it on the sides of mine sometimes) you're watching this process.

Just like the microorganisms, the invertebrates also follow this surge.  Early springtails and nematodes eat fungi, which are in turn eaten by mites, those by millipedes, as they in turn process and shift materials, they follow their own complex web adjusting to different temperatures and environments. Earthworms burrow and eat....larva hatch.. it goes on all the way up, and all the way down till there's nothing for them to eat... and they they move on...

 Leaving behind compost.

 So it's all very cool and sounds very natural and easy... and really it is.. once you know how to kickstart the process... which again, is where I failed, and my 'devil may care' friend succeeded.  There are a few factors that determine how well the process runs, they are:

• The Carbon To Nitrogen Ration (IMPORTANT).
• Surface Area Exposed
• Moisture
• Aeration
• Temperature Reached

CARBON TO NITROGEN RATIO

If you've read the vermicomposting articles you'll see me talk about 'greens and browns' .  That's just a simplification of Carbon to Nitrogen - if you think of green scraps and clippings as being high in nitrogen, and brown paper and dry leaves as being high in carbon.
In your compost heap, when thinking in terms of 'green and brown' you want good 50/50 mix - and that will put you in the ballpark you want.

In terms of actual carbon to nitrogen, you want close to a 30:1 ratio. 


Why? A picture is worth a thousand words.  The ratio is going to determine how hot your compost will get, which in turn will have a direct impact on how long it will take.
Not to mention (as we covered above) how well the process will destroy any unwanted greeblies and things like seed from weeds.








"But you said 50/50!" I hear you cry... indeed, but oils aint oils and and nitrogen/carbon content doesn't equal a straight volume across the board... everything contains it's own ratio of carbon and nitrogen.

 So, that 1lb of paper isn't the same as that 1lb of leaves, but against that 1lb of veg scraps, some grass clippings and few cups of coffee grounds... and we're closer to 30:1 than you'd think!

It's important... but not enough to micromanage your input. The more important thing is understanding why it's relevant, so if things aren't quite right we can identify and fix them.

In a nutshell - those microorganisms we talked about earlier digest (oxidize) carbon as an energy source, and they ingest nitrogen for protein synthesis... the bi-product of this is (ta da) carbon dioxide and heat.  When too little nitrogen is present, they can't process that carbon, and decomposition slows down.  They slow down, your heat decreases, we never get to that magic third stage of thermophilic bacteria...
 What's more, if this unfinished product is in your garden it will take available nitrogen to complete this task - and that nitrogen is what you want IN your soil for your plants...

Problem : things slow down - Solution:  Mo nitrogen.

So, why don't we just put in HEAPS of nitrogen!  (and again - MY FAIL, even without knowing the process... just reading 'LOTS OF CLIPPINGS!').  With too MUCH nitrogen there is lots to use, but nothing to digest - no energy.. no energy means no breakdown and that nitrogen converts to ammonia gas and.... POOF.. there goes the nitrogen in a vent of horrible cat-piss-smell.

Problem: Things slow down AND stanky!  Solution: Mo Carbon.

SURFACE AREA

Bacteria propagate on the surface of material in the compost - more area = more bacteria. Now the immediate thought is that something like a big sheet of cardboard has lots of surface area - well it does, but if you shred it into little bits, all those bits have edges, greatly increasing the total surface area present.  So shredding papergoods, cutting down plants, crushing leaves - it all increases that all important surface area, which gives you a greater population of little critters... But.....
There's always a but.  Too MUCH surface area, where things are shredded down so tiny and crushed - all those things pack tightly together, and that decreases our oxygen flow.  No oxygen = anaerobic fermentation = funky smell.

Do you see a theme here? Just about anything wrong ends up with some funk.. so if you smell the funk, something is amiss.

Looking back at my case in fail. I had a big pile of finely shredded grass, along with a too much water - everything compacted down... whereas my buddy just threw in 'any old crap' with it's any old size, creating space for things to move, for moisture to flow, and oxygen to breathe.

Solution: Add some bigger, chunkier stuff and mix it into your compost.

MOISTURE

Microbial decomposition occurs best on a liquid film covering surfaces - those surfaces we just covered.  Around 40 - 60% moisture is ideal, providing enough moisture without sacrificing air flow.  Too little and the bacteria will slow down, or even go dormant.  Too much and we lose airflow, the compost goes anaerobic.. and... yeah.. funk factor five.
The easiest way to test for a good moisture level is to squeeze it. It should feel like a damp sponge - you should be able to get a few drops out of it, but not a stream... if you have too much water there is an easy fix.. you can add some more brown material (remember, your 'green' material has a high percentage of water!) and turn the compost with a fork - let some water out, let some air in.

Problem: Bad Smells and very wet.  Solution: Add some dry brown material and mix.

AERATION

It's simply the replacing of oxygen deficient air to the center of your compost pile.  Fast composting only happens when there's enough going through it. Thanks to the wonder of physics (and in particular convection) - if we've followed through on the things above, this will be taken care of for us 'as if by magic!' - Hot gasses will rise from that 160 degree center and new air will be pulled in from below.  Of course for that to happen we need some porosity. This is the space between particles.  So long as we have a good mix of materials of different sizes, and we haven't waterlogged our pile, and air can actually get in, this is all taken care of for us... we can also turn our pile with  a fork, or even set up our composter (like a rotating drum composter) so we can aerate it further, speeding up the process... aeration is just 'putting air in'. If no air is in... guess what happens?  Uh huh - smells.. how to fix it? Uh huh, turn it and add air.

SUMMARY

So in summary... going back to my example. I failed because my C:N was totally outta whack, My particle size was so fine it compacted, then I added too much water - blocking the air, which made my pile anaerobic and it fermented into a smelly pile of sludge.. probably better used to kill plants than feed them.  I was overthinking a process that I had didn't understand.

My friend succeeded because, unknown to him, he had a great C:N ratio with particles of many sizes, allowing air and moisture to flow freely. He didn't overwater it or micromanage it, in fact a lot of his water came from his green materials.
He was underthinking a process he didn't need to understand.


It takes a lot of words to describe a process so beautifully simple and elegant.


Cheers!


SOURCES:

Composting to reduce waste stream
Composting Fundamentals
CSWEC