Hot Compost, Workshop Notes
If you are serious about growing good quality food for yourself, your whanau, and maybe some friends or neighbours as well, putting organic matter back in the soil is vital!
There are many ways to do this, listed here in order of simplest to more complex, least effort to most, small garden solution to larger garden solution:
Using worm tubes to add organic waste directly into the soil.
Worm farming and adding the vermicast to the soil
Making bokashi and digging that into the soil (eg by double digging, bokashi only being added to the trench, not the surface)
Making cold compost
Making hot compost
You need to do at least one of these if you are growing food!!
When you become a composter, (another addiction, I warn you!), you will actually be horrified to think that once maybe you threw your food scraps in the bin.
And if you don’t grow food – you still need to either use one of these methods to keep your food scraps OUT OF LANDFILL or at least give your unwanted organic matter to someone who will!
NO food waste/garden waste should be going to landfill. NONE!!
There is an awesome ap called Share Waste https://www.sharewaste.org.nz/ where you can become a donor or receiver of compostable waste. As a receiver you can say what you do and don’t want to receive. If you have food waste to dispose of, you can find someone who will take it!
Yes, it does cover Aotea😊 BUT there are only four people on Aotea registered with Share Waste.
With or without the ap though please DO SHARE YOUR WASTE!
Hot Compost
Hot compost making is great when you have plenty of bulky plant material to deal with – spent crops, weeds, grass clippings, wood chip, plus of course any food scraps and fast-growing grass!! Perfect materials for a compost heap!
When we create a compost pile, we are setting a massive digestive process in place. In fact, I often think about soil and our digestive system as parallel ecosytems. What does all the digesting in our gut? After a few enzymes break things down a little, it is the microbes, mostly bacteria. Billions of them. Likewise in a compost heap. And if you know anything about gut health, it is really important to eat a wide variety of foods to nurture a diversity of flora in our intestines. Ditto a compost heap.
When we create a compost pile, we are setting a massive digestive process in place.
In fact, I often think about soil and our digestive system as parallel ecosystems. What does all the digesting in our gut? After a few enzymes break things down a little, it is the microbes, mostly bacteria. Billions of them. Likewise in a compost heap. And if you know anything about gut health, it is really important to eat a wide variety of foods to nurture a diversity of flora in our intestines. Ditto a compost heap.
So think widely about what you can put in your heap. Really there is very little you can’t put in it. If it was once alive, it can be composted.
Getting the heap hot even deals with disease organisms, weed seeds and persistent weeds like dock so they don’t spread in your garden. It’s like a cleansing process.
To get the heap to heat up, we need
the right mix of ingredients
enough bulk to make a heap at least 1 metre wide, 1 metre deep and 1 metre tall. Ie a cubic metre. It’s a surprising amount of biomass!!
Think widely about what you can put in your heap. Really, there is very little you can’t put in it. If it was once alive, it can be composted. As long as you get the heap hot.
Hot Compost Ingredients: the Greens and Browns!
You have probably heard about layering “greens” and “browns” in your heap.
The greens!
The green layers are just that - fresh plant material. The green- ness comes from chlorophyll, and chlorophyll has lots of nitrogen, as do other proteins in the fresh leaves. When microbes digest high nitrogen materials they start to reproduce really fast as the nitrogen enables them to form protein and divide.
Green/High Nitrogen Compost ingredients
vegetable scraps
weeds
seaweed
tea leaves and tea bags (compostable teabags though)
coffee grounds
aged manure
Very high Nitrogen
fresh manure
fresh grass clippings
fish meal
liquid fish fert
fish guts
blood and bone
The Browns!
Brown materials, you may have heard, provide carbon. As humans we know we need to eat carbohydrates (which are high in carbon) because they are high in energy. And where is the warmest place in our bodies? Our gut – where the microbes are breaking down the carbohydrates. When microbes break down carbohydrates like sugars, starches and cellulose, they release a lot of energy -in the form of heat. Which is what we want our compost to produce!
What are high carbon materials? Pretty much all plant material that is no longer green. These have all lost their nitrogen to the atmosphere so the greenness has gone. Anything woody is VERY high in carbon
Brown/Carbon-Rich Compost Ingredients
dry leaves
old dry grass clippings
eggshells
tree pruning
Very High Carbon
Wood ash (use sparingly in thin layers, untreated wood)
Wood chip
Bark
Untreated sawdust
paper, egg cartons, hand towels
carboard (tape removed and torn up)
Extra Goodies to Supply minerals, trace elements and microbes
rock dusts eg gypsum, dolomite, basalt, rock phosphate
finely ground clay
ripe compost as an inoculant
liquid seaweed
Balancing it out: layering
The trick is to keep those microbes happy multiplying AND digesting. Lots of high carbon material and not enough nitrogen? The microbes stop reproducing and can’t break down the carbon materials any more and your heap won’t heat up. Plenty of nitrogen and not so much carbon? The microbes will go nuts for a short time, and digest all the carbon and then... go to sleep! Your heap will get very hot, very fast, and then collapse in a smelly mess (think of piles of lawn clippings).
So you can see why we need both. It’s all about balance.
Heard of the ratio of 30 Carbon:1 nitrogen? This is the ratio of molecules of Carbon to Nitrogen! Not so helpful really when you’re looking at weeds and grass and manure!! How much does this have, how much does that have ?!
It may be more helpful to think about wheelbarrow loads/ thickness of layers in the heap. A broad guide is 6 parts of brown material to 3 parts of green material to one part of very high nitrogen material (eg fresh manure/grass clippings, chook poop/urine/blood and bone). The “parts” can be wheelbarrow loads/or thickness of layers.
So keeping the proportions of 6 carbon:3 nitrogen:1 very high nitrogen. you could build a layered lasgane compost with the thicknesses at say 18 cm carbon: 9 cm nitrogen: 3 cm very high nitrogen
If your brown layers include woody materials (very high in C) use a more of the very high N materials.
You can also sprinkle mineral rich materials like wood ash, egg shells, rock dust, even good fertile soil throughout the heap -but in thin layers.
Air and Water
Remember a compost is a living system, so as well as the right balance of carbon and nitrogen, it also needs enough oxygen and water to make sure all the helpful microbes are happy and the unhelpful ones are not catered for.
To make sure there is enough air, have a variety of textures and sizes of organic material. If you make a heap with lots of very small stuff, like sawdust and grass clippings, you may get the balance of C: N right, but air will have a hard time getting into all the microbes doing the work. They will run out of oxygen and either die or go dormant. Then anaerobic organisms could take over- and the heap will start to smell bad- and all that precious nitrogen will turn to ammonia and evaporate!
So although compost materials will break down faster the smaller they are chopped up, it does pay to have some coarse material in there. I always make sure I put a coarse layer down first - like small branches, palm/tree fern fronds, prunings etc so air can get into the heap from underneath.
Lastly, it is important to keep everything damp. You can soak dry materials in buckets of water or seaweed to really hydrate them or if you have enough water, you can hose the materials down.
Location Location!
Avoid areas where water may accumulate, like the bottom of a slope - you don’t want your heap to get saturated or sit in water. There should also be enough room for you to gather all your materials and ideally be close to a water source, as you will probably have to water the heap once it starts to heat up, to stop it drying out.
So have a think about what you can gather for your heap, and where you will build it.
When you become a composting king or queen, you never quite look at things the same!! When I was student, I remember walking a couple of blocks with my wheelbarrow to collect elephant poop, and gathering sacks and sacks of oak tree leaves!!
Turning your compost heap
The idea of turning your heap is to make sure everything in it goes through the heating process, so all weed seeds and pathogens are killed.
Usually, you would wait for the first flush of heat to start to drop before turning. The contents should still be really warm/hot though.
Usually, the sides and the bottom of the heap don’t heat up very much after the heap has been built. (If you partially cover your heap, this can help the heat to reach the outer layers, and stop them drying out).
So, when turning, remove all the dry/unheated material on the sides and bottom, and put them to one side.
Set up the area you will turn the heap onto – it won’t need to be as big as the first time, as the heap will have shrunk. Have water on hand, if possible, to wet down any dry patches plus the unheated material you have put to the side.
The idea is the steaming, hot compost material will go on the bottom and sides of the heap. The dry/cold material from the sides and bottom will be wet down again and put in the middle.
Take time to observe what is happening in the heap, dry/uneven patches, weeds which may still be alive and use your nose to tell you if it may have gone anaerobic (strong ammonia, sulfur or vomit smells).
White powdery-looking patches are fungi that appear when the heap is too hot/tending to being anaerobic. This can happen when the heap heats up fast, and the microbes use up the oxygen faster than it can diffuse into the heap from the atmosphere outside.
Breather “chimneys” can be punched into the heap to allow air to get in. Fat bamboo poles (cut on an angle at one end to make it easier to push them into the heap) work very well. Or you can turn the heap around them, which is a little awkward. Leave them there 24 hours then pull them out. The heap will have settled around them, leaving an open chimney so air can diffuse in and stop the heap getting anaerobic.
Cover the heap with some bits of cardboard/ old carpet/tarp, weighed down with rocks to help retain the heat and humidity.
There are no hard and fast rules about how often to turn. The more often you turn, the quicker the heap will be ready, but in the process more of the organic matter will be oxidised (ie vaporise), and there will be less development of fungi in the heap. So, if you're in a hurry for some compost, turn every 2-3 days if you have the time and energy!! Otherwise, two turns should be enough and wait at least 3 months.
When is your compost ready to use? The earliest is when all the bits and bobs have become unrecognisable, and the compost looks a lovely dark brown. This will usually 2-6 months, depending on how often you turn it. The compost will be even better if you allow the worms to move in and process all the organic matter. The compost will be infinitely richer in microbes, and feel silky and smell delicious.
