Ngā Mahi Wairākau / piraurau (Composting)
Compost is made from decomposed organic matter. Composting is the natural breakdown of things like food scraps, uncooked vege peelings, tea bags, dirty paper towels, shells, bones, leaves, lawn clippings, weeds and tree prunings. Compost is a valuable resource and it's pretty easy to make. All you need is a designated area in which to put this garden and kitchen waste such as a large container or a heap. As the material composts, your organic waste will become smaller, finer and richer, ready to go on your garden.
Organic waste (garden and food waste) in landfills breaks down anaerobically (without oxygen) and creates methane. Methane is a valuable fuel if collected but also a greenhouse gas that contributes to climate change. By removing all organic waste from landfill we can reduce the amount of waste that has to be transported around then buried in Papatūānuku as well as reducing methane emissions. By then composting the organic waste we create a nutrient rich material - compost - to feed Papatūānuku and boost soil productivity. Without soil there is no life.
How to Make Compost
Compost is created by layering 3 types of materials:
- green = Nitrogen rich materials such as food scraps, manure, fresh grass clippings, weeds without seeds, seaweed, tea leaves, tea bags and coffee grounds. This is the 'fire' so to speak.
- brown = Carbon rich materials such as tree prunings, dry leaves, bark, untreated sawdust, twigs and sticks, torn newspaper and cardboard, egg cartons and dirty paper such as paper towels. This is the fuel for the fire.
- and a little bit of white = Calcium carbonate materials such as wood ash, egg shells, crushed kaimoana shells, bones or lime. This is a catalyst to really get things going if you want.
Compost also needs oxygen and water to keep the 'fire' going. So keep it moist and aerated.
Avoid composting the following materials, as these may attract rats and mice, or create an unhealthy compost:
- animal fat, cat and dog droppings, diseased plants, large branches, noxious weeds, magazines, meat and dairy products, metals, plastics and glass, and sawdust from treated timbers.
There are many compost systems available to buy at the usual mega retail stores but you don't have to buy one to make good compost. In fact, you don't have to spend any money at all.
Option 1: Create a heap. Designate a space approximately 1.5m by 2m in which to place layer upon layer, nitrogen and carbon rich materials. (Compost ready in 12-18 months)
Option 2: Build a box. Construct two enclosures (approximately one cubic metre each) side by side in which to place your organic matter. Over months, fill one enclosure before transferring it into the adjacent empty enclosure. (Compost ready in 3-6 months). An easy way to do this is to get 3-4 heat-treated 'HT' wood pallets (free from farm/building supply stores or supermarkets) and some stakes like thick manuka or steel warratahs. Whack the stakes into the ground where you want them then wire or tie the pallets to the stakes.
Option 3: Buy a container. Purchase a container for composting from a retail store. Over time fill it up with layers of nitrogen and carbon rich materials. Every few months use your garden fork to turn the compost enabling oxygen to reach the micro-organisms, or alternatively, lift the compost bin up off the compost, place it on the ground empty and then fork the compost back into the bin. An even easier alternative, is once the compost has broken down a bit, when you add new material into the compost bin, scratch it into the old material with a garden fork. (Compost ready in 3-6 months)
Cold vs Hot Composting
Regular composting, also known as “cold composting”, involves placing a variety of organic materials in a suitable container or even just in a large heap, and leaving it there until it breaks down several months later. It’s a very slow process and typically takes 6 to 12 months but doesn't take much effort. It can be sped up by turning the compost, that is, moving around the material at the bottom of the heap to the top and vice versa to mix it up and get more oxygen in there, but it’s still a long wait.
“Hot composting” produces compost in a much shorter time. It has the benefits of killing weed seeds and pathogens (diseases), and breaking down the material into very fine compost. In contrast, cold composting does not destroy seeds, so if you cold compost weeds, any weed seeds will grow when you put the compost into the garden. Cold composting does not destroy pathogens either, so if you put diseased plants into your cold compost, the diseases may spread into the garden, hence the common advice not to (cold) compost diseased plants. The other issue with cold composting is that you can end up with lots of large pieces left over in the compost when the process is completed, whereas hot compost looks like fine black humus (soil).
How to Make Hot Compost
There are lots of recipes and theories on the best hot compost method but the main theme is to:
- get and keep your carbon:nitrogen ratio just right to keep the fire burning.
- Keep it moist too like a wrung out sponge and
- aerate it by turning it often eg. as soon as it starts to cool down, or poke deep holes in it and fill them with nitrogen rich material and water
- Cover the heap with black plastic, carpet or cowhide to keep the heat in.
You can check the temperature with your hand (be careful, it can get really hot!) or get a long thermometer. The hotter the pile gets, the more often added air and water is necessary; the air/water balance is critical to maintaining high temperatures (50° - 70° Celsius) until the materials are broken down. At the same time, too much air or water also slows the process, as does too much carbon (or too little nitrogen). The most efficient composting occurs with an optimal carbon:nitrogen ratio of about 10:1 to 20:1. Nearly all plant and animal materials have both carbon and nitrogen, but amounts vary widely. Fresh grass clippings have an average ratio of about 15:1 and dry autumn leaves about 50:1 depending on species. The main thing is to keep working your compost to maintain its temperature rather than just leaving it to slowly do it's own thing.
There are loads of videos and information on the internet, especially on youtube.com for example this one Tips on making hot compost.
Whether you’re feeding hundreds or thousands of people at your marae, there will always be uncooked food scraps and teabags or tea leaves.
If you want an easy, odourless, low-cost solution to deal with your uncooked food scraps, try worm-farming. Locate the worm farms in a convenient shady spot in summer and a sunny spot in winter near the wharekai. Add regular uncooked food scraps and wait as the humble worm turns everything it eats into nutrient-rich organic fertiliser. As you can imagine worms are small and can only eat their body size in one day - so you will need many well-cared for worm farms to process some of your food waste. Mixing in dirty paper and garden waste will be beneficial for your worm farming.
Worm farming will produce a liquid fertiliser and castings which can then be used on your maara.
Worm farms such as Hungry Bins or Can-O-Worms can be purchased at stores or online and worm farms can also be hand-made at home. A worm-farm can be made out of almost anything, a bucket, a sink, a bath, even old tyres, anything that can drain and have a lid. Worm farms also range in size; from a 20 litre bucket to a 10 hectare commercial worm farm.
Easy steps to making a worm farm
- Make sure your worm farm is off the ground
- Place a container under the worm farm to collect liquid fertiliser.
- Tear paper and cardboard, soak it in water and put in the worm farm (worms like places to hide and sleep).
- Add a thick layer of straw, leaves or hay.
- Add an even thicker layer of compost, or soil and a sprinkle of water.
- Add Tiger worms, Red Wrigglers or Indian Blues (ordinary earthworms aren’t suitable). An average worm farm will need 1000 worms to get started!
- Add food scraps on top of the compost. You can add more food as worms multiply (they can double their population every 40 days).
- Cover the food scraps with soaked sheets of cardboard or an old blanket or carpet to keep it nice and dark for the worms.
- Then add a lid to keep out the rain and rats.
Keeping worms happy
- Feed worms fruit and veges, food waste, tea bags, coffee grounds, dirty paper and soft leaves.
- DON’T feed worms meat, bones, dairy products or fats and oils.
- Worms love variety.
- Worms love good drainage and aeration.
- Keep the bedding moist, not soaking wet.
- Keep your worm farm, dark, moist and shaded in the summer and in the sunlight during winter.
- Remember worms like it, not too hot, not too cold.
Bokashi is another composting system that can be used for food scraps, but you must have a compost or a garden to dig it into at the end. Bokashi was developed in Japan and literally means ‘fermented organic matter’. A fermented wheat- bran mixture called Compost-Zing is used in a bucket system where food is literally pickled. The final product has a slight sweet/sour smell.