Reduce your waste with these expert tips on composts, worm farms and bokashi

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1 January 1970

Reading Time: 4 minutes

Minimising your kitchen waste is good for the plant AND your garden. Follow these expert tips from compost queen Judy Keats and learn how to process your waste.

1. Get the balance right

Aim for a 50/50 balance of “greens” and “browns” in your compost heap. Greens are soft, fresh organic materials such as weeds, grass clippings and food waste, and are full of nitrogen. Browns are leaves, cardboard and woodchips, and are rich in carbon. Often people complain that their compost is smelly, but that’s because they’ve added too much nitrogen. Try to create lasagne-like layers in your compost.

Judy advises layering your compost like a lasagne, with a blend of green and brown materials.

Keep piles of different types of brown materials beside your heap so you can layer it up as required; for example, for every two handfuls of grass clippings, add two handfuls of shredded paper.

2. Attracting fungi and bacteria

Don’t worry too much about turning your heap to aerate it. As long as you get your carbon and nitrogen ratios right, you’ll attract the correct mix of fungi and bacteria to break down your organic matter. Some compost aficionados claim that turning compost actually breaks up the fungal hyphae that you want in your soil, and argue that it’s better to leave it to break down by itself.

At Kelmarna, an old bathtub has been repurposed as a worm farm that helps to generate fertiliser.

3. Keep your compost damp

The smaller your pieces of organic material are, the more quickly they’ll break down. Soak cardboard in water so it’s easy to pull apart before you add it to the compost; you can also do this with prunings as well. Add water to your compost heap during hot weather to speed up the process, aiming for your compost to have the consistency of a wet sponge. Covering your heap will also keep it moist.

A plastic covering heats up a pile of organic matter, speeding up the composting process.

4. Turn weeds into fertiliser

Don’t sends your weeds to landfill! If you have particularly troublesome weeds and you don’t want them spreading seeds or bulbs in your compost – and eventually your garden – compost them separately. Weeds with bulbs, such as oxalis and onion weed, can be rotted down in a sealed bucket of water for six months.

You can then add this mineral-rich liquid to your compost or dilute it with water and apply it as a fertiliser to your plants. Other troublesome weeds, such as kikuyu, can be placed inside a sack or rubbish bag and left to sit for six months until they’ve rotted down, then added to your garden or compost heap.

5. Fill your compost with worms

Fresh, uncooked food scraps can also be added to worm farms. Special composting worms, called tiger worms or red worms, which are a different species from the worms in your soil, can be purchased online or from garden centres. Their faeces, called castings or vermicast, are excellent for conditioning soil. Worms will consume any fresh, raw food, but don’t feed them anything that’s acidic or spicy, such as citrus, chillies and onions.

Even weeds are viewed as a valuable resource at Kelmarna. Those with bulbs are soaked in buckets until they’ve broken down, then applied to the garden.

6. Use a bokashi system for cooked food

Don’t put cooked food in your compost or you’ll attract rats. A bokashi system is an excellent way to dispose of cooked leftovers. Bokashi means “fermented organic matter” in Japanese and is an anaerobic method of pickling your food waste, rather than waiting for it to break down as you do with compost. It’s an excellent option for recycling food waste in small spaces such as apartments.

Food scraps are added to a stacked, two-container system. The top container has holes in the base so liquid can drain into the bottom container, and an organic, bran-based inoculant is sprinkled on every 6cm of food waste to initiate the pickling process. Once the top container is full, the scraps can be left to ferment in a warm place out of direct sunlight for 14 days, then added to your garden or compost. The liquid collected in the bottom container can be used undiluted to clean drains or your toilet, or dilute it with water at a ratio of 1:100 and use it as liquid plant food.

For more information on composting, check out The Compost Collective’s resources at compostcollective.org.nz or post any questions on their Facebook page.

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