Composting and food waste at home or school

Peels, coffee grounds and dry leaves do not have to be rubbish. Composting turns them into a dark, crumbly material that feeds your plants and keeps waste out of landfill.

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Why compost

• The US Environmental Protection Agency (EPA) says composting keeps food scraps and garden trimmings out of landfill and produces free compost that can reduce the need for fertiliser.
• Compost helps soil absorb and hold water, which is especially useful in a dry climate (EPA).
• Gardening experts quoted by Gulf News recommend compost and vermicompost (an organic fertiliser made by earthworms breaking down waste) for home growing.
• The Sustainability module covers food waste in the kitchen; composting is what you do with the scraps you cannot avoid.

Greens, browns, water and air

• Greens are nitrogen-rich: fruit and vegetable scraps, coffee grounds, paper tea bags without staples and crushed eggshells (EPA).
• Browns are carbon-rich: dry leaves, twigs, shredded plain paper and cardboard (EPA).
• The EPA suggests about 2 to 3 times as much brown material as green, by volume.
• The pile should feel like a wrung-out sponge, and it needs air, so turn it now and then (EPA).
• The EPA says to keep food scraps covered by four to eight inches (about 10 to 20cm) of dry leaves or other browns.

What not to add

• Meat, fish, bones, dairy, fats, oils and greasy food can attract animals and often do not break down in home bins (EPA).
• Cooked food and so-called compostable food packaging usually need hotter, industrial composting (EPA).
• Diseased plants, weeds with seeds, pet waste and cat litter can spread problems (EPA).
• Glossy paper, produce stickers and treated or painted wood are not suitable (EPA).

Two ways to compost

• Outdoor bin or heap: choose a well-drained, accessible spot near a water source, start with a layer of bulky browns, then add alternating layers of greens and browns, adding water if dry (EPA).
• Fix problems simply: if it smells bad, add browns and turn it; if it is not heating up, mix in more greens; if it is too dry, moisten and turn it (EPA).
• Worm bin (vermicomposting) for flats: the EPA describes a dark bin with a lid and air holes, moist shredded paper bedding, and red wiggler worms fed chopped fruit and vegetable scraps.
• Avoid citrus, onions, garlic, meat, dairy and greasy food in a worm bin (EPA).
• As general advice for UAE heat, keep any bin out of direct sun and check moisture more often, as it can dry out quickly.

Is it ready, and how to use it

• The EPA says finished compost is dark, loose and crumbly, smells like fresh soil, no longer heats up after turning, and has no visible food scraps.
• A well-maintained pile is usually ready in three to five months; an untended one may take a year. Let it cure for at least four weeks (EPA).
• Sieve out bits that have not broken down and put them back into the bin.
• Mix compost into potting mix or spread it on top of pots and beds. The RHS notes that homemade mixes are not sterile, so they carry a slightly higher risk of pests and disease.
• Handle compost with gloves, avoid breathing in dust, and wash your hands afterwards (Te Whatu Ora).