Every time you mow, you generate a surprising volume of green waste — and in New Zealand a lot of it ends up in the red general-waste bin, where it travels to landfill. That's a shame, because grass clippings are rich in nitrogen and moisture, and when they rot in a sealed landfill they produce methane, a potent greenhouse gas. The good news is that clippings are one of the easiest garden materials to deal with sustainably, and most of the best options cost you nothing.

The simplest eco-friendly choice is grasscycling: leaving the clippings on the lawn where they fall. If you mow regularly and take off no more than a third of the blade height, the short clippings break down within days and feed the soil, returning nitrogen and organic matter straight back to your grass. This can cut your need for fertiliser noticeably. A mulching mower does the job best, but a standard mower with the catcher off works fine too, as long as you're not letting the lawn grow long and clumpy between mows.

If you'd rather collect your clippings, composting is the next best route. Grass is a 'green', nitrogen-rich ingredient, so it needs to be balanced with 'browns' like dry leaves, shredded cardboard, straw or untreated sawdust — roughly equal parts by volume. Adding grass in thin layers and mixing it through prevents the slimy, smelly mat that forms when a big pile of wet clippings goes anaerobic. Turn the heap now and then to keep air flowing, and you'll have crumbly compost for your garden beds in a few months.

Clippings also make an excellent mulch around vegetables, shrubs and fruit trees. Spread them in a thin layer — no more than a couple of centimetres at a time — and let each layer dry before adding more, so they don't form a water-repellent crust. Mulching suppresses weeds, holds moisture in the soil over our dry summers, and slowly feeds your plants as it decomposes. Just avoid using clippings from a lawn recently treated with weedkiller, as residues can harm your veggies.

One important caution: grass clippings do not belong in the yellow kerbside recycling bin — that's strictly for clean paper, cardboard, glass bottles and jars, and certain plastic and metal containers. Some councils accept grass in a green food-and-garden bin, but collection rules vary considerably around the country, so check what your local council offers before you fill a bin.

If you can't use your clippings at home and don't have a green-waste collection, most transfer stations and community recycling centres accept green waste for composting, usually for a small fee. Whichever route you choose, the takeaway is the same: treat grass clippings as a free resource rather than rubbish, and keep them out of the general-waste bin and out of landfill.