Reducing waste, feeding the soil

Gillian Vine makes the case for compost.

A couple of years ago, the Dunedin City Council floated a plan to include green waste in its kerbside collections, but the scheme is yet to be implemented.

The DCC and other councils in the region are lagging behind the likes of Timaru District Council and the Mackenzie District Council which have offered this service for several years.

Something like 1 million tonnes of garden and kitchen waste is buried in New Zealand landfills each year, so until all the councils offer kerbside organic waste collection, the only way to reduce the heap is to tackle it ourselves.

SIX WAYS TO COMPOST

1 Pile it up: A heap of grass cuttings, leaves and weeds, covered with a sheet of plastic, will rot down and make adequate compost. Adding layers of manure to create a sandwich effect gingers it up, as does the addition of lime, blood and bone or general fertiliser.

The advantages are low or no-cost, ease of setting up and rich soil underneath when the heap is cleared. The downside is it is relatively slow to break down, looks a bit unsightly and may attract mice and rats that sneak under that warming plastic cover.

2 Get entrenched: Even easier is to dig a trench or hole in the garden to be composted and fill it with garden waste, vegetable peelings and so on. Manure is optional. When half-full, add a handful each of lime and general fertiliser, then do the same when the trench is full, before covering with about 10cm of soil.

The trench method is speedy and ideal for a vegetable garden. Silverbeet, brassicas (cabbages, kale, cauliflower and broccoli) and celery seedlings can be planted as soon as the hole is covered and by the time they have been harvested, the material underneath will be well-rotted and ready for the next crop.

3 Make a double bin: A double, bottomless box with removable front can be made from old pallets. Put twiggy material on the base of one side, fill with "compostables". When the first bin is full, fork it into the other, water the mix if it looks dry, then cover with heavy plastic or even a sheet of corrugated iron. Weigh it down with bricks and leave it to mature.

This is another cheap and simple means of composting that looks tidy. It is not the fastest method and turning and emptying the bins can be hard work. If there is room for a third bin, this is better, giving the oldest mix more time to break down.

4 Buy a bin: Square or round, black plastic bins are tidy and cost from about $50 each. Sit the bin on bird netting to keep rats from burrowing in from the bottom, then layer material to let air circulate, water if needed and repeat until the bin is full. It should then be turned, either into a second bin or by lifting the bin, moving it and refilling, so the unrotted part goes to the bottom.

Although relatively inexpensive and reasonably efficient, two bins work better than one and digging them out is dirty work.

5 Roundabout: Revolving compost bins take about half as long to process waste as static ones, because the contents are turned two or three times a week. The critical factor is to keep the contents moist. Some models have a single drum, while more recent revolving bins have two, a definite improvement. They cost from about $320 and require less work than a static bin.

6 Bokashi: Unlike other composting systems, a bokashi bin can also be used for fish, meat and cheese scraps. It is anaerobic, meaning scraps break down without oxygen and it needs no turning. When ready, it is put into a hole in the garden or a compost bin.

Bokashi is handy for small households, but some readers report it being less effective than conventional compost if put directly into a garden.

Tip:

Never add chemicals, including oil and paint, or rhododendron clippings to compost.