Autumn produces an abundance or material to make soil-boosting compost. Sometimes there's so much that bins overflow and more space is needed. You then have the choice of buying or making another bin or heap.

Bought plastlc bins have holes around the base to aid air circulatlon and a fully open base that lets worms enter and the compost drain. Just add your organic waste, mix it all up, moisten if necessary and press it down with a rake to expel large air pockets. There's no need to worry too much about layers but, as with most compost heaps, if more than half the bulk is lawn clippings you may end up with a slimy mess.

If you have basic metal-working skills, why not transform an old hot water tank into a nifty compost 'tumbler' like this? A latched and hinged door has been incorporated into the side for putting the organic matter in and getting compost out, while the whole tank rests on a stand with four rollers. Turn the tank a few times a day and you'll have tip-top compost in no time.

Simple interlocking stackable compost bins like this below are sold in kitset packs at major DIY stores, this one came from Mitre10 Mega. You can easily make a similar one with fence palings - cut slots near the end of each one to accommodate the next layer. To get this two-tone look, stain the slats (before assembling) with Resene Woodsman Penetrating Oil Stain tinted to Resene Pitch Black and Resene Smokey Ash.

Where space is an issue, you can convert a small plastic rubbish bin in to a mini composter. Cut generous drainage holes in the base and from the top and built up in layers, as shown. With a smaller open composter like this you may need to wet the contents more often to give developing compost the right amount of moisture. ventilation holes in the side, use a jigsaw or very sharp Stanley knife. If you want, you can even jazz-up your mini bin with exterior paint. We used Resene Smooth Surface Sealer as an undercoat with a topcoat of Resene Lumbersider tinted to Resene Havoc (red) and Resene Clover (green).

A mini compost 'cage', fashioned from an old birdcage, is another space-saver. Organic matter can be added from the top and built up in layers, as shown. With a smaller open compost like this you may need to wet the contents more often to give developing compost the right amount of moisture.

Three adjacent wooden bins work well; the ideal is to have removable slats down the front that can be built up one-by-one as the compost heap grows and then removed later for easy access to the finished product. Fill one bin and then start on the next. By the time the third bin is full, the compost in the first one should be ready to use. You can also use a series of bins like this to rotate the compost, shifting partly decomposed contents of one bin into the next. This means material that was on the top of the first heap ends up on the bottom of the new heap, which aids decomposition.

Instant ideas

• Old wooden pallets make great DIY compost bin walls. Wire or nail four together using galvanised nails or fencing wire.
• Make a square compost 'cage' with four sturdy stakes and netting - strong plastic garden netting makes long lasting walls because it doesn't rot. Attach this to four posts with strong galvanised staples, Chicken wire is another option.
• An old tin drum or wine barrel can make a great compost bin - but you need to ensure there are adequate ventilation holes drilled in the sides and a generous hole at the bottom.

Hints tor healthy heaps

• The recommended size for an average compost heap is 1m x 1m x 1m. Layer your compost materials, alternating twiggy, dry cuttings with green foliage and fine lawn clippings for the best results - a 10cm layer of each is ideal.
• Compost materials should be damp but not too wet. Protect open heaps from excessive rain, a 'lid' of old carpet is the traditional method. Sprinkle contents with water when your mix is starting to took a bit dry.
• The finer you chop trimmings the less time they'll take to decompose - use a shredder for thicker twigs.
• Compost accelerators used as directed, give quicker results.
• Biodegradable materials like shredded paper, natural cotton and wool fabrics can be added to the heap but avoid synthetic fabrics or plastic coated materials.
• Adding cooked food scraps, including bread, and raw meat can attract vermin, especially in open piles.
  

Article by Mark Rayner

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