Compost - the dirt-cheap choice

By GEOFF CUMMING

Jocelyn Rennie has transformed her property from a desert to a forest without spending a cent on fertilisers.

Mixing kitchen scraps and garden clippings, she has churned out a mountain of compost over the years to feed her flower beds, shrubs and trees.

Her family of six send just one council rubbish bag a week to the landfill. Plastics, cans, bottles and paper are sorted for kerbside recycling.

Leftover meat goes to the cat and dog. Most other organic waste - from vegie scraps to the contents of the vacuum cleaner - is tossed on the compost heap. Some choice kitchen scraps are reserved for the worm bin.

Help from willing children minimises the workload and the family effort pays off in more ways than one. Apart from providing an endless supply of rich garden loam, recycling saves heaps on the household's rubbish-disposal bill.

The Rennies live on Auckland's North Shore where residents pay $1.30 a bag for rubbish disposal and a $26 annual charge through their rates.

With more than half the population still wedded to the house-and-garden lifestyle, officials see great potential for home composting to reduce the waste mountain.

For Jocelyn Rennie, it was a natural choice after she bought her Northcote villa on a section that was entirely clay.

She could not afford the quantities of fertiliser needed to tame the desert so she drew on composting skills learned from her father in Palmerston North.

Now, 20 years on, her section is virtually clay-free.

In her job as a recycling education officer with the Auckland Regional Council, Jocelyn Rennie is well qualified to cut through the myths and mystique which put many people off composting.

The biological processes are baffling, and then there is the confusing array of compost bins on sale, priced from $50 to upwards of $300.

The shop models have their advantages - less set-up time, reliable heat build-up, few concerns about smells and rodents and the prospect of continuous supply.

But you can save money by making your own from scrap timber, or wire netting wrapped around stakes in the ground. Jocelyn Rennie says the quality of the end product differs little.

She avoids putting in meat and dairy products, which can smell and attract flies as well as rodents. A little soil sprinkled on top of food scraps keeps the flies away.

Composting gurus emphasise the importance of correctly layering the material. In reality, says Jocelyn Rennie, most people chuck in their garden waste at the weekend and put food scraps in during the week - so the layering occurs anyway.

"The important thing is to get the right mix of wet and dry materials and have enough air circulating. The whole idea is to build up heat which, in conjunction with micro-organisms, worms and insects, carries out the process of decomposition.

"The bottom line is everything rots if you leave it long enough - it's just how to do it tidily without upsetting the neighbours."

MAKING WASTE WORK

1. BUY A BIN OR MAKE YOUR OWN: Commercial models range from a basic bottomless bin with a lid to ones with several chambers for various stages of decomposition. Or you can knock up your own box from treated scrap timber - planks are ideal. Leave some gaps in the sides for ventilation.

Removable sides at the front make it easier to turn the mix with a pitchfork. Even more basic: wrap some wire-netting around four stakes in the ground. Use some old carpet or underlay as a lid to keep the heat in. Black polythene or sacks can be used for lining.

2. SETTING UP: Choose a reasonably sunny site to help heat build up. Ensure your bin is raised off the ground to allow air to get in and assist drainage. Old pallets make a good base.

If worried about rodents, place chicken wire around the bottom, dug a few centimetres into the ground.

Two wooden bins placed side by side allow you to rotate the brew; as one nears maturity, start another.

3. WHAT TO PUT IN: A mix of wet "green" and dry "brown" ingredients is needed for decomposition. Green materials include fruit and vegetable scraps, tea leaves and bags, grass clippings and weeds without seeds. Brown matter includes dried prunings and sticks, leaves, bark, sawdust, vacuum cleaner dust, torn egg cartons, shredded paper and cardboard.

4. DO'S AND DON'TS: Layer the materials and don't put in too much of one thing.

Start with a layer of branches or other coarse material to help aeration. Chop or shred components for quicker decomposition.

Sprinkle a bit of soil on top of food to avoid smell and ward off flies.

Fast-spreading weeds such as oxalis, onion weed and wandering willy are not recommended for beginners, as the process may not kill off seeds.

Stir or turn the mix occasionally to aerate. Keep compost moist but not soggy. If the mix is too wet, add straw or other dry matter. If it doesn't heat up, add more green material such as manure or blood and bone.

5. FURTHER INFORMATION: Contact your local or regional council for leaflets and advice on composting and recycling. The Auckland Regional Botanic Gardens in Manurewa has a demonstration site where there is a variety of compost bins on show.