"Waste not, want not"

Recycling kitchen scraps benefits gardens.
Sunday, 24 August 2014     

Closed compost bins

This week I read an uplifting article in the newspaper about how Sydney chefs are enthusiastically embracing the composting of food waste from their kitchens, turning it into nutrients for their own vegetable patches or local community gardens. The restaurants are using a very sophisticated machine that can produce compost very quickly, but for the home gardener there are several low-cost ways to turn kitchen scraps into valuable organic matter to improve our soil and nourish plants. All soils need organic matter on a regular basis to remain healthy and well structured. Compost also makes a mild, long-lasting plant food, which is gradually delivered to plants as microorganisms in the soil continue to break it down into its basic elements in a plant-available form.

The simplest method is to add the scraps to an existing open compost heap, usually a bay contained by brick walls, chicken wire or wooden slats, along with other organic refuse from the garden. To feed the microorganisms that decompose waste matter, a compost heap needs a balance between nitrogen-rich contents (such as kitchen scraps, animal manure and lawn clippings) and carbon-rich materials (such as shredded shrub and perennial plant prunings, straw and dead leaves). Such a heap can be passive (just left to rot down, with occasional hosings to keep it moist enough - with the materials taking a long time to rot down) or active (the heap being turned over with a garden fork regularly to promote aeration, which in turn speeds up decomposition by the action of aerobic microbes, with compost being produced much more rapidly).

Alternatives to compost heaps can be the plastic, bottomless dome with a lid (a passive type of system; shown at the start of the blog) and the compost tumbler (an active system, comprising a drum mounted on a stand with a handle for turning, which is filled to capacity then turned daily for a few weeks to oxygenate the material). These enclosed receptacles are preferable if you have a problem with rodents or other creatures in your area seeking out the food scraps added to open heaps. Newer fixed models have an aerated core, which hastens decomposition.

Another enclosed system is the worm farm, of which there are various styles. For years, I used one with three vertically interlocking trays, each with a perforated base to enable worms to move between the levels, and a solid-based compartment at the bottom to collect excess moisture in the system, but I had let it lapse in recent times. A kind friend has recently replenished my old worm farm with a complete tray full of worms and castings so that it was up and running from day one, and thus able to deal with all the scraps from my kitchen immediately. Don't use earthworms from your garden in a worm farm, as they are slow growing and have a slow breeding cycle: use the worms sold specifically for a worm farm. If starting from scratch, use moist, homemade compost or cocopeat for their initial bedding.

It is best to chop up the scraps a bit for them - though this may seem like pandering to them, remember that worms have no teeth and have to turn their mouths inside out to enable a morsel of food to pass into their alimentary canal! They will pretty much eat anything that is chopped up, but citrus and onion peelings are usually recommended to be avoided, and meat, fish, bread and dairy scraps should not be given to them. My new worms, like my old ones, seem to have favourite foods, though, with a penchant for strawberry tops, squashed blueberries and Lady Grey teabags, and like naughty little children do not eat up their lovely green vegetable (scraps) straightaway - but eventually everything gets devoured.

The worms turn the scraps into castings, a rich, dark and granular material, in which minerals in the original material have been changed into a plant-available soluble form, and cellulose partially broken down. When the castings are excreted by the worms, bacteria are expelled with them that continue the process of breaking down the organic matter. In my previous worm-farming days, I used to 'harvest' the castings by separating the worms from the finished material (something they appeared neurotically reluctant to do themselves), but this time I am going to focus on collecting the worm 'tea' by occasionally pouring water through the system and collecting it from the bottom box to pour onto the garden. The worms have been given a couple of upended plastic plant pots in the bottom box, by which they can climb back up to the bedding levels if they accidentally get washed down from the upper layers. Newer models of worm farm than mine are apparently designed for easier harvesting of the castings.

Another method of dealing with food waste is the bokashi bucket, which can actually live right in your kitchen. Scraps are placed in a special container and sprinkled with a special dry mixture of bran and microorganisms that in effect ferments the waste, eliminating unpleasant odours. Once the bin is full, its contents can either be dug into the ground or added to an existing compost heap, where it will complete the breakdown process quickly. The juice that collects in the base of the bucket can be siphoned off and used in very diluted form to feed plants. The bokashi bucket can contain any sort of kitchen refuse, including meat, fish, dairy and bread. I haven't yet tried it but hope to soon.

I'd love to know your preferences for turning kitchen waste into nutrients for your garden!

 Reader Comments

1/13  Alain - 4370 (Zone:9 - Cool Temperate) Monday, 25 August 2014

Great blog on composting and how to use kitchen scraps. My kitchen scraps go to my chichen who await (with great anticipation) for the treasures of the scraps every morning. At present my compost heap receive all the vegetable garden waste and it get turned and scratch over by the chichen. Of course! Should have mentioned chickens as recyclers. Sadly I don"t have any chickens at the moment. I hope to get more one day. Deirdre

2/13  Rebecka - 2481 (Zone:11A - Sub-tropical) Monday, 25 August 2014

I live in a caravan park (with some very keen in-ground and in-pot gardeners). We have two worm farms that are used by about 4-6 residents. We collect the tea each time we deliver a drop of compost and every few months one of the residents collects the solid worm castings and divvies it out between us. I find my natives and my oriental lilies in particular love the vermicast. That is so nice, Rebecka - community gardening at its best! Deirdre

3/13  Rebecka - 2481 (Zone:11A - Sub-tropical) Monday, 25 August 2014

Oh I should say: deliver a drop of kitchen scraps (in my mind it"s already compost but that"s not true is it!).

4/13  Chris - 4034 (Zone:11A - Sub-tropical) Monday, 25 August 2014

We have had worm farm that was not successful and a open compost bin which the vermin enjoyed very much. I have noticed that my garden is full of earth worms and there is often a worm in each spade full of soil. So I manage to get my visiting sons and grandchildren to dig a hole about 2 foot deep, which I fill with my chopped kitchen scraps. We place a bin lid and brick over the hole, and when full, place the soil on top and if I remember where it is, I usually plant a salvia plant on top. Thanks, Chris. This method is what my parents used to do in the 1960s and 70s, and they gradually worked their way around the whole block. The soil was originally very sandy (they lived on a ridge in the Blue Mountains) but after a few years, they had wonderful soil. They were my original composting mentors! Deirdre

5/13  Richard - 2112 (Zone:10 - Warm Temperate) Monday, 25 August 2014

I have a passive compost made of hardwood pallets fixed with star pickets, wired on the corners, & store the finished compost in compost bins. I only use lawn clippings & dry leaves, which I spread on my lawn when I mow to get the carbon nitrogen mix without any manual layering or turning. I have a stainless steel composting bucket on my my kitchen bench with carbon filter to eliminate smells, for vegetable scraps etc, which I empty into my worm farm a couple of times a week. Works for me! Sounds a great system, Richard! Deirdre

6/13  Maree - 2118 (Zone:10 - Warm Temperate) Monday, 25 August 2014

I use all those forms of compost especially the chooks for the scraps, but Angus Stewart commented that he puts all scraps into the Bokashi bucket then puts this mixture into the worm farm. I do this at work, with all the children"s scraps-there are lots!We are now looking for more worm farms as it works so well! We don"t chop them up and citrus, dairy and meat all go in there, and the worms are thriving! Maree Thanks for that tip about putting the finished bokashi brew into the worm farm. Also good to know that you can put citrus etc in with no ill-effects. It is great that the kids are learning to recycle at this early age! Deirdre

7/13  Suzanne - 2073 (Zone:10 - Warm Temperate) Monday, 25 August 2014

We also have an old worm farm as pictured and to overcome the problem of drowning worms we have removed the legs and raised the boxes on bricks to enable us to permanently keep a bucket under the tap which is left open-works well. Have found the best way to empty the finished layer and retrieve the worms is to empty the box into the wheelbarrow and leave it in the open light In no time the worms have gone to the bottom and can be returned to the farm or added to our compost pits. That is a great idea to avoid drowned worms, Suzanne! Your wheelbarrow tip is also great. Thanks for your feedback. Deirdre

8/13  Carole - 2230 (Zone:10 - Warm Temperate) Monday, 25 August 2014

Our next door neighbour uses a rubbish bin with the base removed planted over a small hole in the garden. What has been most successful for us so far is a tumbler, we got the best compost I have ever had out of the tumbler. When it is full back-up additions wait in a rubbish bin. However we are now going to start using our neighbour"s method as back-up. Anaerobic waste is too smelly :-p The tumbler method sounds very good and I would like to try this approach. I am trying to be more diligent about turning my heaps. The static dome can produce quite sludgy material, which is why I am going back to the worm farm method now. Deirdre

9/13  Janice - 2069 (Zone:10 - Warm Temperate) Monday, 25 August 2014

Where do I find a bokashi bucket? Janice 2069 Hi Janice - I was given mine by a friend but they seem to be available at hardware shops like Bunnings and you can get the bran mix there too. My daughter has used one with good success. Deirdre

10/13  Chris - 3340 (Zone:10 - Warm Temperate) Monday, 25 August 2014

I laughed when I read about your "neurotic" worms - I thought it was just mine! I"ve had a worm farm for years but separating out the worms does get tedious and they have never eaten enough to keep up with our supply of kitchen scraps. I"ve dug holes all over my acre over the years, but have just started a 3 bay compost system. A a real novice I"m concerned my garden will provide far more nitrogen rich waste than carbon rich. Can anyone suggest options other than buying straw? The three-bay system is good because you can have your different stages of compost in each. With the carbon-rich materials: I have used shredded paper, dead leaves and woody prunings put through a mulcher or mown over. If you have deciduous trees on your property, the autumn leaves would be a good source. I used straw from the hen house when I had chickens. Deirdre

11/13  Gillian - 2119 (Zone:10 - Warm Temperate) Tuesday, 26 August 2014

Enjoyed reading about your thoughts on compost techniques. I use an old "sulo" garbage bin with the base cut out and holes drilled down the sides. I place all the vegetable and fruit scraps, add shredded paper, sawdust, charcoal from our fire, just throw it all in on top of each other whenever and when it reaches the top I lay it flat on the ground and generally scrape out 3/30 litre bags of compost for my garden. How much money I save !! It is black and rich and my garden loves it. That sounds a great system, Gillian! Deirdre

12/13  Marilyn - 2250 (Zone:10 - Warm Temperate) Tuesday, 26 August 2014

I hate to break the thread but our worm farm is located under the bench in our greenhouse and the worms migrate into the pots and I"m sure eat all the plant roots. Please advise how I can safely get them out of the pots while not harming delicate plants! It is a tricky one, Marilyn. How are the worms escaping from the worm farm? I am not sure if they would eat the roots of plants (though other sorts of worms might) but it is not probably a great idea to have them in the potting mix. Some suggestions would be to not use the vermicast in any potting mixture (as it will contain woem eggs that will hatch into the pot) or to maybe move the worm farm to a different position? Sorry I cannot be of more help. Maybe readers might have some ideas?? Deirdre

13/13  Margaret - 2122 (Zone:10 - Warm Temperate) Wednesday, 27 August 2014

Thanks, Deirdre, for the article on composting. Currently, I don"t have a compost system, after having a problem with rats, but am just about to establish one, in my enclosed vegie bed. It always seems such a sin to just discard your waste products, when you know it can be used productively. The rats can be a problem, which is why I went away from putting scraps in our open heap. Even the dome needs to be weighted down with bricks or else the little blighters seem to find their way in. Good luck with your new attempt. Deirdre

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