Viv's Green Living - Composting - 21 May
Composting Systems - Traditional Methods
- Remember that approx 45% of your rubbish bag that ends up in the landfill could potentially be composted (especially the traditional decomposition technique)
- This is a very valuable resource that is effectively being wasted by being buried in a landfill
- The resulting compost can be used to enrich the soil and grow food (fruit and veges) and garden plants
- Composting your organic waste reduces your carbon footprint as it doesn't need to be transported anywhere, it reduces landfill space and it produces a priceless resource - compost for growing your vegetables
- www.createyourowneden.org.nz is an excellent website for simple composting information
- The type of composting system you use will depend on the size of your property, how much organic waste you produce and where you can put it once its made (i.e. volume created)
- There are composting systems that can accommodate all situations
- Traditional - where there is a reasonable sized garden space to make the compost, providing garden waste and kitchen scraps. Mostly decomposition of the organic matter by bacteria and invertebrates (insects and worms). Suits medium to large gardens as large quantities can be made as necessary. Small gardens may suit use small commercial bins.
- Worm farms - composting is achieved by worms breaking down and digesting the organic matter - suits small gardens or small outdoor areas using mostly kitchen or house organic waste.
- Bokashi - fermentation of kitchen waste only (no liquids). Activated decomposition occurs once buried in the ground. Suits apartments as the bins can be used indoors in small spaces (i.e. the pantry) and can be used to enrich communal gardens or public parks.
Traditional composting methods
- These methods suit the garden situation where garden waste such as grass clippings, leaves, weeds and other green waste is produced on site and is mixed with kitchen waste (medium to large gardens). Though small gardens can use mini compost bins as well.
- Decomposition by bacteria, micro organisms, insects and worms is the way the organic waste is changed into compost
- This compost can be mixed with soil to increase fertility, increase the air and water holding capacity as well as provide a wide range of nutrients and effective micro organisms into the soil to be available for plants to use. This in turn grows healthy and nutritious plants which can be eaten, creating optimal health for us.
- The decomposition releases minerals and useful nutrients from the original materials in a form that allows plant uptake e.g. seaweed provides selenium as well a s a huge range of other minerals that are naturally deficient in many NZ soils
- The two main ways of this form of composting are build the heap all at once and allow to break down or build the heap as materials become available (on a daily or weekly basis)
Building a heap all at once
- Have all material present and create layers of green and brown material until the heap is as large as you want it
- Start with a layer of twiggy material to allow airflow from the bottom
- Layer grass clippings, animal manure (not dog or cat), leaves, non noxious weeds, straw, seaweed
- Ideally a 30:1 ratio of carbon materials to Nitrogen materials (see below)
- Designs for this type can be:
- simply piling it in a shady but sheltered and warm corner
- using a circle of wire netting (may need to line with sacking, newspaper or cardboard if in a dry climate to reduce drying out of the heap)
- building wooden stacking bins
- corrugated iron squares (4 lengths of iron nailed together into a square)
- see these useful websites for designs and directions on
building your own bins
- Ideally these heaps should be turned every few weeks to speed up the process, but they can also be formed and left to decompose, but it will take several months to produce results
Building the heap as materials become available
- All above forms can be used for this method, but the production will take longer as the heap may dry out faster.
- There are a number of excellent commercial compost bins that can be used and most suit this method of adding as you get the materials available for example Earthmaker aerobic bins (see www.earthmaker.co.nz)
- Organic material is put into the top section where it is mixed. The black plastic top traps radiant heat to warm the waste and speed decomposition through aeration as the heat draws air up - its aerobic process reduces greenhouse gas emissions.
- When full, a panel is removed and material falls into second chamber and is digested via bacteria, invertebrates and worms
- The material then falls into the lower chamber and matures into rich compost and can be easily removed and used in the garden
- Benefits include no lifting or turning, easy on the back as gravity does the hard work, unique aerobic process meaning faster decomposition and no smell (a sign that no methane gas is being produced), continuous cycle system separates new material from mature compost.
- Compost can be created in 6-8 weeks depending on temperature, quality and volume of materials used.
Another form of commercial composters is the tumbler (see www.gardeningaids.co.nz)
- Ideally, all material is shredded before putting into the tumbler, a mix of green and brown material is used and the material is tumbled daily to aerate and mix
- With the correct ratios of carbon to nitrogen, temperature and aeration this can create compost in around 14 days
- Site your compost in a sheltered but warm place out of direct hot sun
- Use quality materials in the correct ratios i.e. 30:1 carbon to nitrogen.
- Carbon materials are dry "brown" garden waste such as straw, dead dry leaves, sawdust, dry grass clippings, dry seaweed, shredded twigs and branches, paper, cardboard (shredded/ripped and wet if possible)
- Nitrogen materials are "green" garden waste such as green grass clippings, kitchen scraps, animal manures, fresh leaves and weeds (don't use noxious weeds such as oxalis, wandering Jew as they often survive the composting process and regrow - put into a black plastic bag, tie and sit in the hot sun for a few weeks to "cook" them then they can go into the compost once totally broken down
- Ideally shred and chop the ingredients as the smaller they are the faster they break down
- Ensure sufficient air (may need to turn the heap) and moisture (damp not soaking)
- Avoid dog or cat manures (may transmit diseases) and meat scraps and bones (attracts flies and rodents)