One of the permaculture principles centres around the idea of producing no waste, or alternately, finding uses for waste byproducts. Overall it makes sense both environmentally and financially to try and process your own waste into something usuable.
Under that idea I’m going to highlight the pros and cons of each style of handling organic waste byproduct. I don’t believe any one system is the best and I use several personally to process our own food scraps, Garden scraps, paper waste and even old scrap clothes.
1. Cold Compost
Probably the first thought when people think of processing food scraps, cold compost is a simple idea of throwing food scraps and carbon product (paper, leaves etc) and leaving it 6 months or so until it turns to soil. Cold composting if attempted completely passively (input only no management) will decompose, however it also will create methane in the process (as opposed to carbon dioxide). Therefore it still requires to be turned occasionally to keep the pile from becoming anaerobic.
The pros of this method relate to it being fairly low fuss. It’s a sort of set and forget method. It also not uncommon for plants to self seed within such set ups, with tomatoes and pumpkins being very common to appear.
But the self seeding aspect also relates to a con of this type of system, cold composting doesn’t kill seeds meaning using the compost after its broken down may lead to an abundance of accidental tomatoes, weeds or pumkpins self sowing in your garden bed. Cold composts are also fairly attractive to various vermin particularly if the wrong inputs are put into the system. For example snakes are attracted to the mild heat created during decomposing and use it as an opportunity to lay eggs. Mice, rats and bandicoots are attracted to the free feed of not yet fully decomposed food, likewise flies find it a good breeding ground. Finally of all the waste systems this is probably the one that takes the longest to get an output from.
2. Hot Compost
A hot compost is similar to a cold compost however it needs constant input in stirring the heap every few days to keep it aerobic (oxygenated) to help the decomposition process.
A well maintained hot compost can decompose a mass amount of organic waste into useable soil in as little as 18 days (although by most reports it more commonly takes at least a month). A hot compost gets it name due to it ideally being 50-70°C (120-170°F) during decomposition which is temperatures hot enough to destroy seeds, an element that cold composting doesn’t achieve.
They are labour intensive requiring massive amounts of inputs initially and then stirring every second day. The attractiveness to vermin remains however due to constantly being stirred and the quick decomposition there is only a brief window of opportunity for the vermin. Another downside is once you begin the pile of you are aiming for a quick completion you can’t keep adding to it.
3.Chop ‘n Drop
This is exactly how it sounds, pruning plant matter and dropping it where it falls (or to where you desire it). It takes from the idea of fallen organic matter creating a rich humus similar to rainforest systems. Sometimes plants are grown specifically to become chop ‘n drop crops (pigeon pea, comfrey and canna are popular options, as are well placed deciduous trees) other times it’s just taking advantage of what’s available following pruning.
The ease of simple pruning and dropping is the benefit of this method. There is typically no heavy lifting, it feeds soil microbes in situ, and creates a mulch and fertiliser in one.
However it isn’t ideal for kitchen scraps, and takes a long time to decompose.
Bokashi is a system I don’t have a lot of experience with but it’s a type of container compost system that is maintained through adding a range of micro organisms that quickly break down and prevent offensive odours.
Bokashi is ideal for units and people who don’t have access to compost heaps and is ideal in that anything goes (onions, meat, anything can go in although something break down easier than others). The microbes break down quickly in a way that the set up doesn’t require a huge amount of space.
However bokashi is a two step process requiring the waste to be buried or added to compost to finalise it which isn’t ideal if you don’t have the space to do so in the first place. There are also reports from some users that it has a distinctive smell.
5. Black soldier fly
Black soldier fly larvae are native voracious grubs that often find their way into compost heaps or worm farms. It is possible to create a farm specifically for their needs as they generally are attracted to more moist conditions than are ideal for worms or compost. The maggots are rich in protein and sometimes bred for feeding to chickens, reptiles or fish.
While the idea of essentially fly maggots may be off-putting to some, the flies actually don’t feed and aren’t capable of spreading diseases so aren’t a pest species and generally leave humans alone. Furthermore the maggots are capable of self harvesting themselves making for an ideal system if you do want to harvest them for animal feed. There aren’t picky and are generally attracted to the smell of rotting meat which can be great way to attract them in the first place.
While they process a great amount of food daily (1m² of larvae is capable of eating 15kgs per day) the waste byproduct does require further treating in a compost as it tends to be not entirely broken down. The system can also get quite smelly at times however due their voracious nature they tend to outfeed fly maggots.
6. Worm Farm
Most of us already know about worm farm’s and the beneficial castings and worm juice they produce. Kits can easily be bought from large hardware stores or you can also DIY your own worm farm’s and source worms more locally. The worms in worm farm’s tend to be Red Wriggler worms (Eisenia fetida) which are different from the worms you come across when digging in the garden as they live above soil as opposed to within it.
Once established, worm farm’s create very beneficial castings (essentially poop) which are used to make worm juice and can go through a good amount of organic waste in a short time.
However worm farms can be quite particular needing to remain cool, and kept at the right moisture levels. Furthermore there are certain foods that are generally frowned upon to add to a worm farm due to it being overwhelming to the worms (large quantities of citrus or onions) or causing other issues such as attracting pests or making the farm too moist. Seeds put into the worm farm are not killed by the process either.
7. Worm Tower
A worm tower takes the idea of a worm farm but puts it directly into the garden and let’s earthworms do all the work with little of the maintenance. Essentially it’s a pole or a pot with holes on the sides buried into the ground with a lid so you can add organic matter to feed nearby earthworms who then spread their castings directly into the garden.
It’s benefits are it’s ease of maintenance, requiring next to none. If you don’t feed it, no fuss, the worms will find sustenance elsewhere. Also it can’t get overheated like typical worm farms as the worms will just retreat deeper into the ground if required. Worm towers can also be used as an occasional deep watering port which helps the worms by creating the right moisture levels (too dry and nothing happens).
The downsides to worm towers are they are not free from rodents (I had a bandicoot dig up my garden trying to source the delicious smell. He didn’t get it, but my garden was destroyed regardless) and seeds can still germinate within them.
8. Weed Tea
Weed tea is the process of taking plant matter and seeping it in water for a time allowing the nutrients to leech from the plants and be used as a fertiliser once diluted.
It’s a simple process that often makes use of pulled out weeds (hence the name), but can also be made from any plant matter. The process is simple and makes for an easy fertiliser from what would otherwise be waste. It can be used as a starting process for plants prior to adding them to a compost heap helping to break them down faster.
Smell can definitely become an issue with weed tea, particularly if left over a long period and care should be taken to avoid adding seeds to the mix, particularly unwanted ones as the process won’t necessarily kill the seeds.
9. Burning Waste
As far as burning waste is concerned, it’s generally the very last resort and one I reserve predominately for weeds that would otherwise need to be thrown into the garbage for disposal. For example Dutchman’s pipe is a common addition to our fire pits as the plant is too environmentally harmful to risk it spreading through other methods. Once reduced to charcoal and ash, also called potash, a source of potassium, it can be spread lightly amongst plants or compost to assist with nutritional balance, however care must be taken not to overdo it as potash can change soil pH levels.
As far as the downsides of processing waste through fire, it’s more likely to release carbon back into the atmosphere as well as not being suited for all organic materials.
In conclusion, as you can see there is multiple ways to process organic materials to make them beneficial throughout your garden, although not all that are ideal in every situation.