In the ABC of gardening, C stands for composting. Composting is a natural process that converts organic matter, often of vegetable origin, into a biological fertiliser for plants and vegetables. Composting is a clever compromise between rotting and fermenting, two processes that can lead to nasty byproducts such as smelly gases and harmful toxins.
Mother Nature has been using composting for millions of years to keep this planet green and nourished, and farmers have adopted this system for centuries once they realised that what is taken from the land must be returned to the land somehow.
The quickest way on the planet to make compost is to feed a herbivore farm animal with fresh grass and wait 12 hours for it to come out the other end in the form of dung (or manure); the bacteria in the animal guts have broken down the grass fibres into a substance that will contain essential nutrients for the soil and the plants growing in it.
Now, unless you have farm animals foraging and standing on your vegetable plot, all these organic nutrients must be manually reintroduced into your soils and you can choose to either purchase compost or other fertilisers or otherwise, you can make your own.
Bacteria and fungi responsible for this controlled rotting need an environment rich of oxygen and nitrogen; oxygen will support the aerobic ecosystem while nitrogen feeds these tireless micro-organism. Once nitrogen-rich materials such as grass clippings, vegetable food scraps or green pruning are introduced to damp carbon-rich materials such as paper/cardboard shreds or sawdust, the composting process has officially begun. Heat is a byproduct of the organic matter breaking down and the core of a compost heap could raise up to 60°C, an added advantage as any unwanted seed or spore mistakenly added to the heap will die, lowering the risk of annual or perennial weed propagation.
Composting can be called sustainable when the process turns into a cycle – it never stops as long you keep adding good stuff to replace what has broken down, managing temperature and moisture and of course providing the most important ingredient: time.
Types of compost
There are many types of composts, but I like to classify them into two main groups: high fertility and low fertility.
The high fertility are the ones you are likely to purchase from your garden centre and they are commercially made; the nutrient concentration is so intense that it will kill mostly any plants you are going to sow in it. High concentrations of nitrogen, potassium and phosphorous will simply burn the root system of the young seedling or stop the germination of seeds. I will use this type of compost into my garden only if I have severe deficiencies or I am building a garden bed from scratch (maybe from a lawn area) and I am facing a thin layer of topsoil covering an abundance of clay. High- fertility compost worked deeply into the ground and let rest for a season will generate a good soil for your vegetable patch.
Low-fertility compost is a more basic and rustic agglomerate of nutrients and it can be used safely every time as mulching supplement or to reinstate the soil structure; I rank the low- fertility compost (or everyday compost) as the absolute best as it can be literally made anywhere by anyone with ordinary kitchen and gardening scraps.
In recent years, people have shifted to more eco-friendly practices, focusing on sustainable, recyclable and waste-reduction behaviours. Composting is able to tick all those boxes and bring natural agricultural applications into a more urban environment. A forest floor can be replicated in a residential backyard, or a miniaturised farming compost heap built on the kitchen windowsill of a 10th floor apartment.
An average household can produce up to 1kg a day of organic kitchen waste suitable for general low- fertility composting: fruit and vegetables peels, eggshells, coffee grinds, tea bags, plants and flowers clippings. You can take it to the next level by adding grass clippings from your lawn, vegetable plants after cropping and packaging or office waste such as cardboard and paper shreds.
My compost bin also receives an abundant dose of sawdust generated by my woodworking shop.
Getting started
These days, local garden centres sell an unlimited range of composting bins, for all budgets, sizes and applications.
Once you thoroughly inspect their design and construction, you could even decide to build your own out of a sturdy plastic or metal bucket and a considerably basic DIY attitude. The decision on size and design is mostly dictated by the space available; the urban composter’s playground can be found in backyards and balconies, but it can also be in a kitchen sink cabinet, the laundry room floor or even under a carport.
The bin must be of a sturdy construction and able to last years without warping or cracking. Tight lids and hatches are necessary to keep pests at bay and ventilation from vents and holes is paramount in order to maintain an aerobic fermentation process and eliminate foul odors.
The best set-up is the one that allows the harvesting of the composted material from the bottom of the pile; at the end of the day, composting is all about the cycle of matter in/matter out and we want to use the fruits of our hard work and dedication.
A tray at the bottom is always handy to collect any excess liquid that may drain from the perforated bottom of the bin. This liquid can also be used as liquid fertiliser for vegetable gardens and potted plants.
To get started, a layer of wet shredded paper or cardboard will create the perfect base, with a layer of kitchen food scraps topped off with a bunch of dry leaves and small twigs collected from under a tree in your garden. The vegetable scraps and the garden leaves will bring into the system enough natural yeast and mould micro-organism that will start your composting process. From that point in time, continue to add any kitchen waste and from time to time cover it with shredded paper or grass mulching. In less than two months, beautiful, dark and rich compost should be ready to be harvested from the bottom of your urban compost heap.
Worming away
If you have the luxury of a backyard or a balcony, I strongly recommend a worm farm. A worm farm bin is a composting system that is not much bigger than a household waste wheelie bin, but it improves the composting cycle with the help of worms.
Purchase your worms from your local garden centre, then introduce them at the beginning.
After that they will continue to breed indefinitely (that why it is called a worm farm!) while composting your waste in large volumes and incredibly quickly.
Each worm can eat and process waste amounting to 10 times of its own body weight daily and leave at the other end a fine manure of organic matter.
They will also dig their way into the heap, creating micro-tunnels that ventilate the core of the heap so that all the composting cycle happens in a healthy aerobic environment.
Franco’s top tips
If you don’t fancy building a compost heap, buy a compost bin. Pick the perfect location on a level, well-drained spot to help worms to get in and get on with breaking down the content. You can also give Nature a hand with these simple tips.
You need to keep your ‘greens’ (plant clippings and most kitchen scraps) and ‘browns’ (fallen leaves, dried grass, paper and straw) properly balanced. If your compost is too wet, add more ‘browns’. If it’s too dry, add some ‘greens’. Adding scrunched up bits of cardboard is a simple way to create air pockets that will help keep your compost healthy. Air can also be added by mixing the contents.
A well-cared-for compost heap requires regular turning, which can be a tricky job without the right tools. Turning your compost helps to aerate and mix up the waste. Turn the autumns leaves in your garden into your compost heap too.
