City Composting: How and Why to Compost our Food Waste
In Singapore, we dispose of more than 700,000 tonnes of food waste each year. Of that, approximately 17 per cent is recycled, therefore around 83 per cent of all food waste generated is incinerated.
This requires resources and generates carbon emissions, from the time our food is grown, transported to us, refrigerated in our homes, transported to incineration plants and then shipped to Pulau Semakau.
Some of this food waste at home can be reduced by preventing it in the first place. We can do this by buying what we need and will consume, sharing excess with others and finding ways to extend our food’s shelf life through preservation methods like freezing or fermentation. For what we cannot save, we can compost. Instead of expending resources to process waste, we can use this waste as a resource for beneficial outcomes.
The Basics of Composting
For those who are not familiar with composting, it may seem mysterious or difficult, but it doesn’t have to be. We are basically balancing green and brown materials. Greens include fruit and vegetable peelings, plant clippings, coffee grounds, chicken manure and anything that contains high levels of nitrogen. Brown includes dried leaves, cardboard, branches or anything that has high levels of carbon. Remember to always dispose of diseased plant parts, and never add it to your compost bin.
If we do not balance the greens and browns appropriately, this can lead to the composting contents to be overly wet, bad smelling, and little progress. Other important components of composting include moisture (but not too high) and in the case of aerobic composting -- aeration.
You can compost using aerobic or anaerobic methods, or if you are using a food waste digestor, it may not be either. Aerobic composting means that you are composting with air, using microorganisms that require oxygen to survive, and anaerobic, without air, using microorganisms which don’t need access to oxygen.
The aerobic process results in high temperatures, and hence, faster composting, while anaerobic is a cooler process and takes much longer. There are several systems to choose from when it comes to composting in Singapore, so it doesn’t matter if you do not have access to a garden or community garden. Composting can still be a painless affair.
Composting Meat, Dairy and Eggs
1. Food waste Digester - This is for those who prefer a straightforward and easy, high tech option but be prepared to fork out close to $1,000 for a small unit. There is no need to sort your food waste and you can put both raw and cooked food into it, unlike other composting systems. Your food waste can be processed in as little as 3 hours, where it will be ground and dehydrated into dry flakes. Small units will also fit nicely into kitchens with space constraints.
2. Anaerobic system that uses Effective Micro-organisms (EMs) – This comprises beneficial yeasts and bacteria to kickstart the composting process. You may compost eggs, dairy, cooked food, as well as raw and cooked meat, and requires application of EMs each time food is added to the composter.
Once full, the bin is sealed and left to pickle for around 10 -14 days, and is turned into pre-compost. At this point, it is still too acidic to be added to plants, and needs further composting for at least two weeks for it to neutralise. During the composting process, leachate is also produced and can be diluted and used as a nutrient booster for plants.
3. Black Soldier Fly Larvae – If you are not squeamish when it comes to insects and larvae, and you produce a lot of food waste, you can consider having a black soldier fly larvae composting bin. This is not commercially available in Singapore, but some people have made their own system and attracted black soldier flies. The larvae creates by-products such as castings and leachate, which can be used on your plants, the latter should be diluted before application.
Composting Fruit & Vegetable Peelings
4. A worm bin- A vermicompost system comprises of worms and is more suited to those who have moderate amounts of raw fruit and vegetable scraps. Worms don’t like oil, salt, meat, dairy, onions and citrus, so this system is not appropriate for those who plan to compost food of this nature. As a result, you will have worm castings and worm leachate for use on your plants. Both contain micronutrients and beneficial microbes that help with soil conditioning.
5. Aerobic Compost – This can take the form of an outdoor compost heap or you can DIY your own compost bin. Both require the balancing of green and brown materials and can take some trial and error but is not too difficult. The most ideal carbon to nitrogen ratio is 30:1, so try to stick to this guideline. Make sure the bottom layer has lots of leaves to absorb any moisture, and you can include branches at the base to allow for aeration.
Are you ready to start diverting food waste away from incinerators by composting at home? Which of these systems appeal to you more? Leave a comment below to let us know!
About the author
Olivia Choong is a gardener, nature lover, and believer of a sustainable society. She writes about gardening and sustainable living on her blog – The Tender Gardener - and raises awareness of environment-related issues through a non-profit environmental society, Green Drinks (Singapore).
Want to find out more?
Join us and Food Citizen in our Life After Food - Composting Workshop series (27 Jun, 4 July, and 11 July, 2pm), where we cover aerobic composting, bokashi composting with the Urban Composter and vermicomposting.
Find out more at this link