Waste 101: Composting

What, Why and How to compost at Mediamatic

This page serves as an introductory guide to our compost facility explaining in more detail how it all works.

In simple terms, a compost is a living "waste" pile, made of organic materials such as yard clippings and/or food waste, left to decompose in a controlled-environment. This process is the result of the synergy between macro-organisms (animals, insects), micro-organisms (microbes, yeast, fungi) and the environment (temperature, moisture), to create a rich, bio-diverse humus for the garden.

There are currently two types of composts in-use at Mediamatic:

  • The general compost facility located next to the Clean Lab (ideal for yard waste in the garden). 
  • A Bokashi fermentation (green-bin) compost in the Triangle area (located between the Aroma Lab and the Kitchen) dedicated to all food-related organic waste (more details below). 

The benefits of having a good compost are many-fold: It uses waste that would otherwise be "wasted" in landfills. It also improves the soil food web providing nutrients to plants and trees; it eradicates harmful bacteria, like Escherichia coli, due to the heat produced as a result of organisms working.

Other benefits include keeping the soil moist, resulting in less frequent watering. It also helps divert organic waste (e.g., food scraps) from landfills where its usually either incinerated or buried underground, instead, contributing towards soil-creation for community gardens where we can grow more food and flowers.

Tools, such as pitchforks, shovels and sifter are available in the Aquaponics. 

Photo by Norman Nack from Flickr


Fresh_Compost -

 How can I participate?

Easy-peasy: if your waste is organic (i.e., food or yard waste), just throw it in the green bin.

Paper and cardboard in general can be composted as long as they're not waxy or oily. Also, shredding them into smaller pieces helps accelerate the decomposition process. 

Bokashi bins:

Bokashi means fermentation in Japanese, and refers to a distinct method using anaerobic fermentation (without oxygen) using a fermentation starter. Unlike regular compost which requires aeration by turning the piles (~once a week), with Bokashi, you want to minimise air-exposure by pressing down the pile (the same way you tamper down your espresso) and keeping the bin-lids shut.

How it works:

The important factors for successful compost are: Air (Oxygen), Water (Moisture) and Temperature. All those factors will affect the process in varying degrees. Too high a temperature (above 55ºCelcius) will kill the compost micro-organisms (effective microorganisms, or EM), while cold compost will take more time.  

Also, achieving a balanced composition of carbon and nitrogen materials is important (general guideline: 30:1 carbon-nitrogen ratio). Materials rich in carbon are usually brown (branches, dried leaves), whereas Nitrogen includes green grass clippings and other green vegetation. One way to achieve balance is to layer brown-and-green materials when adding to the compost, similar to making a lasagna. 

In the kitchen: A white bucket is dedicated for collecting food-scraps. When done with prepping or cleaning, empty the bucket into the green-bin. Add a scoop of starter and close the lid tight. Give the bucket a quick water-rinse to avoid bad odours.

Bar and Office: Simply empty coffee-ground tray and tea leaves into the green-bin.

  • Every time you add food to the green bin, cover with fermentation starter (1 generous scoop per 5cm-layer of waste).
  • Green bin waste should be moist (~60%), but should not be neither soaking wet in liquid, nor dry.
  • There is a drain tap at the bottom of the bin, which needs to be emptied once a week (you can collect the "tea" for plant fertiliser, or just drain it in the soil).
  • Reminder: bins should always be kept closed to prevent any air from entering as much as possible.

When a bin is full, switch to another empty container. It generally takes anywhere from 4-6 weeks for successful fermentation  which should be covered in white mold (looks like mycelium) with a sweet-and-sour smell.

Once completed, the bokashi bin can be either: emptied onto the general compost pile (next to the Clean Lab). Alternatively, it can be buried in a ditch underground for a couple weeks to enrich the soil. You can also add it in the garden-beds by mixing and covering with soil (1:1 ratio).

What goes in?

- Any vegetables and fruit scraps

- Food leftovers (sandwich, salad, pizza, yogurt...)

- Coffee grounds (including filter) and tea leaves (from office/bar)

- Paper boxes, newspapers, paper towels and any non-waxy paper

** Meats/bones/egg shells are only allowed-in the bokashi bin, not into the compost pile (to avoid rodents)

What doesn't go in?

- No metals, plastics, glass, rubber-bands, cigarette butts (contain harmful chemicals)

Good compost smells earthy, and sweet, sometimes sour like sauerkraut. Trust your smelling senses, and if it smells bad or rotten, sprinkle some ashes or newspaper on top.

Thank you for your attention, and together, we can close the waste cycle to grow more plants (and food!)

FAQ (frequently asked questions)

- How long does it take from start to finish?

General compost [GC]: anywhere from three-months up to a year, depending on many factors such as the composition (incl. particulate size), temperature and moisture content. Because regular compost is aerobic (requires air), the best way to aerate the pile is done by turning it over with a pitch fork (rule of thumb is once a week, or every other week). This can be done with some effort by moving the pile from one to the next one.

When the compost is done, use the sifter (Aquaponics Lab) to separate coarse from finer, ready-to-be-used humus. Discard the larger materials back in the compost for further decomposition.

For Bokashi Compost [BC]: 3-to-8-weeks, depending on environmental factors, and composition. However, in general, bokashi method is much quicker than regular compost, hence why we use it for our food waste.

- The compost smells bad. What can I do?

GC: This is a sign of anaerobic decomposition (rotting). You can either aerate the pile (by using a pitch-fork to turn it around); you can also add ashes, or coffee-grounds on top to absorb the smell. 

BC should have a distinct sweet-sour smell, similar to sauerkraut or pickles. However, it should not have a "puky" rotten smell.  If that is the case, you have couple options:

  1.  You can cover the pile with a few scoops of ashes (from the rocket stove/pizza oven) and/or add shredded newspaper.
  2. Add more starter on the top. This will absorb the smells and help with the fermentation. Also, make sure to drain liquids from the tap every week.

- The green-bin is full. What should I do?

We have 4-bins total we use in rotation. If a bin is full, simply use the empty one next to it. Sprinkle one scoop of ferment starter at the bottom layer. If no bin are available, empty a full-bin on-top of the compost pile.

- No more starter. Where can I find more?

There should be more Bokashi starter in a box, in the Clean Lab. If running low, let someone in the office know to order more. This is the type we currently use (2kg bags)

- What is the blue container next to the kitchen area?

The blue drum-container is used to store used cooking oil. It should be disposed of professionally by contacting ROTI to come collect and dispose of the oil properly. They will process the collected oil and turn it into biodiesel, reducing reliance on fossil fuels. Win-Win!


- Compost is great but.. what else can we use the waste for?

Great question! There are many other methods that either include composting (or not) that can benefit us. 

Protein Production: For instance, calorie-rich food waste makes for excellent feed to breed and harvest Black Soldier Fly larvae (Hermetia Illucens), which in turn, makes great feed for animals rich in proteins and other minerals. This is a great way to turn biomass into protein.

Bio-gas Production: A Bio-digester is like an enclosed compost which harvests gas (e.g., methane) from organic materials decomposition (especially manure), which can be used for local energy production. Useful for cooking, heating, or sterilising substrates (to grow mushrooms!) or all three combined.

Biochar Production: Biochar is essentially charcoal made using a process called pyrolysis (low-oxygen burn) from any carbon source (e.g., corn stalks; coconut stalks; wood/tree pruning..). The resulting coals can be used in a variety ways, with cascading benefits (adding value to each step). For example, charcoal is a great water filter, deactivating harmuful bacteria and pathogens (benefitting context: sceptic system; farm effluents). This is the same system as used in commercial Brita water filters. 

Afterwards, those micro-organism "charged" coals can then be added to a compost to giving valuable housing to microbes, and stabilising pathogens. Finally, when deposited on soil, this EM-charged (effective microorganisms) coal enriches and adds to the soil carbon layer. More information on biochar at www.biochar-journal.org

Heat-Production (Biomeiler): Since good compost releases heat in the process of decomposition, heat recovery is made possible by using a biomeiler, sandwiching a coiled metal element, or water pipe within it, that can provide free-heating to households

Further compost resources from Cornell University: https://smallfarms.cornell.edu/2012/10/compost-power/