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WHAT TO ADD AND AVOID IN COMPOST BIN | GREEN TO BROWN RATIO

In today’s post, we will discuss on the materials that can be used and those to be avoided in composting at home, plus the Ideal Carbon Nitrogen and the Green to Brown Ratios.  

Composting is a controlled and accelerated rotting down of organic matter into nutrient rich compost. Aerobic Composting uses the natural processes of rotting and decay by microorganisms in the presence of oxygen and produces heat and hence it is sometimes called hot pile composting. Whereas Anaerobic or Bokashi composting is the job done mainly by microorganisms in the absence of air which is more like fermentation process.

Aerobic Composting requires 4 things: Carbon, Nitrogen, Oxygen and Water in just the right amount for proper composting. Out of these, we need to provide Carbon and Nitrogen in the right ratio, what is known as the C:N ration or Carbon Nitrogen Ratio.  Things that are rich in Carbon are called the Browns and those that are rich in Nitrogen are known as the Greens.

To be correctly composted, a material needs to have the following two important characteristics:      1. The waste material must be organic and biodegradable.    
2. The waste material must contain things that are liked by micro-organisms to feed on.  

So what types of waste can we can use in aerobic composting method. Firstly, let’s start with what we should NOT put onto our compost bin or compost heap. So let lists the Don’t’s First:

  1. Glass, metal and plastics are obviously prohibited in both types of composting.
  2. Oil, fat, meat, fish or dairy products are avoided because of their tendency to attract insects like flies and rodents. But these products are allowed in Bokashi composting.
  3. Hard woody branches, stems or roots which take a very long time to decompose.
  4. Rubber bands, Latex condoms, diapers and other obvious stuff like metallic objects like for example safety pins.  

Having looked at the things to be avoided, now let’s look at what we can add, and there are literally thousands to choose from. The micro-organisms and even macro-organisms like earthworms need to have a balanced diet and just like animals or humans they need “energy” in the form of food to survive. This energy is supplied to them by carbohydrates which contain Carbon. But micro-organisms also need proteins in the form of Nitrogen and also Phosphorus. Aerobic composting works best if these organisms are fed a mixture of carbon rich materials known commonly as “Browns” and nitrogen rich materials known commonly as “Greens” in proper ratios.

Let’s List the Browns First: Browns are mostly dried woody materials which are high in carbon. Without the browns your greens will decompose too quickly and turn into a smelly pile – that’s called putrified pile. Here’s the List of Browns:

like dry fallen leaves, dried flowers, wood chips, twigs, straw, shredded paper, shredded card board or paper cartons, like this and also the toilet paper rolls, toilet paper or used napkins or facial tissues, coffee filters and tea bags, cotton,  sawdust, pine needles, Pencil Shavings, dried grass clippings, peat moss, cocopeat or coconut fibers, used paper plates, nut shells, wine corks, toothpicks, paper cupcakes, used match sticks, wood ash or ashes from the fireplace, coal, etc.

Now Let’s List the Greens: Greens are mostly wet materials like waste kitchen scraps mostly vegetables scraps, fruit scraps, fresh grass cuttings, animal manure but not your cat or dog poop, bird or poultry droppings and feathers, fleshy plants and leaves, flowers, tea and coffee waste, egg shells, nail clippings (if no nail polish), human and animal hair, etc.

Having said that, now lets look at the Greens Vs Browns Ratio and the Carbon:Nitrogen Ratio. The right mixture of greens and browns, known commonly in the gardening world as the Carbon-to-Nitrogen ratio or C/N ratio, is important for proper composting.  We want Composting and not Putrefaction or rotting.

So what is the ideal C/N ratio for an aerobic composting? Most experts suggest a CN ratio of 25 to 30:1, which means 25 to 30 parts carbon rich material to 1 part nitrogen rich material. High Carbon may result in too slow composting whereas high nitrogen may result in foul smelling putrefaction.

HOW TO USE THE C:N RATIO?  Do not misinterpret this CN ration! This ratio describes the chemical composition of a material and does not mean that you need a volume of brown materials that is thirty times greater than the amount of green matter! Don’t make this mistake!  Here comes the Green to Brown Ration to our rescue. You have to understand this carefully. The Ideal Green to Brown Ration is 2:1 but it can also be 1:1 for those who are starting to compost. This means for one bowl of greens, you can add one bowl of browns. Let me explain this. Every material has its own C:N ratio, like for example Food Scraps has a Carbon:Nitrogen Ratio of 17:1, meaning 17 parts Carbon to 1 part Nitrogen). Saw dust has very high C:N ration of 500:1. Hence this calculation depends on what you add to your compost bin and it gets more and more complicated. You can store this table for reference of C:N values of various materials.

For Ideal Composting – Do Remember these 2 Golden Tips:

  • A 2-to-1 ratio of Greens to Browns is your best bet when creating a Batch Pile. This will aid you in creating about a 30:1 C/N Ratio. Adequate enough to get a hot pile.
  • A 1-to-1 Ratio works well with the Add as You Go Pile as well as for the Batch Pile and is safe for beginners. This will aid you in creating about a 50:1 C/N Ratio, adequate enough to get a warm pile.

In our Next posts of this composting series, we will demonstrate how to do Aerobic and Anaerobic or Bokashi composting at home.

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