Chemistry of Aerobic Composting

You’ve probably heard of composting. You may even have a friend that does it.

But what’s the big deal? And why do environmentalists, farmers and gardeners getting excited when hearing this word “composting”?  The chemistry behind composting is a pretty amazing thing.  I mean, let’s agree that, composting is nature’s recycling system. And nature’s recycling campaign are not funded by big CSR funds , not required actually, it is there at NO cost.

In this post, we’re going to discuss the following:

• Definition of Aerobic Composting
• Green and Brown?
• Chemistry of Composting and Climate Change

Definition of Aerobic Composting:

Aerobic composting is the process by which organic wastes are converted into compost or manure in presence of air. In this process, aerobic microorganisms break down organic matter in the presence of carbon matter and produce carbon dioxide, ammonia, water, heat and humus, the relatively stable organic end-product.

Green or Brown?

Aerobic composting needs a balanced mixture of organic materials, divided into two groups: the browns and the greens. The browns are rich in Carbon (C), low in Nitrogen (N) and so biodegrade slowly; the greens are the “high-energy” stuff for the composting process- they have a high moisture content, are rich in Nitrogen (N), low in Carbon (C) and biodegrade fast.

An effective aerobic composting process needs the right mixture of materials i.e. the browns and the greens. The optimal C:N ratio is between 25:1 and 40:1. Translated into common practice the rule of thumbs is to mix the greens and the browns in a ratio of 2:1. Microorganisms which helps in decomposition of organic material need ~20-30 parts of C:N. Excess of nitrogenous material can lead to production of ammonia (smelly compost)

Chemistry of Aerobic Composting:

Now that we know the difference between greens and browns, we can dig a little deeper into the chemistry on how the decomposition of plants works and why it’s vital to soil health. Nitrogen, a vital element to plant growth, is made accessible to vegetation in 2 simple steps:

1. When plants decompose, they create ammonia (NH₃).
2. Ammonia is converted into nitrate ions (NO₃⁺) by reacting with oxygen in a 2 step process.

Nitrate is the form of nitrogen that plants must have to survive and thrive! Here’s what the chemical equations look like:

Not only is composting good for the soil and our food supply, it’s also an important way to mitigate the production of the greenhouse gas, methane.

Let’s use an apple as an example. When an apple is composted, it decomposes in the presence of oxygen and oxygen breathing (aerobic) bacteria and creates nutrients (nitrates and phosphates), carbon dioxide and water.

When an apple is thrown in the trash and sent to a landfill, it decomposes in the absence of oxygen by non-oxygen breathing (anaerobic) bacteria in a multi-step process that creates carbon dioxide and methane.

Methane is a gas that has a Global Warming Potential (GWP) that is ~25 times greater than carbon dioxide. That means that methane is ~25 times better at trapping heat in our atmosphere than carbon dioxide.

So, by composting our food scraps, we:

• Mitigate the production of methane gas in a landfill
• Build nutrient dense soil which sequesters carbon from the atmosphere
• Create healthy soil for plants to thrive, increasing food production rates to tackle global hunger

Resource to learn more :

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As always, if you have any questions, feel free to drop them in the comments below or contact me via email OR whataspp at +91 9717764262 I’m always happy to help!