Biodegradable “Wet” Waste Management

Categorisation of wet waste

What are some of the methods that work to process biodegradable waste? How do we choose a method?

The largest portion of waste is biodegradable (~60-70%) or often referred to as “wet” waste. Let’s look at methods to process this chunk of waste!

Processing Wet Waste

We humans rely on mother nature’s agents, bacteria, to do the job. In fact we are only beginning to learn about the many wonders that these organisms have to offer.

These bacteria can process waste either in the presence of air – aerobically, or without air – anaerobically. Aerobic bacteria need air to be healthy. On the other hand, anaerobic bacteria thrive in water and exposure to air impedes their growth and well being. The choice of the bacterial methods largely depends on the moisture in the wet waste.

Categorisation of wet waste
Wet waste categories

Our wet waste comes from two sources – plant waste and food waste. The plant waste comes from gardens, trees and bush clippings. While food waste comprises leftover cooked food, canned or bottled food and ingredients. There are some items that fall into both categories such as vegetable peels and fruit. 

If we have a large amount of plant clippings, leaves with some amount of vegetable peels, then aerobic bacteria is our choice with the method referred to as composting.

On the other hand, if we have a major portion of over cooked food with a high liquid content such as purees, soups, dal, rice and curry then we need to use anaerobic bacteria with the method referred to as digestion.

An easy way to think about this, is that the food rots and releases water (food is about 90% water). This messes up aerobic bacteria that need air. There are other considerations like the attraction of vermin, etc. Sometimes we need to utilise both methods – composting for plant waste and anaerobic digestion for food waste. The table below will assist you in making a decision.

Sr Parameter Composting Anaerobic Digestion
1 Bacteria Aerobic Anaerobic
2 Air Yes No
3 Moisture / Water 50% 900%
4 Outputs Compost Biogas + soil enhancer
5 Preprocessing Shredding Pulping
6 Processing Open area Closed tank


The largest portion of your waste is “wet” waste and the only way to address this is by working with bacteria. Bacteria are broadly classified as aerobic – that work in air and anaerobic – that work without air. The choice of process and the kind of bacterial we would work with depends on the kind of waste. Both sets of bacteria and processes can also be deployed.

Top 3 Reasons “waste” matters

Trash mountain

What is the big deal about waste? Is it something we should care about? Here are our top 3 reasons that “waste” matters.

Is waste really such a big deal that the Prime Minister needs to get involved and lead a Swachh Bharat Mission to tackle it? We are all ready to do our bit and put “waste” in the right place – receptacles. It might seem to be just a matter of getting our local bodies to get their act together to keep our cities clean. We’ve all seen images and heard about the fabulous job Indore is doing.

The short answer is that it is a big deal, even though it may not be evident. Here are 3 reasons why:

  1. We don’t like waste receptacles – they are smelly and offensive
  2. We want to be healthy and want our family and friends to be healthy as well
  3. We like and need open spaces, water bodies and fresh air

Reason 01: We don’t like waste receptacles – they are smelly and offensive

Trash mountain
The view from the summit of a trash mountain – this one from Ahmedabad

Currently the majority of our waste ends up in landfills – another name for a humongous receptacle. These landfills are so huge that they are interfering with the funnel zone of aircraft landing in Mumbai! Seems hard to believe, but true – the landfill in Mumbai is about 18 stories high – about the same as the Taj Mahal!

That’s 18 stories of crap that smells worse than your dustbin when it’s full or a garbage truck in the peak of summer! We have versions of these in every city, town and village. I view these areas as an embarrassment to our civilization. Sometimes I wonder if we can even be called civilized when we allow this (crap) to go on?

It’s only natural to want to act and find a resolution to this

Reason 02: We want to be healthy and want our family and friends to be healthy as well

Air pollution from landfill
The white plume is noxious gasses that the trash mountain in Mumbai delivers.

Maybe it’s alright if there are these mountains being created “far away” from our homes. Does it affect us at all? The fact is that it does – in not a very pleasant way.

Our family and friends are all currently breathing in polluted air from these dumps, and the air-conditioning unit can’t clean out the noxious gasses. Have a look at the satellite image of the fumes from a fire in the Mumbai landfill. The fumes can be seen all over the city – in fact all over parts of the city with some of the most expensive real estate in the world! The image is sufficient proof that any gasses emitted are getting into our lungs, and every person in the city is being affected.

We know that a trek in a forest or visit to a clean beach (Goa – at least for now!) is energizing and relaxing. A clean environment is a big factor in our overall well being. Our land and water resources are also being polluted by landfills and we all need to act and pitch in to secure these resources immediately.

Reason 03: We like and need open spaces, water bodies and fresh air

One of the things we enjoy the most is spending time in open spaces. Parks, sports facilities and spaces for children to run around freely is a necessity. The presence of water bodies with fish and birds makes these spaces even more special.

This experience we value is becoming quite a challenge to access in many cities. We are rather coping with traffic and barely even sufficient space to walk on pavements. A walk in the park seems a thing of the past and many of our water bodies smell like sewage and are full of trash.

We have the opportunity to turn our landfill sites to parks – Mumbai’s landfill is over 300 Acres in size. That’s about 200 football fields – right next to wetlands! Wouldn’t it be awesome to have an open space there with the opportunity for bird watching – the flamingos aren’t far away. This is possible. The only thing keeping us away from making this a reality is “waste” .


Waste is getting in the way of the things we value most. It remains a colossal challenge. Even ChatGPT can’t help much. Here’s what it came up with “I’m afraid I can’t physically take care of your waste”.

It’s probably time we get our hands dirty and figure this one out!