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Food waste conversion: Completing the food cycle

Every day, Indian homes, restaurants and food processing units generate unimaginable quantities of food waste, which, until fairly recently, was mixed along with all other waste and sent to a landfill for dumping. Making segregation compulsory did bring about some changes, but do we know what happens to our food waste after it is collected? To understand how food waste conversion is different from organic waste conversion, why it is advantageous and still misunderstood and why everyone must invest in it, Clean India Journal spoke to two passionate food waste entrepreneurs:

Milind Rane, Partner – Siddhi Wastetogreen Pvt. Ltd

Some people say that only garden waste is organic waste. Food waste is not entirely organic; it has inorganic constituents like preservatives, vinegars, and sauces. However, bacteria can work on inorganic component as well. Hence, we call this city compost because even the manure is not 100% organic.

The process of converting food waste is similar to that of converting other organic waste: shredding the entire quantum of waste to a particle size of 1-3 mm, then adding a bacterial culture for curing which converts it into compost within 16-18 days.

The process of converting food waste is similar to that of converting other organic waste: shredding the entire quantum of waste to a particle size of 1-3 mm, then adding a bacterial culture for curing which converts it into compost within 16-18 days.

If you have a waste apple, the bacteria will work only on the surface. But if you crush it, the bacteria have more surface area to work on. If dryers are not in place, we use drying agents like wood shards or dry leaves to absorb the moisture, which themselves get converted to compost. An automatic waste converter de-waters and then practically burns waste; that’s how you get results in 24 hours. That isn’t actually compost.

As a thumb rule, we assume that on average, each family in an apartment building will produce 1 kg of waste (both dry and wet). So, if you have a 100 kg machine for a building, one person can do all the work required by the machine in less than 2 hours.

The only constraint is that if you are not using an automated waste converter, and you get 100 kg of waste every day, you need space to store it (an automated one will have trays that finish the curing process on successive days). Therefore, we offer a service where we shred the waste at the site but take it to our own facility for curing, so that societies have no issues.

Mumbai’s municipal corporations have stopped sending vehicles to restaurants to pick up wet waste, so they have no choice but to go in for composting. It has become mandatory to process your own waste.

Joe Gomes, GM – Waste Management Division, Netel India.

A hotelier’s core business is hospitality. His only reason for investing in a converter is compliance. He is not bothered if the product is compost or not. But if he knows that his waste will do no further harm, he becomes ready to invest.

The many benefits of processing food waste:

Why was this machine invented?

Waste generated in your kitchen comes down to a common area in your society building, and will be there till the municipal truck comes. So, the decay process has already started; methane and ammonia are released, rodents and cockroaches are also attracted. The pickup truck has to navigate traffic and long distances and burns precious fuel, emitting carbon monoxide oxide all the way to your doorstep. Most municipal workers have no protective gear; our waste is a daily health risk for them. The truck goes to the next destination, dropping leachate all over the city. Finally, it reaches its destination, and unloads. The vendor appointed by a Municipal Corporation to process the waste often doesn’t have the capacity or the equipment to process all the waste that comes to him. Only a fraction is processed, the rest becomes mountains of waste. Leachate enters groundwater, and catches fire because of methane.

In 2011, I was one of the first people to design and manufacture an automated waste converter. I designed it to reduce the amount of waste sent to a landfill, truck trips, pest infestation, diesel consumption, risk to human life and leachate.

How is food waste different from other organic waste?

Food waste contains oils, spices, and many other things that are not present in regular organic waste such as garden waste or market waste. Handling food waste is a tough job in itself, but the composting process is similar. However, the microbe culture that we use is slightly different, because it has to do a tougher job. Sometimes, we do have to do pre-treatment, because of the high-water content in kitchen waste. We take out the excess water which is then sent to the sewage treatment plant; 60-70% of moisture content is okay.

Our machines with capacities of up to 250 kg – meant for apartment buildings and small corporate offices – have in-built shredders to reduce particle size. But they have two inlets: one through the shredder, one for direct input. If you have a bucket of wasted rice, you don’t need a shredder, you can feed it directly into the machine. For machines above 250 kg capacity, the design of our blades themselves hammers and pulverises food waste.

We have machines up to 2.5 tonne capacity. These highcapacity machines are used by large corporate houses like the Rahejas (in Cyber City, Hyderabad) and clubs where weddings take place (like Maharashtra Cricket Association, Mumbai).

Before and after converters:

When we are asked for a solution, we do a waste audit, in which we assess the type and quantum of waste before deciding what kind of technology is appropriate. If you have the space and want to go for the natural process, I would suggest drum composting or organic waste converters. If you don’t have space, an automated waste converter is best.

What we get at the end of a process is a soil additive, which can be used as is by amateur gardeners. But ideally, it shouldn’t be blindly used. First, soil needs to be tested for its nutrient values, and what is lacking in it. Compost needs to be tested too. After additions such as neem cake, our customers follow our SOP about how and how much should be used, with excellent results.


When you are processing fresh waste, there is slight odour. We connect this to a drain, or take it up in a chimney to a certain height; once it catches the air flow, it dissipates. What people don’t realise is that part of the odour is caused by the decomposition that started even before waste entered the converter. In our 750 kg-and-above machines, we have wet scrubbers; effluent gases are passed through a carbon filter and shower of water to remove odour.

Why some converters have begun to get a bad name?

When I developed my converter many years ago, I used a heating mechanism in which heaters heat a special oil, which in turn heats the waste, providing uniform heating. Since oil remains hot for some time, the heaters can be turned off from time to time, thus, bringing down electricity consumption. Unfortunately, many others have replaced this with a ceramic heater or a direct heating system. If the waste is wet, there is no problem. But once it starts drying, and when the motor takes a pause or the direction of blade movement reverses, the waste comes in direct contact with the heater, which starts burning it. There have been times when it has caught fire.

There is now a hue and cry against automated waste converters
in some parts of the country, where they are even banned. The
technology isn’t bad, it is misunderstood.

Cost vs benefit:

The monthly cost of maintenance is negligible. The per apartment one-time investment is roughly 3500 rupees. Depending on the size of apartments, the cost of maintenance per flat is 70-100 rupees per month, which includes labour. I was giving a presentation to a housing society, and the first question I got was, what is the return on investment? He was talking about making money after investing money. I asked him if he has heard of another kind of ROI: in 20 years, your child won’t have to buy oxygen cylinders, or drinking water bottles for lots of money. They will thank you for your investment now.

A 100 years ago, almost no one had toilets. Today, the most expensive room in the house – with the best fittings – is the toilet. Just as we have learnt not to leave our waste in the open, we also need to learn to take care of our own waste.

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