The primary reason for the stench generated by the KCDC like units, I feel, is simply because they are trying to handle more than the unit is designed to handle. Every unit has an optimal capacity that it can handle. But either due to bad planning or prestige issues one tries to go over the capacity and then the whole system eventually comes to a grinding halt. It will not even be able to handle what it was capable of.
The second (and important) reason for the stench is because so much plastic is mixed up in the wet waste. Firstly it is not segregated by the residents and even when this is done by some caring residents, BBMP eventually ends up mixing everything.
So even when you attempt aerobic composting (as at KCDC) by making Windrows, the impervious nature of the plastic prevents the essential circulation of air in the Windrow and causes the onset of a rotting process instead of the desired aerobic decomposition. I think, unless we start segregating at all levels, no system will be able to handle it. The more we segregate, the more value addition we can do to ensure that this valuable bio-resource does not become a pollutant.
The segregation should be at all levels – right from individual houses to apartments to wards to land fills. In case of KCDC, I don’t know what percentage of the waste is leaf and coconut litter, what percentage is waste generated by the vegetable vendors, what percentage is wet waste generated by hotels and households, what percentage is dry waste. But if these were segregated and collected & processed separately, we would be able to add enormous value to the waste trail. There is NO ‘One Size Fits All’ type of solution for handling waste.
For e.g. If BBMP simply had separate designated trucks and autos for collecting leaf and coconut litter and simply had a separate guarded land fill exclusively for this and simply let nature do the composting, one would consume a lot of the waste and get wonderful compost without much effort and virtually zero stench.
Reduce burden by dividing the waste
Leaf litter is the easiest waste to handle and it constitutes a sizable percentage of the total waste. This is the lowest hanging fruit in the waste chain and we should give the highest priority to this. As soon as we start adding kitchen waste in this same land fill (and especially if not done properly), anaerobic processes take over and the whole system then gets bad press & eventually comes to a grinding halt. It is sad to see the word ‘Compost’ which is sacred to most of us conjure up horrible images in so many people.
Of course, if we could do leaf litter composts piles (like the BBMP Pilot in Ward#45) in every park, apartment, temple, school, ward etc. it would reduce the amount needed to be handled by the land fill and save enormously on the fossil fuel used on transportation in the bargain. Even the land-fill should be designed properly using a Divide & Rule approach – say divided into 12 sections. Each section handles leaf litter for only one month. By the time all sections are full, the first section is ready to be harvested and accept more leaf litter and so on.
Keep vegetable waste clean enough
Next if they collected all the waste from the vegetable markets properly and delivered it to the many goshalas without mixing in other waste, the Goshalas would gladly accept this waste and the Cow’s magical intestine would turn it into the finest Compost in the least amount of time. The reason Goshalas don’t want to accept this precious freebie is because whatever is delivered to them comes with lots of other unpalatable things mixed in (including plastic).
Next if we had a decentralized, hierarchical approach to wet waste management, it would reduce the strain on any one system. In my opinion large scale centralized units whether in wet-waste composting, leaf litter composting or for that matter any type of processing are not a good idea. They cause too much strain on that small piece of the eco-system and Nature does not have the wherewithal to handle this type of onslaught. In addition it often tends to overwhelm the people handling it. So ideally, we need to have many decentralized units that progressively become larger. Each level should handle only the spillover from the level below and whatever it cannot handle should be sent to the next level.
The following would be the ideal system for handling wet waste at a city level:
Level 0: Family Units
Each family unit uses a Khamba (or similar can be fabricated with inexpensive pots) to compost the vegetable & fruit scraps that come off their cutting board (no cooked food to ensure that the system does not fail). Usage of saw-dust (from the timber yard and not chemically treated wood) ensures a fool proof method that every family can do. The wet-waste that they cannot handle including the cooked food waste is sent to Level 1.
Level 1: Apartment Units
Each apartment unit has a Bio-Bin (or similar solution) to compost (only) the spill-over from the family units. If it is a very big apartment complex, the composting units should be spread over many sub-units.
Level 2: Ward Units
Each ward unit has smaller version of the KCDC unit to handle the spillover from the apartment units and individual houses and restaurants. In addition they will (if required) buy back the finished compost from Level 1 & 0.
Level 3: Segregated Wet-Waste Land Fill
The spill-over from the Ward units finally ends up in a segregated land-fill where microbes can be employed to hasten the break-down. The land-fill can be divided into six sections. Each section is filled for one month only and the next section the next month and so on. By the time all sections are filled, the first section is ready to be harvested and again available to take in new wet waste.
This whole system can be made to work properly using a twin combination of reward and punishment.
For e.g. buying back the Compost would be the reward and a fee imposed on collecting Wet Waste would be the punishment.
Also the workers involved in this sacred work need to be suitably rewarded, incentivized and recognized.