Introduction
With an estimated population of 6 million, Bangalore is among the largest five cities of India. It generates around 3000-4000 t/d of USW and a major constituent (72%) of which is organic waste. Presently, Bangalore employs a quasi-centralized collection system leading to a predominantly open dumping of collected wastes. Various forms of informal waste recycling processes function in the cities of Karnataka and their value addition has been described (Van Beukering, 1994), However, there are constant changes in the extent recycled prior to dumping because the direct collection from houses provides little chance for itinerant collectors to collect the recyclables. However, when wastes were dumped by households in street bins, this provided a good opportunity for rag-pickers to recover many of the recyclables (Chanakya and Sharatchandra, 2005). Today, much of the recycling is done by waste collectors collecting wastes from individual households and the quantity of waste recovered this way is very small.
Today the waste collection system from house holds closely follows the Hon. Supreme Court Guidelines and MSW (H&M) Rules 2000, employing a range of small powered and non-powered vehicles for direct door-to-door collection of wastes. The extent of wastes collected ranges from 75-90% of the wastes generated. In this way there is a significant level of satisfaction among the users for cleanliness thus achieved, albeit occasional lapses at the local level. The primary collection systems transfer the wastes to large bins that are directly transported by tippers and dumper placer trucks to locations outside the city. During the early stages, a large part of the city wastes were sent to a compost plant situated outside the city limits (KCDC). Although the original machinery set up at this unit failed, it was quickly adapted to Indian conditions and made to work till recently when the city grew to encircle the composting yard itself. When the city produced about 650 tpd (1988), about 100 tpd of market wastes were taken back for direct application on land and another 150 tpd was handled by KCDC (Karnataka Compost Development Corporation). The rest, comprising a large fraction of decomposable was ‘open dumped’ along various arterial roads leading out the city (Rajabapaiah, 1988). This trend of open dumping had continued till about 1999-2000 where the extent of wastes removed had increased but the proportion of wastes carried out of these arterial roads remained roughly the same (Chanakya and Sharatchandra, 2005; TIDE, 2000). Today as the wastes generated has increased significantly, most wastes are being openly dumped at about 60 known dumping sites and many unrecorded sites. Composting accounts for 3.14%, but with increase of USW, the number of compost plants has not increased. A significant fraction of the total USW is generally dumped in about 60 shifting open dump sites in and around the city. Among these, more than 35 sites possess a mixture of domestic and industrial waste (Lakshmikantha, 2006). The existing solid waste treatment system in the city is therefore not very effective and not sustainable. Attempts have been made to carry out decentralized waste treatment by rapid aerobic composting with some degree of success (Subramanya, 2009, per. comm.). Simple waste management systems capable of handling between 5-20 tpd corresponding to the output from a single ward (population 30,000) has been tried in a few pockets of the city e.g. Yelahanka. This comprises of a primary segregation system that removes a lot of the recyclables and leaves behind the fermentables that is composted in 50 kg lots. The plastics (LDPE/HDPE) are washed with hot water and sent for recycling. Composting as the main method for rendering acceptable the fermentable fraction of USW, especially in the residential areas, does not yield high throughputs for successful enterprises. Thus considering the operational feasibility having been established for such a decentralized waste system, we propose a more sustainable waste management and processing system based on biomethanation of wastes at the decentralized scale. We attempt to show that this would greatly reduce the costs of SWM at the city level and will pave way for many small entrepreneurs to carry out decentralized processing facilities and be economically, environmentally and socially sustainable.
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