The concept of Industrial Symbiosis brings new way of waste management among industries which suggests, the wastes or by-products of one company become the raw material for another.
Due to rapid industrialization waste generation has become inevitable, so waste management is a main issue for industries. For management of waste there has been a hierarchy incorporated by several countries, i.e., Reduce, Reuse, Recycle, Recovery and Landfill. The Material Flow Analysis (MFA) in two industrial areas, Thandya Industrial State and KIADA Industrial Estate, Nanjangud, 20 kms from Mysore in the southern Indian state of Karnataka, collectively known as Nanjangud Industrial Area (NIA) which is home to over 60 diverse industries mostly multinational corporations exhibit an almost complete recovery of 99.9 percent of all the waste materials that they generate.
NIA generates 897210 metric tons (t) of waste annually out of which 893120 t (99.5 percent) of waste is being recovered or sent by the companies. Remaining 4090 t is either disposed to generating facilities or offsite. After recovering of 893120 t of residuals, 81 percent is reused by generating facilities onsite while 19 percent is transported. The 67 percent (113650) offsite material is being transferred to other parties.
Generated residual material is divided into five categories including Biomass: Bagasse, Biomass: other, Food residue, Non-Hazardous Ash, and Non-hazardous gas, out of which a total of 817360 tones is bio based materials. The biomass and food residue which accounts for 98 percent of the 724630 tons of industrial waste that is reused and recycled at the facilities where it is generated. The 99 percent of biomass residues are combusted to generate steam and electricity. NIA companies interact amongst each other for exchange of different material. They buy, sell and trade primary products and by-products, borrow raw materials on a returnable basis and offer other types of non-material based cooperation. Other than Biomass residues, carbon dioxide, spent acid, non-hazardous ash, and granite polishing residues are other four symbiotic transactions.
Spent acid from an aromatic chemical manufacturer neutralizes the alkaline effluent from an adjacent textile facility before the neutralized effluent is used to irrigate a small onsite sugarcane plantation. The ash reused within NIA is used by a neighboring facility during construction and staging. In addition to materials exchanges, a distillery in the NIA system generates 10 MW of electricity from a methane digester run on paddy husk and exports electricity to a neighboring facility as needed during power cuts via a direct, non-grid-tied connection. Of the verified symbiotic transfers, 95 percent are food residues returned to an industrial process, while 4 percent are biomass residues used as fuel. Apart from biomass residues used for energy recovery and food residues for processing, the largest waste stream from the system is 49,790 t of non-hazardous ash. Companies report a number of different uses for the non-hazardous ash: application as fertilizer, addition to cement bricks, incorporation into incense sticks as pulverized carbon, and for levelling uneven land. While the bulk of material is reused within generating facilities or reused directly within 20 km of NIA, 9,580 t of “All Other” materials are recycled through the theinformal market. More than 99 percent of glass, metals (ferrous & non-ferrous), paper, rubber, waste oil, and wood are reportedly recycled through the informal market.