3.6. C/N ratio
The change in the C/N ratios reflects the organic matter decomposition and stabilization achieved during composting. The decomposition of organic matter is brought about by living organisms, which utilize the carbon as a source of energy and the nitrogen for building cell structures. During initial 60 days of waste loading C/N ratio at inlet zone was reduced drastically from 22–26 to 16–18 due to the reduction in carbon sourced materials, i.e. saw dust as feedstock ( Fig. 5). Similar pattern was followed at outlet zone, where theC/N ratio reduced from 12–14 to 5–6 during 150 days of waste loading. If the C/N ratio of compost is more, the excess carbon tends to utilize nitrogen in the soil to build cell protoplasm. This results in loss of nitrogen of the soil and is known as robbing of nitrogen in the soil. If on the other hand the C/N ratio is too low the resultant product does not help improve the structure of the soil. It is hence desirable to control the process so that the final C/N ratio is less than or equal to 20 ( CPHEEO, 2000). Therefore, it can be concluded that compost with higher or lower initial C/N ratio of feedstock reached primary stabilization after drum composting. Primary stabilized compost from rotary drum composter was further matured in windrow and vermicomposting ( Table 3). In Run 1, initial C/N ratio of primary stabilized compost decreased from 8.5 to 5.8 and 5.4 respectively in M1 and M2, while in Run 2, it decreased up to 4.2 and 4.1. Similar results showed during Run 3 where C/N ratio dropped from 5.9 to 4.6 and 5.9 to 4.2 after 20 days of maturation during M1 and M2 respectively. Results indicated that the highly matured compost was obtained after maturation of primary stabilized composts.