Process dynamics evaluation in co-composting of vegetable solid waste with sawdust

Abstract

In this research selected physicochemical characteristics of organic municipal solid waste was assessed and the effect of composting and co-composting (with sawdust) over a period of 60 days on these parameters were evaluated. For composting and co-composting purpose, three box type units of 60 liters volume were used and filled with the mixture of vegetable solid waste (VSW) and sawdust (SD) in mixing ratio of 100:0, 80:20 and 60:40 v/v and aerobically composted for 60 days. The physicochemical parameters like pH, Electrical Conductivity, Total Volatile Solids (TVS), Total Organic Carbon (TOC), Ammonia Nitrogen (NH3-N), Organic Nitrogen (Norg), Total Kjeldahl Nitrogen (TKN), Nitrate Nitrogen (NO3-N) and Nitrite Nitrogen (NO2-N) were assessed for both raw solid waste and the mixture of VSW with SD. The temperature increase in the compost heaps was not significant due to small size of compost bins. The pH remained above 8.0 throughout the composting process in all three heaps. The effects of co-composting were significant. Use of sawdust resulted in reduced EC and NH3-N of the co-compost in comparison to the increase of the same for only vegetable solid waste compost after 60 days. Addition of sawdust in the co-composting process stabilized the vegetable solid waste better than only vegetable solid waste compost process. Co-composting with sawdust resulted in less increase of Norg and TKN, when compared to only vegetable solid waste compost. Vegetable solid waste mixed with sawdust lowered the degradation rate of organic matter as observed TVS and TOC degradation rates in only vegetable solid wastes were higher than the co-compost. Use of sawdust caused a diluting effect in the solid waste mixture and hence reduced the TVS, TOC degradation rates and Norg, TKN generation rates.