ROTARY DRUM COMPOSTING OF HERBAL WASTE

Abstract

Generation of huge amount of solid waste during processing of herbs is one among the significant environmental related problems. This is often illegally disposed off in open environment, causing high load on open dumps and landfills, thereby creating unaesthetic conditions, obnoxious odors and vectors in the environment. Haridwar city is the hub of herbal industries in India. The industries established in its industrial state and surroundings generate several tones of herbal waste per day. There are several solutions for the management of this kind of waste, such as incineration, landfills and composting. Since, composting is considered as a viable option to utilize and recycle the waste for nutrient cycle, therefore, this study aims to utilize the herbal waste from the residue of the extracted plants like Withania Sornnifera, Raulfia Serpentina, Emblica Officinalis, Asparagus racemosus Acorus Calamus, Lepidium sativum, Anacyclus Pyrethrum and Cassia fistula by high rate composting in a rotary drum. In order to accomplish the objectives, the study was carried out under different phases viz, • Phase 1: Feasibility of rotary drum for composting of herbal waste under one rotation per day during 8-10 days composting followed by 25 day maturation period (Total composting period of approximately 35 days). • Phase 2: Effect of turning frequency (two rotations per day) on composting process. • Phase 3: Effect of addition of microbial innocula on composting process. • Phase 4: Co-composting of herbal waste with vegetable waste. In Phasel and 2; 100kg/day of a mixture of herbal waste (generated from Divya pharmacy, Haridwar India) and cattle (Buffalo) manure (collected from various places of institute campus) was selected as the mixed organic waste to be used in a ratio of 3:1 on wet mass basis during 8-10 days composting (30 min aeration/Ochaust blower operation after every turning) followed by maturation of primary stabilized compost from rotary drum composter for 25 days in a windrows method. In this case primary stabilized compost was formed into trapezoidal piles (length 2100 mm, base width 350 mm, top width 100 mm and height 250 mm) having length to base width (L/W) ratio of 6. Windrow contained approximately 40 kg of primary stabilized compost In phase 3, OXYDOL innocula (highly concentrated blend of enzymes, beneficial bacteria and organic catalyst) was added (100 ml) to 100kg/day herbal waste under one rotation and iii similar blower operating conditions. In phase 4, 80kg/day of mixed vegetable waste collected from Roorkee vegetable market and herbal waste in 1:1 ratio by weight was used. The quality of matured compost was assessed by analyzing various physico-chemical and biological parameters such as moisture content (MC), pH, EC, TOC, TN, C/N ratio, NH4+- N, NO3-N, TP and CO2 evolution rate. A significant decrease of TOC (15-28%, in phase 1; 15.5-29% in phase 2 and 3, and 16-34% in phase 4) with corresponding increase in percent ash content (40-43%, in phase 1 and 2, 35-53% in phase 3 and 58-65% in phase 4) was observed. Similarly, the low values of NH4+-N (0.12-0.18% in phase 1, 0.19-0.22% in phase 2, 0.12-0.14 % in phase 3, 0.26-0.28% in phase 4) and the corresponding increase of percent TN around 2.1-2.4% in the inlet to 2.7-3.5% in the outlet in all cases was observed. A reduction of C/N ratio was noted from 20-23 in the inlet zone to 9-13 at the outlet zone. The CO2 evolution rate of 3.5-4.5 mg/g VS/day in phase 1, 3.9-5.2 mg/g VS/day phase 2, 3.7-4.5 mg/g VS/day in phase 3, and 1.8-2.8 mg/g VS/day in phase 4 at the outlet zone was achieved compared with the value at the inlet 9-10 mg/g VS/day in phase 1, 2, and 3 and 9-13 mg/g VS/day in phase 4. Therefore the observation revealed that 8-10 days are sufficient for herbal waste composting in a rotary drum with 30 min passive aeration period after each turning. It was also observed that two turns per day have no significant effect on the performance of the drum due to higher air exposure which leads to the reduction in thermophilic temperature and moisture content thereby reduce the biological activity. Similarly addition of innocula shows no improvement in the quality of the compost, as already drum conditions itself are conducive for the development of rich & diverse bacterial community. Co-composting of herbal waste with vegetable waste indicates that better and matured compost in terms CO2 evolution and TOC reduction can be obtained by addition of easily-degradabale and high moisture waste (vegetable).