Hydrolyzed urine as a nutrient and condition corrector for enhanced coffee pulp composting

Abstract

The purpose of this study was to examine the physicochemical dynamics during human urine (HU) and coffee processing wastewater (CPWW) supplemented coffee pulp (CP) composting related to compost maturity, phytotoxicity and productivity. An in-vessel composting experiment was conducted in five treatments: C 0 (CP, control), C 1 (CP + CPWW), C 2 (CP + 1:1 CPWW:HU), C 3 (CP + 1:2 CPWW:HU) and C 4 (CP + 1:3 CPWW:HU). It was found that supplementing HU and CPWW optimized conditions for CP degradation manifested by a significant organic carbon (OC) reduction, and increment of NO 3 − –N (12.85–78.14%), P (35.38–47.98%), and K + (>27.57%). The NH 4 + –N reduction, its concentration, and the NH 4 + –N:NO 3 − –N were 62.16–82.66%, <500 mg kg −1 , and 1–2, respectively. The OC reduction was in the increasing order of C 4 (9.59 ± 2.83) < C 0 (11.76 ± 1.64) < C 1 (19.41 ± 3.34) < C 3 (24.15 ± 6.85) < C 2 (25.17 ± 2.21), and C 2 and C 3 were significantly different from C 0 ( F = 10 . 23 , p = 0 . 001 , 0.002) and C 4 ( F = 10 . 23 , p = 0 . 004 , 0.006). A longer thermophilic temperature range, lower C:N ratio (9 and 9.55), high C:N reduction (69.33 ± 2.08% and 67.67 ± 5.03%), higher cabbage productivity (1.82–1.85 kg pot −1 ) with >90% germination index (lowest phytotoxicity) was obtained in C 2 and C 3 , respectively. Thus, using HU can adjust conditions for CP degradation, provide high quality compost, and vital for the combined management of CP, CPWW and HU. Nevertheless, the effect should also be tested on other organic wastes and variety of crops for a large scale application. • Hydrolyzed urine enhanced coffee pulp composting. • The carbon to nitrogen and ammonium to nitrate ratios showed high quality compost. • The pH, organic matter, carbon to nitrogen ratio were in the compost standard range. • Macronutrients increased during the composting period. • Urine supplemented compost had higher productivity with no phytotoxicity effects.