Sensory assessment and characterization of odor nuisance emissions during the composting of wastewater biosolids.

Compost plants produce odorous compounds that can cause an "odor nuisance" to neighbors. Methods to evaluate odors exist, but they are not relevant for determining olfactory nuisance. The objectives of this study were to characterize by sensory means the odor nuisance (character and intensity) from composting plants that treat raw biosolids from wastewater plants. Research determined odor character and intensity by the "odor profile method" from raw biosolids, off-gases from the final compost product, and air samples from compost processing. Odor nuisance categories were defined on a "compost odor wheel". Eleven odor categories were determined from a total of 45 observed primary and secondary odor notes: (1) fishy/ammonia; (2) fragrant/fruity; (3) terpene/pine/lemon; (4) solventy/hydrocarbon; (5) grassy/woody/smoky; (6) earthy/musty/moldy; (7) rancid; (8) putrid/dead animal; (9) sweet; (10) sulfur/cabbage/garlic; and (11) fecal/sewery. The odor profile method and the compost odor wheel are suggested as a way to define odor nuisance from a compost plant.