Submitted to: American Society of Agricultural Engineers
Publication Type: Proceedings
Publication Acceptance Date: 12/30/2003
Publication Date: 10/12/2003
Citation: Kim, H., Mcconnell, L.L., Millner, P.D. 2003. Characterization of odorants from products of 14 different commercial composters using solid phase microextraction. in:air pollution from agricultural operations III. American Society of Agricultural Engineers. Proceedings of the 12-15 October 2003 Conference (Research Triangle Park, North Carolina USA). p.026-033. Interpretive Summary:
Technical Abstract: Historically, composting has been used to treat residuals and by-products generated from a variety of sources: municipal wastewater treatment, animal rearing and processing, residential yard trimmings, and even petroleum refinery. The final product compost has commercial and agronomic value in the horticultural, landscaping, agricultural, and land reclamation sectors. As landfills increasingly restrict recyclables, more of the organic fractions are finding their way to composting; hence, compost products will be derived from a potentially broader source of feedstocks. In the U.S., the number of composting facilities processing sludge from municipal or industrial wastewater treatment facilities, yard debris, animal manure, and food residuals continues to increase. The quality of commercial composts is often evaluated by measuring the content of heavy metals, moisture, pathogen and nutrient content. Odors from the composts produced with different ingredients have not been assessed systematically. Experience in the U.S. has shown that processing and product odors have a major impact on the success of a facility. Previously, odors have been assessed with a human panel or olfactometry, which is subjective and often produce large errors. For better assessment of the quality of compost odors, more objective, scientific and non-human sensory dependent measurement is desirable. Recently, we developed a method to easily analyze representative odorous compounds, i.e., trimethylamine (TMA), propionic and butyric acids (PA and BA), dimethyl sulfide (DMS), dimethyl disulfide (DMDS), and carbon disulfide (CS2), in a gas matrix using solid phase microextraction (SPME) coupled with gas chromatography (GC). TMA, DMS, DMDS, and CS2 were extracted with a SPME fiber coated with carboxene/polydimethylsioxane and quantified using GC/mass spectrophotometer, while PA and BA were extracted with a SPME fiber coated with polyacrylate and were analyzed using GC/flame ionization detector. In this study, odors from commercial composts from 15 different producers were characterized using the new method with SPME/GC. The products analyzed comprise a cross-section of the wide array of compost feedstock ingredients used throughout the U.S., e.g., biosolids, yard trimmings, animal manure, and industrial by-products. Each producer was asked to collect three samples from a pile at the final stage, representating their commercial product, and to send them to the laboratory where a variety of quality tests were performed using test procedures specified in a national certification program offered through the U.S. Composting Council using standardized test methods. Odorous volatiles measurements supplemented other quality aspects. From the results, relatively higher level of sulfur compounds was observed from compost containing sewage sludge. Compost containing industrial by-products produced higher level of acids, compared to those containing non-industrial ingredients.