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Abstract. Odor emission has always been a challenge for intensive animal operations. Various pit additives continue to be developed and improved to mitigate odor and manure solids. A commercial, biological-based additive is being evaluated for effectiveness in reducing manure solids, and gas and odor concentrations. In a semi-long-term test, twelve 3.79-L (1-gallon) glass jars are used to mimic semi-long-term manure storage. Manure was added into jars every week at a rate of 3.8-cm/week (1.5-inch/week) until the jars were full. Jars were arranged into four groups, each had three jars: untreated (control) group, and pit additive treated groups. The treated groups 1-3 were added with 50% dosage for group 1, 100% dosage for group 2, and 200% dosage for group 3. The stored manure was then analyzed for total solid and volatile solid contents, ammonia and hydrogen sulfide concentrations, and pH. After the additive application method and dosage were verified, a six-month and deep manure storage test, or long-term test, followed. Nine, 15 cm (6”) ID, 1.52 m (5‘) long PVC tubes were used to simulate different treatments: 3 for control, 3 for normal dosage, and 3 for 200% dosage. Concentrations of ammonia and hydrogen sulfide of the exhaust are being measured every month, while odor concentrations are measured at the middle and end of the test. Manure was analyzed for important nutrient contents as well. Results of the three-month test showed variable pH values and mitigation effects. While semi-long-term test did not present significant difference between treated and untreated groups, results of the long-term test indicates more promising outcomes. The following months of observations, especially the odor concentrations are necessary to fully evaluate the effectiveness of the additive.