During the three months ended September 30, 2013, Rentech Nitrogen generated an operating loss of $18.3 million, compared to $29.2 million of operating income during the comparable period in the prior year. The primary cause of the operating loss in the current period was a loss of $30.0 million due to the impairment of goodwill related to the Pasadena Facility. The operating loss was also increased by lower gross profits at the East Dubuque Facility, negative gross margin at the Pasadena Facility that reflected a write-down of product inventories, and the addition of selling, general and administrative (SG&A) expenses and depreciation and amortization expenses for the Pasadena Facility.
Adjusted EBITDA for the three months ended September 30, 2013 was $16.1 million, compared to $32.9 million in the corresponding period in 2012. Adjusted EBITDA excluding Partnership level expenses totaled $18.0 million for the current period. The East Dubuque Facility and the Pasadena Facility reported $25.8 million and ($7.8) million in EBITDA, respectively, during the three months ended September 30, 2013. Further explanation of Adjusted EBITDA, a non-GAAP financial measure, has been included below in this press release.
Gross margin for the three months ended September 30, 2013 was 18%, compared to 58% for the same period last year. Gross margin at the East Dubuque Facility was 50% for the current period, compared to 58% for the prior-year period, due to lower product prices and higher natural gas prices, partially offset by lower depreciation expense. Gross loss margin at the Pasadena Facility was 19% for the current period, which reflected inventory write-downs and lower margins on sales of products that were produced from higher-cost raw materials purchased earlier in the year. During the quarter, the Partnership incurred a write-down of ammonium sulfate inventories of approximately $5.0 million because the costs of raw materials purchased in prior months and reflected in inventory were higher than current and projected market prices. Gross loss margin excluding the inventory write-down at the Pasadena Facility was 8%, while gross margin at Rentech Nitrogen excluding the inventory write-down was 23%.