During the six months ended June 30, 2013, Rentech Nitrogen generated operating income of $51.1 million compared to $61.1 million during the comparable period in the prior year. Operating income in the current period was reduced by lower gross profits as well as higher SG&A expenses and depreciation and amortization expenses attributable to the addition of the Pasadena Facility.
Adjusted EBITDA for the six months ended June 30, 2013 was $59.1 million, compared to $66.8 million in the corresponding period in 2012. Adjusted EBITDA excluding Partnership level expenses, totaled $63.7 million for the current period. The East Dubuque Facility and the Pasadena Facility contributed $58.5 million and $5.2 million in Adjusted EBITDA, respectively, during the six months ended June 30, 2013. Further explanation of Adjusted EBITDA, a non-GAAP financial measure, has been included below in this press release.
Gross margins for the six months ended June 30, 2013 were 38%, compared to 63% for the same period last year, primarily due to the addition of the Pasadena Facility, which realizes lower gross margins than does the East Dubuque Facility, and the effects of allocating fixed costs to lower volumes of delivered products. Gross margins at the East Dubuque Facility were 58% for the current period, compared to 63% for the prior-year period. Gross margins at the Pasadena Facility were 9% for the current period, which reflected certain inventory write-downs and sales of products that were produced from higher-cost raw materials. During the six months ended June 30, 2013, the Partnership incurred write-downs of sulfur and sulfuric acid inventory of approximately $0.5 million and ammonium sulfate inventories of approximately $1.8 million.
SG&A expenses were $9.6 million for the six months ended June 30, 2013, compared to $6.5 million for the prior-year period. The increase was primarily due to the addition of $2.6 million of SG&A expenses and an increase in Partnership level expenses to support the Pasadena Facility, partially offset by a 13% decline in expenses at the East Dubuque Facility primarily due to lower unused credit facility fees, legal expenses and other professional fees.