What's happening: Shares of Darling Ingredients (NYSE:DAR) skyrocketed Friday, up as much as 22% in morning trading after the rendering and biodiesel specialist announced better-than-expected second-quarter earnings and authorized a new $100 million share repurchase program.

Quarterly revenue fell 16.7% year over year to $859.3 million, helped by higher raw material volumes, but more than offset by a combination of lower finished product prices and a $113.9 million negative impact from foreign exchange rates. That translated to 7.7% sequential growth in earnings before interest, taxes, depreciation, and amortization to $105.5 million, and adjusted earnings of $0.13 per diluted share.

Keeping in mind Darling doesn't provide quarterly guidance, analysts' consensus estimates called for higher revenue of $891.8 million, but with much lower adjusted earnings of $0.07 per share.

Why it's happening: "This is the third quarter in a row that we have been able to improve margins all while working to offset lower and volatile selling prices," explained Darling Ingredients CEO Randall Stuewe. "Our focus on operational efficiencies and SG&A reductions are also beginning to contribute."

To be sure, Darling reduced working capital by $33.8 million during the quarter, and -- as I noted in my full earnings article yesterday after the close -- all three of its business segments (Feed, Food, and Fuel Ingredients) demonstrated sequential EBITDA margin improvements despite operating in difficult market conditions. Combined with lower capital spending and a $25 million dividend from its Diamond Green Diesel joint venture with Valero, Darling was able to repay nearly $70 million in debt this quarter.

Similar to last quarter, Stuewe also reiterated that DGD's operational performance remained strong, as it shipped more than 44 million gallons of diesel during the period. "We remain optimistic that the U.S. Biofuels Tax Extenders package will be reinstated," he added, "and will retroactively add approximately $25 million to income in the second quarter."

Finally, Darling's board of directors authorized the repurchase of up to $100 million of shares of common stock. Based on Darling's stock price even after today's pop, that's roughly equivalent to 4.6% of the company's entire float.

All things considered, this was another impressive quarter from Darling, which continues to demonstrate its ability to remain solidly profitable and reward shareholders even with these difficult market conditions. Over the long term, when those conditions eventually turn for the better, Darling's current efforts to streamline the business and manage costs should leave it that much stronger.

Steve Symington has no position in any stocks mentioned. The Motley Fool recommends Darling Ingredients. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.