Waste-to-energy firm Covanta Holding Corp. is offering $335 million in tax-exempt bonds to refinance existing project debt and allow for future capital expenditures.

The Morristown, N.J.-based Covanta said in a news release the offerings, expected to close later in November, will refinance project debt at its Havermill, Niagara and SEMASS facilities. It also will fund certain expenditures in Massachusetts.

The move will free up about $280 million of additional cash flow over the next five years that would have gone for debt repayment.

“By replacing secured project debt with unsecured corporate level debt, this transaction will enhance our financial flexibility and further simplify our capital structure going forward," said Brad Helgeson, Covanta vice president and treasurer.