The largest investor in bankrupt Big Island Carbon LLC is looking for a buyer that will complete the construction of the company’s plant in Kawaihae that was designed to turn macadamia nut shells into high-value activated carbon.

The company filed for Chapter 7 bankruptcy on Nov. 5, laying off all 25 employees at the unfinished plant in the Kaie Hana Industrial Park. The plant had been under construction since early 2009.

The facility was expected to cost $20 million when work began but the price tag rose to about $50 million due to unanticipated cost increases, said Adam Carte, an operating partner for Denham Capital, the project’s main investor. Denham Capital is a leading energy-focused global private equity firm.

The company’s board of directors made the decision to file for bankruptcy when funding ran out, according to Carte.

“We are helping the trustee find a buyer to complete the construction of the plant,” which is nearly finished, Carte said Wednesday.

The founders of Big Island Carbon had high hopes for the company when it was launched, saying it would help diversify the island’s economy, create new high-tech jobs, support agriculture, and be ‘green’ in the process. The granular activated carbon produced by the plant was to be sold  for use in pharmaceuticals and other high-value products.

Big Island Carbon filed for bankruptcy in Delaware, where it is incorporated. The company  listed secured claims of $16.4 million, which includes a $5 million loan from Synergy Bank in McKinney, Texas, and $11.4 million in principal and interest to Kona Investment Holdings LLC.

The company also owes $395,684 to dozens of unsecured creditors. The Department of Hawaiian Home Lands, which leased the four-acre site to Big Island Carbon, is owed $150,000, according to court documents.