"All we found in the tanks was water, so it was very ineffective," Coast Guard Rear Adm. Paul Zunkunft, federal on-scene coordinator, told a news briefing.
The 1,115-foot "A Whale," an ore and oil supertanker refitted for skimming, was sent by TMT Shipping Offshore to help clean up oil spewing since April 20 from BP Plc's blown-out Macondo well.
The vessel arrived the first week of July in search of a contract with BP and began undergoing tests, which were hampered at first by bad weather. Conditions have since improved, and the tests have continued.
"The results are the amount of oil recovered by the A Whale is nil," Zunkunft said.
He said the vessel will not be deployed as a part of the Deepwater Horizon oil spill response.
"While its stature is impressive, A Whale is not ideally suited to the needs of this response," Zukunft said.
TMT billed the ship, which skims oil through horizontal slits on its sides, as a vessel that could collect up to 500,000 barrels of contaminated water per day.
The company defended the performance of its vessel and said the large quantity of dispersants poured into the water near the source of the spill made skimming difficult.
"The particular conditions present in the Macondo spill did not afford the vessel the opportunity to recover a significant amount of oil," said a statement by Bob Grantham, spokesman for TMT Offshore.
"This is due to the highly dispersed nature of the oil in the Gulf. When dispersants are used in high volume, virtually from the point that oil leaves the well, it presents real challenges for high-volume skimming," Grantham said.
The company would continue to work with the Coast Guard to improve its technology, he said.
Zunkunft said part of the challenge for the A Whale was maneuvering a large vessel to pick up scattered patches of oil, many no larger than a kitchen table. It also was not equipped with suction but let oily water in the slits as it sailed.
"The A Whale will probably need further modifications, and it may need a different type of oil spill, where you have thick, heavy oil that is concentrated in order to be effective," Zunkunft said.