http://www.nola.com/news/gulf-oil-spill/index.ssf/2010/07/burning_and_flaring_of_oil_lea.html
Published: Friday, July 02, 2010, 7:20 PM
Times-Picayune Staff
With controlled burns temporarily suspended on account of tempestuous weather, Gulf waters have had a reprieve lately from the roaring fires and billowing smoke plumes that, since late April, have come to overwhelm the oily seascape.
But as fire teams prepare to resume their work, the burning and flaring of oil is attracting growing criticism from environmentalists who worry about the hazards it poses to wildlife and Gulf Coast communities. Some say that BP isn’t investing enough energy in other methods of cleaning up the roughly 2.2 million to 4.2 million barrels of oil that have spewed into the Gulf of Mexico as of June 29, according to the latest estimates.
As oil continues to pour into the Gulf, the question of how to optimize cleanup efficiency while minimizing environmental risks is still up for debate. Even comparing the efficiency of different methods of cleanup is difficult.
About 670,000 barrels of oily water have been skimmed as of July 1st, BP says, but there’s no telling what proportion of that is oil.
By comparison, controlled burns, also known as in-situ burns, have collectively removed 238,000 barrels of oil from the water’s surface since they were initiated by the Coast Guard in late April. The burning has cleared up roughly 6 percent to 11 percent of the total spill volume — an amount that exceeds the generally accepted estimate for the total amount of oil spilled during the 1989 Exxon Valdez incident.
But burning is fraught with complications. The crude that litters the Gulf is highly emulsified and depleted in hydrogen, which means it doesn’t burn readily. In many cases, it’s easier to skim it off the surface. For the oil to sustain a fire, it needs to be condensed to several millimeters’ thickness — a task accomplished by retrofitted fishing vessels that work in pairs, dragging a 500-foot line of fireproof boom between them in a narrow U-shaped arc.
On any given day, as many as 10 fire teams are on the water, corralling oil and setting it alight. As the fishing vessels move in tandem at a speed of less than 1 mph, oil at the water’s surface pools at the apex of the U. When roughly one-third of the area encased by the boom — anywhere from 500 to 1,000 barrels of oil in volume — is filled, an igniter boat releases uses a flare to set fire to a plastic container filled with gelled fuel, which floats toward the pooled oil and eventually burns it.
The ships stay in motion as the fire blazes; slowing down would allow the oil to thin out and eventually extinguish the fire. They try to tow into the wind so the smoke blows away from the vessels, but they’re not always able to.
Oil occasionally escapes beyond the boom and creates smaller fires outside the contained area, but the slicks die off themselves within a matter of minutes. The fire inside the boom burns two to three millimeters of oil every 60 seconds, rising as high as 100 feet and generating massive plumes of smoke in its wake.
The National Institute for Occupational Safety and Health, which has been monitoring air quality aboard responder vessels, has recommended that respirators be made available to all burn crew members. As it stands, not all fire team vessels are fully equipped, and crew members head inside the ship’s cabin if the smoke gets too heavy.
“Based on the air monitoring we’ve done to date, we haven’t had any situations where respirators have been required,” said BP consultant Alan Allen. “We’re in the process of determining the best way to [distribute respirators] that so that they have the option to wear masks.”
Gulf Coast residents have requested that controlled burns only be conducted when the wind blows out, according to environmental consultant Wilma Subra, who works with the Louisiana Environmental Action Network. Allen says that hasn’t been necessary because the in-situ burns occur 40 to 50 miles from the shore.
“If we were to do burns within 10 miles or so we would activate the SMART protocols,” he said, referring to a monitoring program for burns and dispersants designed cooperatively by four federal agencies.
Data from the U.S. Environmental Protection Agency show that concentrations of airborne particles from controlled burns are higher than normal at two or more monitoring stations along the Louisiana coast. The agency is also monitoring concentrations of volatile organic compounds evaporating from the oil on the water’s surface. It has classified the air quality along the coastline as “unhealthy for sensitive groups,” at worst.
But some residents have complained about nausea, sore throats, burning eyes, and respiratory problems, and some try to avoid outdoor activity when the wind blows in. Some of the health complaints may not stem from oil burning, but from the oil’s propensity to be churned by wind and waves into an aerosol that can blow onshore.
Subra says BP should cut back on in-situ burns and focus on skimming.
“If they can surround it by a boom they should be able to skim it rather than burn it,” she said.
Critics also note burning can imperil wildlife. Last week, the Center for Biological Diversity filed suit against BP under the Clean Water Act, charging the company with burning endangered sea turtles alive in the course of its cleanup efforts. In response, the National Oceanic and Atmospheric Administration’s National Marine Fisheries Service announced it would place a NOAA observer with each fire team to inspect oil corrals before they are ignited.
“You can’t help but recognize, if we’re collecting oil along the convergence line, the oil will be ideal for collecting but that may also be an area where there’s a potential for turtles to gather,” Allen said. “We go to great lengths…to try to avoid including that in our burn.”
Some oil is being burned using another method: flaring.
Only one of the two rigs collecting oil from the leaking well has the capacity to process and store the crude oil it captures. That ship, the Discoverer Enterprise, is connected to a cap that contains some of the gushing crude and feeds it to the rig through a riser. The Enterprise is able to isolate and burn the gas, store the oil, and pump the leftover water back into the ocean.
Its cohort, the Q4000, can’t process or store the crude oil it collects. So the vessel burns both oil and gas through an “EverGreen” burner, said to provide a relatively clean burn by eliminating visible smoke emissions. Since it went into operation on June 16, the Q4000 has burned an average of 8,556 barrels of oil per day, totaling 119,780 barrels as of June 29 — about half the oil burned thus far.
Burning oil aboard the Q4000 isn’t harmless, says Subra, but it’s far preferable to burning it off the water’s surface. Gas flaring, meanwhile, is a waste of potentially usable energy, and further burdens the atmosphere with unnecessary greenhouse gas emissions, according to NOAA.
Together the Q4000 and the Discoverer Enterprise have flared more than 1 billion cubic feet of gas — eight times the volume of the Louisiana Superdome. That’s a significant amount — it’s more than 1 percent of the total amount of gas flared in the entire United States in 2008, according to satellite data collected by NOAA’s Earth Observation Group.
BP plans to deploy a third containment vessel, the Helix Producer, but has thus far been foiled by the weather. Like the Enterprise, the Helix Producer would separate oil, water, and gas and flare off the gas. The Producer, scheduled to deploy Tuesday, is expected to increase oil collection by 25,000 barrels per day..
That can’t come soon enough for critics of burning oil in-situ and aboard the Q4000.
“At least they’re getting that material off of the slick and out of the water column,” said Subra. “But there’s still a long way to go before they recover all oil that’s coming out of that well head.”
Aimee Miles wrote this report. She can be reached at amiles@timespicayune.com or 504.826.3318.
Special thanks to Richard Charter