Oil spills don’t just damage ecosystems, they also create great amounts of waste that need to be disposed of. Libby Peake investigates what happens to the mess that cleans up the mess

In the immediate aftermath of a marine oil spill, the media is glutted with heartbreaking images of doomed animals and aerial shots depicting terrifying (yet visually striking) slicks of oil streaking the sea. These compelling images of environmental degradation receive the lion’s share of attention, but there’s another, equally important though less reported environmental issue related to oil spills: waste. Pictures of piled bags of contaminated waste might not be so prevalent, but the images and – more importantly – the waste are out there.

An independent team of scientists estimated that the most recent major spill, the blowout of BP’s Deepwater Horizon well in the Gulf of Mexico, resulted in 4.4 million barrels of oil being released into the environment. While scientists are baffled as to where most of it has gone (and, indeed, what impact it will have), some of it was collected by skimmers and booms or washed up on shore, resulting in over 640,000 barrels of liquid waste and more than 60,000 tonnes of solid waste (as of 19 September, at which point most cleanup activities had been completed). So, what happened to it?

According to Ken Haldin, Director of Communications for Waste Management, the company responsible for disposal of waste collected along the coasts of Mississippi, Alabama and the Florida Panhandle: “Collection of the oily waste in liquid form was one of the source reduction imperatives – if you can remove it from the water before it reaches the shoreline, you have an opportunity to separate the oil and to beneficially use a significant amount of oily liquid.” Of the liquid waste, 343,663 barrels were oil and water mixtures or emulsions from which oil could often be recovered – predominantly through centrifuging – and sold on either as crude feedstock or for fuels blending. The water underwent treatment before either being discharged to a sewage treatment plant or pumped into a deep injection well, a common practice with wastewater disposal.

When the oil actually made it to the shore, solid wastes posed more of a problem. Waste Management’s ‘Waste Management Plan for Mississippi, Alabama and Florida’ explicitly states: ‘Initially, the primary effort will be to collect, contain and remove contaminated materials as quickly as possible… As time progresses with spill cleanup activities and understanding of the waste being generated is attained, reuse and recycling of the waste will become more feasible.’ This focus on speed (a practice known as ‘dig and dump’) meant that most of the oil-contaminated solid waste initially headed straight for landfill or, occasionally, incinerators. BP collected nearly 55,000 tonnes of contaminated sand, debris, vegetation, irreparable boom, protective clothing and so on, in addition to 8,074 tonnes of non-contaminated solid waste and just 203.6 tonnes of ‘recyclables and recoverables’. According to the Associated Press, nine Gulf Coast landfills had received over 50,000 tonnes of oily debris and boom by mid-August. These were normal municipal landfills (oil spill waste was not classed as hazardous), three of which were already being investigated for potential environmental violations.

At the beginning of the cleanup process, a great bulk of the waste was contaminated sand, some of which was segregated at the landfills for potential cleaning or reuse by asphalt companies, for example. As the cleanup progressed, techniques became more refined (as the plan suggested they would) and, according to Haldin, the amount of sand collected “declined significantly as they changed procedures at the shoreline – using sifting instead of shovelling tools and different instructions for the cleanup crews”.

While this is the largest oil spill in American history, it may not be the worst as it occurred a mile deep, 50 miles from shore in warm waters. The water temperature is significant as the microorganisms that naturally break down oil thrive in warmer seas and the depth and distance from shore are significant because they (along with 1.8 million gallons of extremely controversial chemical dispersants) prevented most of the oil from reaching the shore and making a mess.
A much smaller spill closer to land, by contrast, can create a great deal of waste. In December 1999, the Erika oil tanker sank about 30 miles from France’s Brittany coast. The tanker split in half and came to a rest less than a tenth of a mile below the surface of the water, releasing between 10,000 and 20,000 tonnes of heavy fuel oil into rough seas. Stormy weather meant little oil could be collected at sea and it was widely dispersed before currents and the tide brought it ashore (even in good weather, booms and skimmers can only remove a small proportion of a large spill at sea – the International Tanker Owners Pollution Federation estimates just 10 to 15 per cent can be captured at best – and even these figures plummet in rough conditions). The Deepwater Horizon spill was 200 to 450 times larger than the Erika, but the smaller accident ultimately resulted in 260,000 tonnes of solid waste, compared to 60,000 in the Gulf.