On the blog post the other day, containing the video of activists sneaking onto the site of Exxon’s Mayflower oil spill, commenters with knowledge and experience in the industry (or just with dealing with oil spills) offered opinions that while the clean-up effort shown in the video is poorly done, the paper towels we see are not exactly paper towels, but more likely hydrophobic oleophilic polypropylene adsorptive pads.
So I took a trip down the internet rabbit hole to find out more.
As far as I can tell, the material most commonly used in making oil-only pads is polypropylene - specifically melt blown polypropylene. Polypropylene is a thermoplastic, which, among other things, means it melts when it’s heated. So with melt blowing, they heat the polypropylene while extracting it through holes and then blowing it with air. The turbulence of the air tangles the very thin individual strands.
All those thin strands mean lots of surface area for the oil to stick to. The structure itself also lends some absorptive properties (pdf) like its pulp-made paper cousin.
The technique for their use seems to be essentially the same “sop-up” that’s familiar with paper paper towels, although I was interested to learn that the dynamic of that “sopping up” is a little different. “Sorbents” can be absorptive or adsorptive. Part of the design of hydrophobic (water repelling) oleophilic (oil attracting) pads is that the oil doesn’t just get sucked in to fill the nooks and crannies of the pad (like a paper paper towel) but actually sticks to the surface area of the material the pad is made of.
The funny thing about melt blowing technology? Its history:
The significance of this work was recognized by an Exxon affiliate and a development program was initiated in the middle 1960s. Five years later, a patented prototype model successfully demonstrated the production of microfibers. At present, Exxon has developed most of the licenses and/or options to produce microfiber nonwoven and MB equipment.
I had a more difficult time answering the question of whether that mess of towels we see on the video are really how they’re supposed to be used. Looking at this 3M catalog, the context of their use makes more sense. At the scale of a pipeline spill the exasperating absurdity seems hard to deny.
Most of the application instructions I find suggest first using higher volume solutions (like skimmers or vaccuums) when possible and point out that overusing the towels can make more waste to clean up and dispose of.
There are frequently strong pressures on those in charge of response operations, however, to adopt other non-technical criteria to decide when to terminate a response measure. Thus, on many occasions, the inappropriateness of cleaning certain types of shorelines will be ignored and as many resources as possible will be deployed in an attempt to persuade politicians, the media and public that everything possible is being done to deal with the problem.
Aside from the question of whether that nest of towels in the Mayflower video is an appropriate use of towels, and more to Rachel’s complaint about whether, seriously, in this day and age and with all of the potential research money, this is what we have to resort to, the answer seems to be yes. Not only is that a standard part of the limited set of clean-up tools, but that same shoreline clean-up paper suggests that our solutions are such blunt instruments that sometimes its best not to clean at all:
Leaving residual oil to weather and degrade naturally is usually recommended for sensitive shoreline types such as salt marshes and mangroves, because they have been shown to be more easily damaged by the physical disturbance caused by clean-up teams and vehicles than by the oil itself.
I understand that bitumen (in tar sands) is compositionally different from typical oil and may respond differently to clean-up materials. That’s next on my list to learn about. As ever, I appreciate your insights and expertise on the matter.
This is a little too apples-to-oranges, but in the course of research I did find one study comparing paper towels with polypropylene towels on food oil. The results, in a nutshell: “Polypropylene absorbed 33.4% of the oils compared to 25.1% for polyester and 24.2% for paper towels.”
Sorry, one more note: Among the sites I’ve been reading is NOAA’s Response and Restoration Blog, and I’m compelled to point out that criticism of state of oil clean-up technology is not a criticism of the hard-working people in the spill response industry who seem to be making the most of the tools available to them.