Features March 2002 Issue

Bilge Absorbers

3M oil-absorber pads are the fastest, most absorbent, most versatile, and cheapest of six products tested. Rarely have we seen less of a brainer. But read on—a couple of the fancier technologies are worth knowing about.

There are people–and we've met some in real life–who blithely fool around with their engines while unprotected by oil-absorbers. This is not what we would call "safe mechanics," and sooner or later everyone regrets their folly. 

Our test was simple: Place each product in a con-
tainer filled with water, oil, and a bit of antifreeze.
Agitate occasionally for a couple of months, and
see what happens.

The second you drop a loaded oil filter into your bilge, you realize that the most important piece of gear on your boat is the bilge absorber. If you're prepared, you already have one strategically placed under the filter, or at least somewhere under the engine. Even then, any errant oil will very quickly turn all the surfaces of the bilge a slick gray-black. It will foul the bilge pump, it will slosh up against the undersides of the floorboards, and it will coat every wire and connection.

An oil or fuel spill has to be cleaned up by hand—pumping it overboard is criminal, as well it should be. A bad spill, or a small spill that's left to slosh around, is a nightmare, and some bilges, particularly those with rough fiberglass or wood surfaces, never look the same again.

We wanted to find out which of the oil-absorbent products on the marine market work best, so we ordered a variety of them and put them in plastic bins filled with six gallons of water, a half a cup of antifreeze, and one quart of oil. We then let the bins sit for about two months in the back of the office, regularly jostling and jouncing them to keep things sloshing.

A couple of the products worked quickly and very well. A couple worked slowly and fairly well. One didn't seem to work much at all.

Absorber Types
There are two basic types of absorber. One type absorbs "mechanically," by means of wicking and adsorption or absorption. ("Adsorption" means that a liquid is attracted and adheres only to the outside of a surface, while "absorption"… well, you know what absorption means.) The other type absorbs the fluid and then reacts with it chemically or biologically, converting it into another state.

In both cases, the products are intended to absorb only oil or fuel—not water.

The products come in three forms—thin sheets, pillows or packets, and rolls or socks (mini-booms). The sheets are intended to be used both during work projects and for long-term maintenance. The pillows and rolls are intended more for long-term absorption; they are typically left in the bilge for several months or one boating season.

3M Sheets
3M sheets are made of random fibers of polypropylene, or plastic, which attract fluid by wicking, a capillary action in which the surface of a liquid and the surface of a solid are drawn together. The polypropylene fibers contain millions of tiny air pockets that hold the oil or gas.

The 3M sheets can be stuffed, packed, laid flat, or turned into a trough or funnel. In our test they soaked up the oil fastest (most of it in a few minutes) and held it in what became otherwise fairly clean water for two months. The soaked pads could be lifted out of the bilge easily without falling apart. They were also the cheapest products we tested.

Bottom Line: Only the MDR Engine Pad did as well soaking up the oil, but the 3M pad's excellent performance, combined with its low cost, make it our Best Buy.

MDR Engine Pad
Like the 3M product, MDR's pads and mini-booms are made of polypropylene and use wicking and air pockets to attract and hold oil and fuel. The engine pad that we tested is actually two 1/4"-thick sheets bound together at one corner. Unlike the 3M sheet, the MDR pad includes a grommet so you can attach a line and more easily pull it out of the bilge. The MDR product, with its two plies, was able to sop up all of the oil in its test container—a feat achieved by only it and the 3M product.

Bottom Line: The MDR's drawback is its price—nearly $11. You could buy nine 3M sheets for about the same amount of money.

MDR Mini-boom
The mini-booms are stuffed with shredded polypropylene that's contained by two layers of mesh netting, and are meant to live in the bilge long-term. You can just throw them in there or use the loops on either end to secure them so they stay clear of your engine's moving parts or the bilge pump.

MDR claims its mini-boom will absorb 4 quarts of oil, but it failed to soak up the single quart of oil in our test container. We moved the mini-boom around the container and it seemed to soak up the remaining oil, but it later released much of it again.

Bottom Line: This product worked pretty well, and we like the rope loops that are provided on each end, but it didn't absorb as well as the pads.

Petrol Rem BioSok
Instead of absorbing the oil, the BioSok tries to eliminate it. It uses the naturally forming bacteria in your bilge to biodegrade the hydrocarbons (it turns them into C02 and O2). The sock itself consists of "physically modified bee's wax" upon which oil-eating bacteria can grow, says John Opsasnick of Petrol Rem, the company that manufactures the BioSok. The bee's wax also binds and holds the oil and provides a food source for the bacteria, he adds.

The BioSok did poorly in our test, but that's not a surprise, says Opsasnick. "As a straight absorber, it's not going to do as well as the other products, but [absorption] is not its attraction."

The BioSok allows you to remove oil and fuel from your boat in an environmentally friendly fashion. Since the product is free of hydrocarbons after the biodegrading process, it can be dumped in the household trash rather than disposed of as a hazardous material, says Opsasnick.

There is a catch, though. That biodegrading process takes a year. Bacteria work slowly, says Opsasnick.

Opsasnick also thought the use of antifreeze and tap water (not salt- or lake water, which have more bacteria to begin with) in our test mixture may have slowed bacteria growth. "It does much better in a natural bilge environment," he said.

Bottom Line: The idea behind this product makes a lot of sense, but do you really want to wait a year to get rid of a puddle of oil or gas in your bilge? Common sense says no. Another drawback is cost: At $21.95 plus shipping, it's the most expensive product tested.

Enviro-Bond Captain's Choice
This is another product meant for long-term use. It has a loop on the end so you can secure it in the bilge. Its guts are stuffed with plastic polymers that are supposed to bond to hydrocarbons and turn them into solids. The result, as is the case with the BioSok, is that you can dispose of the product in the household trash.

Our sample stayed soft, though. The product's distributor, Bob Bergquist, said that it was probably over-saturated and needed to air-dry before it turned solid. He also explained that the molecular structures of gasoline and diesel fuel are more conducive to solidification than the motor oil we used.

Actually, we were less concerned about the product's reluctance to solidify than with the fact that it claims to absorb (or solidify) 2.5 quarts, and yet there was still about a half-pint of the oil remaining unabsorbed.

Bottom Line: We like the idea of the Enviro-Bond product, and would like to see it developed and improved in the future. Its price, at $10.95, is reasonable. Unfortunately, we were unable to get it to work as advertised.

Imbiber Beads
These are small pillows with grommets in one corner. The manufacturer, Imbibitive Technologies, claims its product truly absorbs hydrocarbons, taking in the fluid and distributes it throughout the body of the absorbing material. The result, says John S. Brinkman, president of Imbibitive Technologies, is that you can't squeeze out the fluid after the Imbiber beads absorb it. This makes for cleaner disposal—no dripping, in other words. The Imbiber Bead technology offers safety advantages, too, says Brinkman. The beads decrease the amount of hydrocarbon vapors released. He says polypropylene materials increase vapors because the surface area of the gas, oil, or diesel increases when it is adsorbed.

All this sounds impressive, but the two Imbiber Bead pads we tested did not pick up as much oil as the polypropylene products from 3M and MDS. And when we removed the Imbiber pads, oil dripped off of their surfaces, while the polypropylene materials did not drip because they had taken in all of the oil. Brinkman said his pads were "probably overwhelmed." We don't see how that could be, given the claimed absorption capacity of each of the two pillows we used—at least 3/4 of a pint, which would be more than the 1 quart of oil in the container.

Bottom Line: It's nice to know that the Imbiber Bead pillows decrease hydrocarbon vapors, but the product didn't work as well as the others. This is an expensive absorber: a packet of two costs $14.95. (The price does include a disposal bag that is meant to trap all vapors inside.)

If you have oil or fuel in your bilge you should remove it—immediately. Given this imperative, the products that must remain in your bilge for any length of time to work don't appeal to us much. The BioSok, for instance, requires a year to completely biodegrade the oil it has taken in. This type of product may be useful for long-term light duty, but not when you need to mop up a significant spill.

We appreciate the efforts and conscience behind the BioSok and Enviro-Bond technologies, and hope these products are developed further. For now, though, there's no question that the 3M sheets will be our first line of defense.

Contacts— Marine Development & Research Corp. (MDR), 2116 Merrick Ave., Merrick, NY 11566; 516/546-1162; www.mdramazon.com. 3M, 3M Marine Center, Bldg. 250-1-02, St. Paul, MN 55144; 651/737-4171; www.3m.com. Captain's Choice, Enviro-bond, Petroleum Environmental Technologies, Inc., 5581 Rapid City Road NW Rapid City, MI 49676; 616/258-0400. Enviro-bond distributor: Lakefront Enterprises, Inc., P.O. Box 573, North Hampton, NH 03862; 603/964-2740; www.enviro-bond.com. BioSok, Petrol Rem Inc., 2275 Swallow Hill Rd., Building 2500, Pittsburgh, PA 15220; 800/246-2275; www.petrolrem.com/biosok. Imbiber Beads, Imbibitive Technologies, 8 Hiscott, St., Suite #1, St. Catharines, ON, Canada L2R1C6; 888/843-2323; www.imbiberbeads.com.


Also With This Article
Click here to view "Value Guide: Bilge Absorbers."

Comments (2)

Thanks Robert. I believe the math is correct, but the text is not as clear as it should be. The maker claimed that each pad would pick up 3/4 of a pint. Since the testers used two pads, they expected that the two pads combined would pick up more than a quart of the water/oil/anti-freeze mix. They did not.

Posted by: DARRELL N | December 13, 2011 2:50 PM    Report this comment

Bad math regarding the Imbiber Bead pads: one quart is two pints.

Posted by: ROBERT R | December 13, 2011 2:02 PM    Report this comment

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