PNNL microbiologist George Bonheyo displays the original sawdust material (left) and how it appears after being chemically modified (right) to be oil-attracting and buoyant, qualities that are ideal for cleaning up oil spills in the Arctic. Image: PNNL.Researchers at the US Department of Energy (DOE)'s Pacific Northwest National Laboratory (PNNL) have chemically-modified sawdust to make it exceptionally oil-attracting and buoyant, characteristics that are ideal for cleaning up oil spills in the icy, turbulent waters of the Arctic. The nontoxic material can absorb up to five times its weight in oil and stays afloat for at least four months.
"Most of today's oil remediation materials are designed for warm water use," said PNNL microbiologist George Bonheyo, who leads the modified sawdust's development from PNNL's Marine Sciences Laboratory and also holds a joint appointment in bioengineering at Washington State University. "But as ice retreats in the Arctic Sea, fossil fuel developers are looking north, and we need new oil spill response methods that perform well in extreme conditions."
"The chance of an oil spill in the Arctic is real," said fellow PNNL microbiologist Robert Jeters, who is also taking part in the project. "We hope materials like our modified sawdust can help if an accident happens."
Containing oil spills in cold waters is especially tricky, as bobbing ice chunks can push oil below the water's surface, making it difficult to collect. The same goes for rough waters, where tall, clashing waves disperse oil.
The modified sawdust pulls double duty. As well as absorbing oil, it also enhances another approach to combating oil spills – controlled burns. If changing weather or tides move spilled oil towards a sensitive area fast, the oil can be burned before it causes further harm. Called in-situ burning, the practice can significantly reduce the amount of oil in water and minimize its adverse environmental effects.
Bonheyo and his team wanted to develop an environmentally-friendly and inexpensive material that can float in rough or freezing waters and support in-situ burning. Not wanting to create more pollution if emergency responders can't retrieve the material from the water, Bonheyo's team considered other natural ingredients like rice hulls and silica. But the best candidate turned out to be a fine dust called wood flour; a woodworking by-product, wood flour is often used to make wood composites.
To make the dust into a thirsty oil mop, the researchers chemically attach components of vegetable oil onto the material's surface. These attachments make the modified material oil-grabbing and water-shunning, producing a light, fluffy, bleached powder. The team is also experimenting with adding tiny, oil-eating microbes – fungi and bacteria – to the powder's surface, so that any left-behind material will naturally break down the remaining oil over time.
Applying the modified sawdust is simple: sprinkle a thin layer over oil on the water's surface. The material immediately starts soaking up the oil, creating a concentrated and solid slick that stays afloat thanks to the material's natural buoyancy. This oil-soaked material can then either be burned or retrieved.
The team is using PNNL's unique Arctic simulation lab in Sequim, Washington, to evaluate the material in icy waters. The facility is a customized shipping container that can be cooled to as low as 5°F, prompting researchers to don snowmobile suits and ski masks while they work. These low temperatures cause ice slush to form on the surface of water circulating inside a 290-gallon raceway pond within the container. Oil is spilled on this slushy surface, followed by a sprinkle of modified sawdust. Tests have shown the material's water-repellent nature prevents ice from forming on it, allowing it to soak up oil and remain at the surface.
The researchers are also testing how well the material performs in controlled burns. They recently conducted initial burns at the US Coast Guard and Naval Research Laboratory's Joint Maritime Test Facility near Mobile, Alabama, and burn tests continue today at PNNL's Marine Science Laboratory. Early results indicate that a small amount of material allows the burning of both thin and thick layers of spilled oil.
In the coming months, PNNL will further evaluate the modified sawdust, which will need additional testing and approval by multiple agencies before it can be used at actual oil spills. PNNL is developing the material for the US Department of Interior's Bureau of Safety of Environmental Enforcement (BSEE). This is the lead federal agency charged with improving safety and ensuring environmental protection related to the offshore energy industry, primarily oil and natural gas on the US Outer Continental Shelf.
This story is adapted from material from PNNL, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.