http://www.usda.gov/rus/electric/pubs/1724e302.pdf
Bulletin 1724E-302
Page
74
• Be too fine-grain to permit removal by conventional means such as nets and sieves
• Be abrasive to mechanical pumps
• Require specialized equipment to spread and recover
• Not burn, eliminating burning as a disposal process.
8.2.1 Natural or Agricultural Products
Many agricultural products are available for use in adsorbing oil from water. Most leaf-like
plants contain some natural oils, giving them a greater affinity for oil than water. When dry, they are lightweight enough to float on water. All of these products will become water-wet and sink, carrying the oil with them. Straws with hollow stems will float for longer periods than grass or hay. These sorbents are plentiful in agricultural communities and usually are available within a short distance.
Agricultural products are relatively inexpensive but are bulky. If needed in sizable quantities, they will require large protected storage areas. Rain-wet straw or hay loses a great deal of its affinity for oil, is more difficult to spread, and will sink more readily. The method of packaging or baling is important. Baling wire will quickly rust out in humid climates, rendering the bale useless for transport. Plastic baling line for storage of hay or straw is preferable.
Spreading an agricultural product on the water or along a beach can be a costly and timeconsuming operation unless a mechanical spreader can be used. Such mechanical units usually are available in agricultural communities and also are used by highway construction contractors.
Some of the natural products that have been tested and used as oil spill sorbents include
• Rice straw
• Oat straw
• Wheat straw
• Flax straw
• Johnson grass (hay)
• Coastal Bermuda (hay)
• Bagasse (sugar cane)
• Buffel grass (hay)
• Red top cane
• Cottonseed hulls
• Corn cobs (ground or unground)
• Peat moss
• Sawdust
Straws are the most common and widely used natural sorbent materials. Straws can be oat, wheat, rice, or flax. These are available to most communities. They are the most adsorbent of the agricultural products. Straws will float for longer periods because of their hollow or fibrous stems. Straw is the least expensive of the natural products and, if baled properly, can be stored for many years. Tests have shown that straws have a 30 percent greater oil adsorbing capacity than hays, 40 percent more than canes, and 100 percent more than cottonseed hulls. Straws have been known to adsorb between 8 times and 30 times their weight in oil.
Grass or hay makes a good sorbent. It is generally available as feed for livestock, but since it is a feed, it costs more than straw. This is principally a leafy material that has a high oil-adsorbing capacity. However, it can and will become water-wet and sink with the oil. Its use in shore-side or beach operations may be justified. It can be removed from the water with fine screens and easily raked into piles on a beach.
Bagasse and red top cane are regional products. Bagasse has a high affinity to oil but will readily become water-wet and sink. Red top cane, like bagasse, quickly becomes water-wet and sinks. Also, it has a relatively low oil sorption capability. Peat moss is expensive for oil spill cleanup work. Like cottonseed hulls and corncobs, it will readily become water-wet and sink. These products can be used on land and on beaches but their cost may preclude their use.
Sawdust quickly becomes water-wet, reducing its oil-adsorbing capacity and it tends to sink quite readily. Sawdust is also easily churned at the beach by breakers and dispersed in the water column, adding to the problem. On the beach, sawdust readily mixes with the sand during raking, making it impossible to remove.