Aspen shavings are more expensive than pine shavings, reportedly not as absorbent, and can be more difficult to find, but the absence of volatile oils makes them an attractive choice for some guinea pig owners.
Pros: No volatile oils
Not as absorbent
Slightly higher cost
In the U.S. dried pine shavings are an economical, convenient, and useful bedding material for your guinea pigs. Small bags are sold in most stores that sell pet supplies. Farm supply stores sell a huge bag very reasonably ($5 to $6). This 3.25 cu. ft. compressed bale yields about 9.75 cu. ft. when decompressed.
All bedding materials have pros and cons. Some guinea pig owners object to pine, believing that the shavings' volatile oils may harm the liver when used long term or the respiratory system. Should you have any concerns, opening the bag and dumping a third or so of the shavings into a large open container for several days will allow the volatile oils to dissipate.
The weaker the pine smell, the fewer volatile oils will be present. Be sure that any pine shavings you purchase are dry. If the shavings in the bag are wet (stored outside in the rain), return them to the store. Any wet bedding is subject to mold.
Sticks to towels and fleece.
Not as soft as paper products
Concern with possible respiratory and liver problems (see bedding to AVOID)
Some people swear by this bedding. It is economical, keeps down odors and is easy to use. This product is sold in some grocery, feed, and wood stove stores. Air pellets before use should you be concerned with possible volatile oils (see pine bedding comments above). Some people feel the pellets are hard to walk on. They can be mixed with another bedding type or topped with a soft paper based bedding like Care FRESH. Guineapigcages notes that some wood pellets (which are also used to heat homes) contain an accelerant. Be sure to purchase only a product that is 100% wood.
May be harder to find
Out gassing a problem for some people
Very heavy, especially when wet
May be harder to walk on