Pellet Stoves Inserts - Convert Your Drafty Fireplace Into an Efficient Heating Source Pellet stoves are free-standing heat sources or fireplace inserts that fit into your existing fireplace. They are made of compressed pellets derived from wood byproducts, such as sawdust, and are extremely efficient. They are also "green" since https://www.fireplacesandstove.com/products/us-stove-non-electric-pellet-stove-60-lbs-hopper