How to Burn Cardboard in a Fireplace Insert


Fireplace inserts heat a home more efficiently than a traditional mason-type fireplace. Air from the home is sucked into the insert to feed the fire as it consumes the fuel. Cardboard can be used as a fuel, but burns faster than wood and must be replenished more often. The cardboard will burn at a slower rate when it is layered. Layering displaces the oxygen and so the cardboard burns from the outside in, rather than from the inside out. If a plentiful supply can be gathered and replenished then the cardboard can be used as an alternative to wood, gas or pellet fuels.

Things You'll Need

  • Cardboard boxes
  • Serrated bread knife
  • Pliers
  • Garbage can
  • String
  • Newspapers
  • Matches
  • Hot poker

Preparing the Cardboard

  • Collect as much cardboard as you possibly can. Search dumpsters and ask grocery and department store clerks for their empty boxes. Many locations get new boxed produce and merchandise daily. Put your name on the waiting list so that a store clerk can call you when boxes become available. Call the stores once a week to coordinate a pickup time. Drive down to the stores and break the boxes down. Fold them up and lay them down flat. Inspect them for insects and use a dust brush to brush them off if any are found. Avoid boxes that are wet or have paint or plastic on them.

  • Bring the boxes home and cut them up into 12-inch-by-6-inch squares using a serrated bread knife. Pull staples out of the boxes with a pair of pliers and rip off all packing tape. Discard the staples and the tape in the garbage.

  • Stack the pieces of cardboard into piles six inches tall to form cardboard burning blocks. Wrap a piece of string around the ends of the blocks and tie a knot to hold them together. The strings should be tied around the six-inch width of the block.

Burning the Cardboard

  • Crumple up several pieces of newspaper.

  • Open the door of the insert and line the bottom with the newspaper until it is about three inches deep.

  • Place a few cardboard blocks over the layer of newspaper. Place a couple of them so that the six-inch width side is flat atop the newspaper. Space them so that they are a few inches apart to allow oxygen pockets to feed the fire. Set a couple of more blocks on top of these, staggering them to allow for more airflow among the blocks. The cardboard will sit and smolder if sufficient air isn't available to keep it burning.

  • Light the newspaper on fire and close the door of the insert. Open the air vents to allow oxygen to speed up the burn rate. Adjust the vents after the fire is going to slow down or speed up the burn. Open the door after the cardboard has burned to hot red embers and then stir up the embers with a hot poker. Place more cardboard blocks on top of the embers to keep fueling the fire.

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