[honway]

Thermal depolymerization, Appel says, has proved to be 85 percent energy efficient for complex feedstocks, such as turkey offal: "That means for every 100 Btus in the feedstock, we use only 15 Btus to run the process." He contends the efficiency is even better for relatively dry raw materials, such as plastics.

[boris]

"Thermal depolymerization, Appel says, has proved to be 85 percent energy efficient for complex feedstocks, such as turkey offal: "That means for every 100 Btus in the feedstock, we use only 15 Btus to run the process." He contends the efficiency is even better for relatively dry raw materials, such as plastics."

So long as the efficiency is < 100% (which it must be) you cannot get 'something for nothing'. That 15% simply means you are putting in 100 Btus and getting 85 back as fuel.