TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Blanket: The blanket comprises a single layer, or two or more layers. The blanket comprises a thermal insulation layer capable of withstanding temperatures of 100-1000 degrees C; and a gas impermeable layer that is a different material than the thermal insulation layer, where the thermal insulation layer is disposed closer to the combusting biomass than the gas impermeable layer. The thermal insulation layer comprises a ceramic material, where the ceramic material is selected from ceramic pressed particulate paper and woven ceramic fibers. The gas impermeable layer is a metal foil. The metal foil is selected from stainless steel foil or other refractory metals and alloys foils from them. The blanket has the additional property of durability, such that the blanket is not structurally damaged after repeated exposure to temperatures of 100-1000 degrees C. The blanket further comprises a first protective layer that confers the property of durability, where the first protective layer is disposed closest to the combusting biomass. The first protective layer is a metal mesh layer, where the metal mesh layer is a stainless-steel mesh layer. The blanket further comprises a second protective layer, disposed furthest from the combusting biomass; and a set of air vents disposed peripherally on the blanket, where the set of air vents are configured to provide controllable air flow to pyrolyzing or drying biomass disposed beneath the blanket. Preferred Method: In producing biochar or dry biomass, the biomass is pyrolized at a temperature of 200-650 degrees C, and dried at a temperature of 100-250 degrees C. The step of maintaining the temperature of the biomass covered by the blanket for a sufficient time to produce biochar or dry biomass comprises adjusting the amount of air flowing to the biomass at least once. Adjusting the amount of air flowing to the biomass comprises moving a peripheral edge of the blanket to increase or decrease airflow or operating peripheral vent ports. The air from outside the blanket only reaches the biomass by passing around the periphery of the blanket. EXAMPLE - No suitable example given.