燃やす
environmental
alternative
bio
biofuel
biological
biomass
brown
closeup
compressed
control
cylinder
eco
ecological
ecology
economy
energy
environment
fire
firewood
fuel
granule
heap
heat
heater
heating
industry
nature
particle
pellet
pine
power
radiator
renewable
temperature
thermal
thermostat
thermotatic
valve
warm
winter
wood
wooden