biofuel

biomass

boiler

branch

burn

chimney

chip

clip

collage

collection

crane

crush

cut

ecologic

ecology

economy

edit

environment

equipment

fire

firewood

flame

fuel

fume

furnace

granule

green

heap

heat

industry

lumber

machine

material

montage

mulch

natural

organic

pellet

pollution

production

renewable

screen

set

smoke

split

stove

technology

tree

video

wood