# Example from:
# http://www.islandseeds.org/wiki/Biofuel

   [ solar energy ] { color: blue; },
   [ water] { color: blue; },
   [ soil ] { color: burlywood; }

-> [ vegetation ]
-> [ processing ]
-> [ biofuel ]
-> [ combustion ]
-> [ useful work ] { background: lightgray; }

[ combustion ] -> [ carbon dioxide ]
[ combustion ] -> [ pollution ]

[ processing ] -> [ compost ] -> [ soil ]
[ processing ] -> [ carbon dioxide ]
[ processing ] -> [ pollution ]

[ water ] -> [ vegetation ]
[ solar energy ] -> [ vegetation ]


