( Landfills ( also ( ( produce ( methane gas ) ) . ) ) )
(ROOT (S (NP (NNS Landfills)) (ADVP (RB also)) (VP (VBP produce) (NP (NN methane) (NN gas))) (. .)))
Landfills also produce methane gas.
(ROOT (S (NP (NNS Archaeans)) (VP (VBP produce) (NP (NN methane) (NN gas)) (PP (IN as) (NP (DT a) (NN waste) (NN product)))) (. .)))