( Paper ( also ( ( ( produces heat ) ( when ( ( ( ( burned , ) but ) ( not ( as much ) ) ) ( as plastics ) ) ) ) . ) ) )
(ROOT (S (NP (NNP Paper)) (ADVP (RB also)) (VP (VBZ produces) (NP (NN heat)) (SBAR (WHADVP (WRB when)) (S (VP (VBD burned) (, ,) (CC but) (ADVP (RB not) (RB as) (RB much)) (PP (IN as) (NP (NNS plastics))))))) (. .)))
Paper also produces heat when burned, but not as much as plastics.
(ROOT (S (NP (NNP Heat)) (VP (VBZ is) (VP (VBN produced) (SBAR (WHADVP (WRB when)) (S (NP (NN paper)) (VP (VBZ is) (VP (VBN burned))))))) (. .)))
Heat is produced when paper is burned.