“as airlines seek to break away…” (lines 3-4) – [try].

“...brought about concern among environmentalists…” (line 6) – [brought].

“...the aviation industry is experimenting with biofuels…” (line 7) – [testing].

“...the European Union has condemned the use of agrofuels by airlines…” (lines 9-10) – [disapproved].

“...the airlines are being forced to limit their carbon dioxide emissions…” (lines 27-28) – [reduce].