Abstract: In a method for treating straw placed in a processing chamber (6) with gaseous ammonia, the gaseous ammonia is supplied in aqueous solution (2) and liberated by heating with a heater (5) to circulate within the straw in the processing chamber. By supplying the ammonia in solution, it is possible to use an ammonia source in the form of solutions readily available on most markets, even in less technically developed countries.When the surplus ammonia is removed from the straw (FIG. 3), it is washed out of the air/gas mixture leaving the processing chamber by the use of a scrubber (8) so that no or substantially no ammonia is discharged to atmosphere. The liquid from the scrubber (8) is kept in reservoirs (14,15) for use in treating the next batch of straw, or drained off to liquid manure as shown.