A method wherein a methanol-containing waste gas stream, such as a pulp mill waste stream which contains methanol and other waste products, including methyl mercaptans, is passed in contact with a catalyst comprising a supported or unsupported bulk metal oxide catalyst in the presence of an oxidizing agent; preferably the gas stream is contacted with the catalyst, in the presence of the oxidizing agent, for a time sufficient to convert at least a portion of the methanol to formaldehyde (CH2O).