Question: methane is produced by the decomposition of what
[{'answer': 'natural gas', 'provenance': [{'wikipedia_id': '18582230', 'title': 'Methane', 'start_paragraph_id': 1, 'start_character': 193, 'end_paragraph_id': 1, 'end_character': 204, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '18582230', 'title': 'Methane', 'start_paragraph_id': 54, 'start_character': 0, 'end_paragraph_id': 54, 'end_character': 897, 'bleu_score': 0.9685451587663261, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 1367446984524682283}, 'section': 'Section::::Occurrence.\n'}]}]