The waste gases from burning methane should contain CO2 and H2O, but no Ni or methane. Methane's chemical formula is CH4, meaning that each molecule of methane contains one carbon atom and four hydrogen atoms. When methane is burned, the carbon and hydrogen atoms in the molecule combine with oxygen to form CO2 and H2O. The reaction can be represented as follows:

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CH4 + 2O2 → CO2 + 2H2O

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In this reaction, the carbon atom in methane is oxidized to form CO2, while the hydrogen atoms are oxidized to form H2O. The reaction is highly exothermic, meaning that it releases a large amount of heat energy. This is why methane is used as a fuel for heating and cooking.

The presence of Ni in the waste gases would be unusual and could indicate that a nickel-based catalyst was used in the combustion process. However, it is unlikely that significant amounts of Ni would be present in the waste gases. The presence of methane in the waste gases would indicate that the combustion process was incomplete, and that some of the methane was not converted to CO2 and H2O. This could be due to a lack of oxygen in the combustion process, or it could be due to the use of a poor-quality fuel.