Ethylene (C2H4) is an important natural plant hormone, which accelerates the ripening of fruit. It is present in small amounts in the exhaust gas of engines running on gaseous fuels, and becomes a problem where this exhaust gas is introduced into glasshouses.
Many companies in the horticultural sector use gas engines to provide combined heat and power and then direct some of the exhaust gas from these engines into their glasshouses to increase the carbon dioxide levels and thereby promote photosynthesis. The engines may be fueled with natural gas or biogas. In these situations it is a priority to keep the ethylene levels in the glasshouses under certain thresholds, and this can be achieved by fitting a special type of oxidation catalytic converter into the exhaust of the engine.