Methane emissions from gas engines driving combined heat and power installations

Abstract

In the Netherlands, wide-scale implementation of cogeneration of electricity and heat substantially reduces primary energy use and CO2 emissions. However, gas engines of cogeneration installations in the greenhouse horticultural sector alone are already responsible for a methane emission of roughly 1 Megatonne of CO2-equivalents. This amount has been determined by a series of measurement programmes as ordered by the Dutch Ministry of Infrastructure and Environment. This Ministry aims at reducing that methane slip, amongst others by setting legal emission limit values and stimulating engine innovations. However, the data from those measurement studies neglect important underlying causes of the emissions. Therefore, they are likely to be insufficiently conclusive for policy-making. In this paper, the most important causes of hydrocarbon emissions of combined heat and power (CHP) engines in relation to their design and process conditions have been assessed. An important finding is that a simple approach of just registering the output of measurement instruments and reporting these holds a high risk of methodological errors and neglected causes leading to inappropriate conclusions and subsequently inadequate policies. Overall, the paper not only contributes to the academic understanding of the qualifications and quantifications of these emissions, but also to the relevant policy-making in this field.