Emissions of NO<i>x</i> from blending of hydrogen and natural gas in space heating boilers

As part of climate change commitments, the United Kingdom is considering an incremental transition from natural gas to hydrogen for domestic heating, blending up 20% (by volume) into national network. We consider possible impacts this policy on nitrogen oxides (NOx) emissions, a minor waste by-product combustion. A meta-analysis changes in NOx emissions hydrogen/natural blends used burners undertaken, with focus mixtures between 5% and v/v. Literature reports are highly variable: blend, when compared burning pure gas, vary over range –12% +39%, mean across 14 studies +8%. These estimates required important assumption be made that, not explicitly described, all literature data and/or concentrations were suitably corrected reduced energy density heat output arising once added. increase can rationalized through increased adiabatic flame temperature generated The associated plausible damage costs blend estimated fall within –117 million GBP +362 per year; (the maximum that could accommodated existing infrastructure) would lead –50 +154% –467 +1,146 year. at 292 For poor performing boilers, economic case scrappage replacement based primarily avoided. response older boilers added critical evidence gap needs filling before further decisions as heating fuel made.