• Oxides of nitrogen emissions: 69 kg x 500 = 34 500 kg/year, around a 90% saving on site.
• Carbon dioxide emissions: 12 t x 500 = 6000 t/year, a 26% around saving on site
• Gas savings: £2573 x 500 = £1 286 500/year (or 4 194 500 m3/year saved), around a 15% saving on site
• Electrical savings: £57 x 500 = £28 500/year (or 346 MWh/year saved), around a 65% saving on site. All these figures compare old pressure jet boilers to condensing boilers; the gas, NOx and carbon savings would be around 25% higher if the comparison was made against old atmospheric boilers. The NOx and CO2 savings are just in on-site combustion emissions. On top of this, the mains electricity used to power the pressure jet burners (346 MWh/year) is probably being generated at about 30 to 33% efficiency. This means we could be talking about a generated saving at the power station before grid losses of around 1 GWh a year. Think of the carbon and NOx reductions produced by not generating 1 GWh of electricity a year. We also release more than £1 315 000 a year in energy savings to spend on other carbon-reducing or atmosphere-improving projects across the country. So, by using gas-fired condensing technology, we can save the planet at the same time as we save money by increasing the value of your carbon and NOx saving pound — and making it go further. But, before we can really convince people of this powerful economic argument, I believe there are serious problems of perception that we need to change. It seems to me that the debate over emissions is based on the mistaken assumption that CO2 is the only real greenhouse gas. Rather than concentrating solely on carbon savings, as important as these undoubtedly are, I think we should include other greenhouse gases and air-quality issues in any evaluation we make of global warming. That is why I have included NOx levels in my financial calculations above. NOx gases [especially nitric oxide (NO), nitrogen dioxide (NO2) and nitrous oxide (N2O)] play an important part in keeping heat in the atmosphere —and will continue to do so for at least 150 years into the future. That means the decisions we make now have far-reaching consequences, and it makes the minimisation of NOx emissions as critical an environmental priority as reducing CO2. One member of the NOx family of gases, nitrous oxide, makes up a small amount of the atmosphere and is less than a thousandth as abundant as carbon dioxide. However, it is almost 300 times more effective at trapping heat, so it follows that NOx emissions should have an important part to play in boiler selection. And there are massive differences between boilers.
• The Broag-Remeha Gas 110 Eco modulating condensing boiler has NOx emissions less than 37 mg /kWh at 91% GCV.
• A traditional atmospheric boiler nearing the end of its service has NOx emissions of around 180 to 250 mg/kWh at 50% GCV.
• A boiler with a pressure-jet burner has NOx emissions of 160 to 220 mg/kWh at 80% GCV.
• A new wood boiler has NOx emissions of around 220 mg/kWh at 80% GCV (pellets). The message is clear. Modulating condensing boilers offer a massive reduction in all emissions including, but not limited to, carbon dioxide. Of course we, as an industry, need to be working hard to reduce the output of CO2 from our boilers. But let us not forget other environmentally damaging gases including NOx. Mark Northcott is national sales manger with Broag-Remeha.