Dear Friendrich

Coal combustion with CO2/O2 is one of several promising new technologies associated with mitigating the CO2 rise in the atmosphere. In coal combustion with recycled CO2, the amount of NOx exhausted from the system is reduced to less than one third of that with combustion in air. This result is associated with decreased conversion of fuel-N to NOx and reduction of recycled NOx in the flame zone. The effects of CO2 concentration, reduction of recycled NOx, and interaction between fuel-N and recycled NOx on the decrease of the final NOx exhausted from the coal-combustion system with recycled CO2have been separated for appropriate NOx-reduction mechanisms.

Amine reclaimer wastes (ARW) generated in CO2 capture processes demand suitable disposal means. Such wastes contain remaining amine, NH3 and other degradation compounds. This study investigated the potential of using ARW as a NOx reducing agent, under laboratory conditions in a flow reactor. A simulated flue gas containing about 500 ppm of NO and 5% O2 was injected with liquid ARW under different stoichiometric ratios (TN/NO – total N to nitric oxide ratio) and temperatures.

This optimization extends beyond carbon dioxide emissions to include other significant greenhouse gases such as methane and nitrous oxide. In the case of gasoline vehicles, additional climate change benefits could be obtained by lowering gasoline fuel sulphur levels to enable the use of lean NOx Adsorber catalysts on gasoline lean-burn engines. EPA needs to continue its efforts to review and adjust criteria pollutant programs for all mobile sources going forward to not only provide needed health benefits from technology-forcing emission standards but also the important co-benefits these emission standards have on climate change.

Today, viable emission control technologies exist to reduce diesel exhaust emissions from both  new engines and vehicles, as well as in-use engines through the use of retrofit kits. The major technologies are listed below. Technologies designed to control particulate matter (PM) include:  Diesel oxidation catalysts (DOCs) , Diesel particulate filters (DPFs) , Closed crankcase ventilation (CCV), Technologies designed to control oxides of nitrogen (NOx) include:  Exhaust gas recirculation (EGR),  Selective catalytic reduction (SCR) ,• Lean NOx catalysts (LNCs),  Lean NOx traps (LNTs)Selective catalytic reduction (SCR), using urea as a reducing agent, has also been installed on diesel-powered vehicles. SCR is capable of reducing NOx emissions from 75 to 90 percent while simultaneously reducing HC emissions up to 80 percent and PM emissions by 20 to 30 percent. The greatest benefit came from the introduction of close-coupled catalysts (CCCs). This positioned the diesel oxidation catalyst (DOC) close to the exhaust manifold to allow rapid heating and therefore rapid oxidation of CO and hydrocarbons. The exothermic heat generated in the DOC by this oxidation reaction facilitates the rapid heat up of the downstream catalysts, such as diesel particulate filters lean NOx catalysts, and SCR catalysts. The widespread availability of ultra-low sulphur diesel for on-road vehicles has enabled the application of advanced emission control systems for diesel engines and vehicles .Diesel oxidation catalysts, diesel particulate filters, exhaust gas recirculation and crankcase emission controls have been successfully rolled out  on road vehicles. These technologies offer opportunities to greatly reduce emissions of particulate matter and other pollutants like toxic HCs. Advanced NOx control technologies are being developed to meet EPA  on highway emission standards. Technologies such as lean NOx traps and selective catalytic reduction have been demonstrated to be durable and effective methods of achieving low tailpipe NOx levels from diesel and other lean burn engines. Some of the technologies that reduce particulate matter and NOx are also applicable to the diesel engines already on the road today, offering a cost-effective way to reduce diesel emissions during their remaining life.

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Regards,

Prem Baboo

This is very valid question, not only in power generation but also for many thermal processing industries that use lots of fossil fuels.

If you look at the developments of many high-temperature process industries (metals, glass, ceramics) etc. you can see that over the decades, process temperatures often increased while specific energy consumption (per mass unit of product)  and hence CO2 emissions decreased. The reasons usually were better materials, process improvements and in general a better undertstanding of the process in question. At the same time, legislation enforces stricter limits for NOx emissions which could be realized by advances in burner technology, among other factors..

However, we are coming to a point where further NOx reduction will only be possible by using more energy (for DENOX plants, for example) which also means more specific CO2 per product unit.

It's gonna be interesting to see how the polticial boundary conditions will evolve in this context in the next years, both here in Europe, but also on a global level.

External costs are one way of getting the impacts of both emissions (and others such as PM10) in the same denominator (impacts expressed as € per tonne emitted).

You can find good examples of such methodologies applied to power conversion or transport on ResearchGate (e.g. from the European ExternE project). See one example below applied to both at the same time (electricity production to charge electric vehicles while avoiding emissions of ICE cars).

To complicate things further, this cost per tonne may not be constant over time as the balance of atmospheric reactions changes.

Article Health and environmental benefits related to electric vehicl...

To my knowledge, currently there is no generally accepted approach allowing to "compare" NOx with CO2-emissions. However, the methodology of "Life Cycle Assessment" (LCA) allows evaluating industrial application of technologies in a much wider sense  than micro-economy. There are several types of LCA. You will need to perform something like an eco-LCA (see S. Singh, B. R. Bakshi (2009). "Eco-LCA: A Tool for Quantifying the Role of Ecological Resources in LCA". International Symposium on Sustainable Systems and Technology: 1–6. doi:10.1109/ISSST.2009.5156770. ISBN 978-1-4244-4324-6). As already written in the forgoing answers, you will need information about the macro-economic impact (environmental impact such as flooding of coastal regions due to rise of the sea level, acidification of soil and surface water, health impact due to photo-chemical smog, etc.).

Just a short remark: The effects of NOx emissions are more local than those of CO2-emissions. However, local is relative. Acidification of lakes in southern Scandinavia had been caused by industrial (NOx and SOx) emissions from England!

The direct greenhouse gases are carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4). The indirect greenhouse gases are non-methane volatile organic compounds (NMVOCs), nitrogen oxides (NOx) comprised of nitrogen monoxide (NO) and nitrogen dioxide (NO2), sulfur dioxide (SO2), and carbon monoxide (CO).