CO is an indirect greenhouse gas - CO reduction with Blue Fire catalysts
Carbon monoxide, or CO in chemical notation, is produced every time fossil fuels are burned. CO is an intermediate product of a combustion process, on the way to ultimately forming CO2. It is easily detectable by measurement and it has a lethal effect on humans when inhaled. Carbon monoxide is a colourless and odourless toxic gas that is produced during the incomplete combustion of biomass materials, e.g. wood. It is the second most important gas released during the combustion of biomass material after CO2, with an emission factor of about 130 g/kg of burnt wood. Biomass combustion emits high amounts of CO when the fire smoulders. CO emissions from biomass burning account for about 32% of the total CO produced globally from all sources. It occupies an important place in the environment at local, regional and global levels. At the local and regional level, it affects air quality. High CO mixing ratios can particularly affect human health .
This article explores the formation and the effect of CO on humans and the environment, and it shows a simple solution to the problem.
CO is not a direct greenhouse gas because its atmospheric radiative properties are insignificant compared to CH4 (methane) or CO2 (carbon dioxide). However, CO exerts a complex indirect effect in the atmosphere and thus has an influence on the greenhouse gases CH4 and CO2. Basically, CO emissions reduce the oxidation capacity or oxidising power of the atmosphere. This effect can increase the greenhouse gases CH4 and CO2.
Thermal processes in industry, the operation of heating systems and the use of motor-driven vehicles produce CO in large quantities, through the combustion of fossil fuels. Humans have a considerable influence in this.
Calculations assume that a person burns 400 kg of fossil fuels per year and person. If we assume that the CO content from these combustion processes is 10%, this means that 40 kg of CO per person and year are released into the atmosphere.
Above all, however, the burning of biomass on a very large scale, such as the slash-and-burn of virgin forests or tropical savannah fires, contributes to a high input of CO into the atmosphere. Added to this is the use of biomass fuels for heating and cooking. Taken together, these sources alone are thought to account for 25% of the total CO input.
In the atmosphere, CO is produced by many of the chemical processes. Here, a variety of volatile reduced species produced by global photosynthesis are oxidised mainly to water and carbon dioxide (CO2).
Almost half of all CO in the atmosphere is produced by the photochemically driven oxidation of atmospheric methane (CH4) and other non-methane hydrocarbons. CO produced in and emitted into the atmosphere is eventually removed within a few months.
While neither oxygen nor ozone attack CO in the atmosphere to any significant extent, the CO+OH→CO2+H reaction accounts for up to 90% of CO removal. The remaining 10 % is removed by soils. Since OH is also responsible for many reactions that produce CO, there is a complex coupling between CO, reduced gases, and OH.
Our focus of consideration is thus on the OH group, which is urgently needed for the reduction of the greenhouse gases methane and carbon dioxide, but which reacts much more easily with CO. Accordingly, the OH group is the key to the atmospheric reduction of greenhouse gases.
In the 1960s, when car engines were less efficient and there were no catalytic converters, cars emitted over 5% of the hydrocarbon fuel they burned in the form of CO. At the time, there were fears that CO emissions would rise unchecked - an alarming prospect given its toxicity to humans and other mammals. However, this fear soon disappeared after studies estimated that CO has a limited lifetime. This lifetime is estimated to be less than 0.5 years. It was assumed that photochemical production of OH radicals in the global background atmosphere provides a large natural sink for CO. But a second concern about CO was added, namely that the chemical reactions that produce and destroy CO, combined with increasing CO emissions from industry and transport and from biomass burning, would increase atmospheric ozone (O3). Indeed, characteristic positive correlations between CO and O3 have been observed in urban areas and in plumes from biomass burning.
The third concern, and the most important here with respect to CO, was that increased emissions of CO via the CO+OH reaction would "consume" OH groups and reduce the OH-based oxidative "capacity" or "output" of the atmosphere. This leaves less OH available to remove other reduced gases, especially methane (CH4). This effect affects the radiative properties of the atmosphere and enhances the greenhouse effect. Theoretical studies have shown that mitigation of the methane-induced greenhouse effect can be achieved in part by reducing CO emissions. This is a reasonable perspective .
Carbon monoxide (CO) affects atmospheric chemistry by contributing to ozone formation (O3) in the troposphere and by interfering with methane (CH4) decomposition in the stratosphere.
So if you act responsibly and climate-consciously, you reduce and mitigate CO as soon as it is produced. In the case of vehicles, this has been achieved to a large extent through the use of catalytic converters. The use of catalytic converters in all types of internal combustion engines is now a matter of course and is no longer a subject of discussion.
In Germany alone, 11 million single-room furnaces are in operation, emitting considerable amounts of CO into the ambient air and the atmosphere. The limit value according to the 1st BImSchV from 2010 is 1250 mg/norm m3 for CO. In older furnaces, the proportion of CO emissions is still significantly higher. Depending on the period of use and the fuel quality, the CO quantities described earlier in the text are produced.
What has long been common practice in cars must also find its way into biomass furnaces.
Catalytic converters for such furnaces have been available on the market for a long time. The company Blue Fire GmbH from Ramsloh has dedicated itself entirely to the development of catalysts for biomass combustion. The company has been in existence since 2015 and is a joint venture of the companies ETE EmTechEngineering GmbH and Emission Partner GmbH & Co. KG.
Thanks to the knowledge and experience of the two parent companies, Blue Fire GmbH is a proven specialist in the development and application of catalysts for biomass combustion.
Blue Fire catalysts are oxidation catalysts. CO and OGC emissions can be reduced by oxidising. During oxidation, CO and OGC emissions are combined with oxygen so that CO reacts to form CO2, OGC reacts to form CO2 and shorter chains of CnHm. This oxidation using ambient oxygen only occurs at appropriately high temperatures, which are necessary for the reaction. In the combustion chamber in the post-combustion zone below the flame impingement plate, the emission-rich exhaust gases sweep over the flame tip. With the addition of secondary air, the emissions react to form the reaction products described above. As the flue gases continue their journey through the wood burner, they cool down quite quickly and no further reaction takes place between CO or OGC and oxygen.
This is where the Blue Fire catalyst comes in. Blue Fire catalysts reduce the activation energy of the CO and OGC emissions. By coming into contact with the catalytic surface of the Blue Fire catalyst, they are enabled to react with oxygen again, even though the ambient temperature is already too low for such oxidation.
A catalyst makes this possible through the special catalytic coating.
The Blue Fire catalysts have been developed for use in wood exhaust gases. The focus of the development was on a very high temperature stability of the catalytic coating. When wood fires are lit, there are always long flames that briefly penetrate into the exhaust pipe. Such long flames therefore also strike the catalytic converter and should not damage the catalytic coating.
This is made possible by a coating of mixed metal oxides developed for wood combustion applications. This base coating itself already achieves good conversion rates for CO and OGC reduction. However, this effect can be further supported by adding precious metals to the catalytic surface. It is important, however, that the precious metals are distributed very evenly on the catalytic surface in a very small form - in nano size. The more evenly the precious metals are distributed on the surface, the easier it is for the exhaust gas flowing through the catalytic converter to come into contact with a precious metal cell embedded in the surface.
Due to the brief contact between the exhaust gas and the catalytic surface, the activation energy is reduced and the CO or OGC emissions are again able to react with oxygen. The desired oxidation of CO to CO2 or of CnHm to CO2 and shorter CnHm chains occurs.
The selection of the precious metals as well as their mixing ratio are just as important as the very even distribution of the precious metals on the catalyst surface. There are precious metals that can be used particularly well for emission reduction of the CO and OGC emissions mentioned. However, there are also other precious metals that can be used for the accumulation of oxygen on the catalyst surface. Others are more suitable for use in petrol or diesel exhaust. Still other precious metals and their mixtures are used for application in catalysts for gas or biogas emissions.
The experience of the catalyst manufacturer comes into play when selecting the precious metals and the mixing ratios. It is important to have research and a great deal of knowledge for the various applications. At Blue Fire, this is the case in the area for emissions from wood-fired systems. Blue Fire can draw on the expertise of its two parent companies, ETE EmTechEngineering GmbH and Emission Partner GmbH & Co. KG. The consortium has more than 20 years of coating experience. The companies are closely networked with respected German research institutions and actively pursue research projects with them to further develop catalyst technology for future applications.
For the design of the most suitable catalytic coating, knowledge of the exhaust gas temperature, the flow velocity and the composition of the exhaust gases is important. Of course, as an emission reduction target, the legal requirements or limit values or possibly own targets are of extraordinary importance. So much for the description of the mode of action at the catalytic surface and the basic chemical relationships.
In addition to the catalytic coating of the catalyst, however, the carrier of the catalyst is also of decisive importance. For emissions from wood firing, very good reduction results have been demonstrated with ceramic sponge supports. Ceramic sponge supports are particularly suitable for wood firing systems that are operated with natural chimney draught, as they present only a low resistance on the exhaust side. These ceramic sponge supports are available in different thicknesses and porosities, so that the choice of ceramic sponge support can take into account the pressure conditions in the flue gas system and the firing system. For systems in which only a very low pressure loss is to be tolerated, it is recommended to use ceramic sponge carriers with a low thickness of e.g. 18 mm and a porosity of 10 ppi (pores per inch). In systems that allow a higher pressure drop, smaller pores and greater material thicknesses can also be used. In any case, the catalysts must be tested for each individual application in order to ideally match them to the respective firing system.
Ceramic sponge supports are characterised by the fact that the exhaust gases are deflected relatively strongly when flowing through the sponge structure. The flow still remains laminar in the catalytic converter with sponge support, but it is significantly deflected in the direction of flow to enable as much surface contact as possible with the ceramic sponge structure. The flow deflection in the sponge catalyst generates a pressure loss. This is 0.5 - 1 Pa for sponge catalysts.
Dust settles on the upstream side of the sponge catalytic converters. Due to the existing flow of the exhaust gas, flow channels form in the accumulated dust layer. The accumulation of dry dust does not lead to blockage of the sponge catalysts. Carbon-containing components in the deposited dust are converted to CO2 by contact with the catalytic surface with the help of oxygen from the combustion air. This effect reduces the weight of the deposited dust. The deposited dust must be removed from the incident flow surface of the sponge catalyst at intervals. This is done quite simply by vacuuming with a hoover and a brush attachment or alternatively with a brush or hand brush. Blue Fire sponge catalysts can also be rinsed off with water due to their special coating.
Some well-known German and European manufacturers of stoves, fireplace inserts and heating inserts are aware of their responsibility and equip their latest developments with Blue Fire catalysts. Blue Fire catalytic converters can reduce CO emissions by at least 50%. If the installation and temperature conditions, as well as the design of the bypass, are carried out according to our specifications, CO reductions of over 80% are also possible over the duration of an entire combustion.
As a consumer, it is up to you. Ask your specialist dealer about wood fires with integrated Blue Fire catalysts and actively ensure that the greenhouse effect is reduced. With wood fires you heat in principle CO2-neutral. When biomass is burnt, only the CO2 that was absorbed from the environment during the plant's growth is released. However, by burning biomass, you cause CO emissions and thus support the processes described above for the creation of the greenhouse gas effect.
The time is ripe, the technology of catalysts has been for a long time and that of wood firing is also on its way to becoming clean and future-proof.
The consumer is the relevant actuator for active climate protection. Each individual is responsible for his or her CO contribution to the ambient air and the atmosphere.
Please feel free to contact us, we will help you on your way to CO reduction and thus to reducing the greenhouse effect.