Untitled - MendelNet 2013 - Mendelova zemědělská a lesnická ...

MENDELNET 2013However, the comparison is rather tentative due to the difference in thermal performance. Thermalpower of the boiler for burning wood is 130 kW and a thermal power of cogeneration unit is550 kW. The concentration of NO 2 in biogas is about 519.5 mg.m -3 in an average. For wood, thisparameter is higher, and reaches 588.6 mg.m -3 . The amount of NO by the processing of biogas is183.5 ppm. Their production is to 1.5 times lower in comparing with average emissions from woodfuel (272.8 ppm). However, the average CO emissions from the combustion of biogas (407.9 ppm)are not lower than at the combustion of wood (334.5 ppm). This fact can be explained by more heatoutput of the cogeneration unit. Percentage of CO 2 emissions from the combustion of biogas is7.2 %. In the case of burning wood it is 9.5%. Based on this comparison, we can conclude that thebiogas emissions are lower than in the processing of wood fuel.Tab. 4: Comparison of emissions from the energy use of biogas and wood fuelSubstance Unit Emissions from energyusing of biogasEmissions from energyusing of wood fuelNO ppm 183.5 272.8CO ppm 407.9 334.5CO 2 % 7.2 9.5NO 2 [mg∙m -3 ] 519.5 588.6Increased production of CO and CO 2 from the combustion of wood can justify a higher proportionof carbon in percentage composition of the fuel. Similarly increased production of NO and NO 2depends on a higher nitrogen content in the fuel.CONCLUSIONSWith the investigation carried out, emissions were measured: the largest concentration of CO wasstated - 704.0 mg/m 3 in an average, and for NO 2 ; its average concentration was fixed at519.5 mg/m 3 . The NO 2 concentration in comparison with the concentration of CO is almost1.5 times lower. Amount of emission generated during the processing of biogas in cogenerationunit does not exceed the permitted limits.The results of comparing the biogas and wood fuel substance emissions amount shows, thatemissions of substances which were detected, except of CO, are lower in the case of biogas. Theexcess of CO in the case of biogas can be explained by definitely smaller output boilers for burningwood. The amount of CO is also a result of the high proportion of carbon in the combustion ofwood.Results of the study suggest that the general concerns of the inhabitants of air pollution in case ofbiogas plants in rural areas are unnecessary. Burning of conventional fossil fuels and wood as arenewable source is usually connected with higher emissions. In individual cases, however it mustbe taken into consideration technological processes, technical conditions and efficiency ofcombustion equipment and characteristics of the particular fuel used.But even in this direction it can be expected more and more difficulties in removing problemsespecially in the case of local combustion of fossil fuels or wood, because the effectiveness of localheating is very varied option that controls the minimum fuel usage and sometimes veryinconvenient, including the burning of plastics in local furnaces. Therefore, it is considered, thatburning in local heating brings a much greater risk in rural areas. In poorly ventilated locations(such as narrow valleys) a few local heating are able to cause quite significant air pollution. In thiscomparison, the biogas usage is significantly more environmentally friendly and controllable.Moreover, production of biogas has more perspectives in improving the technological process: „Foran increased dissemination of biogas plants, further improvements of the process efficiency, and thedevelopment of new technologies for mixing, process monitoring, and process control arenecessary“ (Weiland 2010).535 | P age