5. Carbon monoxide and nitric oxide from biofuel fires in Kenya
Evans Kituyi, Lackson Marufu, Shem O. Wandiga, Isaac Jumba, Meinrat O. Andreae and Günter Helas (Energy Conversion and Management 42, 1517 – 1542 )
Emission ratios (ER) of CO and NO relative to CO2 are reported from real time emission measurements on biofuel fires in Kenya. The experiments were based on available fuels burning in local popular traditional and improved stoves. The mean dCO/dCO2 ratios were 71, 79 and 74 mmol mol-1 for firewood, charcoal and agricultural residues, respectively, while the corresponding mean dNO/dCO2 ratios for these fuels, in the same order, were 1.8, 2, and 2.2 mmol mol-1, respectively. Whereas stove design characteristics largely influenced the dCO/dCO2 ratios, the fuel nitrogen content was the major factor determining the dNO/dCO2 ratios. The dCO/dCO2 ratio for fuel derived NO is not affected by fire temperature but linearly depend on the fuel nitrogen content. Other important fuel parameters that influenced the observed emission ratio patterns include fuel moisture content, size and volatile matter content in the case of charcoal. In comparison to savanna and forest fires, biofuel fires tend to favour formation of reduced or partially ixidised compounds. It is clear that a change in energy preference up the “energy ladder” leads to a reduction in the CO ER, an important result for emission mitigation policy design.