Methane and carbon dioxide emissions from different composting periods

Abstract

To investigate greenhouse gas emissions from compost preparations, methane and carbon dioxide concentrations and emission rates at different accumulative times and composting periods were determined. While the accumulative time was less than 10 min with a closed acrylic chamber, methane and carbon dioxide emissions increased slightly but with high fluctuation in the sampling error, and these values decreased significantly when the accumulative time was more than 20 min. During the 8 weeks of composting, the methane emission rate reaches its peak near the end of the second week and the carbon dioxide emission rate does the same near the end of third week. Methane and carbon dioxide emissions had high values at the first stage of composting and then decreased gradually for the maturity of compost. Carbon dioxide emission (y) was significantly related to temperature (x1), moisture content (x2), and total organic carbon (x3); and the regression equation is: y = 3.11907x1 + 6.19236x2 - 6.63081x3 - 50.62498. The regression equation between methane emission (y') and moisture content (x2), pH (X4), C/N ratio (x5), and ash content (x6) is: y' = 0.13225x2 - 0.97046x4 - 1.10599x5 - 0.55220x6 + 50.77057 in the initial composting stage (weeks 1 to 3); while, the equation is: y' = 0.02824x2 - 0.0037x4 - 0.1499x5 - 0.07013x6 + 4.13589 in the later composting stage (weeks 4 to 8). Different stage composts have significant variation of properties and greenhouse gas emissions. Moreover, the emissions may be reduced by manipulating the proper factors.