F. Adani et al., Determination of biological stability by oxygen uptake on municipal solid waste and derived products, COMPOST S U, 9(2), 2001, pp. 163-178
A new scientific apparatus and method are proposed for determining biologic
al stability by oxygen uptake (respiration index, RI), on municipal solid w
aste (MSW) and derived products. For measuring the RT, a dynamic approach (
with continuous aeration) was demonstrated to be more effective than the st
atic approach (without aeration). The validity of the method was tested by
comparing carbon losses calculated using both respirometric (carbon losses(
resp)) and analytical data (carbon losses(anal)) during four trials perform
ed on MSW and products derived from it. Carbon losses (expressed as g kg(-1
)C(i), in which C-i represents initial carbon content) were: 219.0 and 248.
0, 67.9 and 57.1, 39.6 and 36.4, and 250.7 and 280.3, using respirometric a
nd analytical data alternately for Trials 1,2,3, and 4. The comparison betw
een respirometric data using continuous or no aeration showed, for the latt
er, an underestimation of RI of between 70% and 90% that was more evident f
or unstable biomass leading to more similar values when stabilization occur
red. The scientific apparatus proposed made it possible to measure oxygen u
ptake under autothermal conditions and avoid problems connected with the us
e of a preset temperature, biomass temperature being a consequence of the m
icrobial activity, as is also suggested by the significant linear regressio
n of T versus RI (R-2 = 0.84, 0.73, 0.82, and 0.90 for the four trials, res
pectively). The methods proposed could be used with advantage in the future
for biological stability measurements, above all for heterogeneous materia
l such as MSW and its products, thus obtaining respirometric data that bett
er reflect what happens during an aerobic process.