In situ measurements and simulation of oxygen diffusion and heat transfer in maize silage relative to the silo surface

Abstract

Aerobic deterioration is a major concern for silage production and quality change in unloading phase. To simulate silage aerobic deterioration relative to an exposure surface of bunker silo, a partial differential equation system model including oxygen (O2) concentration, silage temperature (Tsi) rise and microbial activity was presented. There is still a need to assess the predictability of the developed model at different bulk densities (BDs). For this study, the Clark oxygen electrodes (COE) was employed for the in situ simultaneous measurements of O2 and Tsi within maize silage samples, which were packed into twelve barrels (i.d.: 35.7cm, length: 60cm, vol. 60L) at three BD levels (low: 520–550kgm−3; medium: 660–730kgm−3; high: 860–950kgm−3). To assure the COE to be insensitive to CO2, a cross calibration for O2 concentrations (0–20% vol.) was made at 15% vol. of CO2 in advance of performing the experiment. For each barrel, two of the COEs were installed at 10cm and 40cm behind the exposure surface, respectively. The model was computed taking the in situ measurements of O2 and Tsi to be targets. Our study showed general well-agreements between the model simulations and the in situ measurements of O2 and Tsi for all BD levels. Some uncertainties and relevant reasons were also addressed. Based on these results, we concluded that the model has sufficient ability to predict aerobic deterioration in silage for bunker silos being unloaded.