Coden Stjsao

Primljeno (Received): 2012-02-21 Prihvaćeno (Accepted): 2012-05-15 Original scientific paper The Nash-Sutcliffe model efficiency coefficient (ENSC) has been modified in order to assess the quality of simulations compared to observed data from the mesophilic monofermentation of grass silage. By applying the ENSC it is not only possible to find parameter sets with the best fit, but also to analyze the sensitivity of each parameter. For modeling the concentration of hydrogen, both the maximum uptake rate for hydrogen km_H2 and half-saturation coefficient of hydrogen KS_H2 are equally sensitive. Modeling the concentration of organic acids as acetate, propionate and butyrate, maximum uptake rate km as well as the free ammonia inhibition constant for acetate uptake KI_NH3 and hydrogen inhibition constants KI_H2, respectively are much more sensitive than their corresponding half-saturation constants KS. Only changes of hydrogen inhibition constants and maximum uptake of acetate compared to the ADM1 suggested values (for mesophilic sludge digestion) were necessary to fit the measurements.