Based on the validation data, we calculated averaged predictions errors on both the acquisitions and the test set Table . For the acquisitions set, the MAPE is 6.8% and 11.0% for the lignin yield and β-O-4 content, respectively. These numbers reflect the estimated experimental error, which was encoded into the surrogate models as a fixed Gaussian noise. The corresponding MAPEs for the test data are 7.8% for the lignin yield and 8.6% for the β-O-4 content. The fact that these numbers are comparable to the MAPEs for the acquisitions set, and thus by extension the estimated experimental noise, implies that the surrogate models are well converged and can provide accurate predictions.