This data set presents supplementary material to Monroy, Oscar; Saucedo, Gerardo; Espinosa, Ruben (2020) Composting a digestate from the organic fraction of urban solid wastes (OFUSW), Revista Mexicana de Ingeniería Química. An interesting design approach to prepare a balanced composting mass is proposed based on the carbon to nitrogen ratio (C/N) and the minimum required inert material to promote aeration. By using Scheffe’s simplex centroid method to design an optimum mixture of three components (digestate, fresh OFUSW and sawdust), using two regression equations for two process variables (C/N and volatile solids), a solution is obtained for a compost with the adequate C/N for a biosolid and the highest organic matter degradation efficiency. This data set contains the diagrams (figures S1 and S2) of the experimental rigs (lab scale and bench scales compost reactors), describing air circulation, mixing and heating devices. Table S1 shows the elemental analysis (C, N and H; O is reported as the difference from the total) and the C/N of the initial compost components. Ten mixtures were prepared to yield a C/N between 25 and 35 and set to compost. The resulting C/N and volatile solids loss due to the composting process are shown in Table S2. From these results, two regression equations were obtained using PASW Statistics 18 software, which generated table S3 and the contour levels of the tricomponents plot (figure S3). Three of these initial mixtures tried in a 95 L bench scale compost batch reactor. The resulting compost was tested for toxicity with the germination index. The results of three different reactor runs were tried by triplicate with ten seeds each are shown in table S4.