Compost-recipe: A new calculation model and a novel software tool to make the composting mixture

For the composting process to begin and proceed regularly, the mixture to be composted must have some well-defined chemical-physical characteristics. For this reason, the software tools often called compost mix calculators are very useful to predict the characteristics that the mixture will have, knowing those of the raw materials that will make it up, and consequently the potential characteristics of the compost obtainable. The objective of this study was the definition of a new calculation model and its implementation in a new software tool, called Compost-recipe, with characteristics of both scientific rigour and ease of use, substantially improving the panorama of these tools. The new calculation model takes into consideration the most important parameters normally used and rather simple to measure: C:N ratio, moisture, pH, Bulk density; to these parameters it adds the possibility of considering the ratio between available carbon and total nitrogen, since it has been seen that it is of fundamental importance to consider the actual availability of carbon, so that composting proceeds quickly and the right process temperatures are reached. Also, the calculation model takes into account the procurement cost of raw materials, which are often of such importance that they deeply influence the decision on the type of mixture to be processed. Through some applicative examples, carried out with literature data, it has been verified the correctness of the implemented mathematical model, which uses a linear programming algorithm, and the effectiveness of the new software tool, that has been able to reproduce the analytical results obtained in the considered literature. The use of the new tool has also allowed us to highlight and discuss some particular trends or failures in composting processes reported in the application examples.