# Thermogravimetry Applicability in Compost and Composing Research: A Review
## 1 Introduction  
The increase in organic waste, whether it comes from food, from the agro-food industry or from forestry waste, is a serious problem due to the consequences that its inadequate management may cause [1]. Composing could be the most suitable solution to the correct treatment and hygienization of organic waste, producing compost that can be used in agriculture. In this sense, the applicability in terms of economy and efficiency of composing has been demonstrated [2]. It has been amply demonstrated that the application of mature compost, in the adequate doses, increases crop yields significantly to different crops. The crops in which the application of compost is possible are very varied, depending on the maturity, granulometry, moisture, presence of impurities, etc. [3]. In addition, new uses are being developed for compost such as its use as an energy source through combustion, gasification or pyrolysis due to the high diversity of compost and qualities that can be offered. On the other hand, thermogravimetric analysis (TGA) allows one to quantify the change in mass weight under a selected heating rate and controlled atmosphere. Both weight changes and temperatures in the resulting thermogram can be studied. Among the advantages of using the TGA [4] that it requires very little sample quantity, (10-100 mg)offers reproducible and very accurate results and are obtained in a short time (depending on the temperature to be reached and the heating rate selected could be highlighted). In addition, due to the low cost of the analyses as well as the speed in the results, it allows one to increase the number of analyzed samples and, therefore, to diminish the implicit heterogeneity in the compost samples. Moreover, thermogravimetric methods could be applied to compost samples, without pre-treatment, and this allows them to be used as routine methods to supervise the evolution of the composting process [5]. [PERSON] and [PERSON] [6; 7] and [PERSON] and [PERSON] (1970) [8] proposed the use of thermal analysis for the characterization of soil and compost humic substances. In this form, thermogravimetric techniques could be used to clarify the degradability of organic matter and to evaluate qualitatively the stabilization rate of this matter, as well as the recalcitrant C in compost [9; 10]. Several authors such as [PERSON]\({}^{\prime}\)[PERSON] et al. [11], [PERSON]\({}^{\prime}\)[PERSON] et al. [12], [PERSON] and [PERSON] [13], [PERSON] et al. [14], [PERSON] et al. [15] and [PERSON] et al. [16] identify thermogravimetric techniques among the useful methods for the identification of compost stabilization. TGA is a technique in which the change in weight (either its increase or decrease) during the heating of the sample is measured. This heating is usually fixed. The first derivative of the weight change with respect to time (DTG) allows a better view of the points (temperatures) at which the greatest speeds of weight change occur. DTG is a more sensitive parameter compared to TGA and it is usually related to the reactions that occur at that temperature. When the temperature at which the weight loss occurs is higher, the organic fraction that is degrading is consequently more resistant and structurally ordered. The identification at which the mass loss is maximum, as well as the overlapping transformations, are clearly shown as peaks in the DTG plot. An additional advantage of these techniques is that they are very synergistic, and commonly used, with other techniques such as calorimetric [Differential Scanning Calorimetry (DSC), Differential Thermal Analysis (DTA)] and analytical (GC-MS, FTIR) techniques. Thermal analysis can give us information on data such as moisture content, certain compounds evolution and behavior of the material in relation to temperature changes among others and to complement chemical characterization data obtained from compost could be used. Moreover, it can be used for the improvement and quality control of the compost production processes.