# Feedback Characterization for Enhanced Heat Recovery from Composing Processes: A Review
## 1 Introduction
Sustainable waste management contributes to the achievement of SDG 12 (Responsible Consumption and Production) by promoting sustainable waste management and resource recovery. In addition, the compost used in agricultural practices increases the soil's nutrient contents, thus assisting in the achievement of SDG 2 (Zero Hunger) by enhancing soil fertility and supporting sustainable agricultural practices. By addressing these interconnected goals, CHRS presents a promising approach to advancing global sustainability. The success and overall efficiency of CHRSs depend on the types and compositions of the materials used as feedstocks. Selecting feedstock is critical as it directly influences heat generation, reaction rates, and the overall energy output during composting. Different organic materials decompose at varying speeds, leading to different heat generation rates, highlighting the importance of choosing feedstocks to optimize energy recovery in CHRSs. Factors such as moisture content, carbon-to-nitrogen (C/N) ratio, and biodegradability play a role in determining how effectively heat is produced and the quality of compost generated. Further exploration into the thermal properties of materials used in composting highlights their impact on temperature and biodegradation throughout the composting cycle. [PERSON] et al. [7] found that well-defined thermal properties of compost materials such as thermal conductivity, thermal diffusivity, and volumetric heat capacity play a vital role in practical thermodynamic strategies. These properties differ based on the type of material used, bulk density, particle size, and water content. Therefore, understanding these characteristics can assist in choosing the most efficient feedstock materials for sustainable waste management practices leading to enhanced temperature control and energy reclamation [7]. When it comes to choosing the materials for composting, one key factor to consider is the ability to deactivate pathogenic microorganisms. [PERSON] et al. [8] investigated how to optimize feedstocks in a vessel composting setup to lower the presence of microorganisms. Their research showed that an ideal mix comprising 50% food waste, 40% manure, and 10% bulking agents led to reaching maximum temperatures that effectively decreased pathogens, like _Salmonella_ and _Escherichia coli_. This research emphasizes the significance of feedstock selection for composting not for energy generation only but also for ensuring the safety and quality of the resulting compost [8]. The performance levels of the feedstocks in CHRSs are also subject to some of the parameters considered. The potential energy available, correctly termed as the lower heating value (LHV) of a feedstock, is vital when optimizing the recovery of heat. Nitrogen content parameters, as well as the C/N ratio, determine the necessary conditions for close-to-optimal microbial activity, which in turn facilitates the process of composting and, therefore, the generation of heat. Bulk density has a direct effect on the airflow and insulation within the compost pile, which significantly influences the rates of heat retention as well as the decomposition rates. The moisture content is essential for the development of microorganisms and the generation of heat, whereas volatile solids could be defined as the fraction of organic matter that is potentially biodegradable and, therefore, fuels energy generation. Proper understanding and adjustment of these parameters is critical for increasing heat generation and, therefore, efficiency during CHRS usage, adequately ensuring that the systems satisfy both energy and environmental targets. The primary goal of this study is to systematically review and synthesize findings on selecting the optimum feedstock to improve the effectiveness of CHRSs. Various research works have shown that specific materials can greatly boost heat production, efficiency, and overall usefulness of CHRSs.