# Feedback Characterization for Enhanced Heat Recovery from Composing Processes: A Review
## 3 Results and Discussion
### In-Depth Feedback Evaluation for Optimizing CHRSs  
The purpose of the radar chart analysis presented in Figure 5 is to estimate the optimal feedstock composition for CHRSs by assessing various materials in terms of standardized competing parameters through the visual comparison of different feedstock types and their performance across a range of variables. This helps determine which materials are most suitable for maximizing both heat recovery and compost quality. The data were subjected to Min-Max normalization, which ensures that all the variables are scaled to fit the range from 0 to 1. This normalization also allows the effective comparison of parameters that are expressed in terms of different units and scales. The radar chart visually identifies the strengths and weaknesses of each feedstock category concerning these normalized values.  
Animal-derived materials show a good degree of balance and fulfill all the core parameters that are essential for composting. They are characterized by a high MC (normalized value: 0.7226), which accelerates microbial activity and causes rapid decomposition and higher heat generation. Moreover, such biomass types have high N (0.4588) and P (0.6667) contents, which make these materials nutrient dense. Thus, they can enhance microbial growth and the final compost quality. The C content (0.6400) and the C/N ratio (0.5854) are also well-balanced, facilitating sustained microbial activity over time and contributing to long-lasting heat production. Across most parameters, these materials perform consistently well, making them the most versatile and efficient feedstock for CHRSs. Animal-derived materials are ideal for composting processes where both rapid heat generation and nutrient-rich compost are desired.  
Plant-based materials are characterized by relatively high contents of VS (0.7034) and lignin (0.3764), which suggest strong potential for energy recovery through composting. However, the high lignin content slows down decomposition in traditional composting systems, which could limit their efficiency in generating rapid heat for CHRSs. Despite this, plant-based materials still offer moderate performance in key composting parameterssuch as MC (0.6556), C content (0.4426), and TOC (0.3283). These materials maintain a healthy balance between moisture and C, making them versatile, though this is not necessarily the best choice for maximizing heat recovery in CHRSs. Due to their slower decomposition, plant-based materials excel in situations where long-term heat release is desired, such as in extended composting cycles. However, in systems where rapid heat generation is required, they may need to be combined with faster decomposing feedstocks to optimize performance.  
Non-agricultural feedstocks lag behind animal- and plant-based feedstocks with respect to most parameters necessary for efficient heat recovery from aerobic processes. Its low normalized MC of 0.5604 and much lower C/N ratio of 0.2327 may cause slower microbial activity and low heat generation. Moreover, data for several key parameters, including cellulose, hemicellulose, LHV, VS, and pH, are not available for non-agricultural feedstocks. The lack of these data makes it difficult to fully assess the material's potential for heat recovery. However, non-agricultural feedstocks show moderate strength in C content (0.4465) and TOC (0.3528), which indicates some potential for microbial activity. This material may still play a role in aerobic processes if blended with other feedstocks that compensate for its deficiencies in nitrogen and moisture.  
In conclusion, based on the radar chart reported in Figure 5, animal-derived materials emerge as the top-performing feedstock for CHRSs due to their balanced nutrient composition and rapid heat generation. Plant-based materials offer long-term heat release but decompose more slowly, while non-agricultural feedstocks, hindered by missing data and lower performance in key areas, may benefit from blending with other materials for optimal heat generation in aerobic processes.