Abstract:: Biochar-Amended Composting (BAC) plays an integral role in sustainable agricultural practices due to its multiple benefits in crop production, soil nutrient retention, carbon sequestration and environmental protection. Although accepted as a traditional method, there is lack of understanding in defining its suitability and efficiency on various base-materials and conditions. Being two carbon-based entities with plentiful nutrients and surface activity, biochar and compost find application in agricultural fields together or separately for improving the soil properties and crop productivity. Recent studies focus on defining the optimum conditions for their preparation, mixing, application and monitoring under various feed, soil, crop and climatic conditions. However, due to the complexity and specificity of the system, many influencing aspects of their interaction are yet unknown in detail. In this review, we analyze the recent advancements in the selection and preparation of new materials for BAC, and explain the mechanisms of Organic Matter (OM) degradation/sequestration happening in soil based on possible chemical/morphological transformations of organic carbon. Most of the performance results are in agreement with the previous records, but a few contradictions observed under diverse experimental conditions. In general, BAC enhanced the mineralization of carbon and sequestration of heavy metals, and stabilized labile fraction of OM due to the development of carbonyl, phenolic and aromatic functional groups on its surface. In addition, aging of biochar resulted in stable N-C=O and amino groups for the adsorption of nitrogen compounds thus decreasing the potential greenhouse gas emissions. The study further identifies potential future research gaps in this area.

The methods of compost preparation from sewage sludge and their modes of application to the agricultural elds have profound impacts on the soil ecology and environment. Besides their chemical conditioning effect on soil organic matter, they also impart physical attributes to the soil texture and structure. Though it is expected that compost addition improves water holding capacity and nutrient sequestration, there is lack of clarity in correlating the outcomes with conditions of excess nutrient storage/leaching despite the bene ts on crop yield. In this study, we present a systematic cause-evidence-impact relationship on the feedstock, processing and applications of co-composted organic matter. Various analytical tools were compared to elucidate the unique characteristics of co-composted sewage sludge to get a realistic understanding of the complex soil-compost interactions. Results from the spectroscopic characterization reveal the implications of selection of bulking agents and sludge pre-treatment in determination of the nal quality of the compost. The results attribute signi cant parent material in uence to the formation of well-de ned porous structures. The impacts of compost quality on the soil and crop can be proactively determined in terms of elemental composition, functional groups and stability indices. Thus the present approach provides good scope for customizing compost preparations and applications to get the preferred eld outputs.

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