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Success and acceptability of the bio energy conversion technology to a large extent depend upon management of the inevitable by-products generated during the conversion process. By-products can be considered favourable as organic fertilizer as they retain nutrients with varying composition depending upon input biomass. However, characteristics of these heterogeneous resources with respect to feedstock and processing conditions have to be assessed to state on their agricultural and environmental benefits. Therefore, 3 types of anaerobic digestion by-products (digestate) from surplus biomass viz. cow dung, Ipomoea carnea:cow dung (60:40 dry weight basis) and rice straw:green gram stover:cow dung (30:30:40 dry weight basis) and one gasification by-product (biochar) from rice husk are considered to understand the fertilizer prospects. Considering 3 potential application options, digestate from each feedstock option was further processed as separated solid, separated liquid and ash from solid digestates. Thus, a total of 10 by-products were investigated for understanding their prospects as fertilizer using Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive X ray Spectroscopy (EDX) and phyto-toxicity test to have a broad insight in terms of their organic, mineral, elemental composition, morphological feature and potential phyto-toxicity. In general, irrespective of origin of feedstock, solid digestate, ash digestate and char showed similarity in terms of composition of functional groups with some degree of variation in relative content as reflected by FTIR analysis. Dominance of organic functional groups in separated solid digestates compared to liquid fraction indicated the former as favourable organic amendments. Quartz was the prevalent mineral phase in all separated solid, ash digestate and rice husk char. Digestates in ash phase represent more concentrated plant nutrient source with higher content of K, Ca, P, Na and Mg than their respective solid phase. Application of ash digestates and char is likely to improve adsorptive capacity of soil for water and nutrient due to presence of relatively uniformly distributed porous particles. Liquid fraction of Ipomoea digestates exhibited inhibitory effect on seed germination of greengram ( Vigna radiate) with significant reduction of germination index. Inhibitory effects of by-products were found to correlate negatively with their electrical conductivity and ammonia-nitrogen content. Understanding on spectroscopic, morphological and phytotoxic properties of different application options of bioenergy by-products would be useful for assessment of their appropriate use in agriculture. [ABSTRACT FROM AUTHOR]

Recycling of nutrients through soil application of bioenergy by‐products (BEBPs) promotes closing of nutrient cycle as well as solves issues related to their improper management. Present investigation reports experimental data on soil fertility, crop growth (rapeseed), and crop nutrition from application of 15 fertilization treatments comprising of 13 BEBPs treatments, NPK and control. The selected by‐products are three types of digestates from anaerobic digestion namely, (i) cowdung, (ii) co‐digested Ipomoea carnea leaves:cowdung (60:40 dry weight), (iii) co‐digested rice straw:green gram stover:cowdung (30:30:40 dry weight) and one char (Rice husk) from gasification system. Fertilizer potential of digestates are assessed in four application phases namely, whole, separated solid, separated liquid, and ash from solid digestates. Significant variations in soil parameters (pH, EC, soil organic carbon, soil available N, P, and K, soil micronutrients) and crop responses were seen with respect to both feedstock type and application phases. BEBP application particularly in solid and whole phase proved significantly better in improving soil organic carbon. Addition of BEBP resulted in increased aboveground productivity, crop yield, plant NPK concentration compared with BEBP unfertilized condition. Overall, the improvement in grain yield over BEBP untreated control can be related to improvement in soil fertility (available fraction of N, P, and K), organic carbon, pH as well as crop physical growth. This study demonstrated that, due to differential partitioning of nutrients, a differentiated planning of BEBP applications, governed by the nature of feedstock and phase of applications would be required. © 2018 American Institute of Chemical Engineers Environ Prog, 38:e13099, 2019 [ABSTRACT FROM AUTHOR]