By-products of bioenergy systems (anaerobic digestion and gasification) as sources of plant nutrients: scope of processed application and effect on soil and crop

Management of the by-products generated during bioenergy conversion technologies is essential for technology sustainability and due to strict adherence to waste minimisation legislation. We investigated the potential of four types of bioenergy by-products (BEBPs), i.e. char from rice husk and digestates from 3 types of feedstocks: (i) Ipomoea carnea:cow dung (ICD), (ii) rice straw:green gram:cow dung (RGC) and (iii) cow dung (CD) as nutrient input for Zea mays L. Digestates were applied in four application phases, i.e., whole, solid, liquid and ash from solid digestates. BEBPs provoked significant changes in soil pH, electrical conductivity, available NPK, organic carbon and micronutrients depending upon both feedstock and phase. Digestates in solid and whole phases were found better as an organic amendment, whereas RGC and ICD digestates were superior in maintaining higher soil available P and K, respectively. BEBP showed satisfactory performance compared to BEBP-untreated control in terms of crop growth and yield, but chemical treatment resulted in the highest yield. N preservation against volatilization loss may be required through appropriate timing and method of application in case of high-ammonia-N-containing ICD digestates. Outcomes of this investigation are expected to be useful to undertake selective utilization practices of BEBPs for better handling and management.