Assessment of by-products of bioenergy systems (anaerobic digestion and gasification) as potential crop nutrient. (January 2017)

• Record Type: Journal Article
• Authors: Kataki, Sampriti; Hazarika, Samarendra; Baruah, D.C.
• Is Part Of: Waste management. Volume 59(2017)
• Page Start: 102
• Page End: 117
• Publication Date: 2017-01
• Subjects: Anaerobic digestion -- Gasification -- Bioenergy -- By-products -- Fertilizer -- Nutrients; Hazardous wastes -- Periodicals; Refuse and refuse disposal -- Periodicals; 363.728
• DOI: 10.1016/j.wasman.2016.10.018
• Languages: English
• ISSNs: 0956-053X

Abstract

Highlights: Fertilizer potential of by-products of two bioenergy systems. Characterization of by-products processed into whole, solid, liquid and ash phase. Significant variation of nutrient status of by-products with feedstock and phase. Solid phase of by-product is richer in total nutrients and organic fraction. By-product in liquid phase is instant source of ammonia-N for plant uptake. Co-digested Ipomoea carnea in all phases shows highest nutrient content. Abstract: Alternative fertilizer resources have drawn attention in recent times in order to cope up with ever increasing demand for fertilizer. By-products of bioenergy system are considered favourable as organic fertilizer due to their ability to recycle plant nutrients. Present study evaluates fertilizer suitability of by-products of two bioenergy systems viz. 3 types of anaerobic digestion by-products (digestate) from local surplus biomass such as cowdung, Ipomoea carnea :cowdung (60:40) and ricestraw:green gram stover:cowdung (30:30:40) and one gasification by-product (biochar) from rice husk. Digestates were assessed considering 4 different application options of each viz. whole, solid, liquid and ash from solid digestates. Digestate characteristics (organic matter, macronutrients, micronutrients and heavy metal content) were found to be a function of feedstock and processing (solid liquid separation and ashing). Ipomoea carnea based digestates in all application options showed comparatively higher N, P, K, NH4 + -N, Ca, Mg, S and micro nutrient content than other digestates. Separation concentrated plant nutrients and organic matter in solid digestates, making these suitable both as organic amendments and fertilizer. Separated liquid digestate shared larger fraction of ammonium nitrogen (61–91% of total content), indicating their suitability as readily available N source. However, fertilizer application of liquid digestate may not match crop requirements due to lower total nutrient concentration. Higher electrical conductivity of the liquid digestates (3.4–9.3 mS cm −1 ) than solid digestates (1.5–2 mS cm −1 ) may impart phyto–toxic effect upon fertilization due to salinity. In case of by-products with unstable organic fraction i.e. whole and solid digestates of rice straw:green gram stover:cowdung digestates (Humification index 0.7), further processing (stabilization, composting) may be required to maximize their fertilizer benefit. Heavy metal contents of the by-products were found to be within the permitted range specified for organic fertilizer (vermicompost) in India. However, higher Al content of the digestates in whole, solid and ash phase (0.06–16.97g kg −1 fresh matter) can be a concern in acid soil which may cause Al toxicity. Understanding on agrochemical characteristics of bioenergy by–products with varying feedstock and application option is expected to promote their valorization opportunities considering user specific requirements. In the context of agriculturally dominant but energy deficient rural Indian scenario, integrated production of bioenergy and by-product based fertilizer could be very significant to meet the critical additional requirement of both energy and fertilizer.