Short-Term Nitrogen Uptake of Barley from Differently Processed Biogas Digestate in Pot Experiments

Claudia Maurer,Rudolf Schulz,Julia Seiler-Petzold,Joachim Müller

doi:10.3390/en12040696

Claudia Maurer, Rudolf Schulz + Show 2 more

Open Access

https://doi.org/10.3390/en12040696

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Journal: Energies	Publication Date: Feb 21, 2019
Citations: 13	License type: CC BY 4.0

Affiliation: University of Hohenheim, University of Stuttgart

Abstract

The use of biogas digestate as fertilizer is limited by the farm nutrient balance. Mechanical separation and drying of digestate increases its transport worthiness as well as the economic feasibility of nutrient export. This study compares the fertilizer effect of four treatments of digestate originating from two biogas plants: untreated digestate, liquid and solid fraction of separated digestate and dried solid fraction of separated digestate. Pot experiments with barley were performed with two fertilization levels for different digestate variants. Above-ground biomass yield, nitrogen (N) and phosphorus (P) content in biomass and plant uptake efficiency were highlighted. The results showed that all variants have higher above-ground biomass yield than the control. Due to the reduced amount of easily available N, short-term N uptake of barley from solid fractions of digestate was low. The treatments with the dried solid fraction at low fertilization level showed up to 59% lower N removal from soil and, at high fertilization level, up to 83% lower N removal compared to the respective fresh solid fraction (100%). Depending on the feedstock of biogas plants and processing of digestate, N availability varied and influenced the short-term N uptake. It is recommended that digestate processing should be combined with ammonia recovery to prevent N losses to the environment.

Highlights

Biogas plants are typically operated to treat organic wastes from agriculture, households or industry and to provide renewable energy at the same time
Germination of the plants occurred 3–5 days after sowing, except for treatments LD1L and LD1H, where germination was delayed by 2–4 days
(solid digestate dried, biogas plant 2, low fertilization level), SDD2H and the control, which might be an indication of chlorosis caused by N deficiency due to the relatively low NH4 -N content in the pot

Summary

Introduction

Biogas plants are typically operated to treat organic wastes from agriculture, households or industry and to provide renewable energy at the same time. The digestate, i.e., the residue of the anaerobic fermentation process, contains numerous nutrients and can be used as a substitute for mineral fertilizers in agriculture or urban greening. The share of ammonium in the digestate from agricultural biogas plants is relatively higher compared to conventional organic agricultural fertilizers such as slurry and manure resulting in a positive effect for plant growth [1,2]. Regarding nitrogen (N), the application as fertilizer is limited at European level with the European Nitrate Directive to prevent nutrient accumulation in soil and groundwater as well as to avoid environmental pollution [3].

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