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

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.

Organic Fertilizers and Bio-Waste for Sustainable Soil Management to Support Crops and Control Greenhouse Gas Emissions in Mediterranean Agroecosystems: A Review

“…Digestates are separated into liquid and solid fractions in order to properly manage their logistics and use. Digestate, as a whole, considering liquid and solid fractions, is characterized by an alkaline pH (7.5-9.0), a total C concentration of about 350-400 g kg −1 with small differences among digestates, a total N content ranging from 15 to 150 g kg −1 mostly represented by the ammonium-N form (up to 81%), P concentration variable in the range of 0.2-170 g kg −1 , and a relatively large K content (from 1 to 400 g kg −1 ); it also contains many micronutrients [26][27][28]88]. Considering its properties, solid anaerobic digestate has the potential to be utilized in agriculture as a soil conditioner and as a replacement for synthetic fertilizers, especially to supply N-P-K, owing to its nutrient contents and partially decomposed organic substrates.…”

Correlations between the Composition of Liquid Fraction of Full-Scale Digestates and Process Conditions

“…The most common current practice of digestate post-treatment is by volume reduction through mechanical solid-liquid separation [6,7]; producing 80-92% of liquid fraction in terms of mass; common separators on sites are the screw press, centrifuge, vibrating screen or rotary drum [8][9][10].…”

Valorisation of Agricultural Digestate for the Ammonium Sulfate Recovery and Soil Improvers Production

“…The application of agricultural digestate has been tested on the soil with the aim to increase the interaction of the soil-plant systems favoring the growth of the foliar area and weight of the vegetal and the distribution of photo assimilates between the different organs of the plants [10,11]. The liquid and solid fractions of digestates contains macronutrients contain N and P compounds, respectively [12] and it was reported to be an alternative source of inorganic P fertilizers in several plant species such as amaranth and sorghum [13,14], maize [13], plant ornamental species [15], ryegrass [16,17], barley [18] and tomato [12]. But the direct digestate application on the soil has some drawbacks: bad odors, the presence of no stabilized compounds, of pathogens and, in some case, of heavy metals [19].…”