Comparative characterization of digestate versus pig slurry and cow manure – Chemical composition and effects on soil microbial activity

Abstract

The growing number of biogas plants in Europe has resulted in increased production of nutrient-rich digestate with great potential as fertilizer for arable land. The nutrient composition of digestate varies with the substrate treated in the biogas plant and may contain compounds that stimulate or inhibit soil microbial activity. This study compared 20 digestates (D) with 10 pig slurries (PS) and 10 cow manures (CM) regarding their chemical content and their effect on soil microbial activities, i.e. potential ammonia oxidation rate (PAO) and soil respiration. The results showed no significant differences within the D group when divided based on substrate type. i.e. manure dominated vs. other organic waste materials in any of the tests. In general D contained significantly higher concentrations of ammonium while the concentrations of total carbon and volatile fatty acids were higher in PS and CM than in D. The D showed both stimulating and inhibiting effects on PAO, while all CM and all PS except one showed inhibiting effects on PAO. However, PAO activity was negatively correlated with the content of volatile fatty acids in the residues indicating that these compounds may be the cause of the inhibition. The maximum respiration activity (h) was lower and the time point for the maximum respiration activity (t) occurred earlier for D compared with CM and PS. This earlier peak time could be indicative of a high proportion of easily degradable carbon in D compared with PS and CM. However, the utilization rate of carbon, i.e. the proportion of added organic C converted to CO-C during 12days, did not differ significantly between D, PS and CM, indicating that overall carbon quality in the different fertilizers was still roughly comparable. In short, our results suggest that digestates were different compared with PS and CM but without posing a higher risk with respect to their impact on soil microbial activity.

Assessment of By-product Valorisation in a Swedish Wheat-Based Biorefinery

“…One such interesting combination is if the fodder scenario is expanded to include biogas production from the manure produced by the animals. Nutrients in digested manure are often more available than applying manure directly [44]. This would improve the valorisation of the wheat.…”

Exploitation of Solar Energy for Ammonium Sulfate Recovery from Anaerobic Digestate of Different Origin

“…Ammonium derives from the biological degradation of nitrogenous matter, mostly present in the form of proteins and urea [31]. Typical protein rich substrates are manure and food wastes [6,7]. It allows to explain the high content of TKN and ammonia in ADWC, respectively of 7.2 and 6.1 g/kg, in ADDC which had respectively 5.0 and 3.8 g/kg and in OFMSW digestate which recorded lower but still significant nitrogen and ammonia concentrations of 3.2 and 1.9 g/kg, respectively.…”

“…The quality and the composition of the digestate are influenced by several factors, such as the type of the feedstocks and the operative conditions during the AD [temperature, hydraulic retention time (HRT), of the organic load rate (OLR) and the solids contents], the presence of inert materials or the content of recalcitrant lignocellulosic materials. In case, of digestate from AD of animal manure, its characteristics depend on also by the type of the animal (omnivore, ruminant), by the sex, the age and the diet fed to the animal as well as the geographical and the climate conditions [7].…”

Challenges and an Implementation Framework for Sustainable Municipal Organic Waste Management Using Biogas Technology in Emerging Asian Countries

“…At the end stream of a biogas plant, digestate is recovered as well as energy of various forms. The volume of digestate is not significantly different, or usually more than the volume of substrates due to additional substances such as water [87][88][89]. Demand for digestate is, therefore, a fundamental factor that shapes the sustainability of a biogas plant.…”