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BTU
The input of biowaste material in biogas plants has increased in the recent years. With that comes a certain amount of residues that can potentially be applied as organic soil amendment in order to recycle nutrients and to maintain and improve soil functions. The aim of this article is to give an impression of preliminary results of our study on characteristics of solid fermentation residues from different German biogas plants using organic waste material as main input substrate. A fundamental analysis shall reveal information such as material composition, nutrient and heavy metal concentration and impurity content. These characteristics are compared to existing data on composts and residues from organic waste treatment and will be evaluated in the context of organic amendment application.
In Lusatia, Eastern Germany, the largest German brown coal (lignite) mining area is located. We study agricultural reclamation of open cast brown coal mining areas over the reclamation period of seven years which is in Germany by law the fixed time after which the agricultural areas are resold to farmers and agricultural cooperatives. This paper shows the development of selected soil physical parameters within the first three and four years of reclamation in dependence of organic fertilization, soil tillage and crop rotation.
The sandy substrate which is used to reconstruct the post mining landscape is of Saaleian origin, free of recent organic matter and characterized by a homogeneous fabric. During excavation, deposition on stockpiles and levelling, the substrate becomes partly severely compacted due to extensive mechanical stresses. The extent of induced stresses depends on the contact area pressure and on the number of wheel passes of the levelling machinery during these processes.
In this context we investigated the effect of different organic soil additives in combination with different crop rotations on the development of soil structure. The experimental area was reconstructed in 2006 and 2007. Directly after site construction, undisturbed soil samples were taken to characterize the initial mechanical and hydraulic properties of the substrate. Three and four years later again undisturbed samples on selected sub plots were taken. In 2010 samples from plots where Alfalfa had been cultivated for three years were collected. The Alfalfa plots were wheeled only twice per year, once for fertilization and once to cut and chaff the biomass. In 2011 samples from plots with annual ploughing and seedbed preparation were taken to show the effects of different crops and tillage intensities in combination with varying soil organic fertilizers on soil structure development. Furthermore, we evaluated the persistence of the loosening effect of subsoiling in dependence on the reclamation practice. First results of our on-going experimental study indicate that initial soil physical properties are very variable on the sub plots. After three and four years, no loosening effect of deep loosening was found anymore. The comparison of the minimum tilled plots (Alfalfa) with the plots of medium tillage intensity showed that with decreasing soil tillage intensity the functionality of the pore system (saturated hydraulic conductivity, air permeability) is improved.
Cycle of Soil Structure
(2013)
Influence of soil amendments made from digestate on soil physics and the growth of spring wheat
(2016)
Every year 13 million tons of organic wastes accumulate in Germany. These wastes are a potential alternative for the production of energy in biogas plants, especially because the financial subventions for the cultivation of renewable resources for energy production were omitted in 2014. The production of energy from biomass and organic wastes in biogas plants results in the accumulation of digestate and therefore causes the need for a sustainable strategy of the utilization of these residues. Within the scope of the BMBF-funded project ‘VeNGA - Investigations for recovery and nutrient use as well as soil and plant-related effects of digestate from waste fermentation’ the application of processed digestate as soil amendments is examined. Therefore we tested four different mechanical treatment processes (rolled pellets, pressed pellets, shredded compost and sieved compost) to produce soil amendments from digestate with regard to their impact on soil physics, soil chemistry and the interactions between plants and soil. Pot experiments with soil amendments were performed in the greenhouse experiment with spring wheat and in field trials with millet, mustard and forage rye.
After the first year of the experiment, preliminary results indicate a positive effect of the sieved compost and the rolled pellets on biomass yield of spring wheat as compared to the other variations. First results from the
Investigation on soil physics show that rolled pellets have a positive effect on the soil properties by influencing size and distribution of pores resulting in an increased water holding capacity. Further ongoing enhancements of the physical and chemical properties of the soil amendments indicate promising results regarding the ecological effects by increased root growth of spring wheat.
In Deutschland fallen jährlich ca. 13 Mio t Bioabfall an. Im Zuge der Novellierung des EEG 2014 erfolgte eine Aufhebung aller Sondervergütungen. Da zukünftig keine erhöhten, einsatzstoffbezogenen Vergütungen (z. B. für Mais, Zuckerrüben und Getreide) mehr vorgesehen sind, wird sich der Ausbau der Biomasse auf den Einsatz von Reststoffen (z. B. Gülle und Abfallstoffe) konzentrieren . Aus diesem Grund ist mit einer verstärkten Zunahme von Gärrückständen aus Bioabfällen zu rechnen. Im Rahmen des vom BMBF geförderten VeNGA-Projektes Grundlagenuntersuchungen zur Verwertung und Nährstoffnutzung der boden- und pflanzenbezogenen Wirkung von Gärrückständen aus der Abfallvergärung, erfolgt die genaue Charakterisierung unterschiedlicher Gärrestprodukte und Aufbereitungsverfahren hinsichtlich ihrer bodenphysikalischen Wirkung und ihrer Effekte auf Wachstum und Entwicklung von landwirtschaftlichen Kulturen.
In dem Projekt werden Gärprodukte aus zwei Laboranlagen und einer Technikumsanlage mittels vier Verfahren aufbereitet und in Gefäßversuchen und einem dreijährigen Feldversuch hinsichtlich ihrer langfristigen boden- und pflanzenbezogenen Wirkung untersucht. Die unterschiedliche Aufbereitung der Gärreste erfolgt nach der Kompostierung aus demselben Material, in Form von Rollpellets, Presspellets, zerfasertem Kompost und einer Referenzvariante aus gesiebtem Kompost. Bei den unter kontrollierten Bedingungen im Gewächshaus durchgeführten viermonatigen Gefäßversuchen wurden die Gärprodukte unter Sommerweizen und im Feldversuch unter Hirse, Senf und Grünroggen getestet.
Erste Ergebnisse nach dem ersten Versuchsjahr zeigen sowohl für die Gefäßversuche als auch im Freilandversuch einen positiven Effekt für die Rollpellets auf den Biomasseertrag im Vergleich zu den anderen Aufbereitungsvarianten. Aufgrund des gleichen Ausgangsmaterials der verschiedenen Varianten deutet der Mehrertrag bei der Applikation der Rollpellets auf eine positive bodenphysikalische Wirkung und verbesserte Porenverhältnissen, die mit einer Steigerung des Wasserhaltevermögens einhergeht, hin. Des Weiteren besitzen die Rollpellets im Vergleich zu den anderen getesteten Varianten gute Lager-, Transport- und Applikationseigenschaften. Auch konnte in Rhizotronenversuch gezeigt werden, dass die verschieden Gärrestprodukte unterschiedliche Einflüsse auf das Wurzelwachstum von Sommerweizen besitzen.