Auswirkungen der Fermentation biogener Rückstände in Biogasanlagen auf Flächenproduktivität und Umweltverträglichkeit im ökologischen Landbau bei viehloser Wirtschaftsweise

Problemstellung/Ziele:Analog zur Entwicklung im konventionellen Landbau ist auch im Ökologischen Landbau eine zunehmende Tendenz zu viehloser Wirtschaftsweise festzustellen. Viehlose Betriebe können auf die Vorteile des Kleegrasanbaues (N-Versorgung, Unkrautbekämpfung) kaum verzichten. Üblicherweise wird der Aufwuchs gemulcht und auf der Fläche belassen, ebenso die übrigen Rest- und Koppelprodukte (Stroh von Getreide und Körnerleguminosen, Zwischenfruchtaufwüchse, u.ä.). Damit können erhebliche N-Verluste verbunden sein, zum Einen als Ammoniakfreisetzungen beim Abbau des Kleegrasmulches (u.a. ANDREN, 1987), zum Anderen durch Minderleistungen der Stickstofffixierung gemulchter Bestände, die mineralisierten Stickstoff aufnehmen und dabei die eigene Fixierung vermindern. Weitere Verlustquellen sind Auswaschung und Denitrifikation beim Verbleib N-reicher Restprodukte auf dem Feld während des Winterhalbjahres (u.a. MÖLLER, 1999; RUSER, 1999). Ein weiteres Problem bei viehloser Bewirtschaftung ist neben der fehlenden Verwertungsmöglichkeit für die Kleegrasaufwüchse, die fehlende Möglichkeit, innerhalb der Fruchtfolge Nährstoffe auf die bedürftigen Kulturen „umzuverteilen“, wie dies bei viehhaltenden Systemen in Form von Gülle, Jauche und Stallmist möglich ist. Die Vergärung der ansonsten nicht genutzten Aufwüchse und Reststoffe einer viehlosen Fruchtfolge in einer Biogasanlage kann nicht nur der Energieerzeugung dienen, sondern gegebenenfalls auch der besseren N-Versorgung über die gezielte Rückführung der Gärreste. Sie könnte auch zu einer Verminderung umweltrelevanter N-Emissionen führen, da der Stickstoff zeitweise – insbesondere über Winter - aus den Ackerflächen entfernt und „zwischengelagert“ wird. Außerdem können durch die Vergärung in einer Biogasanlage betriebsfremde Nährstoffe (z.B. Grünschnitte) erschlossen werden, die bei Einhaltung entsprechender Richtlinien bis zur Grenze von 40 kg N/ha in Ökobetrieben eingesetzt werden dürfen

Einfluss der organischen Düngung auf Wachstum, Zusammensetzung und Nährstoffaufnahme eines leguminosenbetonten Zwischenfruchtgemenges

The effect of different management strategies on growth, composition and nutrient up¬take of a cover crop mixture of summer vetch and oil radish were tested in field ex¬pe¬ri¬ments on the Research Station Gladbacherhof. Slurry application and cereal straw management (incorporation vs. harvesting) affected composition of cover crop signifi-cantly: slurry application decreased legume content and biological N2-fixation signifi-cantly. By this way the N-input in farm cycle were reduced. The higher the amount of straw residues were left on field, the higher the legume content was in the cover crop mixture. High legume content in cover crop mixtures not only increased N2-fixation, but also P uptake of the cover crop. According to available literature additionally mobilised P increased the P supply of following crops. The harvest of cover crop sprout reduced nitrate leaching potential significantly especially when winter crops were following. The harvest of the cover crops increased the amounts of N cycling within the farming system. Hence it allows higher N manuring to selected crops with a high N demand

Biogaserzeugung im viehlosen Betrieb: Effekte auf Stickstoffmanagement, Erträge und Qualität

In organic farming systems without livestock some problems arise concerning the nitrogen management: On the one hand, there is a lack of transportable nitrogen fertilisers, on the other hand there is a potential for high losses with the usual management. The biological N2 fixation is decreased, when clover grass is mulched. If the biomass of intercrops and clover grass gets mineralised in autumn, it can be leached in winter. In the trial referred to here, the impact of fermentation of biomass on some agricultural parameters like yield etc. are investigated within a crop-rotation of clover grass, potatoes, winter wheat, peas, winter wheat and summer wheat with undersown clover grass. Intercrops are sown after winter wheat and peas. In the control variant the coupled products (clover grass, straw and intercrops) are left on the field as mulch. In the biogas system this material is harvested for digesting. The remaining products are used as fertilisers. There are liquid products which were used to fertilise the winter wheat and solid ones, which were used for fertilizing potatoes and summer wheat. This system allows a higher efficiency of the nitrogen management: The yield and the content of raw protein in winter wheat increased. The solid material did not mineralise as fast as necessary. It would be better to add this material to the intercrops

Biogaserzeugungspotential aus Gülle und Koppelprodukten in viehhaltenden und viehlosen Betriebssystemen des ökologischen Landbaus

In two agricultural systems with and without animal husbandry the potential to produce renewable energy by digesting slurry and organic residues to biogas were assessed. In comparison to some other methods of energy production by biomass biogas production has the advantage of keeping the nutrients of the substrates within the agricultural system. They can be used as fertilisers. In the investigated system with milk production (0,8 cows ha-1, 8 crops, among them 4 cereals, peas, potatoes and 2 clover grasses with catch crops after winter cereals and peas (see DEUKER et al. 2005), it is possible not only to ferment slurry, but also catch crops and straw of peas and cereals. The methan production potential by digesting only slurry is the equivalent of around 327 l diesel fuel ha-1. By digesting a well developed catch crop it is possible to harvest the equivalent of around 750 l diesel fuel per ha.-1 sown with such crops. Related to the whole system with 4 catch crops within 8 fields it is possible just by including catch crops in the fermentation process with slurry to duplicate the methan harvest of the digesting plant to around 700 l diesel fuel ha-1 a-1. By utilisation of biomass like the straw of peas and other residues it is possible to generate the equivalent of approx. 450 l diesel fuel ha-1. Total biogas production potential by including all fermentable biomass is the equivalent of approx. 1150 l diesel fuel per each ha and year. Usually one third of this energy is necessary to temperate the digester, one third can be converted to electricity and one third can be used to heat buildings in the neighbourhood of the fermentation plant. In a typical stockless organic agricultural system composed of six crops (clover gras, potatoes, winter wheat, peas, winter wheat and summer wheat with undersown clover grass, with catch crops after winter wheat and peas, see STINNER et al. 2005) biomass of clover grass and catch crops will normally be left on the field and incorporated in the soil. By fermentation of clover grass there is a biogas production potential of around the equivalent of 3300 to 4700 l diesel fuel ha-1 a-1. Digesting catch crops allows a methan yield of ca. 650 to 700 l diesel fuel ha-1, digestion of other residues like straw other 1250 to 1350 l diesel ha-1. The total energy production potential of the whole crop rotation system is the equivalent of around 1700 to 1800 l diesel per ha and year. Removal of crop residues is coupled with removal of substantial quantities of nitrogen, reducing the residual mineralisable nitrogen amounts on fields at the end of the vegetation period and the risk of nitrate leaching

Biogas in organic agriculture: Effects on yields, nutrient uptake and environmental parameters of the cropping system

System effects of biogas fermentation in organic cropping systems with and without livestock (dairy farming) were investigated from 2002-2005. In both systems no differences in yields and nutrient uptake were detected in the legume crops. In the livestock-system non legume crops of the slurry system had no higher yields but a higher nitrogen uptake (6 %) than the stable manure system. Slurry-fermentation had no effect on yields and nitrogen uptake. The inclusion of crop residues in the fermentation system increased the nitrogen uptake about by 10 % and reduced the nitrate leaching potential by ca. 10 %. The inclusion of external substrates lead to a further increase in nitrogen yield of 10 %, but to no significant increase in dry matter yields. Fermentation had no effects on P-availability of manures. In the stockless system fermentation of clover grass, straw and catch crops increased yields and nitrogen content of winter wheat by ca. 10 %, combined with a significant decrease in nitrate leaching potential (10 %) and in emissions of nitrous oxide (ca. 40 %)

Biogas production from sugarcane waste: assessment on kinetic challenges for process designing

Biogas production from sugarcane waste has large potential for energy generation, however, to enable the optimization of the anaerobic digestion (AD) process each substrate characteristic should be carefully evaluated. In this study, the kinetic challenges for biogas production from different types of sugarcane waste were assessed. Samples of vinasse, filter cake, bagasse, and straw were analyzed in terms of total and volatile solids, chemical oxygen demand, macronutrients, trace elements, and nutritional value. Biochemical methane potential assays were performed to evaluate the energy potential of the substrates according to different types of sugarcane plants. Methane yields varied considerably (5–181 Nm3·tonFM−1), mainly due to the different substrate characteristics and sugar and/or ethanol production processes. Therefore, for the optimization of AD on a large-scale, continuous stirred-tank reactor with long hydraulic retention times (>35 days) should be used for biogas production from bagasse and straw, coupled with pre-treatment process to enhance the degradation of the fibrous carbohydrates. Biomass immobilization systems are recommended in case vinasse is used as substrate, due to its low solid content, while filter cake could complement the biogas production from vinasse during the sugarcane offseason, providing a higher utilization of the biogas system during the entire year

Auswirkung der Fermentation biogener Rückstände in Biogasanlagen auf Flächenproduktivität und Umweltverträglichkeit im Ökologischen Landbau – Pflanzenbauliche, ökonomische und ökologische Gesamtbewertung im Rahmen typischer Fruchtfolgen viehhaltender und viehloser ökologisch wirtschaftender Betriebe

Die Effekte der Vergärung von Gülle und Nebenernteprodukten wurden auf der Ebene des gesamten landwirtschaftlichen Systems für einen viehhaltenden Gemischtbetrieb und einen viehlosen Marktfruchtbetrieb untersucht. Dabei wurden die Wirkungen der Vergärung von Gülle und Kleegras auf die Flächenproduktivität, auf die innerbetrieblichen Nährstoffflüsse, auf die Nitratauswaschungsgefahr sowie auf die Gefahr von bodenbürtigen Spurengasemissionen untersucht. Ferner wurde eine ökologische Bilanzierung der Biogasvergärung im ökologischen Landbau mittels Öko-Bilanzierung durchgeführt

Methane emissions from the storage of liquid dairy manure: Influences of season, temperature and storage duration

Methane emissions from livestock manure are primary contributors to GHG emissions from agriculture and options for their mitigation must be found. This paper presents the results of a study on methane emissions from stored liquid dairy cow manure during summer and winter storage periods. Manure from the summer and winter season was stored under controlled conditions in barrels at ambient temperature to simulate manure storage conditions. Methane emissions from the manure samples from the winter season were measured in two time periods: 0 to 69 and 0 to 139 days. For the summer storage period, the experiments covered four time periods: from 0 to 70, 0 to 138, 0 to 209, and 0 to 279 continuous days, with probing every 10 weeks. Additionally, at the end of all storage experiments, samples were placed into eudiometer batch digesters, and their methane emissions were measured at 20 degrees C for another 60 days to investigate the potential effect of the aging of the liquid manure on its methane emissions. The experiment showed that the methane emissions from manure stored in summer were considerably higher than those from manure stored in winter. CH4 production started after approximately one month, reaching values of 0.061 kg CH4 kg(-1) Volatile Solid (VS) and achieving high total emissions of 0.148 kg CH4 kg(-1) VS (40 weeks). In winter, the highest emissions level was 0.0011 kg CH4 kg(-1) VS (20 weeks). The out comes of these experimental measurements can be used to suggest strategies for mitigating methane emissions from manure storage