4 research outputs found
N-Umsatz und Spurengasemissionen typischer Biomassefruchtfolgen zur Biogaserzeugung in Norddeutschland
Im Rahmen des Verbundprojektes Biogas-Expert an der CAU-Kiel wurden an zwei Standorten Schleswig-Holsteins veschiedene Fruchtfolgen zur Bereitstellung von Biogassubstraten unter Verwendung von Biogasgüllen als N-Dünger durchgeführt. Maismonokultur wies die höchsten Trockenmasseerträge auf, wobei keine signifikanten Unterschiede in den Erträgen zwischen Biogasgärresten, organischen N-Düngern und mineralischen Düngern ermittelt wurden. Während in Bezug auf die N-Düngeform bei N2O- und Nitratauswaschungsverlusten kein Einfluss der N-Form auf die Höhe der Verluste festgestellt wurde, war die Düngung mit Biogasgüllen mit signifikant erhöhten NH3-Verlusten verknüpft. Eine abschließende Bewertung der Produktionssysteme ist erst durch Analyse der experimentellen Ergebnisse mit einem Systemmodell möglich
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Greenhouse gas emissions in biogas production systems
There is growing concern that greenhouse gas (GHG) emissions during agricultural energy crop production might negate GHG emission savings. Here a study is presented evaluating two favourable biogas crops in two agro-ecological regions of Northern Germany for their productivity and GHG emissions. A 2-year field experiment was conducted at two sites with different soil type but similar temperate maritime climate. We compared silage maize which is currently the standard crop grown for biogas fermentation purposes to an alternative bioenergy crop at each site. Three forms of fertilizers/manures were given: calcium ammonium nitrate, cattle / pig slurry, biogas waste. GHG emissions of all biogas crops were strongly dominated by N2O emissions. There were very short CH4 emission events immediately after application of slurry and biogas waste. N2O flux patterns usually followed fertilizer application events in all crops and at both sites. Flux patterns indicated pronounced effects of soil moisture which was also seen as responsible for the 20–30 % higher N2O fluxes in maize compared to the other tested crops. Overall, N2O emissions at the loamy soil site were at least 3 times higher than in all crops examined at the site with sandy soil. The present study provides a very good basis for the assessment of direct emissions of greenhouse gases from relevant biogas crops in North-West Europe. It is intended to use measured and simulated data on soil moisture and the N/C inputs by fertilizer/manure application as drivers for a nitrification/denitrification module linked to a crop growth model
Evaluating Bioenergy Cropping Systems towards Productivity and Resource Use Efficiencies: An Analysis Based on Field Experiments and Simulation Modelling
Silage maize (Zea mays L.) is the dominating energy crop for biogas production due to its high biomass yield potential, but alternatives are currently being discussed to avoid environmental problems arising from maize grown continuously. This study evaluates the productivity and resource use efficiency of different bioenergy crops and cropping systems using experimental and simulation modelling derived data. The field experiment consisted of two years, two sites differing in soil texture and soil water availability, different cropping systems and increasing nitrogen (N) supply. Continuous (two years) perennial ryegrass and two crop rotations including winter cover crops (double cropping system) and combining C4 and C3 crops were compared with continuous maize (maize–maize). The productivity of the crops and cropping systems in terms of dry matter (DM) yield was analyzed with respect to the fraction of light interception and light use efficiency (LUE). In addition, water use and water use efficiency (WUE), N uptake, and N use efficiency (NUE) were quantified. DM yield of the double cropping system was similar to that of continuous maize, due to a prolonged leaf area duration, compensating for the intrinsic lower LUE of C3 crops. Perennial ryegrass was less productive than the other crops/cropping systems. Nitrogen uptake and consequently N demand of perennial ryegrass and the C3 crops of the crop rotations were higher than for maize–maize. Groundwater recharge was mainly site-dependent, but was at both sites higher for maize than for the crop rotations or the perennial ryegrass system. Our results indicate that, in terms of biomass productivity, optimized rotations are feasible alternatives to maize–maize, but trade-offs exist in terms of water and N use efficiency