Einfluss von Milchleistung und Nutzungsdauer auf den Product Carbon Footprint von Milch bei ökologisch wirtschaftenden Betrieben in Süddeutschland

Quantification and mitigation of greenhouse gas emissions is an intensively discussed topic. For dairy farms many studies consider a higher milk yield per cow for greenhouse gas mitigation but this often results in a reduction in herd fertility and thus more heifers are needed which may lead to more emissions in total. This paper presents the Product Carbon Footprint of 36 organic dairy farms and analyses the influence of milk yield per cow and longevity of dairy cows. Results are: (1) a product carbon footprint of 1,61 kg CO2eq/kg fat and protein corrected milk on average, (2) increasing milk yield per cow causes decreasing product carbon footprints (coefficient of determination 48 %) and (3) decreasing longevity per cow causes decreasing product carbon footprints but to a lower degree of influence (coefficient of determination 16 %). With regard to climate protection, not considering ethical aspects, a high milk yield per cow should be achieved rather than to focus on longevity

Erhebliche Effizienzpotenziale in der Färsenaufzucht der ökologischen Milchproduktion

In many organic farms there is a huge potential to increase efficiency in rearing heifers for replacement. This is the result of a study in 36 organic dairy farms with pasture from South Germany, which were analyzed economically in the years 2009 – 2011. In particular farms with high production efficiency and low production costs per heifer show decreased production times per cow for some months, but this effect is overcompensated by higher milk yields per cow. This is one reason why they perform economically better with regard to the dairy farm. The most important factors influencing the production costs per heifer are the costs for forage and labor. Based on the results of this study, more efficient rearing of heifers with lower production costs seems necessary and worthwhil

Analysis of viscoelastic soft dielectric elastomer generators operating in an electrical circuit

A predicting model for soft Dielectric Elastomer Generators (DEGs) must consider a realistic model of the electromechanical behaviour of the elastomer filling, the variable capacitor and of the electrical circuit connecting all elements of the device. In this paper such an objective is achieved by proposing a complete framework for reliable simulations of soft energy harvesters. In particular, a simple electrical circuit is realised by connecting the capacitor, stretched periodically by a source of mechanical work, in parallel with a battery through a diode and with an electrical load consuming the energy produced. The electrical model comprises resistances simulating the effect of the electrodes and of the conductivity current invariably present through the dielectric film. As these devices undergo a high number of electro-mechanical loading cycles at large deformation, the time-dependent response of the material must be taken into account as it strongly affects the generator outcome. To this end, the viscoelastic behaviour of the polymer and the possible change of permittivity with strains are analysed carefully by means of a proposed coupled electro-viscoelastic constitutive model, calibrated on experimental data available in the literature for an incompressible polyacrilate elastomer (3M VHB4910). Numerical results showing the importance of time-dependent behaviour on the evaluation of performance of DEGs for different loading conditions, namely equi-biaxial and uniaxial, are reported in the final section