Optimised management of riverine landscapes based on a multi criteria Decision Support System: merging societal requirements and ecologic development in a changing world.

This project serves to promote biogas production from energy crops. The energy crops: sunflowers, meadow grass, wheat, triticale, rye and maize were investigated. All energy crops were harvested in the course of the vegetation period at four to six different times. At each harvest, yield measurements were carried out, as well as biomass sampled for silaging and the subsequent ingredient analyses. Following, laboratory investigations for the determination of the specific methane yield were carried out with the help of Eudiometer-instrumentation. The methane hectare yield and the optimal harvest times were determined for all of the investigated energy crops. Of all the energy crop species investigated in this project, maize showed the highest bio-mass yields and methane yields per hectare (up to 31 t DM ha-1 and up to 12,657 Nm3 CH4 ha-1). Sunflowers achieved approximately 30% of the methane hectare yield obtained by maize, cereals or intensively farmed meadow grass on average 26.5%. Variations of 6 to 38% in methane hectare yield appeared within the examined energy crop species depending on the variety, the place of cultivation, the management intensity or the harvest time. For an economic biogas production, the right choice of variety and the optimal harvest time has a great relevance. The effect of pretreatment measures (acidifying, heat treatment, microwave irradiation and addition of clay minerals) on the specific methane yield of energy crops was examined. heat, microwaves and acid pretreatment aimed to induce a predigestion of the crude fiber fraction. This effect was only observed with meadow grass and sunflowers, not however for cereals. The addition of clay minerals increased the specific methane yield of all energy crops. The optimal hydraulic retention times, determined in this project, lay between 20 days (cereal silage from whole crop) and 42 days (sunflower silage). Besides the energy crop type, the hydraulic retention time also appear to be influenced by the harvest year and the assigned pretreatment measure. These results must be verified in further investigations with dynamic systems. With the data from the project, the Methane Energy Value Model for maize could be continued so far that it can now be used in practice. The data base for the estimation of the methane energy value of cereals, sunflowers and meadow grass requires further investigations. The influence of the protein:energy ratio of mixtures of energy crops on the specific methane yield and on the biogas quality was examined with mixtures of protein-rich clover grass silage and energy-rich maize silage. A higher portion of maize silage in the mixture resulted in a higher specific methane yield. The higher the protein content and/or the portion of clover grass silage in the fermenting mixture, the lower the methane content in the produced biogas and the higher the hydrogen sulfide and ammonia content. Guidelines for (a) optimized biogas production from energy crops, (b) efficient fertilization with fermentation residues of fermented energy crops as well as (c) different uses of biogas are given. In order to achieve long-term success, the cultivation of energy crops must be organized using sustainable crop rotation principles. Locally adapted biological and conventional crop rotations were developed in this project with the prospects of energy crop cultivations as main and intermediate crops. The results of this project show that the potentials of biogas from energy crops are larger than have been assumed so far. The present, new calculations of integrated biogas production systems show an annual total potential of 4.8 million t ROE or 4.8 billion m3 methane. That means if the potentials of biogas production would be used, in Austria more than 16 million t CO2 emissions could be saved per year. This equals exactly the current requirements of reduction in Austria to reach the Kyoto target.