Optimisation of biogas production from maize, sorghum, sugar beet and rye under dry climatic conditions

The optimisation of biogas production from energy crops and their integration into sustainable cropping systems is of great importance. Therefore, plant breeding programmes are necessary to detect the maximum potentials of several energy crops like maize, sorghum, sugar beet and rye as renewable energy source. The main criteria for a high methane yield per hectare are dry matter yield and specific methane building capacity. In context of ideal conservation properties and nutrient composition of the energy crops it is also important to investigate the optimal time of harvesting. Due to the effects of global warming, where water availability is more and more a limiting factor, drought resistant varieties of energy crops are also subject of this plant breeding programme. To avoid environmental problems in form of pests, diseases or soil degradation, energy crop production has to be integrated into site-adapted and sustainable crop rotation systems. In order to fully exploit the available potentials of biogas production, the main aim of this project is to investigate the ideal variety of the energy crops maize, sorghum, sugar beet and rye on the basis of an intensive breeding programme. The breeding focus is to develop high yielding energy crop varieties especially for temperate regions with low rains during summer. Related to an adequate water supply for the main crop of a two-crop system, and consequently a maximum yearly methane yield per hectare, the optimum harvesting time of the pre-crop will be determined. The overall project is divided into two work packages: WP 1 contains an intensive breeding programme to determine high methane yielding and drought resistant varieties of the energy crops maize, sorghum, sugar beet, and rye. The breeding programme, which lasts for four years, covers 10 new varieties of each energy crop. These energy crops are tested by the breeding companies KWS Saat, Lochow-Petkus, and AgroMais in the course of running research programmes on four sites in Germany and Austria regarding their biomass building capacity. In the proximate year, four of the most promising varieties are submitted to an intensive testing programme under dry climatic conditions in accordance with their potential of dry matter yield and specific methane building capacity on the Experimental Farm in Groß Enzersdorf. Based on the test results of laboratory trials (full analysis of methane yield, nutrient composition), the Methane Energy Value Model (MEVM), developed in previous research projects especially for maize, will be further developed, improved in its output reliability and estimate accuracy, also for the other energy crops. The optimum variety (constant dry matter yield, conservation properties, optimal harvesting time, and nutrient composition) and an energy index for each energy crop is developed from a board of experts, which contains plant breeders and agricultural engineers. The 2nd WP investigates the optimum harvesting time of winter-rye (end of flowering stage, milk stage and dough stage) before maize and sorghum, respectively. The maximum biomass and yearly methane yield per hectare in a two-crop system under dry conditions will be investigated. Maize and sorghum will be harvested at the end of the vegetation period. Drought resistant energy crop varieties are selected according to recommendations from WP 1. The methane yield per hectare is calculated from the measured biomass yield of WP 2 and the specific methane yield of the respective energy crop obtained from WP 1.