Expert list Bioenergy / Renewable Energy

Rapeseed and maize are the most widely spread energy crops in Germany. Currently, biodiesel is produced solely from vegetable oils, and maize is the primary crop substrate in German biogas plants. But the strong dominance of these energy crops is being increasingly rejected by the population and the calls for alternatives are getting louder.

As alternatives, Prof. Dr. Iris Lewandowski and Prof. Dr. Simone Graeff-Hönninger are investigating wild herb mixes or new energy crops such as amaranth, dock, the cup plant, and energy grass that can be made into biogas. They enrich the landscape.

Contact:
Prof. Dr. Iris Lewandowski, Department of Biobased Products in the Bioeconomy, +49 (0)711 459 22221, email

Prof. Dr. Simone Graeff-Hönninger, Department of Agronomy, +49 (0)711 459 22376, email

The country needs energy crops. But the problem is: They promote erosion and are harsh on the soils.

Alternative planting systems are a topic at the Department of Agronomy of Prof. Dr. Simone Graeff-Hönninger. She is testing striped planting systems in which different energy plants are combined in spatial and temporal sequence at the same time on one field. This prevents a one-sided use of the soils and the species diversity is increased. The scientist is also looking at the question of how greenhouse gas balances of these planting systems can be reduced.

Contact: Dr. Simone Graeff-Hönninger, Department of Agronomy, +49 (0)711 459 22376, email

Corn is the most popular energy crop because it is the least expensive. But the population is reacting increasingly negatively to the phrase “ ‘cornisation’ of the landscape” in reference to biogas corn planting. As alternatives, Prof. Dr. Iris Lewandowski suggests wild herb mixes or new energy crops such as amaranth. They would enrich the landscape. In the Department of Agronomy headed by Prof. Dr. Simone Graeff-Hönninger, scientists are also looking for further sustainable alternatives. She has run across dock, a plan which grows for 20 years once planted and, depending on the location, makes up to three harvests per year possible.

Other alternative places which could replace corn in the long-term in biogas plants and are being tested in the experimental station are the cup-plant and a  biogas-capable energy grass from Hungary. But currently, these crops are still more expensive than corn, and that is why they are unlikely to be able to replace corn in the short-term.

Contact:
Prof. Dr. Iris Lewandowski, Department of Biobased Products in the Bioeconomy, +49 (0)711 459 22221, email

Prof. Dr. Simone Graeff-Hönninger, Department of Agronomy, +49 (0)711 459 22376, email

Bioenergy helps by reducing greenhouse gas emissions. How much CO2 can be saved depends primarily on the materials. It is possible to save over 90 percent if wood, grass, or straw-like biomass is burned for the production of energy and heat. For biofuel, up to 50 to 70 per cent CO2 can be saved if ethanol is produced from wheat or sugarcane. The requirement, though, is that no land use changes to produce these energy crops have been made. If the rainforest is cut down to produce palm oil, then it might be the case that more CO2 is emitted for biodiesel than is saved, Prof. Dr. Iris Lewandowski notes.

Contact: Prof. Dr. Iris Lewandowski, Department of Biobased Products in the Bioeconomy, +49 (0)711 459 22221, email

Depending on the procedure, varying amounts of climate-relevant emissions such as methane and ammonia are produced when using fermentation residues in biogas plants. This loss of nitrogen and carbon contradicts the idea of a cycle. In order to ensure sustainable use, the team under Prof. Dr. Joachim Müller is working on avoiding emissions when using fermentation products.

The fermentation products of a biogas plant can be generally separated into a solid and liquid phase. From the liquid phase, valuable phosphorous and nitrogen compounds can be regained. With the regained mineral nutrients, the remaining solid materials can be dried and processed to a fertilizer that is precisely suited to the needs of the plants. This also contributes toward climate protection since volatile gases such as ammonia can be reused as elements of fertilizer and do not escape into the atmosphere.

Contact: Prof. Dr. Joachim Müller, Department of Agricultural Engineering in the Tropics and Subtropics, +49 711 459 22490, E-mail

Where should which bioenergy be produced and how much of it? Prof. Dr. Enno Bahrs’ Department of Farm Management is looking into individual bioenergy lines with this focus and into the efficiency and climate-friendliness of biogas plants. Compared with fossil energy sources, the CO2 reductions can be significant. However, very high costs can also result. This depends on how energy-efficient a biogas plant is operated. A generalized statement is therefore not possible, as each biogas plant has its own eco-, greenhouse, and energy balance.

Contact: Prof. Dr. Enno Bahrs, Department of Farm Management, +49 (0)711 459 22566, email

Due to global scarcity of biomass, the future of world food is growing bleaker, warns Prof. Dr. Harald Grethe of the Department of Rural Development Theory and Policy. The answer: No state subsidies for the production of fluid fuels from agricultural products; instead, bioenergy from agricultural waste products. Prof. Dr. Simone Graeff-Hönninger from the Department of Agronomy is investigating how energy can be generated from this.

Contact:
Prof. Dr. Manfred Zeller, Department of Rural Development Theory and Policy, +49 (0)711 459 22175, email

Prof. Dr. Simone Graeff-Hönninger, Department of Agronomy, +49 (0)711 459 22376, email