EKaBio - Energy-efficient cascade utilization of biogenic waste taking into account new requirements for waste air treatment and compost qualityCopyright: © ANTS
In Germany, we separate our waste, so in 2018, a total of about 15 million tons of biodegradable waste could also be collected separately and recycled in fermentation and composting plants. But mass alone is not everything. For high-quality material recycling of waste, the grade purity of the collected waste is crucial. Particularly in the area of biowaste, the rate of misdirected waste is high. Foreign materials, such as waste collection bags made of plastic, make material recycling by means of composting more difficult.
Among other things, the ANTS is pursuing the question of how the material flow management of a biological waste treatment plant must be designed in order to be able to produce a quality-assured compost product despite fluctuating waste qualities. For this purpose, investigations are carried out in a so-called cascade plant. In biological waste treatment, this means the combination of an anaerobic digestion plant and a composting plant. In the fermentation plant, biogas is first extracted from a portion of the biowaste, and the fermentation residue is then recycled into compost in so-called rotting tunnels.
After delivery to the cascade plant, the biowaste is fed into the coarse preparation process. This allows a large proportion of foreign matter, such as waste collection bags, to be removed. However, small particles of foreign matter pass through the screen used for this purpose. While a portion of the screened biowaste is fed to the digester for biogas production, conveyor belts direct the other portion to composting. Before the biowaste can be fed into the rotting tunnels for composting, fermentation residues from the digester and screen overflows from the compost fine treatment are mixed in.
The challenge of material flow management is to produce constant mixtures for composting despite variations in quantity and quality with regard to particle size, water, organic and foreign matter content. To optimize material flow management, ANTS therefore characterizes all material flows of the cascade plant as well as the mixtures produced, taking seasonal fluctuations into account. For this purpose, the material streams are regularly sampled, screened to determine the particle size distribution and then the foreign matter content is determined by manual sorting. The water content and the organic content are analyzed in the ANTS internal laboratory. Based on the generated results, specific recommendations for action to optimize material flow management are subsequently derived.
However, in order to obtain good compost, this topic does not only require research. Freely following the motto "What is not brought in does not have to be sorted out," each and every one of us can make his or her contribution to the production of quality-assured composts. By collecting biowaste by type in one's own household in accordance with the sorting specifications of the respective municipality, the input of foreign substances can be avoided directly at the source. So we are all in demand on the subject of compost!
The research question described is part of the EKaBio joint project funded by the BMWK. In this joint project, a consortium of a total of 6 university, industrial and municipal partners is dedicated to the optimization of cascade plants, taking into account new legal requirements for exhaust air treatment and compost quality.
This photo shows organic waste with a high proportion of garden waste. The foreign matter content is low, making the material ideal for composting.