Research "Bioplastics"

Research on anaerobic pre-treatment of Bioplastics

Project description:
Current environmental policy developments, such as the introduction of nationwide separate collection of biowaste from 2015 (KrWG §11, Para. 1) and the cascade use of organic waste (energy recovery before material recovery), will mean that biowaste will be increasingly recovered in anaerobic digestion plants or in composting plants with an upstream anaerobic digestion stage in the future. In some disposal regions in Germany (e.g. Straubing or Bad Dürkheim), biowaste bags made of biodegradable bioplastics are already being offered or recommended for use by public waste management authorities, although this is almost exclusively done in disposal regions with aerobic biowaste recycling. Surveys carried out as part of a pilot project in the area covered by the Straubing Stadt und Land Waste Management Association (ZAW-SR) showed that the citizens involved in the separate collection of biowaste using compostable biowaste bags primarily value cleanliness, hygiene and practicality as decisive criteria for their use [ZAW-SR 2005].

Currently, there is no certification in which manufacturers have to prove trouble-free and effective anaerobic recycling of biodegradable bioplastics. For this reason, malfunctions can occur when they are recycled in anaerobic digestion plants, especially in pumping and agitating units. Since these are only applied in wet fermentation, these problems are not to be expected in dry fermentation plants.

Therefore, the pretreatment methods investigated in this project are to be carried out in a hydrolysis unit connected upstream of the methanation unit in order to ensure optimum plant operation. In this process, the biodegradable bioplastics are made more available to fermentative microorganisms by means of the simplest possible process technology, so that they can then be anaerobically utilized to the greatest possible extent.

The pretreatment is to be carried out in an aqueous medium, with the exclusion of oxygen, and the dissolved organic components are then transferred to the fermentation process. It must be ensured that the process parameters are only exceeded to an acceptable extent (e.g. pH value).