Experiments on methanogenesis from horse dung were conducted in laboratory-scale batch reactors in order to determine the substrate performance in a solid-phase digestion process, more specifically in terms of potential energy recovery and suitable process technology. Dung from a horse stable with straw bedding was used. The temperature was kept in the mesophilic range. In the percolation process (with process water sprinkled over the stacked biomass) a proportion of 10-20% of solid inoculum (pre-digested horse dung) was found to be suitable. Comparative experiments with both percolation and flooding revealed a higher biogas production per volume for the flooded process, as no addition of solid inoculum was necessary. Methane yield from fresh material was similar in both processes: around 170 L(N) CH(4) per kg VS added was obtained in six-week cycles with untreated material under optimized conditions. Methane production was increased after chopping the substrate. Pre-aeration resulted in decreased methane production.

Waste electrical and electronic equipment (WEEE) is difficult to sustainably manage. One key issue is the challenge of planning for WEEE flows as current and future quantities of waste are difficult to predict. To address this, WEEE generation and gross domestic product (GDP) data from 50 countries of the pan-European region were assessed. A high economic elasticity was identified, indicating that WEEE and GDP are closely interlinked. More detailed analyses revealed that GDP at purchasing power parity (GDP PPP) is a more meaningful measure when looking at WEEE flows, as a linear dependency between WEEE generation and GDP PPP was identified. This dependency applies to the whole region, regardless of the economic developmental stage of individual countries. In the pan-European region, an increase of 1000 international $ GDP PPP means an additional 0.5 kg WEEE is generated that requires management.

Various leachate recirculation strategies were applied to a batchwise operated one-stage solid-phase digestion system in laboratory-scale tests. Comparative experiments with both continuous and intermittent leachate recirculation revealed no advantages of a continuous flow. Results suggest that leachate recirculation should not be carried out continuously during process initialisation when methanogenesis is the rate-limiting step. Continuous watering resulted in the accumulation of Volatile Fatty Acids (VFA) during process start-up. In addition, no need for continuous water circulation was found for the following digestion process when hydrolysis was rate-limiting. Even in the absence of liquid recirculation, degradation was only slightly retarded when the biomass moisture content was adjusted.