Environmental assessment of biowaste management in the Danish-German border region

Abstract

The treatment of organic waste from households has gained significant interest in recent years. Each country in the EU and the rest of the world treat their organic waste in many different ways, and Denmark and Germany are no exemption in this regard. The treatment of household organic waste in these two countries has taken a very different turn in the last century. Denmark has been incinerating organic household waste as part of a residual waste policy for more than a century, but it has only attempted biological treatment to a limited extent. Germany, on the other hand, has focused intensely on source separation followed by biological treatment and a mixture of incineration and mechanical and biological treatment for any organic matter remaining in residual waste. In recent years, Denmark has increased its focus on moving away from incineration and increasing material recycling, both on its own initiative and also incentivised by the EU’s 50% recycling target for 2020. This focus includes recycling organic waste from households as well as dry recyclable waste fractions. This PhD project was carried out as a cross-border partnership with five waste management companies, three located in Denmark and two in Germany, all with the wish to increase the source separation and treatment of organic household waste. The current practice in the Danish border region does not include source separation, and all organic household waste is incinerated as part of the residual waste. The German region already has a well-established source separation system, but it wants to increase its efficiency. The main aim of this Ph.D. thesis was to compare current organic waste management systems across the Danish-German border with future scenarios intended for the treatment of organic waste using LCA. The outcome of the project was a recommendation to waste management companies through life cycle assessment and experimental work at a biological treatment plant. A major part of the PhD study was collecting data on all aspects of the waste management chain. Waste generation through to collection, transportation, treatment and final disposal were analysed. The most detailed analysis took place at a combined biogas and composting plant, where solid and liquid samples were taken and air emissions measured through whole-site fugitive emissions. The assessments were done by using a combination of material flow analysis, substance flow analysis, life cycle inventories and life cycle assessments, using the EASETECH modelling software. The life cycle assessment assessed the management of organic household waste in the Danish-German border region. The main output was a life cycle assessment showing large differences in the environmental performance of the two different regions, with the Danish region performing better in most impact categories. Furthermore, the importance of the energy systems was investigated, showing that a large influence on the results was the surrounding energy system. Besides comparing the two regions’ current performances to each other, they were compared to four future scenarios featuring increased source separation and different biological treatments. In this case the life cycle assessment was used as a planning tool for a future waste management system where environmental hotspots could be identified for both current and possible future systems. In all cases, the results showed that local conditions can play a major role in where the system can be improved, and conclusions made on an overall level (all five waste management companies together) can lead to suboptimal decisions; it is therefore important to look at each waste management company individually. Major differences in environmental performance were seen when changing from incineration or mechanical and biological treatment to biological treatment, such as increased savings of phosphorous and increased loadings of ammonia. Most important for the environmental performance of the biological treatment facilities were high biogas production and low fugitive methane, nitrous oxide and ammonia emissions. Fugitive emissions measured at a combined biogas and composting plant were very significant and led to a turnaround in the environmental performance of the plant, going from a saving in greenhouse gas potential to a loading when including the measured emissions and applying the life cycle assessment principles. Ultimately, increasing the source separation of organic household waste for the five waste management companies is a viable option, if the focus of the companies is on flexible fuel (biogas), compost production and subsequent resource savings. However, the picture is not clear, as the current waste management system (mainly incineration) is already working well, and in some cases it outperforms the biological treatment option.