Impressum

Ohne Zusammenfassung     

Anaerobic digestion potential of urban organic waste: a case study in Malm?.

A study of existing organic waste types in Malm?, Sweden was performed. The purpose was to gather information about organic waste types in the city to be able to estimate the potential for anaerobic treatment in existing digesters at the wastewater treatment plan (WWTP). The urban organic waste types that could have a significant potential for anaerobic digestion amount to about 50 000 tonnes year(-1) (sludge excluded). Some of the waste types were further evaluated by methane potential tests and continuous pilot-scale digestion. Single-substrate digestion and co-digestion of pre-treated, source-sorted organic fraction of municipal solid waste, wastewater sludge, sludge from grease traps and fruit and vegetable waste were carried out. The experiments showed that codigestion of grease sludge and WWTP sludge was a better way of making use of the methane potential in the grease trap sludge than single-substrate digestion. Another way of increasing the methane production in sludge digesters is to add source-sorted organic fraction of municipal solid waste (SSOFMSW). Adding SSOFMSW (20% of the total volatile solids) gave a 10-15% higher yield than could be expected by comparison with separate digestion of sludge respective SSOFMSW. Co-digestion of sludge and organic waste is beneficial not just for increasing gas production but also for stabilizing the digestion process. This was seen when co-digesting fruit and vegetable waste and sludge. When co-digested with sludge, this waste gave a better result than the separate digestion of fruit and vegetable waste. Considering single-substrate digestion, SSOFMSW is the only waste in the study which makes up a sufficient quantity to be suitable as the base substrate in a full-scale digester that is separated from the sludge digestion. The two types of SSOFMSW tested in the pilot-scale digestion were operated successfully at mesophilic temperature. By adding SSOFMSW, grease trap sludge and fruit and vegetables waste to sludge digesters at the wastewater treatment plant, the yearly energy production from methane could be expected to increase from 24 to 43 GWh.     

A life cycle approach to the management of household food waste - A Swedish full-scale case study

Environmental impacts from incineration, decentralised composting and centralised anaerobic digestion of solid organic household waste are compared using the EASEWASTE LCA-tool. The comparison is based on a full scale case study in southern Sweden and used input-data related to aspects such as source-separation behaviour, transport distances, etc. are site-specific. Results show that biological treatment methods - both anaerobic and aerobic, result in net avoidance of GHG-emissions, but give a larger contribution both to nutrient enrichment and acidification when compared to incineration. Results are to a high degree dependent on energy substitution and emissions during biological processes. It was seen that if it is assumed that produced biogas substitute electricity based on Danish coal power, this is preferable before use of biogas as car fuel. Use of biogas for Danish electricity substitution was also determined to be more beneficial compared to incineration of organic household waste. This is a result mainly of the use of plastic bags in the incineration alternative (compared to paper bags in the anaerobic) and the use of biofertiliser (digestate) from anaerobic treatment as substitution of chemical fertilisers used in an incineration alternative. Net impact related to GWP from the management chain varies from a contribution of 2.6 kg CO₂-eq/household and year if incineration is utilised, to an avoidance of 5.6 kg CO₂-eq/household and year if choosing anaerobic digestion and using produced biogas as car fuel. Impacts are often dependent on processes allocated far from the control of local decision-makers, indicating the importance of a holistic approach and extended collaboration between agents in the waste management chain.     

Echoes from the Past: A Healthy Baltic Sea Requires More Effort

Integrated sediment multiproxy studies and modeling were used to reconstruct past changes in the Baltic Sea ecosystem. Results of natural changes over the past 6000 years in the Baltic Sea ecosystem suggest that forecasted climate warming might enhance environmental problems of the Baltic Sea. Integrated modeling and sediment proxy studies reveal increased sea surface temperatures and expanded seafloor anoxia (in deep basins) during earlier natural warm climate phases, such as the Medieval Climate Anomaly. Under future IPCC scenarios of global warming, there is likely no improvement of bottom water conditions in the Baltic Sea. Thus, the measures already designed to produce a healthier Baltic Sea are insufficient in the long term. The interactions between climate change and anthropogenic impacts on the Baltic Sea should be considered in management, implementation of policy strategies in the Baltic Sea environmental issues, and adaptation to future climate change.     

Persistent organochlorine contaminants in hair samples of Northern Poland population, 1968-2009

The European regulation on chemicals, REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals), came into force on 1 June 2007. With pre-registration complete in 2008, data for these substances may provide an overview of the expected chemical space and its characteristics. In this paper, using various in silico computation tools, we evaluate 48 782 neutral organic compounds from the list to identify hazardous and safe compounds. Two different classification schemes (modified Verhaar and ECOSAR) identified between 17% and 25% of the compounds as expressing only baseline toxicity (narcosis). A smaller portion could be identified as reactive (19%) or specifically acting (2.7%), while the majority were non-assigned (61%). Overall environmental persistence, bioaccumulation and long-range transport potential were evaluated using structure-activity relationships and a multimedia fugacity-based model. A surprisingly high proportion of compounds (20%), mainly aromatic and halogenated, had a very high estimated persistence (>195 d). The proportion of compounds with a very high estimated bioconcentration or bioaccumulation factor (>5000) was substantially less (6.9%). Finally, a list was compiled of those compounds within the applicability domain of the models used, meeting both persistence and bioaccumulation criteria, and with a long-range transport potential comparable to PCB. This list of 68 potential persistent organic pollutants contained many well-known compounds (all halogenated), but notably also five fluorinated compounds that were not included in the EINECS inventory. This study demonstrates the usability of in silico tools for identification of potentially environmentally hazardous chemicals.