Erwin Binner

Strategic environmental assessment as an approach to assess waste management systems. Experiences from an Austrian case study

Waste management has evolved from the simple transportation of waste to landfills to complex systems, including waste prevention and waste recycling as well as several waste treatment and landfill technologies. To assess the environmental, economical and social effects of waste management systems, several tools have been developed. Strategic Environmental Assessment (SEA) is an approach for integrated assessment enhancing involvement in the planning of a decision supporting process. The aim of this paper is to show how SEA can be applied in a waste management context. For this purpose a case study is described where a SEA process was undertaken to develop a regional waste management plan. The approach from this case study is compared to other methods.

Investigations of biological processes in Austrian MBT plants.

Mechanical biological treatment (MBT) of municipal solid waste (MSW) has become an important technology in waste management during the last decade. The paper compiles investigations of mechanical biological processes in Austrian MBT plants. Samples from all plants representing different stages of degradation were included in this study. The range of the relevant parameters characterizing the materials and their behavior, e.g. total organic carbon, total nitrogen, respiration activity and gas generation sum, was determined. The evolution of total carbon and nitrogen containing compounds was compared and related to process operation. The respiration activity decreases in most of the plants by about 90% of the initial values whereas the ammonium release is still ongoing at the end of the biological treatment. If the biogenic waste fraction is not separated, it favors humification in MBT materials that is not observed to such extent in MSW. The amount of organic carbon is about 15% dry matter at the end of the biological treatment.

Determination of MBT-waste reactivity - An infrared spectroscopic and multivariate statistical approach to identify and avoid failures of biological tests

The Austrian Landfill Ordinance provides limit values regarding the reactivity for the disposal of mechanically biologically treated (MBT) waste before landfilling. The potential reactivity determined by biological tests according to the Austrian Standards (OENORM S 2027 1-2) can be underestimated if the microbial community is affected by environmental conditions. New analytical tools have been developed as an alternative to error-prone and time-consuming biological tests. Fourier Transform Infrared (FT-IR) spectroscopy in association with Partial Least Squares Regression (PLS-R) was used to predict the reactivity parameters respiration activity (RA(4)) and gas generation sum (GS(21)) as well as to detect errors resulting from inhibiting effects on biological tests. For this purpose 250 MBT-waste samples from different Austrian MBT-plants were investigated using FT-IR spectroscopy in the mid (MIR) and near infrared (NIR) area and biological tests. Spectroscopic results were compared with those from biological tests. Arising problems caused by interferences of RA(4) and GS(21) are discussed. It is shown that FT-IR spectroscopy predicts RA(4) and GS(21) reliably to assess stability of MBT-waste materials and to detect errors.

Humification and Degradability Evaluation During Composting of Horse Manure and Biowaste

Performing compost quality assessment such as compost stability is quite necessary for rating the quality of horse manure and biowaste composts and meeting specific regulatory requirements on the composition and compost process. The aim of this study was to identify an appropriate feedstock composition for use in the production of high quality compost. The objectives were to (1) identify an appropriate feedstock composition (2) determine organic matter decomposition and humic acids (HA) development in various composts; (3) compare changes in temperature, C/N ratio and respiration activity, occurring during decomposition of organic matter; (4) evaluate phytotoxicity effects of the final compost on cress seed germination and growth. The above changes in physical, chemical and biological parameters were monitored during the laboratory composting process over a period of 20 weeks. Five organic waste blends of horse manure (HM) and biowaste (BW) were used. The results indicated that at the beginning of the experiment, the highest C/N ratio of 59 was recorded in the pure horse manure. This is attributed to the presence of higher amounts of bedding materials (wood chips and wheat straw). The degradation rate of pure HM was slower than that of BW and the degradation had not been completed by the end of the 20 weeks composting period. An ANCOVA with time as the covariate showed that pure BW was more significantly humified than pure HM (p<0.05). Consistently higher contents of HA and lower E4/E6 ratio were obtained in pure BW than in pure HM throughout the processes. Statistically significant difference (p<0.01) among treatments were found for the shoot fresh weight percentage (SFW%). Correlations between the latter and E4/E6 ratios were significant at (p<0.001). Chemical and biological changes indicated an increase in compost quality in correspondence with BW composition increment. Largely the 50/50 blend was not significantly different from other feedstocks (p<0.01) except from pure HM. It was therefore concluded that composting using a combination of HM and BW (50/50) could be used as an alternative method to pure HM composting.

How to enhance humification during composting of separately collected biowaste: impact of feedstock and processing

Conventional parameters (loss on ignition, total organic carbon, total nitrogen, C/N-ratio, respiration activity (RA4), compost status (= ‘Rottegrad’), NH4-N and NO3-N) are not correlated to humification. At best, they provide information on the biological stability (status of degradation) of composts. Humic substances which are a source of stable organic matter and nutrients are discussed as a parameter describing compost quality. Thus, in the present research project a photometric method evaluating humic acids was used to characterize the quality of 211 Austrian and foreign composts made from source-separated collected biowaste or sewage sludge. Furthermore, parameters influencing the formation of humic acids during the rotting process were investigated by implementing rotting experiments in the laboratory as well as in composting plants. The analysed composts showed humic acid contents between 2.5 and 47 %, calculated on a organic dry matter (oDM) basis. In addition to the duration of treatment the main influence on humification was the feedstock used. Stabilized sewage sludge, biowaste after intensive anaerobic pre-treatment or biowaste with low reactivity (RA4) or uniform composition (e.g. mainly grass) showed a low formation of humic acids. For optimum humification the feedstock needed to contain components that are well balanced from scarcely to easily degradable compounds. Processing also influenced humification. Open windrow systems and reactor systems allow the same quality to be produced when operated well, but optimizing mineralization (e.g. very intensive aeration) showed negative effects. The positive condition required for humification is an unhurried (not too intense) degradation with long-lasting biological activity in which microbes have enough time to use the metabolic products of degradation for humification.

Development of Mechanically Biologically Treated Municipal Solid Waste under Different Vegetation Types

The use of mechanically biologically treated (MBT) waste as cover material for landfills during the aftercare period has gained in importance since the previous decade. The question arises how such materials change their properties under open field conditions. For field experiments, two MBT plants in Austria with related landfills were selected. A cover layer consisting of MBT material was applied on the surface and planted with grass and rape. The development without any vegetation served as a reference. Leaching, mineralization, and humification of waste organic matter were quantified. The impact of time, sampling depth, respective oxygen supply, and vegetation on the material was investigated. Intensive grass vegetation promoted mineralization and humification. Leaching of salts and the transformation of nitrogen were mainly influenced by time and depth. Aerobic conditions advanced degradation of still-reactive material. Under aerobic conditions, the remaining respiration activity was about two times lower than in the anaerobic zones. It was proven that well stabilized MBT material can be used as a cover layer with adequate vegetation.

Influence of Mechanical-Biological Pretreatment On the Toxicity of Municipal Solid Waste

Mechanical-biologically pretreated residual waste was tested for toxicity, chemical quality and reactional behavior. Samples were taken from different composting plants at different stages of treatment. Acute toxicity was determined using Daphnia magna (crustacean) and Vibrio fischeri (luminescent bacteria), chronic toxicity was tested with Selenastrum capricomutum (green algae) and Lepidium sativum (cress). Samples were analyzed for various physico-chemical parameters and for biological parameters (respiration activity, gas-generating potential). Toxicity tests were carried out from eluates and toxicity was expressed in German regulatory G-values. The results of this study indicate that high toxicity was observed in untreated MSW samples and in samples with a short treatment period. In most cases toxicity decreased significantly when the treatment period increased and marked differences were observed in the susceptibility among the species. Toxicity varied between a G-value of 1 and 256. For some tests a...

Composting Conditions Preventing the Development of Odorous Compounds

Laboratory tests allow to compost biowaste under defined boundary conditions. By varying these conditions we found out parameters responsible for the production of odorous compounds during the composting process. Parameters describing the composting conditions were pH value, content of fatty acids in the rotting material and CO2 production. The most important influences to prevent the production of odorous compounds are fast and careful mechanical pretreatment of the biowastes and sufficient well oxygen supply.

Influence assessment of a lab-scale ripening process on the quality of mechanically–biologically treated MSW for possible recovery

In this study, the influence of an additional ripening process on the quality of mechanically-biologically treated MSW was evaluated in the prospective of recovering the end material, rather than landfilling. The biostabilised waste (BSW) coming from one of the MBT plants of Rome was therefore subjected to a ripening process in slightly aerated lab test cells. An in-depth investigation on the biological reactivity was performed by means of different types of tests (aerobic and anaerobic biological tests, as well as FT-IR spectroscopy method). A physical-chemical characterisation of waste samples progressively taken during the ripening phase was carried out, as well. In addition, the ripened BSW quality was assessed by comparing the characteristics of a compost sampled at the composting plant of Rome which treat source segregated organic wastes. Results showed that the additional ripening process allowed to obtain a better quality of the biostabilised waste, by achieving a much higher biological stability compared to BSW as-received and similar to that of the tested compost. An important finding was the lower heavy metals (Co, Cr, Cu, Ni, Pb and Zn) release in water phase at the end of the ripening compared to the as-received BSW, showing that metals were mainly bound to solid organic matter. As a result, the ripened waste, though not usable in agriculture as found for the compost sample, proved anyhow to be potentially suitable for land reclamation purposes, such as in landfills as cover material or mixed with degraded and contaminated soil for organic matter and nutrients supply and for metals recovery, respectively. In conclusion the study highlights the need to extend and optimise the biological treatment in the MBT facilities and opens the possibility to recover the output waste instead of landfilling.