Gintaras Denafas

Application and evaluation of forecasting methods for municipal solid waste generation in an eastern-European city

Forecasting of generation of municipal solid waste (MSW) in developing countries is often a challenging task due to the lack of data and selection of suitable forecasting method. This article aimed to select and evaluate several methods for MSW forecasting in a medium-scaled Eastern European city (Kaunas, Lithuania) with rapidly developing economics, with respect to affluence-related and seasonal impacts. The MSW generation was forecast with respect to the economic activity of the city (regression modelling) and using time series analysis. The modelling based on social-economic indicators (regression implemented in LCA-IWM model) showed particular sensitivity (deviation from actual data in the range from 2.2 to 20.6%) to external factors, such as the synergetic effects of affluence parameters or changes in MSW collection system. For the time series analysis, the combination of autoregressive integrated moving average (ARIMA) and seasonal exponential smoothing (SES) techniques were found to be the most accurate (mean absolute percentage error equalled to 6.5). Time series analysis method was very valuable for forecasting the weekly variation of waste generation data (r2 > 0.87), but the forecast yearly increase should be verified against the data obtained by regression modelling. The methods and findings of this study may assist the experts, decision-makers and scientists performing forecasts of MSW generation, especially in developing countries.

Characterization of waste printed circuit boards recycled using a dissolution approach and ultrasonic treatment at low temperatures

Recently, the separation of waste printed circuit boards (WPCBs) using organic solvents has become more prevalent because it is an environmentally friendly and efficient technique. However, the relatively high temperatures (∼135 °C) used during the separation process lead to higher energy consumption, faster solvent degradation, and possibly higher emissions of toxic fumes. This work aims to develop a new approach to separate all layers of WPCBs at lower temperatures to avoid the above-mentioned drawbacks. Di-methyl formamide (DMF) was used in the present technique as an organic solvent, while ultrasonic treatment was applied in order to accelerate the breakage of the internal van der Waals bonds of brominated epoxy resin (BER), thus decreasing the separation time. The experiments were conducted on five WPCB samples with the same surface area of 100 mm2, cut from five different WPCB models. The experiments were carried out at 25 °C (used as a reference), 50 °C, and 75 °C to study the effect of heating rate on the separation time and on the concentration of the BER dissolved in DMF. Ultraviolet-visible spectroscopy, metallographic microscope, and SEM-EDS were used to examine the recovered BER and fiberglass structure as well as the main metal compositions of each sample, respectively. The results showed that separation time and concentration of BER strongly depended on the WPCB models. In addition, the dissolution process at 50 °C resulted in the concentration of BER close to 25 °C for most of the models, while the concentration was lowest at 75 °C. At the same time, the trend in separation time was exactly opposite, with 75 °C resulting in the fastest separation time and 25 °C in the slowest. This facile approach appears promising for its potential applications in WPCB recycling and could be applied on an industrial scale.

Potential of energy and nutrient recovery from biodegradable waste by co-treatment in Lithuania

Biodegradable waste quantities in Lithuania and their potential for the co-treatment in renewable energy and organic fertilizer production were investigated. Two scenarios were formulated to study the differences of the amounts of obtainable energy and fertilizers between different ways of utilization. In the first scenario, only digestion was used, and in the second scenario, materials other than straw were digested, and straw and the solid fraction of sewage sludge digestate were combusted. As a result, the amounts of heat and electricity, as well as the fertilizer amounts in the counties were obtained for both scenarios. Based on this study, the share of renewable energy in Lithuania could be doubled by the co-treatment of different biodegradable materials

Report: Environmental assessment of Darmstadt (Germany) municipal waste incineration plant

The focus of this study was the emissions from waste incineration plants using Darmstadt (Germany) waste incineration plant as an example. In the study the emissions generated by incineration of the waste were considered using three different approaches. Initially the emissions from the waste incineration plant were assessed as part of the impact of waste management systems on the environment by using a Municipal Solid Waste Management System (MSWMS) assessment tool (also called: LCA-IWM assessment tool). This was followed by a comparison between the optimal waste incineration process and the real situation. Finally a comparison was made between the emissions from the incineration plant and the emissions from a vehicle.

Paradigms on landfill mining: From dump site scavenging to ecosystem services revitalization

Abstract For the next century to come, one of the biggest challenges is to provide the mankind with relevant and sufficient resources. Recovery of secondary resources plays a significant role. Industrial processes developed to regain minerals for commodity production in a circular economy become ever more important in the European Union and worldwide. Landfill mining (LFM) constitutes an important technological toolset of processes that regain resources and redistribute them with an accompanying reduction of hazardous influence of environmental contamination and other threats for human health hidden in former dump sites and landfills. This review paper is devoted to LFM problems, historical development and driving paradigms of LFM from ‘classical hunting for valuables’ to ‘perspective in ecosystem revitalization’. The main goal is to provide a description of historical experience and link it to more advanced concept of a circular economy. The challenge is to adapt the existing knowledge to make decisions in accordance with both, economic feasibility and ecosystems revitalization aspects.

Forecasting medical waste generation using short and extra short datasets: Case study of Lithuania

The aim of the study is to evaluate the performance of various mathematical modelling methods, while forecasting medical waste generation using Lithuania’s annual medical waste data. Only recently has a hazardous waste collection system that includes medical waste been created and therefore the study access to gain large sets of relevant data for its research has been somewhat limited. According to data that was managed to be obtained, it was decided to develop three short and extra short datasets with 20, 10 and 6 observations. Spearman’s correlation calculation showed that the influence of independent variables, such as visits at hospitals and other medical institutions, number of children in the region, number of beds in hospital and other medical institutions, average life expectancy and doctor’s visits in that region are the most consistent and common in all three datasets. Tests on the performance of artificial neural networks, multiple linear regression, partial least squares, support vector machines and four non-parametric regression methods were conducted on the collected datasets. The best and most promising results were demonstrated by generalised additive (R2 = 0.90455) in the regional data case, smoothing splines models (R2 = 0.98584) in the long annual data case and multilayer feedforward artificial neural networks in the short annual data case (R2 = 0.61103).

Molecular structure of mercury(II) thiocyanate complexes based on DFT calculations and experimental UV-electron spectroscopy and Raman studies

In this work, we report a combined experimental and theoretical study on molecular structure, vibrational and electronic spectra of [Hg(SCN)n](2-)(n) complexes (where n=2, 3, 4) in the aqueous solution. Molecular modeling of the mercury(II) complexes were done by the density functional theory (DFT) method using B3LYP functional with Stuttgart relativistic ECP 78MWB basis set for Hg and 6-311++G(d,p) basis set for all other atoms. The effect of different solvation models with explicit (ligand) and/or implicit water environment upon its geometry, vibrational frequencies and UV spectrum have been studied. The influence of H2O/D2O exchange on the experimental and calculated vibrational frequencies of studied complexes has been established. The double-peak character of the νHgS vibrational mode of the all analyzed mercury complexes and νCN mode of [Hg(SCN)3H2O](-) complex, respectively, were proposed here for the first time. The formation of four-coordinated Hg(II) complexes with thiocyanate and (or) water ligands was verified.

Former dump sites and the landfill mining perspectives in baltic countries and Sweden : The status

Landfills are considered as places where the life cycle of products ends thus meaning that resources and materials, which before were valuables, become useless and are disposed forever in places aw ...

An assessment of the current and future options for domestic waste management in Kaunas, Lithuania.

The main purpose of this study was to carry out a retrospective analysis of solid waste generation in Kaunas city from 1994 to 2003 and to calculate the theoretical waste generation in the future. This paper also presents measurements of the annual variations of waste amounts and calculations on a theoretical waste incineration facility. Two waste treatment scenarios were considered. •Scenario A: waste deposit at the landfill with ‘implementation of domestic waste separation and recycling’. •Scenario B: waste removal to a landfill with ‘multi-treatment: household separation, recycling and energetic recovery’. Three levels of waste treatment were proposed. The first level was implementation of the recycling system, which included household waste separation. The next step involved mechanical-biological treatment. The third level was the construction and operation of a new waste incineration plant in Kaunas. Two sites in Kaunas city were proposed; however, more detailed analysis, including the economic factors, will need to be done.

Characterization of residues from physicochemical treatment of waste fluorescent lamps.

Fluorescent lamps are widely used world-wide due to their long life and energy saving capability. These lamps contain mercury (Hg) as a source of fluorescent radiation. The object of this study is a new technology for physicochemical treatment of waste fluorescent lamps. The residuals of the technological process were evaluated for potential leaching of heavy metals into the environment. Evaluation was performed using standardized extraction tests. Additionally, X-ray diffractometry (XRD) analysis, as well as tests with complex-forming agents and under pH-stable conditions were performed aiming to predict stability of the residuals in various environmental conditions. According to the XRD analysis, the minerals fluorapatite and hydroxylapatite were dominant in analyzed samples. The results of total extraction by aqua regia revealed that residuals contain relatively high total concentrations of Hg, Mn, and Zn. Concentrations of heavy metals, leaching to aqueous solution, were compared to leaching limit values (according to EU legislation). The concentrations of available Hg in the waste fluorescent lamp treatment products, according to its solubility in the water, exceed the limit values. The measured water-leachable Hg concentration was 4.88 mg kg-1, while the value for waste acceptable at hazardous waste landfill sites is 2 mg kg-1. Concentrations of other measured heavy metals did not exceed the limit values. According to the results, Hg stabilization potential for presented technology exceeds 99%.