• Energy Research

Abstract Municipal solid wastes incineration (MSWI) in modern waste-to-energy plants reduces the volume of MSW by up to 90%. Incineration process also produces two types of by-products – bottom ash (BA) and fly ash (FA). Municipal solid wastes incineration BA is rich in heavy metals and salts. The disposal of MSWI BA may cause serious environmental problems. The objective of this study is to assess fresh bottom ash chemical composition and heavy metals such as copper (Cu), lead (Pb) and zinc (Zn) leaching values. The chemical composition determination indicates that Cu (400–800 mg kg -1 ), Pb (680–1760 mg kg -1 ) and Zn (1330–2010 mg kg -1 ) are major heavy elements in MSWI bottom ash. The results showed that the concentrations of Cu were 0.1–2 mg kg -1 , Pb – 0.2–12.2 mg kg -1 , Zn – 0.4–5 mg kg -1 . In order to reduce the leaching of heavy metals from bottom ash, they should be pre-treated. The most commonly used technologies are weathering, washing and metals separation.

Abstract Increasing amounts of glass waste present serious challenges in waste management to avoid environmental problems that might be created if it was to be deposited in landfills. Theoretically, glass waste is fully recyclable, but, if contaminated, containing impurities, broken or mixed colour, it makes the re-melting process impractical. A great practice of using secondary recycling material was reached by the construction industry involving glass waste in concrete mixtures as fine aggregates – reuse of waste glass in concrete production not only preserves natural resources, reduces greenhouse gas emissions, saves energy, furthermore, it may improve concrete sustainability and enhance the properties of concrete when used at the optimum quantity. In this study the container glass waste evaluation was performed, as well as experimental research of mechanical properties of four types of concrete mixtures containing glass waste as fine aggregate. The best alternative of replacement of sand by glass waste scenario in concrete production was determined, employing the multicriteria decision-making method TOPSIS.

Abstract Production of biogas using bioresources of agricultural origin plays an important role in Europe’s energy transition to sustainability and to a climate-neutral economy. The usage of some substrates like maize has been increasingly denounced in the last years and there is currently an active discussion about future subsidies to biogas producers depending on the substrate used. The aim of this study is to compare and rank different substrates for biogas production considering their economic feasibility, substrate efficiency and environmental aspects. During the research, eight substrates were evaluated: cattle manure, pig manure, poultry manure, straw, wood, maize silage, waste, and sewage sludge. In order to reach the research goal, multi-criteria analysis using TOPSIS methodology was applied to objectively determine which of the substrates considered would be the most suitable for biogas production in Latvia. The results obtained showed that pig manure is the most suitable raw material for biogas production in Latvia, while poultry manure was ranked second, with little difference in value from pig manure.

Abstract In this study, a commercial aqueous dispersion of nZVI was applied for the removal of Cd(II), Cu(II), Ni(II), and Pb(II) ions from their aqueous solutions. The removal efficiency was studied using two mass ratios of nZVI to heavy metal: 7–9:1 and 140–180:1. In the first case, the capacities of heavy metals removal were found to be 79.33–102.00 mg per g of nZVI for Cd, 111.11-142.85 mg per g of nZVI for Cu, 107.30–137.96 mg per g of nZVI for Ni, and 110.97–142.68 mg per g of nZVI for Pb. In this treatment, nanoparticles formed larger structures with heavy metals and they were easily removed from water by filtration. In the second case, the removal efficiencies of heavy metals were lower. There were more discrete nanoparticles that not formed larger structures and could not be easily filtered. In this treatment, the acidification of the filtered solutions caused the formation of deposits and subsequent re-dissolution of some heavy metals back to solutions.

This study conducted an in-depth examination of the delamination process of multi-layer packaging waste (MLPW) recycling, intending to find an effective solution for recycling MLPW. The recycling process for such materials can be challenging due to the complexity of separating the different layers and components. However, this study proposed using nitric acid to facilitate delamination and recover the polymers from multilayer food packaging—the research aimed to investigate the mechanical properties of the polymers obtained through this recycling method. Our study on polymer materials exposed to chemicals revealed differences in fracture and tensile strengths among three polymers, P1, P2, and P3. P1 showed fluctuating fracture strengths between 5.11 MPa and 3.55 MPa, while P2 maintained a consistent but lower value of around 0.09 MPa. P3 exhibited a wider range from 3.19 MPa to 1.79 MPa. Tensile strength analysis showed P1 averaging 4.99 MPa and P3 3.17 MPa, with P2’s data inconclusive due to its softness. Understanding the mechanical characteristics of recycled polymers is crucial to determine their potential use in different industries, including packaging, construction, or manufacturing, thereby promoting a more environmentally friendly approach to MLPW management.

Almost 500 municipal solid waste incineration plants in the EU, Norway and Switzerland generate about 17.6 Mt/a of incinerator bottom ash (IBA). IBA contains minerals and metals. Metals are mostly separated and sold to the scrap market and minerals are either disposed of in landfills or utilised in the construction sector. Since there is no uniform regulation for IBA utilisation at EU level, countries developed own rules with varying requirements for utilisation. As a result from a cooperation network between European experts an up-to-date overview of documents regulating IBA utilisation is presented. Furthermore, this work highlights the different requirements that have to be considered. Overall, 51 different parameters for the total content and 36 different parameters for the emission by leaching are defined. An analysis of the defined parameter reveals that leaching parameters are significantly more to be considered compared to total content parameters. In order to assess the leaching behaviour nine different leaching tests, including batch tests, up-flow percolation tests and one diffusion test (monolithic materials) are in place. A further discussion of leaching parameters showed that certain countries took over limit values initially defined for landfills for inert waste and adopted them for IBA utilisation. The overall utilisation rate of IBA in construction works is approximately 54 wt%. It is revealed that the rate of utilisation does not necessarily depend on how well regulated IBA utilisation is, but rather seems to be a result of political commitment for IBA recycling and economically interesting circumstances.

Abstract This paper provides some information about mathematical modelling that was prepared for natural attenuation of petroleum hydrocarbons contaminated soil. Concentration of initial contamination with hydrocarbons and time that is needed to degrade it was compared with the results that were received from experimental research of the bioremediation of hydrocarbons in soil by the use of silica nanocomposite. The aim of the mathematical modelling was to check if microorganism that was used in previous research was effective enough when their effectiveness is compared with natural attention effectiveness. The results of natural attenuation shows that in some cases in-situ remediation might be more effective than ex-situ bioremediation, however the effectiveness of natural attenuation depends on many factors and due that the results might vary in different areas.