The fate of nitrogen in the urban area - The case of Zielona Góra, Poland.

The anthropogenic change of the nitrogen (N) cycle is strongly triggered by urban demand (such as food and meat consumption, energy demand and transport). As a consequence of high population density, impacts on human health through water and air pollution also concentrate on a city environment. Thus, an urban perspective on a predominantly rural pollution becomes relevant. Urban N budgets may be considered less intrinsically connected, so that separation of an agri-food chain and an industry-combustion chain is warranted. Results have been obtained for Zielona Góra, Poland, a city of 140,000 inhabitants characterized by domestic and transport sources and forest-dominated surroundings. In addition to food imports in Zielona Gora amounting to about 30 %, in the suburban area a significant share of N amounting to 41 % is related to fertilizer imports. The remaining imports are in fuel, electronics, textiles, plastics and paper. Most of the agri-food N (45 %) is denitrified in wastewater treatment. N associated with combustion (mainly NOx emissions from vehicles) represents a much smaller share than N entering via the agri-food system, amounting to 22 % of the total N imports. This overall picture is maintained also when specifically addressing the city center, with the exception of mineral fertilizer that plays a much smaller role, with just 7 % of N imports to the city.

Composition and selected properties of bio-waste collected in towns from single- and multi-family housing and in rural areas.

The progress of civilisation contributes, among other things, to an increase in the mass of waste produced in households. A significant part of it is bio-waste (about 31% in Poland). It is generally agreed that bio-waste is a suitable substrate for valorisation through fermentation with biogas production. Designing new and optimising existing facilities, however, requires precise data on the composition of bio-waste and its properties, which is challenging due to seasonal variability, place of origin (single- or multi-family housing, urban or rural) and collection method. This paper presents the method adopted for conducting the study and the results of an annual, monthly analysis of the morphological composition and selected properties of bio-waste from source-segregated households from 4 rural municipalities and 4 cities, from neighbourhoods with single-family and multi-family housing in Poland. In household bio-waste, the proportion of food waste content ranges from 36.7 to 47.6% (annual average values). The proportion of edible food waste in relation to the total weight of food waste is 5 to 7 times lower. The yearly percentage of garden waste varied from 35.8 to 52.8%. A considerable amount of impurities (such as plastics, glass, and stones) is present in the bio-waste stream. The waste collected in containers in urban areas with multi-family houses is the most polluted (16.6%). The proportion of pollutants in bio-waste collected in bags (rural areas and cities with single-family housing) does not exceed 10%.

Seasonal variability of the quantity and morphological composition of generated waste and selectively collected waste.

Waste delivered to the Marszów Plant was tested in order to research the effect of seasonal fluctuations on the quantity and composition of generated municipal waste and on the quantity and composition of selectively collected waste. Waste samples were collected once a month from November 2019 to October 2020. The results of the analysis showed that the quantity and composition of municipal waste generated during a week are different in terms of the subsequent months of the year. The quantity of generated municipal waste per capita per week ranges from 5.75 to 7.41 kg (cap·wk)-1, on average 6.68 kg (cap·wk)-1. The maximum values of the weekly indicators for generating the main material components of waste per capita were higher than the minimum by several up to more than 10 times (textiles). The total quantity of selectively collected paper, glass and plastics increased significantly during the conducted research at a rate of approx. 5% per month. The level of recovery concerning this waste over the period between November 2019 and February 2020 averaged at 29.1%, and between April and October 2020 it was nearly 10% higher (39.0%). The material composition of selectively collected waste in subsequent measurement series often differed. It is difficult to link the observed changes concerning the quantity and composition of the analysed waste streams with the seasons of the year, although weather conditions undoubtedly impact the consumption and functioning models of people, thus impacting the size of waste streams.

Morphological composition of bio-waste collected selectively in towns and villages during autumn and winter.

It is generally believed that bio-waste is a suitable substrate for valorizations through fermentation with biogas production. An increasing number of municipalities in Poland implement selective collection of bio-waste. Limited qualitative and quantitative data are available on the composition of household bio-waste, including the contaminant content. This paper presents the adopted research method and the analysis results of the composition of household bio-waste segregated at source from 4 rural and 4 urban communes, from districts with single-family and multi-family housing. Household bio-waste is mostly food waste (43.9 to 56.0%), with a smaller percentage of garden waste (27.4 to 46.3%). According to data from other countries, in Poland, "fruit and vegetable" waste constitutes the main part of household bio-waste (from 40.0 to 53.8%). The share of "contaminants" is relatively high. The most contaminated waste is that collected in containers in city districts with multi-family housing (16.6%). The share of contaminants in bio-waste collected in bags (rural areas and cities with single-family housing exceeded 10.0%).Implications: This article presents the results of an empirical analysis of the morphological composition, occurring contaminants and seasonal fluctuations in the stream of biodegradable waste delivered to the mechanical-biological treatment (MBT) installation in Marszow (Poland, Lubuskie province). This installation serves the area of 22 municipalities with more than 200.000 residents. Nearly 98% of households and housing estates are covered by regular waste collection. The study covered 12 streams of bio-waste delivered to the installation, divided into rural and urban areas with single-family and multi-family housing during the 2 seasons of autumn and winter.The importance of the conducted research is emphasized by the fact that the analysis of the morphological composition of bio-waste generated in households is rare, which is probably due to its labor- and time-consuming nature.The data obtained are a source of valuable information for both national and local governments, as well as can help meet the ambitious targets set for EU member states in terms of preparing for reuse and recycling of municipal waste, which are unlikely to be achieved without proper management of bio-waste.Another important argument is to reduce food waste in line with the sustainable development goal of reducing food waste by 50% by 2030.

Use of a novel water separation process for the recovery of the mineral fraction from the stabilized organic fraction found in municipal waste.

Currently, the Stabilized Organic Fraction (SOF) 0-80 mm separated from the municipal waste stream is sent in its entirety to landfill in the mechanical-biological treatment plants operating in Poland. Such action does not align with the adopted EU strategy focused on waste management in the circular economy. This study aimed to assess the technical feasibility of the process of purification of mineral fractions with a grain size of 10-80 mm separated from SOF on a technological installation designed for glass recovery, built at the Marszów Plant. In terms of material, mineral fractions are a mixture of stones, rubble and glass, contaminated with various components, mainly organic. In 2020, the glass recovery installation was expanded with an innovative process of gravity separation to separate mineral fraction from SOF with the use of a jigging machine. A pulse jig used in the mining industry for coal enrichment processes was used for the first time in municipal waste management. The installation allows for the recovery of between 71.1 and 96.6% of mineral fractions contained in the input (84.8 ± 9.5% on average). The proportion of organics, plastics and other impurities in the waste is 4.1 ± 2.1% of the fraction mass. The process consumed water at an average rate of 0.34 ± 0.10 m3 tonnes-1 of treated waste and generated 0.26 ± 0.09 m3 tonnes-1 of wastewater. Electricity consumption averaged 1.20 kWh tonne-1 input.

Risk and Opportunity of Using Plastics from Waste Collected in a Yellow Bag.

The article presents the results of research aimed at analysing the share of fractions suitable for recycling and pollutants in waste collected in a yellow bag. The research was carried out in an area inhabited by 200,000 people. The amount of waste collected in the communes in yellow containers in 2016-2019 increased systematically in communes: rural by 75.8, urban-rural by 44.9 and urban by 17.8%. The collection efficiency expressed in the degree of collection was the highest and grew fastest in rural areas (from 25.1 to 35.5%). In cities, it practically did not change (14.4-15.8%). The weight of recyclable components represented on average 39.9% of the weight of yellow bag waste. Plastic bottles (PET) packaging prevailed, the share of which changed from 19.6 to 14.8%, including the share of colourless PET decreasing from 7.9 to 5.8%. At present, revenue from the sale of secondary raw materials obtained from waste collected separately to yellow bags covers only 26% of the costs related to the recycling and recovery of waste delivered to the installation. Support for separate collection of plastics through recovery organisations, i.e., entrepreneurs who are obliged to recover and recycle waste, is symbolic.

Potential of Mineral Fraction in Compost-Like-Output, Methods of Its Obtaining and the Possibility of Using It in the Context of Circular Economy.

Most of the systems for the mechanical and biological treatment of waste used in Poland send the 0-80 mm fraction separated from the municipal waste stream, after biostabilization, entirely to a landfill. Such action is not in line with the adopted EU strategy focused on waste management in the circular cycle. The purpose of this work was to assess the technical feasibility of recovering the mineral fractions contained in compost-like-output (CLO) on the proprietary technological line designed for glass recovery. The research was launched in January 2019, and lasted for a subsequent 12 months. In the article, the amounts of mineral fractions possible to be separated from CLO are presented, as well as their morphological composition and selected properties being determined. The processing of CLO on the line allowed to recover on average 69.4 ± 7.0% of the glass. This product was accepted by glass recycling plants. Mineral fractions constituting waste from the glass separation process were tested for their use in winter road maintenance. Tests were also carried out confirming the possibility of using selected mineral fractions (0-10 mm) from CLO to obtain a waste cement mix useful for constructing road foundations using a standard amount of cement.

Recovery of Stabilizer Glass in Innovative MBT Installation-An Analasys of New Technological Procedure.

The data published by the European Container Glass Federation shows that the EU28 average collection rate for recycling of glass containers has grown to a rate of 76%. However the stabilizer produced at mechanical-biological treatment (MBT) installations at landfills still contains large amounts of recyclable glass. An industrial-scale study has been undertaken in order to assess the possibility of recovering this glass from the stabilizer. A new pilot installation was built at the MBT plant in Marszów, Poland. Tests were conducted on stabilizer samples produced at the plant (13 samples) and others collected from several MBT plants based in Poland (six samples). Processing the stabilizer on the designed line made it possible to recover on average 68.4 ± 7.0% of the glass contained in it from Marszów samples and 58.4 ± 14.2% in the case of samples acquired from other MBT installations. It is demonstrated that the concentrate quality largely depends on the stabilizer's moisture content. A concentrate with glass content from 98.0% to 99.5% was obtained for samples of low-moisture stabilizers (for 14 out of 19 samples). The product was accepted by glass recycling plants due to its low level of contamination with other materials and its appropriate particle size.

Efficiency of waste processing in the MBT system.

In the professional literature there is no information on the efficiency of waste treatment in MBT (mechanical-biological waste treatment) systems in Poland. This knowledge is currently particularly important as it will decide on the role of the MBT system in the new reality of the circular economy, and consequently on the direction and necessary scope of modernization of these systems. The article presents a series of technical and technological indicators designated for one of the recently commissioned MBT plants against the background of minimum, maximum and average values of these parameters set for 20 systems with various MBTs covered by the research as part of the review of technological solutions used in Poland, made in 2015. For the system in Marszów, respectively in 2017 and 2018, the average value of the ratio of underscreen to overscreen fraction was 1.4; the losses of mass in the biological treatment process amounted to 28.7 and 29.4%; energy demand - 46.6 and 44.3 kWh/Mg; the aeration index - 16.7 m3/(Mg h); the average waste recycling rate - 15.2 and 17.3%; the share of fuel fraction recovery - 11.6 and 16,6% and the share of waste sent to landfill - 33.2 and 32.3%.

The Evaluation of Indicators Used to Assess the Suitability of Agricultural Waste for Fermentation.

To ensure high fermentation efficiency, it is necessary to assess the biodegradability of a substrate. These parameters are most often determined on the basis of the amount of loss on ignition and total organic carbon. We are more and more often using chemical indices. However, these indices do not provide information on how much an organic substance is susceptible to biodegradation. The actual assessment of the content of easily biodegradable matter in substrates that are used for fermentation should be performed on the basis of aerobic (AT4) and anaerobic tests (BMP), which require specialised equipment and are time consuming. The AT4 index is being more and more frequently adopted for the analysis of substrates that are used in the fermentation process, because AT4 takes a much shorter time than BMP and provides information on the biodegradability of substrates. The aim of the article is to answer the question of whether the AT4 parameter can be used to assess the suitability of the substrate from the agricultural sector for the fermentation process. The results show that the AT4 index could be used instead of the BMP parameter.

A Comparison of Waste Stability Indices for Mechanical⁻Biological Waste Treatment and Composting Plants.

Achieving high efficiency of biological waste treatment in mechanical⁻biological treatment (MBT) plants requires reliable methods for measuring the degree of biodegradation of organic substances. For this purpose, several physical, chemical, and biological indices are used. This paper presents respirometric activity (AT4), biogas potential (GB21), total and dissolved organic carbon (TOC and DOC, respectively), and loss on ignition (LOI) values, as well as the correlations between the indices selected for stabilized waste produced in 18 MBT plants in Poland, which use various technologies for biological processing of the organic fraction of municipal solid waste. The study confirms that there is a linear relationship between AT4 and GB21 for stabilized waste produced in MBT plants, regardless of the waste treatment technology used. It has also been found that there is a linear relationship between AT4 and the concentration of dissolved carbon in water extract from stabilized waste. This indicates that DOC can be used for monitoring the organic matter stabilization process in mechanical⁻biological waste treatment plants. Its advantage is a shorter time needed for measurements in comparison to AT4 and GB21 tests.

A review of municipal solid waste composition and quantities in Poland.

A review of results of the research involving the quantitative and composition analyses of household waste conducted in Poland in recent years is presented in this paper. For these analyses various methodologies have been employed, as there is not one obligatory methodology how to characterise municipal solid waste. The results of the research in large Polish cities indicate great variability, which is difficult to be reasonably explained. This situation is affected by a number of factors, such as various methods and places for sample collection, various methods for tests, fractional character of most of the studies (studies carried out only in some periods during a year). Consequently, it is neither possible to measurably compare their results, nor to generalise them. Hence, within this article only individual data for large cities is provided. It is therefore necessary to standardise methodology for such analyses in Europe, taking into account local variability (such as different housing patterns, climate and waste collection schemes) to allow comparison of results. Reported yearly household waste generation in Polish cities varies from 238 to 309 kg per inhabitant. Biodegradable waste is a strongly dominated fraction in household waste from Polish cities, followed by paper/cardboard and plastics. Historical data shows that waste composition has undergone profound changes, the most significant being an increase of the share of plastics and decrease of fine fraction. The presented data indicates that waste composition strongly depends on the type of housing and its heating system. In the new multi-family buildings with central heating the share of paper and plastics is higher than in old houses with individual heating. In the latter ones the share of fine fraction is higher.