Dataset for a full-year time series characterization of separately collected organic fraction of municipal solid waste from rural and urban regions in Germany

In the municipal context and depending on the collection scheme, different waste streams are of relevance. This article contains year-round data on the chemical composition of organic fractions of municipal solid waste (OFMSW) of rural and urban origins. All samples were collected in the municipality of Tübingen, which is located in southern Germany. The sampling procedure was executed in accordance with standard procedures mentioned in the German Biowaste Ordinance. The data presented in this article include (1) sampling area and process specifications (2) organoleptic examinations (3) dry matter and organic dry matter contents (4) impurity concentrations and (5) elemental compositions (major, minor and trace elements). All datasets are presented as a time series for the year 2018. Thus, this article especially presents the influence of season and settlement structure on the physico-chemical characteristics of OFMSW. Researchers, waste management companies and municipalities can compare and expand their own OFMSW data with those presented in this article. The dataset can also be used to calculate energy yields of OFMSW when utilized in anaerobic digestion. Based on the data, it is also possible to discuss and to evaluate the material utilization of OFMSW-based digestates and compost products, especially with regard to concentrations of major, minor and trace elements. For further discussion, please refer to the original scientific article Sailer et al. (2021).


a b s t r a c t
In the municipal context and depending on the collection scheme, different waste streams are of relevance. This article contains year-round data on the chemical composition of organic fractions of municipal solid waste (OFMSW) of rural and urban origins. All samples were collected in the municipality of Tübingen, which is located in southern Germany. The sampling procedure was executed in accordance with standard procedures mentioned in the German Biowaste Ordinance. The data presented in this article include (1) sampling area and process specifications (2) organoleptic examinations (3) dry matter and organic dry matter contents (4) impurity concentrations and (5) elemental compositions (major, minor and trace elements). All datasets are presented as a time series for the year 2018. Thus, this article especially presents the influence of season and settlement struc-ture on the physico-chemical characteristics of OFMSW. Researchers, waste management companies and municipalities can compare and expand their own OFMSW data with those presented in this article. The dataset can also be used to calculate energy yields of OFMSW when utilized in anaerobic digestion. Based on the data, it is also possible to discuss and to evaluate the material utilization of OFMSW-based digestates and compost products, especially with regard to concentrations of major, minor and trace elements. For further discussion, please refer to the original scientific article Sailer et al. (2021).  Table   Subject Waste Management and Disposal Specific subject area Physico-chemical characterization and comparison of rural and urban organic fraction of municipal solid waste (OFMSW) samples for a one-year period. Type of data 21 Tables and 7 Figures  How data were acquired Datasets for rural and urban OFMSW were acquired using standard physico-chemical analyzes (methods in experimental design chapter) and instruments: • Fresh mass (FM) and dry matter (DM) contents through oven drying (UNP 700, Memmert, Schwabach, Germany) • Organic dry matter (oDM) contents with a muffle furnace (AAF 1100, Carbolite, Neuhausen, Germany) • C, H, N contents through elemental analyzer (vario MACRO cube, elementar, Langenselbold, Germany) • Trace elements (TE) through inductively coupled plasma-optical emission spectroscopy (ICP-OES) (Spectro Blue, ASX-260 auto sampler, SPECTRO Analytical Instruments, Kleve, Germany) The procedure for the organoleptic examination of OFMSW was based on sampling protocols following [2] and subjective assessments during the sampling process. Data format Raw, processed (mean values, aggregated) and analyzed data within this article; Excel spreadsheet in the Appendix for supplementary data on the sampling area, organoleptic examinations and ICP-OES analyzes Parameters for data collection Each sample collected in the course of the year 2018 was immediate processed (drying, sorting, crushing) and stored airtight in dry state until further experiments were carried out. Due to the year-round sample collection, physico-chemical analyzes were executed with the total number of samples in 2019. This procedure was chosen to optimize the sample handling. The whole amount of OFMSW was dried for the DM content determination of each sample. The repetition number varied between double and ninefold depending on the volume of the available drying vessels. The sorting analyzes and consequently the determination of impurity levels was done based on dry OFMSW samples. All impurities were excluded from all further chemical analyzes. Elemental compositions and oDM content analyzes were done in triplicate or quadruplicate for each sample. A suitable sampling process for OFMSW as a complex material with different ingredients and varying optical properties was a crucial factor for the data quality. A drum vehicle constantly mixed the total amount of OFMSW during the collection process. This procedure increased the homogeneity of the OFMSW amounts and facilitated the sampling process. However, detailed information on the sampling are and the established collection scheme can be found in the original research paper [1] .
Description of data collection An extensive and year-round dataset on the physico-chemical properties of rural and urban OFMSW. In Germany, OFMSW is a typical municipal solid waste that is collected separately via green or brown biowaste bins . The data collection  includes the following parameters: organoleptic examination, DM contents,  impurity concentrations, oDM contents and concentrations of 37 major, minor and  trace elements (C, H

Value of the Data
• For an efficient utilization of OFMSW, detailed data on physico-chemical properties, especially with regard to different settlement structures or seasonal changes are valuable. This article provides a year-round dataset for the characteristics of German OFMSW of rural and urban origins with constant sampling locations • This data will be useful for biomass and bioenergy-researchers as well as for municipalities and waste management companies. OFMSW data can be used for the comparison or for identification of energetic and material use potentials • OFMSW datasets are both relevant for the determination of practical application potentials (energetic and material utilization) and for the establishment of efficient biowaste value chains • In the biogas or composting sector and from a legal perspective, this data may serve as a basis for discussion, particularly in relation to feedstock pre-treatment, technical process parameters and digestate or compost utilization

Data Description
Biomass is a common energy source and a versatile commodity with different characteristics depending on the origin or type. Available biomass types and their potential compositions as well as suitable conversion technologies have been reviewed within recent literature [3] . In addition to agricultural, silvicultural or aquatic biomass species, biogenic residues from municipalities such as the organic fraction of municipal solid waste (OFMSW) are available in large quantities. However, the characteristics of OFMSW depend on various parameters (e.g., season, collection scheme or geographical region). Within literature [4 , 5] , several OFMSW characteristics have already been reviewed. In order to expand the existing literature, this Data in Brief (DIB) article provides a new dataset for the chemical composition of rural and urban OFMSW samples for a one-year period in Germany. All data are presented within this article -either  in section two or in the form of supplementary data in the Appendix. Fig. 1 (municipality of Tübingen together with rural and urban sampling areas), Fig. 2 (amounts of OFMSW collected) and Fig. 3 (size distribution of biowaste bins) as well as Table 1 (general characterization of sampling areas) and Table 2 (number of biowaste bins in relevant areas) focus on the sampling areas with relevance for this article. Those data deliver background information and describe framework conditions that are relevant for the interpretation of all other data. Table 3 defines uniform sample codes used throughout the article and furthermore presents key facts of the sampling process for both rural and urban OFMSW. Table 4 and Fig. 4 (both relevant for rural OFMSW) as well as Table 5 and Fig. 5 (both relevant for urban OFMSW) show different sampling process data such as collection rate, total amount, sample amount, ambient temperature, density and estimated composition. Fig. 6 presents the analyzed data of the organoleptic examination during the sampling process itself. For a better understanding of Fig. 6 and all other data, Fig. 7    Size distribution of biowaste bins in the sampling areas compared to Tübingen municipality [11] . The raw data can be found in the Appendix A.
on impurity categories such as stones or plastics is not available within this DIB article. Single measurements and mean values for organic dry matter (oDM) contents in rural OFMSW can be found in Tables 12 and 13 while oDM contents of urban OFMSW can be found in Tables 14 and  15 . Single measurements and mean values for C, H and N contents of both OFMSW types are presented in Tables 16-19 . Data for C, H and N can be used to estimate energy yield potentials based on fresh mass (FM), DM or oDM by calculating stoichiometric CH 4 yields as described in the literature [6 , 7] . Therefore, values for S and O contents are needed additionally. S contents Table 2 Total number of biowaste bins in the city of Tübingen broken down into rural or urban sampling areas (31 December 2018) [11] .

Sampling region Total Households Commercial
Tübingen municipality

9258 497
Sampling sites urban 719 * 674 * 45 * rural 589 568 21 * Calculated with data for the total city area of the municipality (6142 bins in total, 5754 households, 388 commercial) and the percentage of the urban sampling area (11.7%) based on the share of inhabitants in the urban sampling area (6300) compared to the total inhabitants of the city area (53,900) according to [10] . Table 3 Identification (ID) for each organic fraction of municipal solid waste (OFMSW) material and annotations referring to the sampling process.

Material
Remarks ID
BT-TÜ * The sampling procedure had to be matched with the staff's schedule at the collection site. In some CW, the sampling of OFMSW was not possible (e.g., due to holidays). In CW 26 and 43, no urban OFMSW samples were available.
can be obtained by converting data of the inductively coupled plasma-optical emission spectroscopy (ICP-OES) to the designated reference unit (% DM). The calculation of O contents can be done by subtracting DM-based contents for C, H, N, S and ash from 100% DM. Tables 20 and 21 add information on boxplot data and mean values (annual values) of the ICP-OES analysis for rural and urban OFMSW. Single measurements and mean values for each sample and each major, minor or trace element (TE) can be found in the Appendix. The data presented can be used for the discussion of energy potentials as well as for the evaluation of OFMSW compositions especially with regard to legal limits that exist for impurities and TE such as heavy metals. In addition, conversion technologies such as the anaerobic digestion, delivering energy, digestates or compost products, can be assessed based on the data in this article.      6. Organoleptic examination of rural and urban organic fraction of municipal solid waste (OFMSW) during the sampling process subdivided into the categories composition, moisture, phase separation and odor intensity. Composition indicates the level of overall homogeneity of the total OFMSW amount. Moisture describes the visual differences in terms of free or bound water in the sample (free water only occurred within the category relatively high). Phase separation depicts whether unloading processes of collection vehicles lead to partially higher shares of structural material (green waste). Odor intensity indicates the level of unpleasant smell from a distance of 5 m. The raw data can be found in the Appendix A.

Experimental Design, Materials and Methods
Detailed descriptions for all sampling procedures and experimental methods can be found in the original research paper [1] . This DIB article mainly focuses on additional information regarding the sampling areas. Fig. 1 presents the municipality of Tübingen together with the rural and urban sampling areas located in the state of Baden-Württemberg in southern Germany. Separately collected OFMSW (biowaste bin) served as a sampling material for all analyzes. Throughout the year, the sampling locations did not change.

Sampling material, area and procedure
All sampling procedures were executed in accordance with the German Biowaste Ordinance and followed standard procedures [2 , 8] . Urban OFMSW samples originated from the inner city of Tübingen ( Kernstadt ), while rural OFMSW samples sourced from surrounding villages ( Kilchberg, Weilheim, Kreßbach, Bühl ). Each OFMSW collection in the municipality of Tübingen was temporarily stored on a concrete surface at the central collection site ( Schinderteich ) of the Waste Disposal Association ( Zweckverband Abfallverwertung Reutlingen/Tübingen, ZAV ) and Waste Management Corporation of the administrative district of Tübingen ( Abfallwirtschaftsbetrieb des Landkreises Tübingen ). Therefore, the sampling location for all samples was at Schinderteich, which is located approx. 20 km away from the inner city of Tübingen.
According to [10] and presented in Table 1 , the total surface area combining rural and urban districts of Tübingen municipality (10,812 ha) can be subdivided into settlements and traffic areas (2455 ha), agriculture (2931 ha) and forests (5231 ha) . No detailed classification except for the total surface area was available for the urban sampling area. It can be assumed that the total surface area represents only residential and commercial settlements as well as traffic areas. The total rural sampling area (1891 ha) is characterized by high shares of agricultural and garden surfaces (561 ha) as well as forestry areas (979 ha) while the share of settlement areas can be described as relatively low (126 ha). In order to classify the chosen sampling areas (rural and urban), population densities were calculated ( Table 1 ) before starting the experiments.
According to the Statistical Office of the state of Baden-Württemberg and Tübingen municipality [10] , the number of inhabitants in the municipality of Tübingen was 87,579 in the year 2017 ( Table 1 ). A growth to 91,655 inhabitants until the year 2020 has been monitored but as the way of data presenting changed from "primary residence" to "total residents", the data of 2017 were used. Based on data of the Waste Disposal Association Tübingen, 3754 tons FM of OFMSW were collected in 2018 ( Fig. 2 ). Additional information on waste collection processes in the municipality of Tübingen and in the sampling areas can be found in Table 2 and Fig. 3 . Due to the growing population, the amount of available OFMSW will increase in the future.

Analytical methods
This chapter presents a summarizing overview on the analytical methods that were executed for the generation of the OFMSW data. Extensive descriptions of all analytical methods can be found in the original research paper [1] .
The organoleptic examination was based on the procedure according to guidelines [2] supplemented by own subjective assessments during the sampling process. The DM content of each OFMSW sample was determined by drying the whole sampling material at 105 °C in a drying oven (UNP 700, Memmert, Schwabach, Germany) for at least 24 h [12] .
The impurity concentrations were determined based on the dry OFMSW samples. Therefore, all impurities (metals, plastics, stones) were manually removed from the dry samples and their weight was measured. Thus, the impurity concentrations as presented in this DIB article describe the total mass of all impurities (sum of plastics, metals, stones). The remaining DM was manually pre-crushed, partitioned by a sample divider and then sieved with mesh sizes of 63 and 45 mm (flat screening machine AS400 control, Retsch, Haan, Germany). Afterwards, the coarse fraction was shredded (AXT rapid 2200, Bosch, Gerlinen-Schillerhöhe, Germany), recombined with the fine fraction and then milled to particle sizes of approx. 1 mm with a customary mixer equipped with chrome steel blades (WMF Kult Pro 1400 W, WMF Group, Geislingen-Steige, Germany). This procedure has to be considered when evaluating the elemental concentrations, especially those of Fe, Ni and Cr.
The contents of oDM were determined via incineration in a muffle furnace (AAF 1100, Carbolite, Neuhausen, Germany) in accordance with standard procedures [13] by using approx. 1 g of DM in a ceramic crucible. Elemental analyzes (C, H, N contents) were carried out with an elemental analyzer (vario MACRO cube, elementar, Langsenbold, Germany) for all OFMSW samples [14] . Thereby, approx. 40 mg DM were pressed into a zinc foil coated tablet for each single measurement of each sample. S was not measured simultaneously in favour of the measurement accuracy for C, H and N. Instead, S and other TE were measured via ICP-OES [15] after digestion in aqua regia. Therefore, 300 mg DM of each sample were transferred into 50 mL Teflon vessels and combined with 1 mL of H 2 O 2 . Before microwave digestion at 190 °C, 3 mL HNO 3 (69%) and 9 mL HCL (35%) were added. The digested residues were aliquoted to 50 mL with aqua bidest and measured with the ICP-OES system (Spectro Blue, ASX-260 auto sampler, SPECTRO Analytical Instruments, Kleve, Germany). The solid residues consisting mainly of Si were separated by a centrifuge before spectroscopy and their mass was deducted from the sample mass. Thus, the values for Si only represent a partial amount of the total concentration since Si is not completely digestible with aqua regia. When evaluating ICP-OES measurements, all values below the detection limit (highlighted in each table of this article and in the supplementary data) were equated with this limit. Hence, some of those values might be slightly overestimated as the actual values could be even lower than the detection limit (0 < value < detection limit).