The study comprises an in-depth characterization of compositional groups of the liquid by-products obtained from the pyrolysis of swine manure at 500 degrees C, with the aim of providing an alternative and efficient approach for the valorisation of this waste stream, alongside with the production of biogas and char, the latter of which can be further converted into activated carbon. Two samples were considered: de-watered cake and solid product from anaerobic digestion of swine manure. Biocrude oils were fractionated into weak acidic, strong acidic, alkaline and neutral oil fractions. Subsequently, the neutral oil fraction was separated into paraffinic-naphthenic, slightly polar and polar fractions. All fractions were analyzed by GC-MS. The major identified compositional groups were: (i) for de-watered cake: steroids (40.7%), fatty acids, FAs (23.7%) and n-alkenes/n-alkanes (23.3%); (ii) for solid product from anaerobic digestion: FAs (31.0%), phenols/methoxy phenols (26.6%), n-alkenes/n-alkanes (10.8%) and steroids (10.6%). A variety of short-chain FAs (i.e., linear saturated, mono- and di-unsaturated, cis (i-), trans (ai-), isoprenoid, phenyl alkanoic, amongst others) and methyl esters (FAMEs) were identified as well. FA distribution, nC12-nC20, was similar for both manures studied with nC16 and nC18 as major compounds. FAMEs (nC14-nC28, with even carbon number dominance) in the slightly polar fraction of both samples were accompanied by considerable amounts of oleic (nC18:1) and linoleic (nC18:2) acids, and corresponding methyl esters. Hydrocarbons, i.e., n-alkenes/n-alkanes, were in the range of nC15-nC34, with nC18 maximizing. Anaerobically digested manure has resulted in (i) an increase in the portion of longer homologues of hydrocarbons and FAMEs and (ii) the appearance of new FAs series of long chain members nC22:1-nC26:1, omega-9. The comprehensive analysis of the biocrude oils obtained from the slow pyrolysis of swine manure indicates their potential for use as biodiesel additives or as feedstock to produce value-added materials.

The open-pit exploitation of the Maritsa Iztok lignite field (Bulgaria) generated sedimentary waste rocks of low organic matter content that were deposited in internal dumps. Immediately after deposition the re-deposited sediments underwent weathering, including organic matter oxidation leading in some cases to self-heating. The aims of the research were to study the impact of weathering and self-heating on the maceral alterations in the dump site associated with the sediment re-deposition, and organic compounds identification and distribution. The 27 samples collected from Troyanovo-3 Mine internal dump differed in degree of alteration. The first group contained unaltered macerals and showed normal distribution of n-alkanes, phenols were absent and Rock-Eval T-max ranged from 420 to 430 degrees C. The second group contained macerals with irregular cracks, paler oxidation rims, higher reflectance, Gaussian distribution of n-alkanes, high concentration of phenols and PAHs, and lowered T-max values (below 400 degrees C). The samples contained elevated amount of pyrite which oxidation might contribute to self-hating.

Pyrolysis coupled “off-line” with thermal desorption gas chromatography–mass spectrometry (TD-GC/MS) instrument for flue gas analysis is used to specify qualitatively/quantitatively organic functionalities in “Maritsa-Iztok” lignite lithotypes thermal decomposed in the range 250–900 °C. The aim of the study is to specify organic volatiles and to assign identified components to the lignocellulose biomass building blocks of coal forming vegetation. In pyrolysates the total amounts of the analyzed organics, expressed in mg/g TOC, amount up to 58.14 for liptain, 21–37 for humoclarain and xylain, and the lowest values are determined for humovitrain, 12. The samples immaturity reflects in high diversity of phenols, methoxy phenols (only guaiacyl structures), furans, etc. maximizing at xylain lithotype, 68% of the total analyzed amount. Carbohydrate degradation products, i.e. furaldehydes, 2-cyclopenten-1-ones, etc. are identified as well. In lithotypes studied, coal biomarkers as n-alkene/n-alkanes, sesqui-, di-, polar diterpenoids and hopenes/hopanes, are present in different proportions.

Drill core samples from a lignite-mudstone succession with variations in organic matter maturity from Troyanovo-3 Mine (Mini Maritsa Iztok EAD) were analyzed for trace element contents. All elements except Hg and Th show one positive spike in their distribution, located at different depths. Molybdenum and Ni peak at the deep level (52.6-3 m); Fe, V, As, Hg, Zn, U, and Th peak at 29.3-29.5 m; Pb and Cu peak at shallow depth - 19.2-20.1 m. All measured concentrations are much higher than the Clarke for low rank coal and sedimentary rocks and comparable with published data for black clays from Troyanovo-3 Mine. The lack of significant correlation between total organic carbon and all analyzed trace elements points to other hosts for the trace elements. The strong positive correlations found for Fe and V, Ni, Cr, As, and Mo suggest incorporation of these elements into Fe sulfide phase(s). The strong positive correlations for Al and Ni, Co, Mo and U, and a weak correlation between Al and V suggest a terrigenous and/or sorbed form of presence. The lack of a strong correlation between mercury and total organic carbon, ash, sulfur and uranium confirms the well-known complex Hg affinity. Our previously outlined hypothesis for OM enhanced maturity as a result of ascended hydrosulfide injection is here further supported by the trace element differentiation at different depths.

A sequence of carbonaceous mudstones interlayering three lignite seams is characterized by geochemical proxies. The core samples studied came from a borehole drilled in Trojanovo-3 Mine of Maritsa Iztok Basin. The n-alkane molecular composition is dominated by the > C29 long-chain homologues, with a strong “odd” over “even” homologue predominance. In addition to, the prevailing smooth signature of n-alkane distribution attests for one major organic matter source – land-derived higher plants. The sesqui- and di-terpenoid assemblage specifies the prevalence of Cupressaceae, Taxodiaceae, and Podocarpaceae species in the coal-forming mire. The lupane-type triterpenoids registered are a sign for Betulaceae family presence. Biomarkers for herb, macrophyte and algal/bacterial contribution are also recognizable.

The study fills the informative gap on occurrence, distribution, and carcinogenicity of polycyclic aromatic hydrocarbons (PAHs) in Bulgarian coals. It presents quantitative data for content and carcinogenicity of PAHs in different rank raw coals from eight basins with geological age from Late Carboniferous to Late Miocene, Ro=0.17–5.20%. The high amounts of alkylated naphthalene and alkylated phenanthrene determined in the bituminous coals reflect the diagenetic conversion of the plant-derived terpenoids into alkylated PAHs. In this first systematic study of PAHs in Bulgarian raw coals three concentration ranges are established: for Miocene/Eocene age coal – from 1.08 mg/kg to 5.79 mg/kg; for Late Cretaceous/Late Carboniferous age coal – from 77.9 mg/ kg to 137.2 mg/kg; and, for the Late Carboniferous coal – 1.85 mg/kg. The relationship of the total PAHs content vs. raw coal Ro shapes as a “bell” and matches with the published data for the native PAHs from all over the world provenance. The maximal PAHs amount of 137.2 mg/kg at Ro =0.96% for the Late Cretaceous coal lies within the “oil-generation window”, Ro =0.5–1.3% for the kerogen. For all raw coal studied relatively low carcinogenicity is determined based on the well correlated values for B[a]Peq and TEQ parameters.

Organic matter (OM) presence in fly ashes (FA) might be a serious obstacle towards their utilization or beneficial use. Though, it is imperative to enhance the knowledge of FA geochemical composition and environmental impact. Feed coals and FA from thermoelectric power plants (TPP) in Bulgaria (Maritza East 2 TPP), Greece (Megalopolis TPP and Agios Dimitrios TPP) and Serbia (TENT A, Nikola Tesla A TPP and TENT B, Nikola Tesla B TPP) were comparatively studied by geochemical proxies. Extractable organic matter, 0.45-6.10% for the feed coals and 0.013-0.025% for the FA, was subjected to extensive chromatographic separation and species in different chemical series were GC-MS identified and quantified. Changes in the biomarker assemblages triggered by combustion in the pairs feed coal/FA were picked up, series of chemical classes quantified and subsequently alterations in chemical series were expressed in rel. %. Combustion has affected the biomarkers separation mode though the signatures for FA keep some features of the parent coals. Feed coal biomarker were rich in functionalities as were composed by a broad range of series, i. e., n-alkanes, regular isoprenoids, terpenoids, hopanoids and their aromatized counterparts. Polycyclic aromatic hydrocarbons (PAH) are of especial environmental concern. After combustion, FA biomarkers pattern of distribution was simplified as only two main series remained at appreciable amounts, n-alkanes and diterpenoids. Aromatic triterpenoids were also recognizable. Combustion has altered the n-alkanes separation mode as in the distribution curves for FA samples was visualized well-expressed shift to the shorter-chain n-alkanes, nC15-nC19. There were some similarities in PAH assemblages for FA from the studied thermoelectric power plants (TPP) as the combination of fluoranthene, pyrene, benzo[a]anthracene, chrysene and benzo[k]fluoranthene was rather frequent. Also, in all samples (except Maritza East 2 TPP) there was a preponderance of the four rings (4R) PAH and considerable presence of 5R PAH, i.e., benzo[k]fluoranthene. Ranges for SPAH (16 USEPA) and SCPAH for FA were: SPAH (16 USEPA), 1.5-33.0 mu g/kg, and SCPAH, 0-12.0 mu g/kg. Respectively, values for FA Benzo[a] pyrene equivalent (B[a]Peq) up to 0.80 mu g/kg and toxic equivalency quantities (TEQ) up to 1.22 mu g/kg values were calculated. The range of 4-12 mu g/kg for.CPAH was considerably lower than 300 mu g/kg designated by the Swedish Environmental Protection Agency (Swedish EPA) for FA used in soil remediation. Enrichment ratios, ER < 1, for all TPP located on the Balkan Peninsula implied that PAH were mostly emitted into the atmosphere by the flue gases.

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Presence of organic matter in fly ashes (FAs) might be a serious problem with regard to their beneficial use. In order to enhance the knowledge of FAs geochemical composition and their environmental and human health impact feed coals and FAs from TPPs in Bulgaria (Maritza East 2 TPP), Greece (Agios Dimitrios TPP and Megalopolis TPP) and Serbia (Nikola Tesla TENT A and TENT B TPPs) were studied. Extractable organic matter, 0.45-6.10 % for the feed coals and 0.013-0.025 % for the FAs, was subjected to extensive chromatographic separation and their molecular compositions were investigated by gas chromatography–mass spectrometry (GC-MS). The results from feed coal/FA pairs outline changes in the biomarker assemblages triggered by combustion. Biomarker classes were quantified in mg/kg and alterations in their chemical compositions were expressed in rel. %.Combustion has affected the OM composition though the signatures for FAs retain some features of the parent coals. Feed coal biomarker assemblages include a broad range of compound classes, i.e., n-alkanes, regular isoprenoids, terpenoids, hopanoids and their aromatized counterparts. PAHs were of especial concern. After combustion, FAs biomarkers distribution was simplified as only two main series remained at appreciable amounts, n-alkanes and diterpenoids. Aromatic triterpenoids were also recognizable. Despite of their numerous biological activities, aromatic abietanes were not referred to pollutants.Combustion has affected the n-alkanes distribution, as FAs samples show a well-expressed shift to the short-chain n-alkanes (nC15-nC19). In the Pr/nC17 vs. Ph/nC18 diagram no appreciable change in the position of corresponding coal/FAs pairs exists. Feed coals and FAs plot close to the boundary ofType II - Type II/III kerogen.There was some similarity of PAHs assemblages for FAs from the studied TPPs as the combination of Fl, Py, B[a]A, Ch and B[k]Fl was rather frequent. Also, in all samples (except Maritza East 2 TPP) there was a preponderance of the four rings (4R) PAHs and considerable presence of 5R PAHs, i.e., B[k]Fl. Ranges for ΣPAHs (16 USEPA) and ΣCPAHs for FAs were in perfect coincidence with the determined magnitudes from the previous study: ΣPAHs (16 USEPA), 1.5-33.0 µg/kg, and ΣCPAHs, 0-12.0 µg/kg. Respectively, values for FAs BaPeq up to 0.80 µg/kg and TEQ up to 1.22 µg/kg values were calculated. The range of 4 - 12 µg/kg for ƩCPAHs was considerably lower than 300 µg/kg designated by the Swedish EPA for FAs used in soil remediation. Enrichment ratios, ER < 1, for all studied TPPs located on the Balkan Peninsula imply that PAHs were mostly emitted into the atmosphere by the flue gases.

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The paper reports the first results of the organic geochemical characterization of mudstones from the Shavar Fm (eastern Rhodope Mt., Bulgaria). The rock matrix is unevenly impregnated by amorphous organic matter at the onset of the oil generation (T-max 445oC; PI - 0.1-0.2). High total organic carbon contents (avg. TOC - 5.9 wt. %) and HI (720 mg HC/g TOC) argue for oil-prone source-rocks with very good hydrocarbon potential. The n-alkane distributions with maxima in the range n-C20-25 are consistent with organic matter origin from submerged plants. Additionally, sterane distributions dominated by C28-30 4-methyl steranes, indicate dinoflagellate contribution. High pristane/phytane ratio (Pr/Ph = 2-4) argue for deposition under oxic conditions.

We sampled and studied a borehole located in the southern part of Maritsa Iztok lignite field (Bulgaria) which comprises Late Miocene-Pliocene sediments of Maritsa Formation. The current report of Troyanovo-3 Mine sequence is the first to our knowledge. It represents a lignite-mudstone succession with variations in organic matter (OM) maturity. Thirty eight coal and mudstone core samples showed predictable ash and sulfur content. The XRD study showed illite/muscovite, illite/smectite, kaolinite, chlorite and quartz as main constituents that argue for a detrital origin. Additionally, we identified pyrite and gypsum and some peaks of marcasite and elemental sulfur. A set of eight mudstone samples rich in OM was selected for further geochemical analyses. The OM was classified as type III and II/III kerogen based on Rock-Eval pyrolysis data. The low amounts of extractable organic matter (0.01-2.25%) we found are consistent with the samples' low maturity and kerogen type. The yields of two samples were too low for further fractionation. Asphaltene amount (26.1-79.7%) pre-dominates in the extracts. Diterpenoids (neutral fraction) and their polar analogues (slightly polar fraction) are highly abundant. In slightly polar fractions we registered ketotriterpenoids (mainly lupenones) in addition to the linear n-alkan-2-ones. OM elevated maturity of the deepest sample (59.60 m depth) was evidenced mainly by hopane distributions, i. e. Ts/(Tm + Ts), homohopane H31 alpha beta index, hopane ratios (H29 alpha beta/H30 alpha beta) and H27 beta/H27 alpha. The organic geochemistry results do not fit the ordinary regional maturity trend. OM maturity variation, superimposed over natural low coalification degree, could be ascribed to an interaction with ascending hot reductive fluids. The sulfide mineralization found in the fractures also gives indications about the fluid circulation. Another thermal alter-ation affecting the middle part samples (24.0-28.3 m) was suggested due to elevated Tmax values and HI and OI relation for a charcoal piece and carbonaceous mudstone. Smoldering processes affecting these samples were presumed. Low-temperature alteration processes were identified by n-alkanes, n-alkan-2-ones, and n-alcohols expulsion and downwards migration (from 18.0 m to 30.0 m) accompanied by a clear terpenoids depletion. The 17,21-seco- hopane-17,21-dione found for the first time for Maritsa Iztok Basin (MIB) samples further suggested processes of water seepage and wash-out. Microbial degradation activities usually accompanying water-washing possibly led to a specific n-alkan-2-one distribution. All the features we report point to either an even-numbered n-alkanoic acid decarboxylation or to a selective microbial degradation of odd-numbered n-alkanes to n-alkan-2-ones. In all, the history of the coal-mudstone sequence is complex, overprinted by variable alteration processes, first ever reported for MIB samples.

The study presents analyses of aromatic components in bitumen extracts from Bulgarian medium and high rank coals. Bulk samples from Balkan, Ro = 0.96%, Dobroudzha, Ro = 1.13%, and Svoge, Ro = 5.20% coal-bearing provinces, were considered. After extensive chromatographic separation and GC-MS study of the aromatic fractions, our attention was focused on polycyclic aromatic hydrocarbons (PAHs) compositions. Aromatic indices, based on quantification of individual compounds, revealed that: (i) the highest amounts of PAHs were present in Balkan and Dobroudzha samples, 219–365 μg/g TOC, and dropped to 3.5 μg/g TOC at Svoge sample; (ii) the alkylated naphthalenes and phenantrenes prevalence confirmed published data; (iii) the relationship between aromatic indices vs. Ro, % is in agreement with the previously obtained results, indicating their decrease with thermal maturity. For some indices only weak correlation was obtained, suggesting that PAH concentrations are not solely affected by coal rank, but also by environmental conditions and vegetation.

The first thorough study of PAHs in feed coals and FAs from combustion in six Bulgarian TPPs was done. Since coal-derived FAs are applied to many targets, it is imperative to enhance the knowledge for their geochemical composition and environmental impact. The gap of information on PAHs in feed coals and coal-derived FAs has outlined the aim of the study: (i) to compare by geochemical proxy PAHs in feed coals and FAs generated in six Bulgarian TPPs; (ii) to track the changes in PAHs compositions with feed coal ranks and in different ESP rows; and (iii) to estimate the potential toxicity of FAs (if any). Extractable organic matter (EOM) was prepared. PAHs were isolated in aromatic fractions and quantified in mu g/kg. The total PAHs for lignite feed coal are in the range 400-530 mu g/kg and for FAs 0.30-12.60 mu g/kg: for subbituminous feed coal, they are 4000 mu g/kg, and for FAs, 1.10-32.50 mu g/kg. For bituminous feed coals, they are - 860 mu g/kg and 9305 mu g/kg, and for FAs from both TPPs, they are several times lower, from 69.4 mu g/kg to 103.3 mu g/kg, for the five ESP rows of Varna TPP and from 100.4 to 182.20 mu g/kg, for the three rows of ESPs of Russe TPP. The EOM for low rank feed coals is strongly dominated by coal biomarkers, i.e., perylene and phenyl substituted PAHs. Therefore, calculations and ratios based on PAHs compositions are done only for bituminous feed coals and their FAs. Combustion has resulted in a regular shift to lighter PAHs compared to the signature PAHs of feed coals. PAHs distributions in FAs are dominated by phenanthrene. Distribution profiles according to the number of aromatic cycles (R) in PAHs are dominated by threering (3R) PAHs > four-ring (4R) PAHs. Only in the last row of ESP from the Varna TPP is there evidence for the presence of heavier PAH, five-ring (5R) benzo[g,h,i]fluoranthene, trapped by the finest particulate matter. Relatively low PAHs concentrations determined for FAs are compared with the values for PAHs in soils according to the Bulgarian regulation.

A sequence of three lignite seams and interlayering carbonaceous mudstone is characterized by geochemical proxies. The study is extended by the palaeoenvironmental details given by the fossil fauna (gastropods, ostracods, and fishes). The predominant minerals (quartz and kaolinite) and main oxide relations of the carbonaceous mudstone point to sand and clay washed from weathered and/or altered felsic rocks from the catchment area. The mudstone features to deposition from suspension in standing or slow to persistently moving fresh waters at the bottom of the core log, and slightly aerated, warm, fresh to low saline, acidic to alkaline waters on the top. Three communities of organisms are depicted. The first is the pre‐swamp environment characterized by standing or slow moving fresh waters and detrital organic matter deposition. The second is the environment of swamp of detrital forest trunks. Depending on the climate and water table, the main forest communities are of trees of families Cupressaceae, Taxodiaceae, and Podocarpaceae accompanied by trees of family Betulaceae, and herbaceous plants. Different Sphagnum species are also abundant. The dry/cold environment is reflected in the herbaceous organic matter deposition. Polar terpenoids ratio differentiates slight climatic oscillations for the samples with a strong Gymnospermae dominance. The second coal seam development reflects the optimum tectonic conditions for peat growth in a cold and dry climate leading up to 25 m lignite deposition. The third is the moss swamp environment with very fluctuating elements. At the top of the log, a Sphagnum ‐dominated peat has developed.

A study of 13 fresh mudstones compared to 7 dump samples by Rock-Eval technique is targeting to the organic matter features. The fresh mudstone samples are collected from three bore-holes of the mines operating in the Maritsa Iztok lignite field. The dump samples characteristics are a result of anthropogenic weathering in the mild continental climate. S-2 versus Total organic carbon (TOC) graphs indicate Type III approaching Type II kerogen for the both sample sets. Both S-1 and S-2 values decrease proportionately by 26-29% for the dump samples. A marked depletion in TOC and HI for the dump samples has been also obtained. The inert carbon content is high (ca. 42 % of the average TOC) for both sample sets. Expectedly, T-max and Oxygen index (OI) show elevated values for the dump samples.

In the biogeosphere to polycyclic aromatic hydrocarbons (PAHs) and their alkylated derivatives were assigned two main origins – biogenic and anthropogenic (Simoneit, 1998). Solid wastes of coal combustion in thermal power plants (TPPs) were pointed as the biggest sources of PAHs in the environment (Mastral, Callen, 2000). Worldwide few studies on the composition of PAHs, from fly ashes were performed (Fabianska et al., 2017). For the purpose full scale of alkylnaphthalene and alkylphenanthrene ratios were used for indices calculation (Radke, Welte, 1981; Radke et al., 1982, 1986) The aim of the present study is to compare alkyl derivatives of PAHs in feed coal and fly ashes generated during lignite, subbituminous, bituminous feed coals combustion in seven Bulgarian TPPs. Attention was focused on the distribution patterns of methyl (m/z 142), dimethyl (m/z 156), and trimethyl (m/z 170) naphthalenes, as well as on methyl (m/z 192), dimethyl (m/z 206), trimethyl phenanthrene (m/z 220) and indices calculated on their intensities. The purpose was to assess their relevance in appraisal of coal organic matter transformation during combustion.

Presence of organic pollutants in environment is directly related to human health and quality of life. Hence, harmful organic pollutants tracking and monitoring in the environment is of great importance for the life processes. In the present study the potential organic pollutants generated during lignite mining and combustion in the most significant thermal power plant Maritsa Iztok-2 in the Energy Complex Maritsa Iztok are appreciated. The following contents of Polycyclic aromatic hydrocarbons (PAHs) were determined: in combustion flue gases - 458 mu g/g; in flying ash of the flue gases from lignite combustion - 17 mu g/g. Organic pollutants in flue gases after cleaning by Electron beam technology (EBT) application has decreased PAHs amount to 68 mu g/g (reduction by 85% of the total PAH content). Harmful organic sulphur pollutants formed during house-hold briquettes burning were determined as well. Amounts of PAHs in four dumps generated during Maritsa Iztok lignites open-cast excavation were measured. Negligible PAHs amounts in the range 7-41 mu g/kg dump sample were registered. These values are under the limits for permissible amounts of PAHs in soils according to the Bulgarian legislation. Finally, potential organic anthropogenic pollutants in aqueous leachates of Maritsa Iztok lignites were measured. Low PAHs values in leachate pyrolysates were determined, again in comparison with the legislation norms for soils.