Regeneration Costs Research Articles

Removal of per- and polyfluoroalkyl substances (PFASs) in a full-scale drinking water treatment plant: Long-term performance of granular activated carbon (GAC) and influence of flow-rate

Per- and polyfluoroalkyl substances (PFASs) have been ubiquitously detected in drinking water which poses a risk for human exposure. In this study, the treatment efficiency for the removal of 15 PFASs was examined in a full-scale drinking water treatment plant (DWTP) in the City of Uppsala, Sweden, over a period of two years (2015–2017). Removal of the five frequently detected PFASs was influenced by the total operation time of granular activated carbon (GAC) filters, GAC type and surface loading rate. The average removal efficiency of PFASs ranged from 92 to 100% for “young” GAC filters and decreased to 7.0–100% for “old” GAC filters (up to 357 operation days, 29 300 bed volumes (BV) treated). Flow-rates were adjusted in two full-scale GAC filters of different operational age to examine the removal of PFAS and organic matter depending on GAC operational age and operating flow. The decrease in flow-rate by 10 L s−1 from 39 to 29 L s−1 led to an average increase of 14% and 6.5% in total PFAS removal efficiency for an “old” (264 operation days, 21 971 BV treated) and a “young” GAC filter (63 operation days, 5 725 BV treated), respectively. A cost-analysis for various operation scenarios illustrated the dominating effect of treatment goals and costs for GAC regeneration on overall GAC operation costs. The unit costs for GAC filters ranged from 0.08 to 0.10 € m−3 water treated and 0.020-0.025 € m−3 water treated for a treatment goal of 10 ng L−1 and 85 ng L−1, respectively, for ∑11PFAS. Furthermore, it was concluded that prolonging the GAC service life by lowering the flow-rates after reaching the treatment goal could lead to a 26% cost-deduction. The results and methods presented in this study give drinking water providers valuable tools for the operation of a full-scale treatment train for the removal of PFAS in contaminated raw water.

Tuning of halobenzenes uptake in montmorillonite from gas phase through a functionalization process involving Cu(II)-phenanthroline and heptanethiol

In this paper, montmorillonite functionalized with a Cu(II)-phenanthroline complex (Mt-CuPhen) and then exposed to heptanethiol vapors (Mt-CuPhen-HPT) was tested for the capture of halobenzenes in gas phase. The treatment of Mt-CuPhen with heptanethiol vapors produced important compositional changes involving Cu(II) reduction, oxidation of thiol to disulfide and dehydration of the mineral interlayer space.Entrapping experiments were carried out on fluorobenzene, chlorobenzene and bromobenzene at 25 and 45 °C. The hybrid material proved to be very efficient for all halobenzenes and especially for fluorobenzene. Observed performances are slightly affected by temperature. Halobenzene desorption occurred even at 100 °C, a temperature quite lower than that required for decomposition of Mt-CuPhen-HPT. The Mt-CuPhen-HPT hybrid material, therefore, can be reused several times and requires low energy costs for regeneration. An alternative regeneration procedure based on disulfide removal has been proposed as well.Mt-CuPhen-HPT was extensively characterized before and after halobenzenes immobilization through elemental analysis, UV–Vis measurements, thermogravimetric analyses, FTIR, NMR and X-ray absorption spectroscopies.

Does stump removal reduce pine weevil and other damage in Norway spruce regenerations? – Results of a 12-year monitoring period

Although impacts of intensive forest harvesting practices such as removing logging residue and stumps for bioenergy on forest ecosystem has been extensively studied, no information is available about the long-term effects of stump harvesting on the health status of young Norway spruce stands. In the present study, we surveyed damage caused by the large pine weevil (Hylobius abietis L.) and other causal agents as well as the height growth of the Norway spruce seedlings for 12 years in stump-harvested and non-harvested experimental plots. The overall effect of stump harvesting combined with mounding on the health and survival of spruces was positive: 70% of spruce seedlings in stump-harvested plots were spared any damage, while 58% of seedlings remained undamaged in undisturbed control plots. The positive effect of stump removal and mounding on tree health was mainly due to reduced pine weevil damage. In all, 14.8 and 24.6% of spruce seedlings were gnawed by pine weevil in stump-harvested and control plots, respectively. In stump-harvested plots, pine weevil damage was slighter and lasted for a shorter time than in control plots. In addition, damage caused by Hylastes spp., black root beetles, was significantly less on stump-harvested plots. By contrast, vole damage was most frequent in stump-harvested plots during the population peak when the vole density was exceptionally high. Irrespective of whether stumps were harvested or not, stump roots provided a source of Heterobasidion inoculum in the next spruce regeneration. During this early stage of stand development only a few spruce seedlings were killed by Heterobasidion root rot and there were neither temporal nor quantitative treatment-related differences between the treatments. From the third year onwards the height growth of undamaged seedlings was more rapid in stump-harvested than non-harvested plots. Our results suggest that the overall risk of damage in young Norway spruce stands can be reduced by stump harvesting. Thus, stump harvesting and mounding seem to decrease the need for supplementary planting, which reduces regeneration costs that represent a considerable financial investment for a forest owner.

Recent Developments and Future Challenges of Hydrogels as Draw Solutes in Forward Osmosis Process

Forward osmosis (FO) has been recently regarded as a promising water treatment technology due to its lower energy consumption and lower membrane fouling propensity compared to the reverse osmosis (RO). The absence of suitable draw solute constraints the wide-range application of the FO. Hydrogels are three-dimensional hydrophilic polymer networks that can absorb a huge amount of water. Particularly, stimuli-responsive polymer hydrogels can undergo a reversible volume change or solution-gel phase transition in response to external environmental stimuli, including temperature, light, pressure, solvent composition, and pH. These intrinsic properties indicate the lowest regeneration cost of draw solutes compared to the thermal method and other membrane processes. This review aims to introduce the research progress on hydrogels as draw solutes, clarify the existing problems and point out the further research direction.

Comparison of two typical regeneration methods to the spent biological activated carbon in drinking water.

The spent biological activated carbon (BAC) should be disposed properly; regeneration was a better choice. Performances of thermal and ultrasonic regeneration to the BAC with various service time (3years, 5years, and 10years) were compared comprehensively; the recovery of the BAC's pore structure, variation of mechanical hardness, influence of bioactivity, and removal efficiency of typical pollutants in the reuse were examined. The results showed that thermal regeneration was an utterly regeneration, and almost all the pore structure was restored, whose recovery rate was above 90% for BAC used 3years and disfavored by the longer BAC's service time (83% for the BAC used 5years). Ultrasonic regeneration could recover part of the BAC's pores (including micropores) and the restoration mainly focused on the BAC's surface, so the recovery rate was not influenced by the BAC's service time, and the recovery values of specific surface areas and iodine value were kept at 120m2/g and 200mg/g, respectively. In addition, the ultrasonic treatment enhanced the BAC's biological activity even with a significant decrease of the biomass on the BAC. The mechanical hardness of BAC decreased from 95 to 89% for the first regeneration and further to 79% for the second regeneration, whereas relatively lower decrease happened for the ultrasonic regeneration (less than 10% after 5 regeneration cycles). The mass losses in the thermal and ultrasonic regeneration were about 13%, 0.5%, and 25%, 3% for the first and second regeneration, respectively. The thermal-regenerated activated carbon (AC) exhibited excellent adsorption ability, good adherence of biofilm, and maintain higher removal rate for more than 2years, which were similar with that of the fresh AC, but relatively lower removal performance was found. However, the ultrasonic regenerated BAC retained the biodegradation ability, restored the fast-adsorption ability, and the higher removal process lasted about 6months. Taking the regeneration cost, operation, variation of the AC's characteristics, and the removal performance in reuse, ultrasonic regeneration was more suitable for the BAC filter and better used as a regular measure to maintain the higher removal performance, whereas thermal regeneration was more applicable to the activated carbon adsorption tank.

The forest mitigation-adaptation nexus: Economic benefits of novel planting regimes

Previous studies have examined the economic trade-offs of climate change mitigation in forestry. However, most have not explicitly accounted for the impact of climate change on productivity or the value of carbon sequestration when considering the higher costs of adaptive planting. Here we build on previous studies from north-western Canada, using the Woodstock optimization model to assess the economic trade-offs of the standard and two adaptive planting regimes under historical climate and a severe climate change scenario. We considered planting and harvesting costs and revenue from timber and carbon sequestration over 100 years. The analyses were done at a forest level using a continuous production process to identify the best combination of stand-level management to achieve multiple objectives, because that is consistent with strategic decision-making on public land in North America. Our results showed there are potential negative risks from climate change to: harvest volumes, net present value, growing stock, and ecosystem carbon sinks. Despite increased regeneration costs, we found some risk mitigation through adaptive planting, with the greatest benefits through diversification which had higher net present value, growing stock and ecosystem carbon than historic climate with standard stocking. This was a result of planting more valuable species, higher growth rates in mixed stands, and adaption of novel species to new climates. Adaptation through novel planting regimes is a cost-effective forest management strategy that can potentially offset some negative impacts of climate change.

Numerical study on flow and pressure drop characteristics of a novel type asymmetric wall-flow diesel particulate filter

In order to reduce the pressure drop and regeneration cost of diesel particulate filters (DPFs), and improve the power and economic performance of the diesel engines, a novel type of asymmetric channel wall-flow filter was proposed, including the regular hexagonal and triangular channels, as well as the rectangular channels. A one-dimensional mathematical model was built to study the flow characteristics, especially pressure drop performance, for this type of particulate filter, as well as a square symmetric and a square asymmetric channel filter for comparison. The effects of exhaust gas flow rate, cell density, wall thickness, and aspect ratio were numerically accessed. The results show that the novel asymmetric channel filter can effectively reduce the lifetime pressure drop by increasing the utilization ratio of the filtration wall and the filtration area. Specially, with the novel asymmetric channel structure, the wall pressure drop is considerably reduced owing to a lower mean wall penetration velocity. Furthermore, the depth layer and soot layer pressure drops of the novel type filter are much lower than those of the square symmetric channel filter owing to the smaller penetration velocity and thinner thickness of the soot layer, nearly the same as those of the square asymmetric channel filter. Additionally, the filter with a smaller aspect ratio can slightly reduce the pressure drop, so it can be practically applied if the distribution of the inlet gas is uniform. The novel asymmetric channel filter can meet the current and future demand for miniaturization and light-weighting of particulate filters, and has excellent market adaptability.

Selection of efficient absorbent for CO2 capture from gases containing low CO2

Amine-based absorption processes are widely used in natural gas processing, but recently they have been considered for CO2 capture from flue gas emitted from thermal power plants. The main issue of amine used in the CO2 capture process is the high cost of solvent regeneration. So, this issue can be solved by using efficient amine absorbent. The amine type absorbents employed in the experimentation were an aqueous blend of 2-(Diethylamino)ethanol (DEEA) with different types of diamine activators such as piperazine (PZ), 2-(2-aminoethylamino)ethanol (AEEA), hexamethylenediamine (HMDA), ethylenediamine (EDA), and 3-(Dimethylamino)-1-propylamine (DMAPA). An absorption experiment was performed to evaluate the CO2 absorption performance in terms of CO2 loading, absorption capacity, and absorption rate. The experiment was performed to assess the CO2 desorption performance in terms of desorption capacity, desorption rate, cyclic capacity, and regeneration efficiency. From the results of absorption-desorption and comparison with benchmark amine absorbent MEA, the aqueous blend of DEEA and HMDA indicated the best performance for CO2 capture applications among all the tested amine blends.

Evaluation of thermo-kinetic and absorption characteristics of pure desiccants and desiccant mixtures

Air conditioning systems are used to control the air dry-bulb temperature and humidity level for human thermal comfort. In order to control the humidity level, air dry-bulb temperature needs to be brought down below its dew point temperature to condense out the moisture from the air. This eventually consumes a significant amount of total building energy in terms of electricity. Therefore, to minimize the energy consumption, researchers are stimulating their study towards an alternative latent heat load control system. In this regard, desiccant based sorption technologies are more effective compared to the conventional vapor compression system. Therefore, it is necessary to analyze the different desiccants' individual properties and their physical behavior in material perspective. In this study, an effort is devoted to explore the thermo-kinetic properties of pure LiBr, CaCl2, as well as their mixtures (LiBr:CaCl2 of 90:10; 85:15; 80:20 and 75:25) by X-ray diffraction (XRD), thermo-gravimetric (TG) and absorption rate, analyzes through numerous control experiments. The XRD study confirmed that peaks of CaCl2 and LiBr were shifted slightly for LiBr and CaCl2 mixtures due to interaction effects. The results of present investigation elucidated that mixtures of LiBr and CaCl2 showed less moisture regeneration cost than pure CaCl2 and all the mixtures revealed more rate of moisture absorption than pure LiBr and CaCl2. Further, 85:15 mixture of LiBr:CaCl2 showed higher rate of moisture absorption when compared to other prepared samples.

Дослідження ефективності очищення стічних вод від іонів Хрому(ІII) бентонітовими глинами

The work is devoted to the development of scientific bases of wastewater treatment of various industrial enterprises from chromium ions by adsorption by bentonite clays. The prospect and effectiveness of bentonite clays for wastewater treatment is confirmed by their advantages over other sorbents, namely: they are affordable, not high cost, the possibility of regeneration and multiple application. The main advantages of using bentonites in water treatment technologies are their powerful geological resources, cheap rock extraction, easy preparation for transportation and use, the ability to use waste sorbents in other technologies, which eliminates the need for expensive regeneration costs. Heavy metals form a group of the most dangerous pollutants in the environment. In surface natural reservoirs (seas, lakes, rivers, reservoirs) with industrial wastewater, a considerable amount of heavy metal ions enters, which become a significant obstacle in the life of microbiota. Heavy metals are supplied to wastewater from non-ferrous metallurgy, electronic radio and leather and fur industries, as well as from all industries where electroplating is used. Sewage may contain one component, but very often their number is higher. The work is devoted to experimental studies of the process of sorption of Chromium ions (III) with a fixed sorbent layer by bentonite clays. The influence of various factors (process duration, adsorbent layer) on the degree of purification of waste water from nickel ions, the effect of pumping speed on the dynamic capacity of the sorbent was investigated and the effective volume was determined. We observe that the total adsorption capacity in the case of bentonite can be achieved in 4 ÷ 6 hours Research has proven the feasibility of using bentonite clays for the treatment of wastewater from Chromium(IIІ) ions.

Minimizing Cost of Regeneration at Regeneration Sites–A New Approach for Dynamic Lightpath Establishment in Translucent Optical Networks

Lightpaths in translucent optical networks have to undergo regeneration at certain nodes designated as regeneration sites to maintain its quality of transmission. Regenerating an optical signal necessitates optical-electronic-optical conversion and is thus a costly affair due to use of regeneration resources. Thus minimizing the cost of regeneration in such networks is vital. Minimizing cost of regeneration leads to two different problems; 1) the problem of minimizing the total cost of regeneration for the connections served and 2) the problem of minimizing the cost of regeneration at regeneration sites while serving the connections. The previous works on lightpath establishment in such networks have mostly addressed the first problem. In this paper we study the second problem i.e. the problem of minimizing the cost of regeneration at regeneration sites during dynamic establishment of lightpaths. As the problem is NP-Complete, we propose an Integer Linear Program for small networks and then propose two heuristic routing approaches for large networks. Time complexity analysis shows that our heuristic algorithms run in polynomial time. Extensive simulation experiments reveal that our approaches are not only efficient to address the problem but can also provide better blocking performance when regeneration resources are scarcely deployed at regeneration sites.

Experimental study of CO2 chemical absorption kinetics by a thermomorphic lipophilic biphasic solvent

Chemical absorption is a frequently used post-combustion process that separates CO2 from gaseous compounds of the flue gases with the use of specific solvents for which the main drawback is their cost of regeneration. In order to overcome this problem, the new Thermomorphic Lipophilic Biphasic solvents are here studied. The limited solubility of the Lipophilic amines in water offers a new degree of freedom while optimizing the global process: it is in fact possible to carry out the absorption with an initial biphasic solvent (organic, aqueous) that evolves towards a mono-phase solvent after a certain amount of CO2 is absorbed. This work aims at assessing experimentally the CO2 absorption kinetic into a Lipophilic amine based solvent, namely 3 M 1:3 DPA (dipropylamine) + DMCA (dimetylcyclohexylamine) + water using a Lewis Cell type reactor. Activation energy values obtained by the Arrhenius law show similar values for those of benchmark amines and the selected solvent seems to require less energy to start the chemical reaction.

Impacts of forest tax under timber price uncertainty

We examine the effect of forest taxes on the optimal harvest decision and the forest land value using an adaptive optimization framework– the stand is harvested when the stumpage price is equal or higher than an age-dependent reservation price. We prove that the site value tax or site productivity tax does not change the optimal reservation prices; the timber value tax reduces the optimal reservation prices; the yield tax increases the optimal reservation prices when the non-timber benefits are increasing with stand age, or when they are independent of the stand age and the regeneration cost is positive; and the unit harvest tax increases the reservation prices when stand age is relatively high and could reduce the reservation price when stand age is low. Numerical results show that the optimal harvest age is only sensitive to the unit and timber value tax. The tax burden is reduced for all types of taxes except the site value tax. Under a taxation budget constraint, recognition of stumpage price uncertainty may change forest owners’ preferences for different types of taxes.

A High-Performance Alumina Desiccant

The effect of the synthesis conditions – features and content of an alkali used for hydration of the gibbsite thermal activation product, and the content of nitric acid (acidity modulus) used to obtain the extrusion paste – on the properties of alumina desiccants was studied. The synthesized desiccant outperforms foreign and Russian analogs in dynamic capacity (above 10.0 g/100 g) at close values of specific surface area (ca. 300 m2/g) and static capacity (20–22 g/100 g). The desiccant has a high strength (above 8.0 MPa). Its application can increase the performance of existing adsorbers and decrease the cost of sorbent regeneration, which is certainly of practical interest.

Recent advances in adsorptive membranes for removal of harmful cations

ABSTRACTAdsorptive membranes with filtration and adsorption functions are one of the best strategies to remove harmful cations from wastewater and drinking water. In view of adsorptive capacity and regeneration cost, the most promising application field of adsorption membrane is the production of drinking water at present. An overview is given about the research progress of adsorptive membranes for removing heavy metal ions from drinking water. The removal mechanism of adsorptive membranes is explained by a schematic representation of electrical double layer. The types of adsorptive membranes are summarized. Future research outlook regarding adsorptive membranes is also discussed in order to promote research and application in drinking water for adsorptive membranes. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48579.

Fermentative Production of N-Alkylated Glycine Derivatives by Recombinant Corynebacterium glutamicum Using a Mutant of Imine Reductase DpkA From Pseudomonas putida.

Sarcosine, an N-methylated amino acid, shows potential as antipsychotic, and serves as building block for peptide-based drugs, and acts as detergent when acetylated. N-methylated amino acids are mainly produced chemically or by biocatalysis, with either low yields or high costs for co-factor regeneration. Corynebacterium glutamicum, which is used for the industrial production of amino acids for decades, has recently been engineered for production of N-methyl-L-alanine and sarcosine. Heterologous expression of dpkA in a C. glutamicum strain engineered for glyoxylate overproduction enabled fermentative production of sarcosine from sugars and monomethylamine. Here, mutation of an amino acyl residue in the substrate binding site of DpkA (DpkAF117L) led to an increased specific activity for reductive alkylamination of glyoxylate using monomethylamine and monoethylamine as substrates. Introduction of DpkAF117L into the production strain accelerated the production of sarcosine and a volumetric productivity of 0.16 g L−1 h−1 could be attained. Using monoethylamine as substrate, we demonstrated N-ethylglycine production with a volumetric productivity of 0.11 g L−1 h−1, which to the best of our knowledge is the first report of its fermentative production. Subsequently, the feasibility of using rice straw hydrolysate as alternative carbon source was tested and production of N-ethylglycine to a titer of 1.6 g L−1 after 60 h of fed-batch bioreactor cultivation could be attained.

Magnetic tuned sorghum husk biosorbent for effective removal of cationic dyes from aqueous solution: isotherm, kinetics, thermodynamics and optimization studies

Dyes containing effluents constitute hazards to the environments and endanger human and aquatic lives. Although activated charcoal has been adjudged the best for adsorption treatment of wastewater, its regeneration and high cost have limited their applications, hence the quest for alternative adsorbent. Magnetic tuned biosorbent was prepared from sorghum husks by in situ co-precipitation of Fe3O4. It was characterized using Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy and scanning electron microscopy. The biosorbent was then used for the removal of crystal violet (CV) and methylene blue (MB) dyes from aqueous solutions in a batch process. The effects of temperature, initial dye concentration, dosage, contact time as well as pH were investigated, and data obtained were analysed with appropriate kinetic and isotherm models. Response surface method was used for the optimization study of the adsorption using Box–Behnken experimental design. Pseudo-second-order kinetic model was the most appropriate model for both dyes with correlation coefficient (R2) > 0.9 and low % standard error values. The equilibrium data were best fitted with Langmuir isotherm with maximum adsorption capacity (Qmax) of 18.87 and 30.00 mg g−1 for CV and MB, respectively. The thermodynamic parameters for the adsorption processes showed that it was spontaneous, endothermic and random systems with free energy changes less than zero, enthalpy changes (∆H) of + 49.81 and + 51.18 kJ mol−1, entropy changes (∆S) of + 178.39 and + 177.34 J mol−1 K−1 for MB and CV dyes, respectively. Optimization studies revealed that 95% of the dyes are removable at 1.0 g adsorbent dosage and pH of 4.05 at 50 °C with initial dye concentration of 50 mg L−1. The prepared adsorbent is cheap, easily recycled and highly effective for the treatment of dye-contaminated water.

An Ultrastable Metal Azolate Framework with Binding Pockets for Optimal Carbon Dioxide Capture.

In the evolution of metal-organic frameworks (MOFs) for carbon capture, a lasting challenge is to strike a balance between high uptake capacity/selectivity and low energy cost for regeneration. Meanwhile, these man-made materials have to survive from practical demands such as stability under harsh conditions and feasibility of scale-up synthesis. Reported here is a new MOF, Zn(imPim) (aka. MAF-stu-1), with an imidazole derivative ligand, featuring binding pockets that can accommodate CO2 molecules in a fit-like-a-glove manner. Such a high degree of shape complementarity allows direct observation of the loaded CO2 in the pockets, and warrants its optimal carbon capture performances exceeding the best-performing MOFs nowadays. Coupled with the record thermal (up to 680 °C) and chemical stability, as well as rapid large-scale production, both encoded in the material design, Zn(imPim) represents a most competitive candidate to tackle the immediate problems of carbon dioxide capture.

An Ultrastable Metal Azolate Framework with Binding Pockets for Optimal Carbon Dioxide Capture

AbstractIn the evolution of metal–organic frameworks (MOFs) for carbon capture, a lasting challenge is to strike a balance between high uptake capacity/selectivity and low energy cost for regeneration. Meanwhile, these man‐made materials have to survive from practical demands such as stability under harsh conditions and feasibility of scale‐up synthesis. Reported here is a new MOF, Zn(imPim) (aka. MAF‐stu‐1), with an imidazole derivative ligand, featuring binding pockets that can accommodate CO2 molecules in a fit‐like‐a‐glove manner. Such a high degree of shape complementarity allows direct observation of the loaded CO2 in the pockets, and warrants its optimal carbon capture performances exceeding the best‐performing MOFs nowadays. Coupled with the record thermal (up to 680 °C) and chemical stability, as well as rapid large‐scale production, both encoded in the material design, Zn(imPim) represents a most competitive candidate to tackle the immediate problems of carbon dioxide capture.

Comparative analysis of natural and artificial regeneration in Nowa Dęba Forest District

Abstract New challenges related to the multifunctional role of forests in consideration of both natural environment and economy come into view sequentially. In current forestry practice, an important element is not only the quality of forest cultivations (silvicultural aspect) but also the costs incurred for their production and tending (economic aspect). The main purpose of this article is to show the prospect of increasing positive silvicultural effects depending on the method used in management of Scots pine stands under given site conditions. The comparative analysis was carried out using the study results obtained in the Forest District Nowa Dęba and those presented in other relevant studies. In the present study, we examined whether the site conditions have significant effects on silvicultural and economic effectiveness of regeneration and development of Scots pine stands or those predominated by Scots pine in the initial stages of stand growth. Significance of the regeneration method effects on growth characteristics of Scots pine regeneration as well as the costs of forest cultivation management was analysed. The study on silvicultural and economic effectiveness was carried out in the Forest District Nowa Dęba. The results obtained showed that using Scots pine natural regeneration under the conditions of fresh coniferous forest site and fresh mixed coniferous forest site was the way of management based on reason. This was supported by both the values of regeneration growth parameters and silvicultural quality along with clearly lower expenditures incurred to achieve these effects. In wet mixed coniferous site, Scots pine seedlings regenerated naturally; however, the results indicated their lower silvicultural quality and growth parameter values when compared to those artificially regenerated. In fresh mixed broadleaved forest site, equally for silvicultural and economic reasons, the more optimal option was to regenerate forest using traditional planting material as natural Scots pine regeneration showed lower silvicultural effects. The unit costs of regeneration and maintenance of stands with self-sown Scots pine in fresh mixed broadleaved forest site were higher when compared with other examined forest sites. On the basis of the results of the present study, it can be concluded that regardless of the regeneration method examined, the most differentiating factor of the final economic effect of Scots pine stand establishment and maintenance was the cost of regeneration operation. The expenditure for this purpose consumed the largest part of expenses incurred in artificial regeneration variant. The higher cost of corrections in artificially planted forest cultivations in poorer forest sites was one of the reasons behind the profitable final balance of naturally regenerating Scots pine stands. Differences between other costs analysed were not significant. The results of the present study may contribute to comprehensive assessments of natural and artificial ways of forest regeneration and indicate forest production costs that are the most closely related to site conditions.