Resources, Volume 10, Issue 8 (August 2021) – 13 articles

Urban vegetation is generally exposed to high levels of air pollution in airborne particles, with the greatest exposure in the EU being seen in Poland. With the continuing growth of urban populations, there is a need to confirm whether honey produced from urban areas is of similar high quality to that from rural areas. A total of 27 honey samples were collected from urban and rural apiaries and tested for the concentrations of 19 elements by ICP-OES. The results were compared with data on honey produced in old and new EU countries (metadata). Our evaluation used a novel approach to determine threshold values in the identification of the bioproduct contamination index. The analysed urban honey samples demonstrated higher concentrations of K, Sr, Ba, Ni, and Co, and lower levels of Mn and B than rural honey samples. Contamination by PM10 particles and the toxic elements contained in them proved to be a poor predictor of the content of these elements in honey, in contrast to the effect of atmospheric pollution measured during firework shows, which demonstrated higher concentrations of Ba, Pb, Ca, Cu, and Mg. The non-carcinogenic risk assessment indicated that the analysed honey samples are of good quality and are comparable or of even better quality than honey products from other EU countries. Full article

The COVID-19 epidemic surprised economic operators around the world. The very existence of many businesses, and thus jobs, was at stake. However, one year after the WHO declared the outbreak a pandemic, contrary to the pessimistic forecasts of business analysts, some industries did not experience the predicted negative effects of the crisis. This article presents the results of a pilot study on micro and small enterprises in the rubber products industry in Poland during the COVID-19 pandemic, with the aim of analyzing the phenomenon of sustainable resource management that led not only to the survival of these enterprises but also to a significant increase in their turnover. Therefore, the purpose of the study was to analyze the key success factors of the indicated economic entities, with particular emphasis on the perspective of sustainable resource management and relationship management. On the basis of best research practices, a triangulation of research methods was applied (integrative literature review, computer-assisted telephone interviewing, and individual in-depth interview). A relationship was observed between the sustainable management of resources and the structure of the relationship network and the strength of its connections. In micro and small enterprises in the rubber products sector in Poland, sustainable resource management is related to the structure of the network of relations and the strength of connections in the network (relations/networking), as enterprises form a group of entities with a high level of loyalty, especially between the suppliers and buyers of raw materials. The formulated conclusions will become the basis for further in-depth research that can be conducted (a) in the same group of respondents, but using a representative research group, (b) in the same industry among a group of large enterprises, and (c) in a group of small and medium-sized enterprises (SMEs) from other industries. Full article

Energy consumption is associated with economic growth, but it comes with a toll regarding the environment. Renewable energies can be considered substitutes for fossil fuels and may contribute to reducing the environmental degradation that the world is presently facing. With this research, we aimed to offer a broader view of the state-of-the-art in this field, particularly regarding coal and biomass. The main objective is to present a viable and sustainable solution for the coal power plants still in operation, using as a hypothetical example the Pego Power Plant, the last operating coal fueled power plant in Portugal. After the characterization of land use and energy production in Portugal, and more particularly in the Médio Tejo region, where the power plant is located, the availability of biomass was assessed and it was concluded that the volume of biomass needed to keep the Pego power plant working exclusively with biomass is much lower than the yearly growth volume of biomass in the region, which means that this transition would be viable in a sustainable way. This path is aligned with policies to fight climate change, since the use of biomass for energy is characterized by low levels of GHGs emissions when compared to coal. The risk of rural fires would be reduced, and the economic and social impact for this region would be positive. Full article

Social and economic changes make it necessary to put in a great deal of conscious effort to shift towards a closed-loop economy, where waste provides a source of raw materials. The low level of selective collection of municipal waste poses a challenge in many countries, including Poland. One of the major causes of the problems in Poland lies in the fact that waste collection points (WCPs) do not have adequate waste containers. The paper aims to put forward a proposal to improve the operation of WCPs. Seeking for new solutions, it is necessary to account for the conditions under which the bodies responsible for waste management take their decisions. They have to comply with the legislation in force, and at the same time, choose the options that generate the lowest costs. The study concerned a typical residential district with housing in multi-family buildings. For two fill rate variants and four emptying schedules, the number of above-ground containers was calculated. Two variants: for above-ground containers (variant I) and for semi-underground containers (variant II), were compared in terms of operating costs and investment outlays. The proposed increase in the number of above-ground containers, and additionally providing semi-underground containers, will contribute to increased engagement of the local community in the selective collection of waste. Full article

This work presents characterization data and viscosity of 34 secondary vacuum gas oils (H-Oil gas oils, visbreaker gas oils, and fluid catalytic cracking slurry oils) with aromatic content reaching up to 100 wt.%. Inter-criteria analysis was employed to define the secondary VGO characteristic parameters which have an effect on viscosity. Seven published empirical models to predict viscosity of the secondary vacuum gas oils were examined for their prediction ability. The empirical model of Aboul-Seud and Moharam was found to have the lowest error of prediction. A modification of Aboul-Seoud and Moharam model by separating the power terms accounting for the effects of specific gravity and average boiling point improves the accuracy of viscosity prediction. It was discovered that the relation of slope of viscosity decrease with temperature enhancement for the secondary vacuum gas oil is not a constant. This slope increases with the average boiling point and the specific gravity augmentation, a fact that has not been discussed before. Full article

Urban landscapes are under great pressure and particularly vulnerable, due to climate change, population growth and economic development. Despite the growing understanding that Nature-Based Solutions (NBS) represent efficient solutions to facilitate adaptation to climate change and increase cities’ resilience, their wide-scale adoption is still limited. There is a need to include NBS in urban governance and planning agendas through policy instruments, such as plan/legislative, economic and information instruments. However, there is a lack of studies that assess such policy instruments and, through the use of specific examples, how they can foster NBS adoption. The objective of this study is to address this gap by conducting a systematic literature review, using a bibliometric and a content analysis, collating and reviewing papers that consider policy instruments and NBS in order to: (i) assess the existence of policy instruments that influence the adoption of NBS; and (ii) evaluate the existence of specific examples of policy instruments. Results show that plan/legislative instruments are most mentioned, followed by economic and information instruments. However, examples of specific policy instruments being used in practice are still scarce in literature, as most studies remain theoretical. Full article

Humic-like substances (HLS) are among the most used biostimulants in agriculture as a means for improving plant growth, nutrient uptake, crop yield, and stress tolerance. HLS derived from municipal biowastes were applied as a substrate drench in order to evaluate their biostimulatory effect on the growth and ornamental quality of Orange Jasmine (Murraya paniculata L. Jacq.) potted plants. Two HLS, derived from the digestion of the organic humic fraction and from composting of a mix of sewage sludge digestate and gardening residues, were compared with a commercial leonardite-based product in the framework of a greenhouse experiment in soilless culture. The application of the two biowaste-derived HLS resulted in plants showing a 39.9%, 87.0%, 111.6%, 35.4%, 37.9%, 35.3%, and 81.3% increase in plant height, number of flowers and fruits, leaf production, total dry biomass, root length, and water use efficiency, respectively, compared to those treated with the commercial product and the untreated (control) plants. The enhanced growth performance of HLS-treated plants was due to the higher chlorophyll relative content (+24.2% on average) and net photosynthesis (+114.7% on average) of their leaves. The positive results obtained from the application of non-commercial HLS suggest that biowaste recycling is a sustainable and environment-friendly source of biostimulants, as an alternative to agrochemicals and existing leonardite-based plant biostimulants. Full article

Supply risk assessments are an integral part of raw material criticality assessments frequently used at the country or company level to identify raw materials of concern. However, the indicators used in supply risk assessments to estimate the likelihood of supply disruptions vary substantially. Here, we summarize and evaluate the use of supply risk indicators and their normalization to supply risk scores in 88 methods published until 2020. In total, we find 618 individual applications of supply risk criteria with 98 unique criteria belonging to one of ten indicator categories. The most often used categories of supply risk indicators are concentration, scarcity, and political instability. The most frequently used criteria are the country concentration of production, depletion time of reserves, and geopolitical risk. Indicator measurements and normalizations vary substantially between different methods for the same criterion. Our results can be used for future raw material criticality assessments to screen for suitable supply risk indicators and generally accepted indicator normalizations. We also find a further need for stronger empirical evidence of widely used indicators. Full article

A wastewater treatment plant (WWTP) can be considered a system where dirty water enters and fresh water (by means of treatment processes) and other co-products such as sludge and biogas exit. Inside the system, typically, the following steps occur: preliminary treatment, primary treatment, secondary treatment, tertiary treatment, disinfection, and solids handling. The system transforms biomass into several energy and non-energy products, which fall into the definition of a biorefinery. This research compares three simulated WWTP in terms of their environmental greenhouse gas (GHG) emission release to the atmosphere: a generic one (without co-product valorization), one that converts co-products into fertilizer, heat, and electricity, and a third one that converts co-products into heat, electricity, fertilizer, and bioplastic. Heat and electricity are used to provide its energy needs. The chosen impact category is GHG, and the aim is to project the best scenario to the European context in terms of GHG avoidance (savings). The scope is the upstream electricity and natural gas production, the in-use emissions, and the avoided emissions by substituting equivalent fossil-based products. The functional unit is 1 L of sewage (“dirty water”). The GHG savings are evaluated by comparing a generic WWTP scenario, without co-product valorization, with alternative scenarios of co-product valorization. Conventional LCA assuming all the emissions occurs at instant zero is compared to a more realistic environment where for each year, the average of the variable emission pulses occurs. Variable emissions pulses are taken from variable inflows data publicly available from European COST actions (COST Action 682 “Integrated Wastewater Management” as well as within the first IAWQ (later IWA) Task Group on respirometry-based control of the activated sludge process), within the later COST Action 624 on “Optimal Management of Wastewater Systems”). The GHG uncertainty is estimated based on the inputs benchmark data from the WWTP literature and by having different available global warming potential dynamic models. The conventional LCA versus dynamic LCA approach is discussed especially because a WWTP is by nature a dynamic system, having variable inputs along time and therefore variable output GHG emission pulses. It is concluded that heat needs are fully covered by biogas production in the anaerobic digester and combustion, covering its own energy needs and with a potential for heat district supply. Only 30–40% of electricity needs are covered by combined heat and power. Bioplastics and/or fertilizer yields potentially represent less than 3% of current European needs, which suggests the need to reduce their consumption levels. In comparison to generic WWTP, GHG savings are 20%, considering the uncertainty in the benchmark input assumptions. The former is much higher than the uncertainty in the dynamic global warming potential model selection, which means that the model selection is not important in this case study. Full article

The reduction of bed temperature in fixed-bed biomass combustion is an effective measure to lower pollutant emissions. Air staging and bed cooling solutions are active strategies to decrease the fuel bed temperature. This work presents a CFD study of a biomass fixed-bed combustion plant that is equipped with an internal cooling bed system. Eight different cases are calculated to analyze the effect of the total airflow, air staging ratios and bed cooling system on biomass combustion. The findings are validated against experimental data from the literature. The results show good accordance between the numerical results and the experimental data. The primary airflow rate has the biggest influence on the bed’s maximum temperatures. The internal bed cooling system is able to achieve an average bed temperature reduction of 21%, slowing the biomass thermal conversion processes. Bed cooling techniques can be combined with air staging and primary airflow reduction to reduce bed temperatures in order to reduce pollutant emissions and other undesirable phenomena, such as fouling or slagging. Full article

This article focuses on the development of a conceptual framework guiding the adoption of biogas technology in selected rural areas of the Limpopo province. The theoretical framing of the study emanated from the critical evaluation of models and work that privileged the technical design and optimisation of a biogas system over the adoption of the technology at the household level. Based on the empirical evidence, and using logistic regression analysis, the study highlighted that determinants of biogas technology adoption in communities are complex, context-dependent and spatially varied. Hence, the policy of biogas adoption should be tailored based on the principle of fit-for-purpose, instead of using existing unimodal approaches for all settings. Based on the findings, the study developed a robust conceptual framework that harnesses the relationships between the influencing variables that can enhance the adoption of biogas technology. Full article

Thirty crude oils, belonging to light, medium, heavy, and extra heavy, light sulfur, and high sulfur have been characterized and compatibility indices defined. Nine crude oil compatibility indices have been employed to evaluate the compatibility of crude blends from the thirty individual crude oils. Intercriteria analysis revealed the relations between the different compatibility indices, and the different petroleum properties. Tetra-plot was employed to model crude blend compatibility. The ratio of solubility blending number to insolubility number was found to best describe the desalting efficiency, and therefore could be considered as the compatible index that best models the crude oil blend compatibility. Density of crude oil and the n-heptane dilution test seem to be sufficient to model, and predict the compatibility of crude blends. Full article

Biofuels derived from renewable plant materials are considered promising alternative fuels to decrease emissions of ICEs. This study aimed to justify the possibility of using vegetable oils of different sources as a 10% additive in blended biofuel for diesel engines of agricultural machinery and commercial vehicles. Seven different vegetable oils were investigated. Experiments have been performed by fueling a diesel engine with blended biofuels of 90% petroleum diesel fuel and 10% vegetable oil. In the maximum power and maximum torque modes, the brake power drop was no more than 1.5%, and the brake-specific fuel consumption increase was less than 4.3%; NOx emissions were reduced by up to 8.3%, exhaust smoke—up to 37.5%, CO—up to 20.0%, and unburned HC—up to 27.9%. In the operating modes of the European 13-mode steady-state test cycle, the integral specific emissions of HC decreased by up to 30.0%, integral specific emissions of CO—up to 15.0%, and integral specific emissions of NOx—up to 16.0%. The results obtained show the feasibility and rationality of using the investigated vegetable oils as a 10% additive in blended biofuel for diesel engines of agricultural machinery and commercial vehicles. Full article