High CO2 Emissions Research Articles

A low carbon embedded low water/binder cement-based composites (LW/BCC) based on steel slag powder and microwave pre-curing: Experiments and Life Cycle Assessment (LCA)

This paper proposes a new design and preparation method for low carbon embedded low water/binder cement-based composites (LCE-LW/BCC), including experimental investigation and Life Cycle Assessment (LCA). To be specific, a recycled steel slag powder (SSP) is utilized to replace the cementitious material with high CO2 emission in normal LW/BCC, while an effective microwave pre-curing is employed to treat the developed samples at early age. After that, to determine the optimal parameters of microwave time duration (MTD) and microwave time zero (MTZ) for LW/BCC, its macro and micro performance are analyzed. Finally, the Life cycle Assessment (LCA) method is used to evaluate the whole cycle of low-carbon LW/BCC from production to service. The results show that a reasonable microwave pre-curing system can effectively shorten the curing cycle during the preparation of LW/BCC. A 1-minute microwave pre-curing during the induction period can improve the compressive strength of the sample by about 150% and increase its long-term strength. Based on LCA results, it can be noticed that the newly proposed method could decrease the natural resources depletion, ecotoxicity, ozone depletion and carbon emissions of LW/BCC by 94.71%, 90.36%, 87.3% and 84.45%, respectively.

Nitrogen Photoelectrochemical Reduction on TiB2 Surface Plasmon Coupling Allows Us to Reach Enhanced Efficiency of Ammonia Production.

Ammonia is one of the most widely produced chemicals worldwide, which is consumed in the fertilizer industry and is also considered an interesting alternative in energy storage. However, common ammonia production is energy-demanding and leads to high CO2 emissions. Thus, the development of alternative ammonia production methods based on available raw materials (air, for example) and renewable energy sources is highly demanding. In this work, we demonstrated the utilization of TiB2 nanostructures sandwiched between coupled plasmonic nanostructures (gold nanoparticles and gold grating) for photoelectrochemical (PEC) nitrogen reduction and selective ammonia production. The utilization of the coupled plasmon structure allows us to reach efficient sunlight capture with a subdiffraction concentration of light energy in the space, where the catalytically active TiB2 flakes were placed. As a result, PEC experiments performed at -0.2 V (vs. RHE) and simulated sunlight illumination give the 535.2 and 491.3 μg h-1 mgcat-1 ammonia yields, respectively, with the utilization of pure nitrogen and air as a nitrogen source. In addition, a number of control experiments confirm the key role of plasmon coupling in increasing the ammonia yield, the selectivity of ammonia production, and the durability of the proposed system. Finally, we have performed a series of numerical and quantum mechanical calculations to evaluate the plasmonic contribution to the activation of nitrogen on the TiB2 surface, indicating an increase in the catalytic activity under the plasmon-generated electric field.

CO2 emissions embodied in bilateral trade in China: An input-output analysis

The effects of export goods on CO2 emissions in China were calculated using input-output analysis via the hypothetical extraction method (HEM). The seven largest export partners of China were taken into account for the analysis: the US, Japan, South Korea, Germany, India, the UK and the Netherlands. First, using input-output analysis, the effects of CO2 emissions were allocated between the non-tradable goods, total export goods, exported final goods and exported intermediate goods sectors. Then, using a weighted multipliers approach, efficiency in CO2 emissions was allocated among the sectors. It was found that although non-tradable goods caused the highest CO2 emissions, export goods, especially intermediate goods showed the largest growth in emissions. In addition, export goods contributed more to emissions efficiency. Second, the HEM was implemented to explore which countries had significant effects on both emissions and emissions efficiency. The US was the largest source of CO2 emissions in China in terms of final goods. Nevertheless, the US also increased the role of exported intermediate goods on emissions. It was also an important country in stimulating efficiency in CO2 emissions. Hence, China does not have a chance to decrease its export performance against the countries such as the US, as their demand is the source of efficiency in CO2 emissions. However, it can focus on exported intermediate goods to mitigate emissions, and take the US into account for new policies.

Design and analysis for chemical process electrification based on renewable electricity: Coal-to-methanol process as a case study

Electrification of traditional large-scale chemical industry based on renewable electricity can greatly reduce process CO2 emission, and store intermittent renewable electricity into chemical products locally to decrease power grid frequency regulation caused by fluctuating renewable electricity. This study presents a framework for electrification of chemical industry from indirect and direct aspects using the state-of-art coal-to-methanol process as a case study. Traditional coal-to-methanol (Process 1) suffers from high CO2 emission due to mismatch of H/C ratio between coal and methanol. A pulverized coal gasification-integrated SOEC process (Process 2) has been investigated, the water–gas-shift unit is avoided and a simplified acid gas removal process is implemented to replace traditional acid gas removal unit in Process 2. Electric heaters and heat pump system are applied in Process 2 as direct electrification methods to form semi-electrified scenario (Process 3). To discuss the effect of electrification levels on process performances, a fully electrified process (Process 4) is also designed. The results show that: CO2 emissions of the four processes are 2.19, 0.71, 0.52 and 0.63 t/t MeOH, and energy efficiency are 57.40 %, 62.32 %, 64.31 % and 57.63 %, respectively. Production costs are 159.1, 294.3, 301.0 and 358.3 $/t MeOH, IRRs are 14, 31, 29 and 14.5 %, respectively. Through this research and analysis, we hope to explore integration potential of renewable electricity and traditional chemical industry, and design a greener methanol production route based on renewable electricity.

Geopolymers for 3D print

3D print of building materials has increasing popularity in the construction industry all around the world. However, geopolymer material, which stands out for its high temperature resistance and low CO2 emissions compared to concrete, is very rarely used for 3D printing. This work is focused on a composite material based on a geopolymer binder, which is suitable for 3D printing of building elements. The properties of the developed geopolymer composite and the parameters that influence them are described in detail. One of the most important properties of the geopolymer composite for 3D print is setting time and its influence possibilities. The optimal setting time of the developed geopolymer material was 50 minutes. This composite reached up to 70 MPa at room temperature and 35 MPa after exposure to temperature of 800°C.

Comparative study on the electric resistance of mortars made of low carbon binders

Against the background of the high CO2 emissions generated in the production of Portland cement (OPC), research is being carried out worldwide into alternative binders that can be produced with lower energy consumption. These have a lower clinker-cement factor or contain no Portland cement at all. To enable these binders to be used on a large scale, also in reinforced concrete structures, their performance in terms of durability must be ensured. The specific electric resistance is a parameter for characterizing different binders. At a young age, the hydration progress and the formation of the pore structure can be observed based on the specific electric resistance. In connection with the electrical conductivity of the pore solution, statements about the pore structure and the resistance to the penetration of corrosion-promoting substances are possible. Finally, the electric resistance is an influencing factor for estimating possible corrosion rates after depassivation of the steel reinforcement. In this study, a wide range of mortars produced with different alternative binders were characterized in terms of their resistivity as a function of age and water content. From the group of clinker substitutes (SCMs), calcined clays and modified steel slag were investigated. The other binders included in the investigation program are produced entirely without Portland cement: In addition to a calcium sulfoaluminate (CS̅A) cement and the C-S-H binder Celitement®, alkali-activated materials (AAMs) in the form of geopolymers and alkali-activated slags were also investigated. The results show a wide range of specific electric resistances in a naturally water-saturated state of the mortar specimens between 5.5Ωm for an alkali-activated metakaolin and 971Ωm for the Celitement®. Clinker replacements with calcined clays metakaolin, or metaillite result in increased specific electric resistances. In addition, the different binders show a very different influence on the dependence of the resistivity on the water content.

Contribution of land use and cover change (LUCC) to the global terrestrial carbon uptake

Terrestrial carbon uptake is critical to the removal of greenhouse gases and mitigation of global warming, which are closely related to land use and cover change (LUCC). However, understanding terrestrial carbon uptake and the LUCC contribution remains unclear because of complex interactions with other drivers (particularly climate change). By proposing an innovative approach of “trajectory analysis”, this study aimed to isolate the LUCC contribution to terrestrial carbon uptake over different scales. Methodologically, global land was first divided into sub-regions of land transformations and stable land trajectories. Then, the carbon uptake change in the stable land trajectory was taken as a synthetic influence of climate change, which was used as a reference to isolate the carbon uptake alternation generated from the LUCC contribution in the land transformation trajectories. Finally, future LUCC and the terrestrial carbon uptake response were predicted under different development pathways. The results showed the global mean net ecosystem production (NEP) was 27.44 ± 36.51 g C m−2 yr−1 in the past two decades (2001–2019), generating 3.15 ± 0.88 Pg C yr−1 of the total terrestrial carbon uptake. Both the NEP and total carbon uptake showed significant increasing trends. Specifically, the mean NEP increased from 17.96 g C m−2 yr−1 in 2001 to 37.37 g C m−2 yr−1 in 2019, with the trend written as y = 1.20× + 15.20 (R2 = 0.62, p < 0.01). Meanwhile, the total carbon uptake increased from 2.35 Pg C yr−1 in 2001 to 4.13 Pg C yr−1 in 2019, which could be written as y = 0.12× + 1.93 (R2 = 0.56, p < 0.01). Climate change acted as the dominant factor for the trends at the global scale, which contributed 21.26 g C m−2 yr−1 and 1.59 Pg C yr−1 of the mean NEP and total carbon uptake changes in the stable land trajectories (94.30 million km2 that covered 63.29 % of the global land area), and the historical LUCC contributed −6.30 g C m−2 yr−1 (−40.85 %) and − 0.046 Pg C yr−1 (−57.50 %) of the mean NEP and the total carbon uptake change in the land transformation trajectories (6.64 million km2 that covered 4.46 % of the global land area), respectively. The maximum LUCC contribution (−61.85 g C m−2 yr−1) to the mean NEP occurred in the land transformations from evergreen needleleaf forests to woody savannas, while the maximum contribution (−0.034 Pg C y−1) to total carbon uptake was in the deforested regions from evergreen broadleaf forests to woody savannas. Eight SSP–RCP scenarios predictions demonstrated that future terrestrial carbon uptake would increase by an average of 0.015 Pg C yr−1 in 2100 due to global afforestation. SSP4–3.4 and SSP5–3.4 had the greatest potential for increasing carbon uptake, which is expected to reach a maximum increase (0.045 Pg C yr−1) in 2100. In contrast, the minimum terrestrial carbon uptake would occur in SSP5–8.5, which had the highest CO2 emissions. In conclusion, although relatively limited at the global scale, LUCC (particularly forest change) exerted an unneglectable role on terrestrial carbon uptake in land transformation regions. The results of this study will help to clarify terrestrial carbon uptake dynamics and provide a basis for carbon neutral and climatic adaptation.

Experimental Study of the Combustion of and Emissions from Olive and Citrus Pellets in a Small Boiler

Agro-industrial activities generate a great amount of bioproducts as biomass residues containing energy and with potentially useful applications in the thermochemical conversion process. The management of this feedstock as uncontrolled combustion (“open burning”) can often be a problem within the supply chain for disposal practices, both in environmental and economic aspects. The residual matrices from agroforestry biomass processing can be treated to increase their energy levels and economic value. A widespread practice for sustainable disposal is the production of pellets from residual biomass, such as pruning. The aim of this study is to explore the combustion of pellets obtained from olive and citrus pruning, and their emissions into the atmosphere. This study confirms the possibility of using waste biomass to obtain a high-energy biofuel that is usable in a controlled combustion system and to monitor the process and its related emissions (CO, CO2, NOx, SO2, PM). Three different pellets (olive pellet, citrus pellet and a pellet obtained from a mix of olive and citrus) were characterized to determine their physicochemical properties and burned in an 80 kWth boiler equipped with multicyclone filter bags as an abatement system to evaluate relative emission. The characterization results show that citrus pellet has a higher ash content, moisture content and lower energy value than mixtures of olive pellet. The emission results suggest that, during combustion, higher emissions of CO and SO2 were monitored from mixtures of citrus pellet compared to burning only olive pellet.

Substitution of Fossil Coal with Hydrochar from Agricultural Waste in the Electric Arc Furnace Steel Industry: A Comprehensive Life Cycle Analysis

The iron and steel industry remains one of the most energy-intensive activities with high CO2 emissions. Generally, the use of fossil coal as chemical energy in an electric arc furnace (EAF) makes up 40–70% of the total direct emissions in this steelmaking process. Therefore, substituting conventional fossil fuels with alternatives is an attractive option for reducing CO2 emissions. In this study, the environmental impacts of EAF-produced steel were comprehensively assessed using pulverized hydrochar as the charged and injected material as a replacement for fossil coal. An environmental analysis was performed based on the LCA methodology according to the framework of ISO 14044. This study evaluated two different outlines: the use of fossil coal and its replacement with hydrochar from the winemaking industry as a carbon source in the EAF steelmaking process. The environmental impacts from the manufacturing of the hydrochar were calculated using different scenarios, including novel industrial ways to use vinasse as a moisture source for the co-hydrothermal carbonization of vine pruning and exhausted grape marc (EGM). The environmental impacts per unit of steel were reported as a function of the ratio between the fixed carbon of the injected material and the material amount itself. The results highlight the sustainability of the hydrothermal carbonization process and the use of the hydrochar in EAF steelmaking. Moreover, the electricity mix used for the EAF process has significant relevance. The main outline of the results might assist decision-makers to determine which technological route is most likely to be effective in reducing future CO2 emissions from the iron and steel industry.

Carbon footprints in minimally invasive surgery: Good patient outcomes, but costly for the environment.

Advancements in technology and surgical training programs have increased the adaptability of minimally invasive surgery (MIS). Gastrointestinal MIS is superior to its open counterparts regarding post-operative morbidity and mortality. MIS has become the first-line surgical intervention for some types of gastrointestinal surgery, such as laparoscopic cholecystectomy and appendicectomy. Carbon dioxide (CO2) is the main gas used for insufflation in MIS. CO2 contributes 9%-26% of the greenhouse effect, resulting in global warming. The rise in global CO2 concentration since 2000 is about 20 ppm per decade, up to 10 times faster than any sustained rise in CO2 during the past 800000 years. Since 1970, there has been a steady yet worrying increase in average global temperature by 1.7 °C per century. A recent systematic review of the carbon footprint in MIS showed a range of 6-814 kg of CO2 emission per surgery, with higher CO2 emission following robotic compared to laparoscopic surgery. However, with superior benefits of MIS over open surgery, this poses an ethical dilemma to surgeons. A recent survey in the United Kingdom of 130 surgeons showed that the majority (94%) were concerned with climate change but felt that the lack of leadership was a barrier to improving environmental sustainability. Given the deleterious environmental effects of MIS, this study aims to summarize the trends of MIS and its carbon footprint, awareness and attitudes towards this issue, and efforts and challenges to ensuring environmental sustainability.

Are green cars an optimal and efficient choice for motorists? Evidence from Italy

This study evaluates whether a motorist's choice over green cars (i.e., cars with featuring low CO2 emissions) and non-green cars (i.e., cars featuring high CO2 emissions) is efficient. To this end, we present a micro-founded model of motorist choice incorporating the impact of eco-incentives and taxation on CO2 emissions. Subsequently, we implement data envelopment analysis on a large database of new cars registered in 2019 to evaluate efficiency. The results show that the motorist's optimal choice (green car) does not coincide with the efficient choice. Moreover, motorist choice is mainly guided by the high price of green cars. On average, the efficient choice coincides with cars that end up in the dark area (they do not benefit from eco-incentives and do not pay the pollution tax), being the cheapest, the lightest, the least powerful (low Kw) and petrol fuelled. On average, these elements pertain to Italian motorists with respect to their tastes; most importantly, their budgets do not go well with the high costs of green cars.

A new approach to CO2 capture and sequestration: A novel carbon capture artificial aggregates made from biochar and municipal waste incineration bottom ash

Sequestering carbon dioxide (CO2) in concrete through carbonation has the potential to mitigate high CO2 emissions in the construction industry. In this study, we innovatively produced new carbon capture artificial aggregates (CCAAs) with environmentally-friendly and carbon sequestration capacity by combining sawdust biochar and municipal domestic waste incineration bottom ash (MSWIBA). Here, we investigated the carbon sequestration performance of CCAAs with different incorporation rates of biochar (1%, 3%, and 5%) and the changes in mechanical properties of CCAAs before and after carbonation at different curing ages (7 days and 28 days). The results indicate that the maximum carbon uptake was up to 26.67 kg/ton at an incorporation rate of 5% when left in the natural environment. The appropriate amount of biochar incorporation improved the strength of CCAAs, with 3% and 5% showing the highest strength at 7 and 28 days of curing, respectively, compared with the control group. After carbonation, the early strength decreased at 7 days due to the decalcification of C-S-H, but the long-term strength increased at 28 days due to the densification of calcium carbonate generated by carbonation. Overall, this study demonstrates the high potential for carbon sequestration in biochar-bottom ash composite CCAAs, while the incorporation of biochar improves their mechanical properties.

Metabolic syndrome criteria and severity and carbon dioxide (CO2) emissions in an adult population

BackgroundMetabolic syndrome (MetS) has become a growing risk factor of some non-communicable diseases. Increase of greenhouse gas emissions affects the planet.AimsTo assess the association between MetS severity and amount of carbon dioxide (CO2) emitted in an adult population.DesignCross-sectional study (n = 6646; 55-76-year-old-men; 60-75-year-old-women with MetS).MethodsDietary habits were assessed using a pre-validated semi quantitative 143-item food frequency questionnaire. The amount of CO2 emitted due to the production of food consumed by person and day was calculated using a European database, and the severity of the MetS was calculated with the MetS Severity Score.ResultsHigher glycaemia levels were found in people with higher CO2 emissions. The risk of having high severe MetS was related to high CO2 emissions.ConclusionsLow CO2 emissions diet would help to reduce MetS severity. Advantages for both health and the environment were found following a more sustainable diet.Trial registrationISRCTN, ISRCTN89898870. Registered 05 September 2013.

Rate-based modeling and energy optimization of acid gas removal from natural gas stream using various amine solutions

Reduction in energy consumption of industrial plants is always an essential need due to high cost, CO2 emissions and global warming caused by energy supply from fossil fuels for boilers and electricity consumers. Iran has been struggling to compensate the lack of gas supply for domestic and industrial demands in winter within the past decade despite of having large natural gas resources. One of the most economical methods to decrease energy requirements in hydrocarbon plants is process improvement and revamping by changing existing solvents. There are already 44 identical acid gas removal units under operation in the South Pars Gas Complex (located in Iran) with the same feed composition. The gas-sweetening unit in the Phase 12, operating with the solution of 45.5 wt% methyldiethanolamine (MDEA), was modeled by Aspen Plus for acid gas removal (CO2 and H2S) as a rate-based model with the application of electrolyte non–random two–liquid (E-NRTL) activity model and Peng–Robinson equation of state in addition to the actual characteristics of the absorber and regenerator, and the operational conditions of the gas and liquid streams. After validation of the model by the real data from the plant, the incumbent amine solution was replaced with five proposed amine solutions – one single and four blended amine mixtures – in the same mass concentration to select the most efficient alternative from the aspects of outlet acid gas concentration, H2S content in the treated flash gas, required total power, reboiler power supply, and regeneration heat duty. The simulation results revealed that H2S was sharply absorbed on the top of the column, while CO2 was smoothly removed from the gas phase to the MDEA and blended solutions along the absorber and it occurred at the bottom of the column for the DEA solution. The blended amine solution of 1.5 wt% sulfolane + 44 wt% MDEA (Sulfinol-M) has shown to be the most appropriate option instead of the solution of MDEA compared to other suggested absorbents, with several advantages such as higher selectivity of H2S over CO2, low temperature bulge, highest H2S loading, and outlet sweet gas flow rate while required total power, reboiler power supply, and regeneration heat duty were reduced by 21.19%, 21.26%, and 23.54% respectively. The operational conditions of the unit with the application of the Sulfinol-M solution were optimized to achieve three specifications (constraints) and the minimum required total power (objective function) through a sensitivity analysis and optimization using a genetic algorithm to assure the reliability of values for three independent parameters, namely, amine solution temperature, amine solution flow rate, and gas temperature. The optimum limits and values of these parameters were 47–50 °C, 220 – 240 ton/h, and 34 °C respectively.

Design and deployment of sustainable recovery strategies in the supply chain

When a disruption hits the supply chain, recovery strategies are deployed using either preparedness backup plans or ad-hoc situational reactions. Ad-hoc recovery actions usually imply expensive air transport, which produces higher CO2 emissions, to compensate for material shortages and avoid production stops. Despite the large variety of methods developed to improve resilience in supply chains, literature is silent about the environmental impact of recovery strategies. Through a simulation-based analysis using the anyLogistix digital supply chain model, we examine the impact of two sustainable recovery strategies – additive manufacturing and electric trucks – on supply chain environmental and resilience performance. We demonstrate that the proposed strategies allow recovery sustainability to be improved as compared to ad-hoc reactions with high CO2 emissions. Our findings contribute to the literature on supply chain resilience by extending the existing knowledge on the trade-offs between resilience and sustainability in line with the Industry 5.0 framework toward building sustainable resilience.

The role of resource rent in shaping CO2 emissions in BRICS countries: A panel data approach

This study investigates the impact of resource rent on CO2 emissions in the presence of GDP, renewable energy consumption, and research and development spending for BRICS nations from 1990 to 2020. Employing quantile regression approach, this study finds that resource rents are responsible for rising CO2 emissions in BRCIS countries. However, there exists a threshold level of resource rents beyond which the nature of the relationship between variables changes. Since, the extraction of natural resources requires a significant amount of energy, it may result in excessive levels of energy consumption as well as the reckless discharge of waste chemicals into the water, land, and air. We find that the impact of GDP on CO2 emissions is greater for nations with a low level of CO2 emissions and is lower for nations with relatively high CO2 emissions. The findings of the research paper highlight several policy implications for the BRICS nations to reduce their CO2 emissions. Policymakers should prioritize investment in renewable energy sources such as wind, solar, and hydroelectric power and encourage research and development spending in renewable energy technologies. The study encourages channelizing resources revenue for a sustainable environment and development.

Retrospective carbon reduction potential of residential buildings in China based on equity and efficiency coupling

Carbon dioxide (CO2) mitigation in the residential building sector has become critical for China in achieving its carbon peak and neutrality goals. This study is the first to retrospect the historical carbon reduction potential in China's 30 provinces by establishing an equity and efficiency coupling model and comparing the differences in carbon reduction potential under three scenarios: equity priority, efficiency priority scenario, and balance equity with efficiency. The core findings of this study reveal that: (1) China's total CO2 emissions in residential buildings increased from 975.67 Mt to 1328.47 Mt during 2010–2020, where the provinces with the highest CO2 emissions are Shandong, Hebei, and Henan; energy intensity and energy carbon emission coefficient are the most critical driving factors affecting the CO2 emission, followed by floor area per capita and population size. (2) The carbon reduction potential index of residential buildings in eastern provinces is generally higher than that in western provinces; the growth rate of carbon reduction potential is the fastest under the equity priority scenario, and Beijing, Shanghai, and Inner Mongolia have the highest carbon reduction potential. (3) The provinces gradually enter a strong coupling status associated with the climate zones of residential buildings, while the coupling status of the urban area is higher than that of the rural area. Overall, this study adopts a new coupling perspective of equity and efficiency, where the proposed assessment model serves as a reference for measuring the retrospective CO2 mitigation effect in residential buildings in other countries.

Techno-economic analysis of a glycerol to methanol, ethylene glycol and 1,2-propanediol cogeneration process integrated with biomass chemical looping hydrogen generation

Glycerol hydrogenolysis to alcohols such as methanol, ethylene glycol and 1,2-propanediol is regarded as a promising technology. Nevertheless, conversion of fossil fuels to H2 suffers high CO2 emissions. Therefore, a new glycerol to methanol, ethylene glycol and 1,2-propanediol process integrated with biomass chemical looping hydrogen generation was designed and simulated via Aspen Plus. The prediction results demonstrated that under the flow rate of glycerol 20 t/h and H2 feed 2.4 t/h, the output of methanol, ethylene glycol and 1,2-propanediol was 11095, 1142 and 5000 kg/h, respectively. It also demonstrated that the total efficiency of energy for the proposed process was 53.8%. Additionally, under the condition of glycerol price 725 $/t and corn straw price 59 $/t, the production cost of methanol, ethylene glycol and 1,2-propanediol was 310, 523 and 1100 $/t, respectively. Moreover, the return on investment as well as payback period were 93% and 0.85 years, respectively. Additionally, sensitivities analysis results showed that glycerol price was responsible for the largest impact factor, whereas the influence of oxygen carrier price was relatively small.

Technical, Economic, and Environmental Review of Waste to Energy Technologies from Municipal Solid Waste

Global municipal solid waste production and electricity demand gradually increased as a result of urbanization, population increase, and economic growth. The appropriate selection of Waste to energy (WTE) technologies needs consideration of energy efficiency, financial, and environmental aspects. This article discusses the technical, financial, and environmental side of existing WTE technologies. Waste-to-energy (WTE) technologies include thermal, physical, biochemical, and bio-electrochemical technology. Pyrolysis, gasification, and incineration are thermal technology used to generate energy from waste in the form of heat and syn-gas. Anaerobic digestion and landfill are biochemical technology to to generate energy from waste in the form of biogas. Physical technology is used to to generate energy from waste in the form of refuse-derived fuel (RDF). Microbial fuel cells (MFC) and microbial electrolysis cells (MEC) are the most recent WTE technology that produces electricity and hydrogen fuel. The results of the assessment of existing technology show that anaerobic digestion and landfill are low-cost WTE technology but have a low potential for energy generation. Plasma gasification is WTE technology with a high potential for energy generation, cold gas efficiency (CGE), carbon conversion efficiency (CCE), and H2/CO ratio, low CO2 emissions, and high operating costs. MEC has a high H2-potential for energy generation, low CO2 emissions, and the highest capital cost. Incineration is a common conversion technology with a low potential for energy generation, high CO2 emissions, and high capital costs. The selection of WTE technologies is influenced by technical, economic, and environmental factors.

Mehanička svojstva morta s dodatkom aditiva EarthZyme

Concrete is the most widely used building material in the world. However, owing to the high CO2 emissions from the production of cement, its use has been questioned, and attempts have been made to improve it. Various chemical additives are being used to improve concrete properties. Enzymes are organic materials and have been especially favoured in recent years owing to their low costs when used in traditional soil stabilisation methods. This study used the ‘EarthZyme’ enzyme as a plaster mortar additive and investigated its effects on the mechanical properties of mortars. EarthZyme completely biodegrades in nature and is used for soil stabilisation. By producing mortar specimens with additive enzyme ratios of 0 %, 0.01 %, 0.02 %, 0.03 %, and 0.04 %, the effects of the enzyme additions on the mechanical properties of the mortars (ultrasonic pulse velocity UPV, flexural strength ff and compressive strength fc) were determined. The flow table values of the mortar specimens in the flow table test varied within the range of 15–17 cm. According to the results, the flow table values of the mortars increase with an increasing addition rate of EarthZyme. Although the additive ratio of the EarthZyme does not significantly affect the mechanical properties of mortars at early ages (3 days), the enzyme addition ratio reduces the UPV and fc while improving ff at late ages (28 days). The enzyme addition ratio has no significant effect on the UPV and ff but has a significant effect on fc.