Lime Production Research Articles

Mitigating life-cycle environmental impacts and increasing net ecosystem economic benefits via optimized fertilization combined with lime in pomelo production in Southeast China

Excessive fertilization is acknowledged as a significant driver of heightened environmental pollution and soil acidification in agricultural production. Combining fertilizer optimization with soil acidity amendment can effectively achieve sustainable crop production in China, especially in Southeast China. However, there is a lack of long-term studies assessing the environmental and economic sustainability of combining fertilizer optimization with soil acidity amendment strategies, especially in fruit production. A four-year field experiment was conducted to explore pomelo yield, fruit quality, and environmental and economic performance in three treatments, e.g., local farmer practices (FP), optimized NPK fertilizer application (OPT), and OPT with lime (OPT+L). The results showed that the OPT+L treatment exhibited the highest pomelo yield and fruit quality among the three treatments. The OPT treatment had the lowest net greenhouse gas (GHG) emissions among the three treatments, which were 90.1 % and 42.6 % lower than those in FP and OPT+L, respectively. It is essential to note that GHG emissions associated with lime production constitute 40.7 % of the total emissions from fertilizer production. The OPT+L treatment reduced reactive nitrogen (Nr) emissions and phosphorus (P) losses, compared to FP and OPT. Moreover, the OPT+L treatment increased the net ecosystem economic benefit by 220.3 % and 20.3 % compared with the FP and OPT treatments, respectively. Overall, the OPT and OPT+L treatments underscore the potential to achieve environmentally friendly and economically sustainable pomelo production. Our study provides science-based evidence to achieve better environmental and economic performance in pomelo production through optimized NPK fertilization and alleviating soil acidification by lime.

Characterization and Provenance of Carbonate Rocks for Quicklime and Dololime Production in Twin-Shaft Regenerative Kilns from the Arabian Peninsula and Neighboring Countries

This study analyzes high-grade carbonate rocks from several strategic deposits in the Arabian Peninsula and neighboring countries. The rocks are used locally for quicklime and dololime production in twin-shaft regenerative kilns. Stable C-O-Sr isotopes, along with chemical, mineralogical-petrographic analyses, micropaleontological investigations, cathodoluminescence microscopy, organic carbon speciation, and electron paramagnetic resonance spectroscopy, were used to trace the provenance of these rocks from economically significant non-metallic deposits. The resulting database can help identify and differentiate industrial raw materials that may appear similar chemically and/or macroscopically but have different textures/microstructures that can affect the properties of the derived burnt lime products. Various technological tests, including slaking reactivity, sticking tendency at high-temperature (i.e., 1300 °C), and physico-mechanical behavior of the lime, were performed to evaluate their suitability and predict lime performance in twin-shaft regenerative kilns. Comparison of laboratory and plant results validated the resulting database.

A new source of calcium carbonate nanofibres from recarbonated lime in subsoils at European archaeological sites

Calcium carbonate nanofibres have been described from a number of natural environments and have generally been found in similar locations to those of needle-fibre calcite, such as caves, palaeosols and calcretes. Here we report large amounts of calcium carbonate nanofibres in buried archaeological stratigraphy consisting of recarbonated lime from mortar or plaster. The materials were observed in Roman and medieval contexts and could have been associated with either manufacture or use of the lime products. The phenomenon appears to be widespread, occurring in examples from UK and Latvia, with related nanosized material from Spain. Possible mechanisms are discussed, but the reason for nanofibrous crystallisation occurring in these situations is not currently understood.

Penggunaan Kapur Palupuh dan Kapur Rao-Rao pada Asphalt Concrete - Wearing Course

Indonesia has the many area of the lime production including in the West Sumatra Province. The use of lime as a filler in asphalt mixtures is expected to improve the performance of asphalt mixtures. There are two types of lime used, namely Palupuh and Rao-Rao limestone. This study aims to see the effect of using these 2 types of lime as a filler on Asphalt Concrete-Wearing Course (AC-WC) pavements mixture. The bitumen used is Pen 60/70. Marshall testing was carried out to see the characteristics of the pavement mixture. From Marshall's testing on a pavement without lime, has an optimum asphalt content of 6.015%. Furthermore, with a variation of lime 0%, 25%, 50%, 75%, 100% by weight of filler for both types of lime gave an optimum lime content yield of 50% with an increase in stability of 12.024% and flow of 19.375% for Palupuh lime. Meanwhile, the use of Rao-Rao lime cannot improve the Marshall stability of the AC-WC pavement mixture

Investigation of the influence of lime content in the charge and its quality on the sintering process of iron ore raw materials

Main objectives of the work was to study the influence of degree of roasting of lime contained in the charge on the sintering process and sinter quality, as well as comparing the impact of changes in the mass fraction of active CaO in the charge by varying degrees of burning lime, and by varying the content of lime in the charge. It is shown that the intensifying effect of lime on the sintering process occurs as a result of a decrease in the content of small classes in the charge. When the lime content in the charge is equal to 3 %, an increase in the degree of lime firing from 5 to 96 % led to an increase in the specific productivity of the plant from 0.96 to 1.87 t/(m 2 · hour). The independence of sintering parameters from the content of active CaO in lime with its constant content in the sinter charge and the decisive role of the content of active CaO in the sinter charge with its constant content in lime are confirmed. A new approach to the production of lime for agglomeration processes is proposed: it should have the lowest cost of the active CaO contained in it.

Development of Lightweight Grouting Materials Based on By-Products of Ukrainian Industry

A new competitive class of grouting materials has been created. These lightweight grouting materials (LGM) with a density of 1370–1650 kg/m3 consist of oil-well Portland cement PCTI-100, fine powder of PE grade (a by-product of fireclay production from kaolin), acidic fly ash from state district power plants, and lime dust (a by-product of lime production). The composition of the products formed during LGM hydration was clarified by X-ray phase and differential thermal analysis. The rational optimal ratios of ingredients and temperature regimes for the LGM hardening were determined according to the criteria of cement stone strength.

The Increase in Kaffir Lime Leaf Production Due to Gibberellin Is Diminished by Pruning

Gibberellin regulates the flowering and fruiting response of fruit-oriented citrus, but there are a lack of studies on the methods for boosting the production of leaf-oriented citrus. This study aimed to analyze the effects of exogenous gibberellins and pruning on the leaf production of kaffir lime. Kaffir lime seedlings, grafted into rangpur lime, were arranged in a split-plot design under an open field condition. Four gibberellin concentrations (control, 0.005%, 0.01%, and 0.02%) and two pruning levels (no pruning and pruning at 30 cm main stem) were subjected to selected seedlings. The result showed a contrasting effect between gibberellin and pruning on the plant height and shoot number. Pruning significantly reduced the flush number, flush length, leaf length, leaf area, and leaf weight by 38%, 44%, 17%, 26%, and 28%, respectively. Without pruning, applying 0.02% gibberellin could produce the longest flush, with an increase in the number and weight of leaves by about 77% and 64%, compared with the control, respectively. Multivariate analysis also confirmed the positive effect of gibberellin on leaf production. However, these positive results are diminished by pruning due to limited source capacity, as indicated by the fewer leaves. Future research is required to analyze whether increasing gibberellin concentrations can speed up the recovery of post-pruned kaffir lime.

Geotechnical and engineering properties of expansive clayey soil stabilized with biomass ash and nanomaterials for its application in structural road layers

Clayey soils often pose issues such as swelling, high plasticity, low permeability, and low bearing capacity, particularly in regions with seasonal rainfall. Consequently, soil improvement techniques are necessary for constructing road base layers. Currently, the most used method for road stabilization involves the application of traditional binders such as lime and cement. However, the production of cement and lime has negative environmental impacts and depletes natural resources.In this study, new stabilizing materials based on waste and by-products, as well as a new generation of nanomaterials, are investigated for stabilizing highly plastic and expansive soils. The geotechnical and mechanical properties of soils stabilized with waste materials like biomass ashes from electricity generation, along with small amounts of a silica-based nanotechnological stabilizer, are examined. The obtained results suggest the potential reduction in the use of traditional binders by incorporating by-products, while still maintaining soil properties, and even improving the properties through the application of nano-sized additives.

Transformation pathway to a green lime offer

AbstractThe Autoclaved Aerated Concrete (AAC) industry has announced an ambitious decarbonization roadmap to 2050 to keep its place as a reference product in the future market of building materials. AAC raw materials are contributing to a large share of the CO2 footprint of AAC and need to be carefully assessed. Lime is today an essential raw material in the production of AAC and will remain so in the future as, unlike some other raw materials, it cannot be interchanged by a less carbon‐intensive alternative. Lime is essential in the formation of Tobermorite and provides the alkaline conditions required for the formation of the hydrogen bubbles structuring the mineral foam. Lime is produced by the calcination of limestone (CaCO3) releasing carbon dioxide (CO2). The CO2 footprint of lime is considerable, and the production process is considered hard‐to‐abate. Today roughly two‐thirds of the CO2 is inherent to the production process while only one‐third of the CO2 is due to the required fuel. Lhoist has developed a Carbon Action 2030 plan with a range of low‐carbon and carbon‐neutral lime solutions. The approach is based on the principle of three pillars: Avoiding, Reducing, and Compensating with a pipeline of effective carbon reduction initiatives behind each pillar. The paper will provide a status update on the key projects in Belgium, France, and Germany. The transformation to low‐carbon lime has triggered projects in energy improvement, sustainable fuels, the usage of hydrogen, kiln electrification, oxyfuel kilns, carbon capture, and storage as well as CO2 utilization. Once the CO2 is captured during the production of lime, the carbonation of the AAC will lead to a carbon‐negative building material. Our roadmap will position Lhoist as a preferred partner for the AAC industry in the future. Our lime product portfolio ranging from Level|Blue™ to Level|Green™ will support the AAC industry to consolidate and develop its referential position in the building materials industry.

Development of a New Type of Electrochemical Reactor for Low Temperature Lime and Cement Production

The cement industry is responsible for more than 8% of the global CO2 emissions, making it one of the largest contributors to global warming. Two-thirds of these emissions are coming from unavoidable process gases caused by the calcination reaction of limestone (CaCO3). The remaining emissions are mainly coming from the combustion of fossil fuels. Due to the high temperature requirement (≈1500°C), direct electrification is difficult to consider. For these two reasons, the cement industry is therefore known as a challenging sector to decarbonize.A new electrochemical pathway for cement production has gained prominence in the scientific literature in recent years [1]. This technology has the potential to electrify the cement and lime production while producing at the same time valuable gases (O2, CO2, H2). It is based on a new type of hybrid electrolyser capable of working with solid, liquid and gaseous phases. Thanks to the acidity generated by water oxidation at the anode, the solid limestone feed, precursor of cement, is being dissolved. This dissolution produces pure CO2 which is mixed with pure O2 generated by electrolysis and which is easily captured for later use. The calcium ions are then migrating towards the cathode under the effect of the electric field. The OH- hydroxyl ions, produced at the cathode by water reduction, meet the calcium ions to form the final solid product, hydrated lime (Ca(OH)2). This lime can be used as such or converted into cement by additional steps.In this research, a laboratory-scale setup has been developed to study the feasibility of such a process. Different geometries have been tested and the main operational parameters affecting the different steps of the process have been investigated. Our results show first of all the formation and stabilization of a pH gradient within the electrolyser, which allows at the same time for the complete dissolution of CaCO3 in the acidic anodic environment while producing a white precipitate of Ca(OH)2 at the cathode. The setup also presents ideal faradaic efficiencies when using an IrO2 coated titanium anode and a nickel cathode in a 1M NaClO4 electrolyte. Alternative electrode materials, including a 316L stainless steel anode and an Inconel 718 cathode, have been considered as well. Finally, it was shown that the energetic efficiency can be further improved by pushing the kinetics of the dissolution and precipitation reactions through increasing the mobility of calcium ions, using Ca-based electrolytes, like Ca(ClO4)2. Based on our results, all the elementary concepts behind the hybrid electrolyser have been established, and a first blueprint of a continuous industrial process will be proposed.[1] - L. D. Ellis, et al. (2019). Toward electrochemical synthesis of cement—An electrolyzer-based process for decarbonating CaCO3 while producing useful gas streams. PNAS , 117, 12584-12591. Figure 1

DEM/CFD simulations of a generic oxy-fuel kiln for lime production

Shaft kilns are the common type of reactor for the production of quicklime. Limestone (CaCO3) particles of cm-size are converted to quicklime (CaO) with the energy provided for calcination by the conversion of a typically gaseous fossil fuel. The CO2 emissions of lime production are severe due to the calcination reaction and the CO2 from combustion. Therefore, methods which pave the way for CO2 capture, such as the Oxy-Fuel technology, are of great interest for the lime industry. This motivates the current contribution, which examines the Oxy-Fuel operation of a single-shaft kiln fired by methane and the results are compared to conventional air operation. A generic, down-scaled version of a kiln has been examined. The height of the kiln is 2.5 m and its diameter is 0.64 m. It contains 23,000 limestone particles with four size classes approximating a polydisperse distribution. The particles are assumed to be spherical. The thermal input of the kiln has been fixed to 80 kW. The evaluation is based on 3D DEM/CFD simulations of the kiln. For simplicity, to avoid the combustion simulation, the exhaust gas produced by the burners of the system is precomputed by Cantera and added to the computational domain as a source term. The source terms are added in two different ways: homogeneously distributed over the cross section at a certain kiln height and spatially distributed at four different locations in a cross section to mimic the presence of burner lances, which are used in industrial kilns.The study shows that the average calcination degree is around 5 % lower for Oxy-Fuel operation compared to the conventional air-fired mode since the increased CO2 concentration hinders the reaction. Further, it is evident that considering a spatially resolved fuel inflow results in an improved degree of product calcination in the order of 5 %, implying that the positioning of burner lances is crucial for the design of industrial kilns.

Historical Use of Lime in Some Islands of the Tuscan Archipelago (Italy) Where Stone for Lime Is Almost Absent

The Tuscan Archipelago lies between the Ligurian Sea to the north and the Tyrrhenian Sea to the south and between Corsica to the west and the Tuscan coast to the east. It is made up of seven major islands, Elba, Giglio, Capraia, Montecristo, Pianosa, Giannutri and Gorgona (in order of size), and several smaller ones. Geologically, these islands are very different from each other. Elba combines all the characteristics of the northern Apennines with a large granodioritic pluton and a sequence of tectonic units with sedimentary successions of the Ligurian and Tuscan type. Giglio is a granitic pluton with a small patch of sedimentary cover. Capraia is an entirely volcanic island. Montecristo is a granitic pluton. Pianosa consists exclusively of Mio-Pliocene carbonate rocks. Giannutri consists of Mesozoic Cavernous Limestone, and Gorgona consists of calcschists, serpentinites and metabasites. This article examines the mortars used in the historical architecture of Capraia, Gorgona and Giglio, islands where limestones are almost absent, trying to investigate the provenance of the carbonate stones used to produce the lime through mineralogy–petrographic analyses. Mineralogical and petrographic analyses proved useful in identifying the raw materials used for the production of lime, also contextualising them in the historical and administrative vicissitudes of the islands. In particular, a magnesian lime of Ligurian origin was used in Capraia during the period when the island was under the rule of the Republic of Genoa. On Gorgona in the Middle Ages, the few outcrops of carbonate rock on the island, consisting of saccaroid marble, were exploited for the local production of lime, while in later times lime was sourced from the mainland. In Giglio, the small outcrops of dolostone and marbles on the western side of the island were exploited. This work has broadened knowledge in the use of materials and highlighted man’s knowledge of the area and its resources to such an extent that even small outcrops suitable for lime production were exploited. Attention is also drawn to the fact that, although sophisticated techniques provide excellent information, in many cases only a careful petrographic investigation allows the most useful information to be obtained in a cheap and easy way.

Integrating Soil pH, Clay, and Neutralizing Value of Lime into a New Lime Requirement Model for Acidic Soils in China

Modelling the lime requirement (LR) is a fast and efficient way to determine the amount of lime required to obtain a pH that can overcome the adverse effects caused by soil acidification. This study aimed to model the LR based on the properties of soil and lime. A total of 17 acidic soils and 39 lime samples underwent soil–lime incubation in the laboratory. The predictive equations for the LR (t ha−1) were modelled using ∆pH (the difference between the target pH and initial pH), the neutralizing value (NV, mmol kg−1) of lime, soil pH, soil clay content (%), soil bulk density (BD, g cm−3), and the depth of soil (h, cm) as the factors in an exponential equation. The generic predictive equation, LR=∆pH×e−3.88−0.069×NV+0.51×pH+0.025×Clay×BD×h, was validated as the most reliable model under field conditions. Simplified predictive equations for different soil textures when limed with quicklime and limestone are also provided. Furthermore, the LR proportions provided by hydrated lime, quicklime, limestone, and dolomite in commercially available lime can be expressed as 0.58:0.64:0.97:1.00. This study provides a novel and robust model for predicting the amount of lime product containing components with different neutralizing abilities that are required to neutralize soils with a wide range of properties. It is of great significance to agronomic activities and soil remediation projects.

First report of Aegomorphus quadrigibbus and Thryallis undatus (Coleoptera: Cerambycidae) damaging Persian lime orchards in Veracruz, México

The species Aegomorphus quadrigibbus (Say) and Thryallis undatus (Chevrolat) (Coleoptera: Cerambycidae) were identified causing damage to Persian lime trees in Martínez de la Torre municipality orchards, in central Veracruz state, Mexico. Ovipositions made by the adults to lay eggs on trunks and branches were observed, with galleries between two and five cm deep, which caused the branches to dry up and, in some cases, complete death of the trees. In trees previously affected with vascular pathogens or with nutrient deficiencies, the damage was more severe because the larvae formed galleries that surrounded the trunk or branches, preventing the flow of nutrients. The average incidence in the sampled trees was 10.8%. Since the Martínez de la Torre area is the most important Persian lime production region in Mexico, it is necessary to monitor crops to determine the presence of insects and develop studies to define levels of damage and management strategies for their insects’ populations when required. This is the first record of A. quadrigibbus and T. undatus associated with trees of the Rutaceae family and causing damage to Persian lime orchards.

Study on Carbon Emission Characteristics and Emission Reduction Measures of Lime Production—A Case of Enterprise in the Yangtze River Basin

A scientific carbon accounting system can help enterprises reduce carbon emissions. This study took an enterprise in the Yangtze River basin as a case study. The accounting classification of carbon emissions in the life cycle of lime production was assessed, and the composition of the sources of carbon emission was analyzed, covering mining explosives, fuel (diesel, coal), electricity and high-temperature limestone decomposition. Using the IPCC emission factor method, a carbon life cycle emission accounting model for lime production was established. We determined that the carbon dioxide equivalent from producing one ton of quicklime ranged from 1096.68 kg CO2 equiv. to 1176.96 kg CO2 equiv. from 2019 to 2021 in the studied case. The decomposition of limestone at a high temperature was the largest carbon emission source, accounting for 64% of the total carbon emission. Coal combustion was the second major source of carbon emissions, accounting for 31% of total carbon emissions. Based upon the main sources of carbon emission for lime production, carbon emission reduction should focus on CO2 capture technology and fuel optimization. Based on the error transfer method, we calculated that the overall uncertainty of the life cycle carbon emissions of quicklime from 2019 to 2021 are 2.13%, 2.07% and 2.09%, respectively. Using our analysis of carbon emissions, the carbon emission factor of producing one unit of quicklime in the lime enterprise in the Yangtze River basin was determined. Furthermore, this research into carbon emission reduction for lime production can provide a point of reference for the promotion of carbon neutrality in the same industry.

Treatment of cadmium-contaminated soil using ladle slag with and without CO2

Cement and lime are widely used to stabilize/solidify (S/S) contaminated soils, however, the production of ordinary Portland cement (OPC) and lime causes CO2 emission and consumption of energy and non-renewable resource. In this context, this study proposes a sustainable S/S approach by utilizing an industrial by-product, ladle slag (LS), and carbon dioxide (CO2), to substitute cement and lime for treating cadmium (Cd)-contaminated soil. In laboratory investigation, contaminated soils spiked by Cd with concentrations of 0–32,000 mg/kg were treated by LS with a binder content of 10 % and subjected to conventional curing and carbonation curing for different periods varying from 3 hours to 112 days. The results showed that LS with conventional curing could reduce the leaching of Cd, however, it was still less effective than OPC in S/S of Cd-contaminated soils under the same curing period of 28 days. When CO2 was introduced, LS with CO2 rapidly decreased the leaching of Cd in soils by five orders of magnitude, using only 104 hours to achieve better S/S efficacy than OPC with conventional curing for 28 days. The LS with carbonation curing also sequestered CO2 up to 16 % of LS mass and yielded higher strength than that without CO2.

Measurement of lime movement and dissolution in acidic soils using mid-infrared spectroscopy

Acidification of surface and sub-surface soils limits agricultural production globally. Conventional surface application of lime is the most common amelioration approach for surface acidity. However, amelioration of sub-surface acidity is challenging to achieve using this approach. Testing the efficacy of liming to treat acidity through the soil profile via the measurement of lime movement requires high throughput information about soil properties at a high spatial resolution, which can be time consuming and expensive using traditional laboratory analysis. Here, we investigated the potential of Mid Infrared (MIR) spectroscopy as a tool to monitor lime dissolution and vertical movement through soils at high spatial resolution. Soil samples were collected at 2.5 cm intervals to 20 cm depth at three trial sites in South Australia, with various lime treatments applied either 6 years or 1 year prior to sampling. MIR Partial least squares regression (PLSR) predictions were undertaken to measure lime dissolution and alkalinity movement via soil pH, and undissolved lime presence via soil carbonate concentrations. Lime balance calculations were then performed to determine the fate of applied lime and assess efficacy of various rates of lime products applied at the surface only or via incorporation. MIR-PLSR prediction model performance was strong for both soil pH (R2 = 0.923 and RMSE = 0.202) and carbonate (R2 =0.829 and RMSE=0.042 CO3%). Results indicated the movement of alkalinity at all sites was limited, and revealed increased movement at the longer-term (∼6 years) vs shorter-term (∼1 year) sites where lime was surface applied. Lime balance calculations indicated that residual lime remained in the top 7.5 cm of the soil profile while soils remained acidic below this depth. Findings suggest that incorporation of residual lime and additional lime applications may be necessary to remediate sub-surface acidity. A decision tree was developed to inform management of surface and sub-surface soil acidity. The study validates the potential of MIR spectroscopy to measure and monitor the effectiveness and movement of lime with improved resolution in acidic soils.

Negative CO2 emissions in the lime production using an indirectly heated carbonate looping process

Lime is an essential raw material for iron and steel production, in construction and agriculture, in civil engineering, in environmental protection, and in manifold chemical manufacturing processes. To address the problem of unavoidable process CO2 emissions associated with the production of lime, efficient capture technologies need to be developed and implemented. The indirectly heated carbonate looping (IHCaL) process is an efficient candidate for this application because it utilizes lime as the sorbent for the CO2 capture. In this work, a retrofit configuration of this process is presented and analyzed for net negative CO2 emissions. This is done considering different fuels that provide the heat required for the regeneration of the sorbent. The different scenarios were simulated with an AspenPlus® model, key performance indicators were calculated, and the process was compared with other post-combustion capture methods. The results show that net negative CO2 emissions as high as −1805 kgCO2/tCaO, calculated with a state-of-the-art coal power plant energy scenario (ηe = 44.2 %; eref,el = 770 kgCO2/MWhel), can be obtained. This represents an equivalent CO2 avoidance of more than 230% with respect to the reference plant without capture (1368 kgCO2/tCaO). A specific primary energy consumption for CO2 avoided (SPECCA) lower than 1.5 MJLHV/kgCO2,av was achieved for the same energy scenario. Particularly promising results can be accomplished when applying fuels with high biogenic fraction and low specific CO2 emissions, such as solid recovered fuels (SRFs) with a high calorific value.

An investigation of the global uptake of CO2 by lime from 1930 to 2020

Abstract. A substantial amount of CO2 is released into the atmosphere from the process of the high-temperature decomposition of limestone to produce lime. However, during the lifecycle of lime production, the alkaline components of lime will continuously absorb CO2 from the atmosphere during use and waste disposal. Here, we adopt an analytical model describing the carbonation process to obtain regional and global estimates of carbon uptake from 1930 to 2020 using lime lifecycle use-based material data. The results reveal that the global uptake of CO2 by lime increased from 9.16 Mt C yr−1 (95 % confidence interval, CI: 1.84–18.76 Mt C) in 1930 to 34.84 Mt C yr−1 (95 % CI: 23.50–49.81 Mt C) in 2020. Cumulatively, approximately 1444.70 Mt C (95 % CI: 1016.24–1961.05 Mt C) was sequestered by lime produced between 1930 and 2020, corresponding to 38.83 % of the process emissions during the same period, mainly contributed from the utilization stage (76.21 % of the total uptake). We also fitted the missing lime output data of China from 1930 to 2001, thus compensating for the lack of China's lime production (cumulative 7023.30 Mt) and underestimation of its carbon uptake (467.85 Mt C) in the international data. Since 1930, lime-based materials in China have accounted for the largest proportion (about 63.95 %) of the global total. Our results provide data to support including lime carbon uptake into global carbon budgets and scientific proof for further research of the potential of lime-containing materials in carbon capture and storage. The data utilized in the present study can be accessed at https://doi.org/10.5281/zenodo.7896106 (Ma et al., 2023).

Urban PM2.5 concentrations in a small Colombian city and the impact associated with particle emissions generated by small-scale lime production

The stricter guidelines for fine particles PM2.5 recently published by the World Health Organization also motivate smaller cities to assess the exposure levels. In this study, PM2.5 was assessed in the municipality of Vijes, an important lime production center in the Cauca River Valley, Colombia. The main objective was to determine PM2.5 concentration levels in the urban background of the city and to estimate the contribution from industrial sources located west of the urbanized area. The assessment of PM2.5 concentrations in a city without fixed air quality monitors, meteorological stations, and information on emission sources, was designed to be expedient and possible to perform with a very restricted budget. Four low-cost optical sensors and one low-cost meteorological station were installed during two separate campaigns, each three to four months long. The PM2.5 measurements were analyzed with the support of meteorological data and dispersion modeling. Mean levels of PM2.5 in the urban background were found to be below the Colombian limit value of 25 µg m–3, in the range of 14 to 19 µg m–3, and with lower levels in the city center. The monitor located in the westernmost urban area, closest to the industrial plants, registered a high 24-h mean level close to the national limit value. The industrial contribution to long-term PM2.5 concentrations in the urban background of Vijes was estimated to be within a maximum of 6 µg m–3, i.e., a minor fraction of the monitored PM2.5 mean levels in the urban background. The dominating part of the PM2.5 concentrations could be attributed to other anthropogenic sources within or east of Vijes, as well as originating from the regional background concentration characterizing the Cauca River Valley to the east of Vijes, where pre-harvest sugar cane burning is common.