Practical and Thermodynamic Constraints on Electromicrobially-Accelerated CO2 Mineralization

By the end of the century tens of gigatonnes of CO2 will need to be removed from the atmosphere every year to maintain global temperatures. Natural weathering of ultramafic rocks and subsequent mineralization reactions can convert atmospheric CO2 into ultra-stable carbonates. But, while natural weathering will eventually draw down all excess CO2, this process will need hundreds of thousands of years to do it. The CO2 mineralization process could be accelerated by weathering ultramafic rocks with biodegradable lixiviants like organic acids. But, in this article we show that if these lixiviants are produced from cellulosic biomass, the demand created by CO2 mineralization could monopolize the world's supply of biomass even if CO2 mineralization performance is high. In this article we demonstrate that electromicrobial production technologies that (EMP) combine renewable electricity and microbial metabolism could produce lixiviants for as little as $200 to $400 per tonne at solar electricity prices achievable within the decade. Furthermore, this allows the lixiviants needed to sequester a tonne of CO2 to produced for less than $100, even with modest CO2 mineralization performance.

Electrophoresis-Aided Biomimetic Mineralization System Using Graphene Oxide for Regeneration of Hydroxyapatite on Dentin

Graphene oxide (GO) is an emerging luminescent carbon nanomaterial with the ability to foster hydroxyapatite (HA). A specially designed electrophoresis system can be used to accelerate the mineralization process. The aim of this study was to promote HA crystal growth on demineralized dentin using a GO incorporated electrophoresis system. GO was successfully synthesized by carbonization of citric acid and its presence was confirmed by Fourier transform infrared and UV-visible spectrophotometry evaluation. Dentin slices were placed in demineralized solution and divided into control (without the electrophoresis system) and experimental group. Demineralized dentin slices in the experimental group were remineralized using the electrophoresis system for 8 h/1.0 mA, with one subgroup treated without GO and the other with GO. Energy dispersive spectroscopy evaluation showed that the calcium/phosphate ratio of the crystal formed in control and experimental group with addition of GO was close to natural hydroxyapatite. However, scanning electron microscopy evaluation showed that the exposed dentinal tubules were occluded with rod-like crystals, which is similar to native enamel morphology, in the experimental group with addition of GO compared to the flake-like crystal in the control group. Mechanical evaluation revealed that the nanohardness and modulus of remineralized dentin were significantly higher in the experimental group. In conclusion, GO is a promising material to remineralize dentin and the introduction of an electrophoresis system can accelerate its process.

Mineralization of residue from the drying of black pepper when applied to the soil

The use of residues from the black pepper bean drying process as fertilizer for agricultural crops implies the need to know the dynamics of their decomposition and release of the nutrients to guide it’s management, especially regarding the best time of its application in the soil. This study aimed to evaluate the dynamics of organic carbon and nitrogen during the mineralization process of this residue. The experiment was conducted in a completely randomized design with ten treatments related to different post-disposal periods to the soil (0, 7, 13, 20, 27, 34, 48, 69, 98, 147 days). Samples were collected to quantify easily oxidized organic carbon (OCeo), organic nitrogen (ON) and the determinations of their respective mineralized fractions. The evaluation of OCeo mineralization, being more stable and less susceptible to climatic variations, was the most appropriate for estimating the mineralized fraction of the residue. The application of the residue in dystrophic Yellow Red Latosol soil during the month of August provides, after 140 days, OCeo and ON mineralized fractions around 99 and 60%, respectively, in the climatic conditions of Espirito Santo state, Brazil.

Geochemical and Mineralogical Characteristics of Garnierite From the Morowali Ni-Laterite Deposit in Sulawesi, Indonesia

The Morowali Ni-laterite deposit is located in the East Sulawesi Ophiolite, which is a large ophiolite belt on Sulawesi Island, Indonesia. The Morowali deposit is developed on a laterite profile due to ophiolite weathering, with saprolite, limonite, and ferruginous cap horizons from the bottom to top. Based on the occurrence of garnierite as the main ore, occurring in the saprolite horizon, it can be classified that the ore deposit is hydrous Mg silicate-type. The Ni ore is classified into different types based on color and XRD and electron probe micro-analyzer analyses. Whole-rock geochemical study was also conducted to understand the mineralization process. The Morowali Ni deposit consists of serpentine-like and talc-like phases. The serpentine-like phase consists of Ni-lizardite and karpinskite (0.76–38.26 wt% NiO) while the talc-like phase is mainly composed of kerolite (4.02–8.02 wt% NiO). The serpentine-like garnierite exhibits high Ni and Fe contents and occurrence similar to that of the serpentine observed in the saprolite horizon, suggesting the serpentine-like garnierite originated from the bedrock, and Mg-Ni cation exchange occurred during laterization. Contrastingly, the lower Fe content of the talc-like phase (0.01–0.05 wt%) than the serpentine-like phase (0.14–7.03 wt%) indicates that the talc-like garnierite is of secondary origin since Fe is immobile during weathering. The Morowali Ni-laterite deposit was mainly formed during laterization. The repetition of dry and wet cycles in each year results in the formation of secondary garnierite.

Prospective Life Cycle Assessment at Early Stage of Product Development: Application to Nickel Slag Valorization Into Cement for the Construction Sector

Pyrometallurgical nickel industry in New Caledonia produces several tons of slag per year, which is stocked on site. There is no valorization today, except for a small transformation into sand. Pyrometallurgy highly consumes fossil-fuel energy and electricity for ore pre-treatment and nickel extraction inside electrical furnaces, which produces significant CO2 emissions. A new valorization approach is suggested to use these two local productions (slag and CO2) to mineralize slag and produce silico-magnesian cement for the construction sector. In order to ensure suitable environmental performances, many questions arise about the target valorized product: where and how to capture CO2 and produce cement, what constraints should be targeted for the mineralization process, can products be exported and where? Moreover, New Caledonia aims to develop renewable energies for electricity grid, which would mitigate local industries impacts in the future. A prospective Life Cycle Assessment (LCA) is used to define constraints on future product development. Two hundred scenarios are defined and compared as well as electricity grid evolution, using Brightway software. Thirteen scenarios can compete with traditional Portland cement for 12 of the 16 impacts of the ILCD midpoint method. The evolution of electricity grid slightly affects the performance of the scenarios by a mean of less than+/−25%, bringing a small difference on the number of acceptable scenarios. The main constraint requires improving the mineralization process by considerably reducing electricity consumption of the attrition-leaching operation. To be in line with scenarios concerning carbon neutrality of the cement industry by 2050, a sensitivity analysis provides the maximum energy consumption target for the mineralization process that is 0.9100 kWh/kg of carbonated slag, representing a 70% reduction of the current energy measured at lab scale. Valorization of nickel slag and CO2 should turn to carbon capture and utilization technology, which allows for the production of supplementary cementitious materials, another product for the construction sector. It will be the topic of a next prospective study.

Alkaline phosphatase activity present in serum influences osteogenic differentiation cultures

Fetal bovine serum (FBS) is a widely used supplement in cell culture medium, despite its known variability in composition which greatly affects cellular function and consequently the outcome of studies. In bone tissue engineering, the deposited mineralized matrix is one of the main outcome parameters, but using different brands of FBS can result in large variations. Alkaline phosphatase (ALP) is present in FBS. Not only is ALP used to judge the osteogenic differentiation of bone cells, it may affect deposition of mineralized matrix. The present study focused on the enzymatic activity of ALP in FBS of different suppliers and its contribution to mineralization in osteogenic differentiation cultures. It was hypothesized that culturing cells in a medium with high intrinsic ALP activity of FBS will lead to higher mineral deposition compared to media with lower ALP activity. The used FBS types were shown to have significant differences in enzymatic ALP activity. Our results indicate that the ALP activity of the medium not only affected the deposited mineralized matrix but also the osteogenic differentiation of cells as measured by a changed cellular ALP activity of human bone marrow derived mesenchymal stromal cells (hBMSC). In media with low inherent ALP activity, the cellular ALP activity was increased and played the major role in the mineralization process; while, in media with high intrinsic ALP activity contribution from the serum, less cellular ALP activity was measured and the ALP activity of the medium also contributed to mineral formation substantially. Our results highlight the diverse effects of ALP activity intrinsic to FBS on osteogenic differentiation and matrix mineralization and how FBS can determine the experimental outcomes, in particular for studies investigating matrix mineralization. Once again, the need to replace FBS with more controlled and known additives is highlighted.