Provided herein are methods and systems to form calcium carbonate comprising vaterite, comprising dissolving lime in an aqueous base solution under one or more precipitation conditions to produce a precipitation material comprising calcium carbonate and a supernatant solution, wherein the calcium carbonate comprises vaterite.

A process of sequestering CO.sub.2 is generally described. The process involves the use of geopolymeric precursors to which the CO.sub.2 is added. The process for a solid, cementitious material comprising geopolymer(s) and CO.sub.2.

A CO.sub.2 separation/recover method in cement production exhaust gas has a step of harmful component removal that removes an acidic component and a harmful component from exhaust gas discharged from a cement production facility; and a step of CO.sub.2 separation and recover that separates and recovers CO.sub.2 by bringing the exhaust gas from which the acidic component and the harmful component are removed into contact with a CO.sub.2 absorption material, so that the acidic component and the harmful component are removed before separating and recovering CO.sub.2, resulting in deterioration of the absorbing ability of the CO.sub.2 absorption material being suppressed; and the cement production exhaust gas can be appropriately disposed.

Apparatus and methods for curing composite compositions that react with CO.sub.2. The apparatus in general includes an easily transportable and easily assembled curing structure, such as a plastic sheet housing supported by gas pressure and/or by mechanical supports. Apparatus for providing reagent CO.sub.2, for measuring water content and for removing water, and for controlling temperature, flow rates and flow directions through the curing structure. Examples of curing procedures and examples of cured materials in desired shapes are described.

The invention relates to a method for obtaining a mineral substance from a base comprising mineral matter, the method comprising obtaining the base comprising a predetermined quantity of the mineral matter synthesised by a living structure or a portion of the latter, characterised in that obtaining the base comprises providing the living structure and providing at least one lactic acid microorganism suitable for symbiosis with the living structure for the synthesis of the mineral matter of the mineral substance. The invention also relates to a mineralising composition comprising a living structure, a lactic acid microorganism, a nutritive substance; the mineral substance used in the method; and the use of a combination of a living structure and a lactic acid microorganism in symbiosis with each other as a mineralising agent in a self-regenerating material.

Methods for preparing a carbonated supplementary cementitious materials, including semi-wet carbonation, cyclic carbonation, non-slurry carbonation, high temperature carbonation and/or granular carbonation of a carbonatable material.

The disclosure provides a method and a system for processing concrete granulate for subsequent recycling of the concrete granulate. In the method, a container of the system is filled with concrete granulate, said container being gas-tight at least in some regions. Subsequently, gas comprising CO2 is fed, continuously or noncontinously, according to a level of CO2 absorption by the concrete granulate in the container, said level being determined by means of at least one sensor. After a predefined CO2 saturation of the concrete granulate has been detected, the concrete granulate, which have been enriched with CO2, are removed.

Generating methane by adding hydrogen to CO.sub.2 in exhaust gas discharged a from cement production facility or CO.sub.2 that is separated and recovered from the exhaust gas, and using the methane as an alternative fuel to fossil fuel such as coal, petroleum, natural gas and the like, by methanation of CO.sub.2 in the exhaust gas from the cement production facility that includes exhaust gas originated from lime stone not from the fossil oil and effectively utilizing it, it is possible to reduce usage of the fossil fuel, suppress CO.sub.2 originated from energy, and improve an effect of reducing greenhouse gas.

Divalent ions are extracted from solids by leaching to form a divalent ion-containing solution. The divalent ion-containing solution is subjected to concentration to form a concentrated divalent ion-containing solution. Precipitation of a divalent ion hydroxide salt is induced from the concentrated divalent ion-containing solution. In other cases, the concentrated divalent ion-containing solution is exposed to carbon dioxide to induce precipitation of a divalent ion carbonate salt.

A method and system for producing nano-active powder materials. The method can be used with a reactor system comprising stages in which input particles flow under gravity progressively through stages of the reactor. A powder injector first stage in which ground input precursor powder is injected into the reactor. An externally heated preheater stage may be in the reactor, in which the precursor powder is heated to a temperature of calcination reaction. An externally heated calciner stage in the reactor, in which primary precursor volatile constituents can be rapidly removed calcination reactions as a high purity gas stream to produce the desired nano-active product. A post-processing reactor stage in which there is a change of the gas stream composition to produce the desired hot powder product by virtue of the nano-activity of the first powder material. A powder ejector stage in which the hot powder product is ejected from the reactor.