The present disclosure provides systems and methods that combine direct capture of one or more moieties from a gaseous mixture with one or both of calcium oxide production and power production. The systems and methods can utilize combinations of a capture unit, a regeneration unit, a calcination unit, a slaking unit, a heat exchange unit, a separation unit, and a power production unit. The present disclosure provides the ability to remove carbon dioxide and other moieties from air or other gaseous mixtures in a truly carbon negative manner by utilizing electricity from a power production unit that is operated in a carbon neutral or carbon negative manner and simultaneously provide useful products, such as calcium oxide and calcium hydroxide.

The invention relates to a plant for generating negative emissions of CO.sub.2. The plant 100 comprises a gasifier 110, a lime kiln 130, a separator 150, and a CO.sub.2 permanent storage 170. The gasifier is suitable for receiving as input a fuel 111 and for producing as output a high-temperature syngas flow 114. The lime kiln is suitable for receiving as input carbonate mineral 131 and the high-temperature syngas flow, the lime kiln being further suitable for producing an oxide 134 and for releasing as output a flow of syngas 133 enriched with CO.sub.2. The separator is suitable for receiving as input a gas flow containing CO.sub.2 and for treating it so as to separately provide at least CO.sub.2 151. The CO.sub.2 permanent storage is suitable for enclosing along time the CO.sub.2. The invention also relates to a method for generating negative emissions of CO.sub.2.

Cement and concrete compositions are produced via metal hydroxides and metal oxides isolated from aqueous sources such as seawater or wastewater. Aqueous solutions are electrolyzed to produce an alkaline component stream having an elevated pH, which when mixed with mineralized seawater causes metal ions dissolved therein to precipitate out in the form of metal hydroxides such as Mg(OH).sub.2 and Ca(OH).sub.2. These metal hydroxide products are then utilized as feedstocks for production of cement and concrete structural elements, or are converted to metal oxides suitable for the same purpose. The hydroxide products are then subjected to pressure and prolonged exposure to carbon dioxide to accelerate carbonation of the hydrated product. The resulting carbonates exhibit sufficient compressive strength for use in making structural components for construction, while reducing or eliminating the carbon footprint associated with traditional methods of cement and concrete manufacturing. Excess demineralized alkaline component can be recycled for additional electrolysis, or returned to a neutral pH for use in water desalination processes or even returned to the environment.

A process and apparatus for manufacture of biocide products are described. The biocide properties arise from the caustic calcined powder, from carbonates such as such as magnesite and dolomite, and from hydroxides such as brucite. The method of manufacture is based on the production of high surface area oxide particles using an indirectly heated counterflow reactors for specifically calcining the carbonates and the hydroxides without significant sintering. The biocide products may be a powder or a hydrated slurry. A hydrated slurry is preferred for agricultural applications as a spray. For aquaculture applications, the products have a preferred particle size distribution to impact the aquatic and benthic ecosystems, and a Ca/Mg ratio that promotes the growth of the cultivates species when applied as a powder or a slurry. For applications such as a marine paint, the powder product or the slurry product is mixed with various agents to form a setting coating, and is applied to the infrastructure that is otherwise subject to biofilm growth.

A process and apparatus for manufacture of biocide products are described. The biocide properties arise from the caustic calcined powder, from carbonates such as such as magnesite and dolomite, and from hydroxides such as brucite. The method of manufacture is based on the production of high surface area oxide particles using an indirectly heated counterflow reactors for specifically calcining the carbonates and the hydroxides without significant sintering. The biocide products may be a powder or a hydrated slurry. A hydrated slurry is preferred for agricultural applications as a spray. For aquaculture applications, the products have a preferred particle size distribution to impact the aquatic and benthic ecosystems, and a Ca/Mg ratio that promotes the growth of the cultivates species when applied as a powder or a slurry. For applications such as a marine paint, the powder product or the slurry product is mixed with various agents to form a setting coating, and is applied to the infrastructure that is otherwise subject to biofilm growth.

Disclosed are a method for separately preparing light magnesium oxide and calcium oxide by using dolomite and an application thereof in preparation of a calcium-magnesium composite expanding agent. In the method for preparing light magnesium oxide and calcium oxide, based on the difference in decomposition temperature between magnesium carbonate and calcium carbonate during the calcination and decomposition of dolomite and the difference in the weight of the materials after decomposition, the effective separation of magnesium oxide and calcium oxide is realized by a one-step method, thus separately preparing light magnesium oxide and light calcium oxide. The calcium-magnesium composite expanding agent is prepared by using the foregoing light magnesium oxide and calcium oxide. On the one hand, the present invention solves the problem of the limited origin of the light magnesium oxide raw material of the magnesium expanding component in the calcium-magnesium composite expanding agent.

Admixture for cementitious building materials can provide a self-healing mechanism to improve material longevity. In certain embodiments, the admixture can include the combination of both a quicklime-based replacement for fine and coarse aggregates and an SCM replacement for OPC in standard mortar and concrete.

Admixture for cementitious building materials can provide a self-healing mechanism to improve material longevity. In certain embodiments, the admixture can include the combination of both a quicklime-based replacement for fine and coarse aggregates and an SCM replacement for OPC in standard mortar and concrete.

Aspects of the invention include a method of producing a cement material comprising step of: first reacting a calcium-bearing starting material with a first acid to produce an aqueous first calcium salt; second reacting the aqueous first calcium salt with a second acid to produce a solid second calcium salt; wherein the second acid is different from the first acid and the second calcium salt is different from the first calcium salt; and thermally treating the second calcium salt to produce a first cement material. Preferably, but not necessarily, during the second reacting step, reaction between the first calcium salt and the second acid regenerates the first acid.

Provided herein are methods comprising a) calcining limestone in a cement plant to form carbon dioxide and calcium compound selected from calcium oxide, calcium hydroxide, or combination thereof; b) treating the calcium compound with N-containing salt in water to produce an aqueous solution comprising calcium salt and N-containing salt; and c) contacting the aqueous solution with the carbon dioxide under one or more precipitation conditions to produce a precipitation material comprising calcium carbonate and a supernatant aqueous solution wherein the calcium carbonate comprises vaterite.