Closing the loop
on emissions

In the controlled environment of a laboratory, the use of a TOC-L analyzer makes it possible to evaluate the uptake of carbon dioxide by microbial metabolism. The initial amount of CO₂ introduced into the closed bacterial culture medium was precisely measured by TIC analysis. The experiment was then meticulously replicated after 3 and 24 hours, allowing accurate quantification of the carbon used to increase microbial biomass (Table 1). This detailed approach provides valuable insights into the dynamics of microbial carbon utilization.

Notably, this natural process showcases the inherent ability of microorganisms to actively capture and utilize carbon dioxide. Within a span of 24 hours, an amount of approximately 5 g CO₂ per liter of medium could be effectively bound, all the while producing valuable biomass that could be processed into biofuel or other valuable feedstock. The biomass produced can be accurately measured as well using TOC analysis. This allows researchers to precisely quantify the organic carbon content, providing a comprehensive understanding of the microbial biomass generated during the process.

Building materials against climate change: carbon-sequestering concrete

Cement production is a significant source of CO₂ emissions (approximately 4.5 % of global emissions [1]), contributing to the greenhouse effect and global warming. CO₂ is released during the cement manufacturing process when limestone, a key component of cement, is heated to high temperatures in a kiln to producing clinker. Subsequently, when concrete is produced by mixing cement, water and aggregates, additional CO₂ is released as the cement undergoes hydration and hardens.

Carbon-sequestering concrete is a specialized form of concrete that actively captures and stores CO₂ during its curing process. This innovative approach involves incorporating materials that react with CO₂, such as certain mineral additives, into the concrete mix. As the concrete cures, these materials react with atmospheric CO₂ and convert it into a mineral form, effectively storing the carbon within the concrete structure.

TIC analysis is used to evaluate the carbon sequestration capabilities of this concrete. While other methods such as thermal analysis or titration of a hydrochloric acid solution can also be used, they require significant time and effort and can only measure small sample quantities, leading to biased results due to uneven sample distribution. Using the TOC-L with the solid sample measurement system SSM-5000A, milled and dried concrete samples can be analyzed quickly, easily and accurately by simply weighing them into a sample boat for analysis.

In an experiment (Table 2), two types of concrete samples were examined: ordinary concrete and CO₂-sequestering concrete. The samples were ground into powder, and 50 mg of each were weighed into sample boats. Phosphoric acid was dripped onto the samples, and the inorganic carbon (IC) content was measured in the SSM-5000A solid sampling module. The CO₂-sequestering concrete showed about up to five times higher CO₂ absorbing potential than the ordinary concrete, highlighting its effective CO₂ absorption capability.

DACCS: Direct Air Carbon Capture and Storage

While efforts to reduce emissions by binding CO₂ in products are commendable, they alone may not achieve negative emissions. Direct air carbon capture and sequestration (DACCS) technology, which is still in development, may offer an innovative way to actively remove carbon from the atmosphere and safely store it as stable carbonate rock. The integration of an online total organic carbon (TOC) analyzer provides valuable information on various process steps. It continuously monitors the TOC and TIC content of the DAC fluid before injection into an underground storage site, ensuring that any organic or inorganic impurities are accounted for. This facilitates accurate carbon accounting and evaluation of the overall carbon sequestration process.

The process begins with direct air capture (DAC) technology, which uses specialized equipment to extract CO₂ directly from the air. After purification to meet storage standards, the compressed gas is transported to the designated site. There, it is injected into underground rock formations using pumped-up groundwater or seawater. The CO₂ is dissolved in the carbonated water, recombines with minerals and over months forms pockets of carbonate rock within the porous basalt that are stable for geologic timespans. Subsurface injection with water eliminates the risk of gas leakage and provides safe long-term carbon storage. Other methods under development involve injecting gaseous CO₂ or supercritical fluid into suitable storage sites, such as saline aquifers or depleted oil and gas reservoirs.

With the ability to quantify both organic and inorganic carbon sources, TOC analyzers facilitate the advancement of effective negative emission technologies (NETs) that mimic natural carbon sequestration mechanisms. They provide invaluable insight into carbon dynamics and play a key role in achieving carbon neutrality by evaluating the efficiency of carbon-sequestering materials like concrete. Analyzers with TIC analysis capability, like the TOC-L and TOC-4200, are important in the development and implementation of carbon sequestration and emerging technologies like direct air carbon capture and sequestration (DACCS). By enabling complete accounting of the flow of carbon through TOC/TIC analysis, these analyzers contribute significantly to the creation of a sustainable future. They provide a comprehensive understanding and quantification of carbon dynamics in these processes, thus paving the way for effective carbon management and a greener planet.