|from Pete Smith, Global potential and impacts of terrestrial carbon sequestration measures (2017)|
"We allow no reduction in existing cropland area, but we assume grazing lands in forested ecoregions can be reforested, consistent with agricultural intensification and diet change scenarios. This maximum value is also constrained by excluding activities that would either negatively impact biodiversity (e.g., replacing native nonforest ecosystems with forests) or have carbon benefits that are offset by net biophysical warming (e.g., albedo effects from expansion of boreal forests). We avoid double-counting among pathways."
The DAC process starts with a “wet scrubbing” air contactor which uses a strong hydroxide solution to capture CO2 and convert it into carbonate. This occurs within an air contactor structure modelled on industrial cooling tower design, which effectively contains the liquid hydroxide solution. Our second step is called a “pellet reactor” which precipitates small pellets of calcium carbonate from the aqueous carbonate solution. This calcium carbonate, once dried, is then processed in our third step, a circulating fluid bed calciner, which heats it to decomposition temperature, breaking it apart into CO2 and residual calcium oxide. The calcium oxide is hydrated with our make-up water stream in our fourth step, called a slaker, and is returned into the pellet reactor to precipitate calcium carbonate, and close the chemical loop.
Pozzolanic reaction of volcanic ash with hydrated lime is thought to dominate the cementing fabric and durability of 2000-year-old Roman harbor concrete. Pliny the Elder, however, in first century CE emphasized rock-like cementitious processes involving volcanic ash (pulvis) “that as soon as it comes into contact with the waves of the sea and is submerged becomes a single stone mass (fierem unum lapidem), impregnable to the waves and every day stronger” (Naturalis Historia 35.166). Pozzolanic crystallization of Al-tobermorite, a rare, hydrothermal, calcium-silicate-hydrate mineral with cation exchange capabilities, has been previously recognized in relict lime clasts of the concrete. Synchrotron-based X-ray microdiffraction maps of cementitious microstructures in Baianus Sinus and Portus Neronis submarine breakwaters and a Portus Cosanus subaerial pier now reveal that Al-tobermorite also occurs in the leached perimeters of feldspar fragments, zeolitized pumice vesicles, and in situ phillipsite fabrics in relict pores. Production of alkaline pore fluids through dissolution-precipitation, cation-exchange and/or carbonation reactions with Campi Flegrei ash components, similar to processes in altered trachytic and basaltic tuffs, created multiple pathways to post-pozzolanic phillipsite and Al-tobermorite crystallization at ambient seawater and surface temperatures. Long-term chemical resilience of the concrete evidently relied on water-rock interactions, as Pliny the Elder inferred. Raman spectroscopic analyses of Baianus Sinus Al-tobermorite in diverse microstructural environments indicate a cross-linked structure with Al3+ substitution for Si4+ in Q3 tetrahedral sites, and suggest coupled [Al3++Na+] substitution and potential for cation exchange. The mineral fabrics provide a geoarchaeological prototype for developing cementitious processes through low-temperature rock-fluid interactions, subsequent to an initial phase of reaction with lime that defines the activity of natural pozzolans. These processes have relevance to carbonation reactions in storage reservoirs for CO2 in pyroclastic rocks, production of alkali-activated mineral cements in maritime concretes, and regenerative cementitious resilience in waste encapsulations using natural volcanic pozzolans.
|Deer Lake peroditite with traces of magnetite|
Woolf et al, 2010, Nature Communications 1, 56
We use a commercially viable process of rapid carbonization to convert biomass into a copy of fossil fuels; in a process that mimics natural processes — but “measured in minutes instead of millions of years”. The technology has been tested on industrial scale and the proven process is ready for global deployment.
|"The Most Comprehensive Plan Ever Proposed to Reverse Global Warming"|