Saturday, August 11, 2018

Carbon Capture: Other Types of Sorbents

A previous post discussed temperature swing adsorption, wherein carbon dioxide is captured when the sorbent is at low temperature and released when raised to sufficiently high temperature. Desorption temperatures of five to seven hundred degrees Celsius are typical with known sorbents, imposing a substantial energy cost to heat and cool the material.

There are other sorbent materials where the capture and release cycle is controlled not be temperature but by other factors. The two most common are:

  • pressure-swing, where adsorption is controlled by the pressure of the gases in the process. In one study, activated carbon was used as the sorbent to capture carbon dioxide.
  • moisture-swing, where the presence of water or water vapor controls the adsorption cycle. A great deal of recent work on moisture swing sorbents for carbon dioxide has been done at the Arizona State University, apparently focused on a Metal Oxide Framework material containing zirconium.

The goal with both of these technologies is for a carbon dioxide removal process requiring less energy than for temperature swing adsorption. The Temperature Swing Adsorption processes are much further along in development, with several commercial carbon capture systems (detailed in the earlier post). Pressure Swing Adsorption is used to scrub CO2 in high-oxygen feeds like for hospitals, but is not currently used at scale for carbon capture from the atmosphere. So far as I can tell, Moisture Swing Adsorption has thus far only been used in the lab and small scale trials.

Friday, August 10, 2018

Flatulenating, Wherein We Attempt to Rectify a Dictionaric Injustice

Flatulenating: having the property of inducing flatulence.

Example: "Beans are flatulenating. I get such terrible gas every time I eat them."



At the time of this writing on August 10th, 2018,"flatulenating" shows zero results. This blog post is an attempt to resolve this dictionaric injustice.

Wednesday, August 1, 2018

Career & Interviewing Help

Something I find rewarding is helping others in their careers. I am quite happy to conduct practice embedded software engineer or manager interviews, answer questions about engineering at Google or in general, advise on career planning, etc.

I keep a bookable calendar with two timeslots per week. I am in the Pacific timezone, and can set up special times more convenient for people in timezones far from my own. If the calendar doesn't work for you, you can contact me at to make special arrangements.

Anyone is welcome, you don't need an intro or to know me in person. The sessions are conducted via Google Hangout or by phone. My only request for this is to pay it forward: we all have opportunities to help others. Every time we do so, we make the world a slightly better place.

Sunday, July 29, 2018

Carbon Capture: Ocean Farming

The ocean has absorbed approximately a third of the extra carbon released since the industrial age. A previous article focused on countering acidification of the ocean either directly by adding massive quantities of alkalines or indirectly by adding minerals to encourage phytoplankton growth. This post discusses a more purposeful effort, using the carbon in the ocean to grow plant life which can be used for other purposes.

Much discussion about ocean farming revolves around kelp, for several reasons:

  1. Kelp propogates amazingly quickly, growing up to a foot in a single day in ideal conditions.
  2. Profitable uses for kelp already exist as a food source for humans and in animal feed. Additional uses by processing kelp into biofuel or as feedstock for other chemical processes appear to be feasible.

Despite its tremendous growth rate, kelp in nature is confined to a relatively small portion of the ocean: it has to anchor itself to the sea floor and take up nutrients present in deeper waters, but must be able to reach the surface to photosynthesize. Therefore, natural kelp only grows near coastlines and islands.

Several startups aim to vastly increase the capacity of the ocean to grow kelp by providing the conditions which the plant requires:

  • The Climate Foundation proposes to build Marine Permaculture Arrays stationed about 25 meters below the surface, to provide a point of attachment for kelp. Pumps powered by solar or wave energy would draw water from the depths, providing an artificial upwelling to provide nutrients for the kelp and plankton.
  • Marine BioEnergy proposes robotic submarine platforms which would descend to depths overnight to allow the kelp to take up minerals and nutrients, then ascend close to the surface during the day to allow the plants access to sunlight. The platforms would also be mobile, periodically returning close to shore to allow harvest of the grown kelp and any needed maintenance and replenishment of the platform.
  • GreenWave has developed a training program, legal permitting assistance, and market development for ocean farmers, along with optimized layout for a kelp farm. The plans appear to be for coastal farms, not involving deep water platforms nor extensive automation like the earlier firms.

The major food crops like soybeans, wheat, corn, and rice have been tremendously modified from their original forms. As we develop uses for kelp as feedstock in the production of fuels or chemicals or other uses, it is likely that the specific kelp population can be bred to better fit the applications.

Carbon Capture: Ocean Acidification Remediation

The ocean has absorbed approximately a third of the extra carbon released since the industrial age. When carbon dioxide is absorbed by seawater it becomes carbonic acid, leading to the gradual acidification of the oceans.

There are several methods proposed by which the carbon stored in the ocean can be more rapidly sequestered, reducing carbonic acid levels (though the ocean would promptly take up more carbon from the atmosphere):

  • alkalinization: to counteract the carbonic acid by adding huge quantities of alkalines to the ocean, such as bicarbonate. Quite usefully, bicarbonate is one of the bi-products of large scale enhanced weathering, which also appears to be quite promising as a mechanism to remove carbon from air.
  • fertilization: the carbonization of the oceans could be addressed by encouraging phytoplankton to grow, which would take up carbon from the water. Different parts of the ocean contain phosphorous, nitrogen, and iron in differing amounts. There are large dead zones in the ocean where plankton and algae grow is stalled due to lack of the needed minerals, not lack of food energy to support them. By adding these three minerals in the correct ratio, phytoplankton will be enabled to consume more carbon.
  • circulation: encourage movement of acidic water from near the surface to the deeper ocean where mineralization processes can absorb it. Ocean-based Climate Solutions, Inc has a description of the mechanism to do this.

The main issue with these ideas is that they are not self-funding, they do not produce an output which can be used to generate revenue to continue the effort. These kinds of projects would depend on massive external support, as by governments or the (very) wealthy.