Carbon Capture in the City by mcrone

Interesting idea ! You may want to do some more research into how they store CO2 (if at all), and what happens at night, when they don't photosynthesize. For example, trees store CO2 as long as they're alive, and they release it when they die and decay. And then additional research and development would be required to actually turn this into a building product, that may be usable in at least some parts of the world. Cheers !..

An interesting paper on a cyanabacterial CO2 sequestration mechanism freely available for PLoSone: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0071581

More updates will definitely be added soon (as soon as I have some more time to research it more thoroughly). Interestingly, at night cyanobacteria fix nitrogen and can release hydrogen. This actually makes them a very good source for fertiliser when the biomass outgrows the available medium. There is the possibility the the provision of light may a little unrealistic as they produce very little light (which is why I have looked into dinoflagellates for supplying flashes of light which could be useful in advertising and art). I think that realistically they are far better at carbon sequestration (about 7 liters of culture sequesters the same amount of carbon as one tree [I have to redo the calculations though before I add it to the proposal]). This is an extraordinarily large amount of carbon dioxide that can be sequestered. Another advantage is that these bacteria can be engineered or optimised to produce other products.

I want to encourage you to keep promoting this concept. Just as bacteria are incredibly prolific and important in ways we are just beginning to understand your research and the support of similar projects could become THE viable solution to resource depletion, emissions sequestration and photosynthetic fuel sources. I agree with Gunesh and others that more details are needed, but the proposal is excellent.

Traditional bioreactors are designed for other functions, not primarily to fix carbon. This system is primarily designed to fix carbon, with the added benefit that bacteria can be engineered for other functions (like biofuel and pharmaceutical production). The idea is to make this as closed as possible so that it remains sterile (to prevent the overgrowth of other bacterial species). This would actually be ensured through a few mechanisms. (1) is the design of the actual incubator, the polyurethane bag allows for a sterile culture once and then it can be discarded, the incubator in an urban setting is more complicated, but could be adequately sealed and (2) the alkalinity of the medium ensures that pretty much only the cyanobacteria can grow (some people actually grow spirulina at home as a source of food and this alkalinity ensures the safety of that) and (3) the specific medium required would limit the growth outside of the bioreactor environment.

Thank you for your feedback saravanan. In response to your questions: (1) The function is relatively limited to mitigation of CO2 emissions. It decreases the net emissions of CO2 rather than directly affecting CO2 emissions. Reactors could in future be incorporated into the outside walls of buildings, allowing for an insulating effect of the medium. (2) The carbon will be sequestered in the form of biomass in this example. This would be no more complicated that cleaning leaves off of a sidewalk in the long run and in fact would probably be simpler. This technique is essentially similar to Iron fertilisation of marine water (encouraging phytoplankton to grow and sequester carbon) which is recognised as a way to remove carbon from the atmosphere for a period of time, although the long term effects are not known at this point. [http://www-formal.stanford.edu/pub/jmc/progress/iron/iron.html] (3) I agree that logistically the hydrogen part does not make sense at this point. That is used merely as an example of how bacteria can be engineered for additional functions. Small multiple reactors are suggested to replace trees in urban settings. It is far easier to house a bioreactor than 360 trees. This individual effort may have little effect compared to large forests, however, if it is implemented on a large scale it could be more beneficial (and additional products can be produced). The greater the adoption the more logistical sense it would make to collect the products produced by the bioreactors.

Novelty: 3/5 Small-scale cultivation of cyanobacteria in bioreactors is not particularly novel. Workability: 3/5 Relatively easy to create a prototype, but scalability of the technology is much more challenging. Effectiveness: 2/5 Climate impacts will depend on life-cycle of the biomass produced, which is not considered in detail in the proposal. Additional focus on the usage of the biomass (for biofuel or fertilizer) would strengthen the proposal. Emphasis on the biomass production is understandable, but the proposal needs a description of the context and rationale for the production technology. Overall net benefits may be questionable, considering embodied energy, nutrient provision, biomass drying, pH adjustment, etc. Thoroughness: 3/5 Not very clear what is proposed to do and when. What specific actions will be taken, who will take them, and when? The various component costs should be summed and a total proposed cost should be indicated. The time line should be elaborated on—what does “short term” mean? Presentation: 3/5 OK generally, but lacking in several key areas (biomass usage, proposed activities, costs). The proposal hasn’t made a compelling case that this will lead to benefits. --- (1) It is a very complete list of items that are addressed in this presentation. (2) It provides a good cost and actions description. (3) The program is best suited in large cities that will house urban bioreactors. The project plans to place it in sub-Saharan Africa. (4) The key benefits information is an inadequate explanation.

- Proposal for small-scale cultivation of cyanobacteria in bioreactors. Proposal has not been updated since initial review. - Interesting idea, but who would carry it out, and what are the costs? Needs a lot more work. Maybe the proposer should come back next year with some more detail. - No improvements to second round of submissions. Earlier comments are noted here: (1) The proposal has a very complete list of items that are well addressed in this presentation. (2) It provides a good cost and actions description. (3) The program is best suited to large cities that will house urban bioreactors. The project plans to place it in sub-Saharan Africa. (4) The "key benefits" section contains an inadequate explanation.