A question that excites and motivates me is repurposing the current tech to making single-cell protein bacteria, or making low-tech but efficient reactors.

### Rationale
Single-cell proteins had sparked my interest long ago as they:
- are usually very resilient (more so than an algae, usually)
- are less sensitive to temperature (Solar Foods' patent [states 25-40 C](https://data.epo.org/publication-server/document?iDocId=6530856&iFormat=0)) and light conditions compared to an algae or other sources
- require less 'starting' material to work with - starting with [methane, hydrogen, wood or starch](https://www.luxresearchinc.com/blog/strategies-for-success-in-single-cell-protein-production/), [one more source](https://www.frontiersin.org/articles/10.3389/fbioe.2021.733753/full)
- the material they produce makes a valuable food supplement, and can be used as a [staple food basis](https://www.forbes.com/sites/daphneewingchow/2022/02/28/here-are-the-two-craziest-ingredients-in-alternative-protein-this-year/), i.e. *"Solein consists of 65-70 % protein, 5-8 % fat, 10-15 % dietary fibres and 3-5 % mineral nutrients"* for the proprietary Solar Foods protein
- are among the top efficiency for the [electricity-to-calories conversion ratio](https://allfed.info/images/pdfs/chemical_snythesis.pdf), [required power and bioreactor weight](https://allfed.info/images/pdfs/Food_in_space_from_hydrogen_oxidizing_ba.pdf)
- have the potential to be fed e.g. [biologically synthesized hydrogen](https://www.sciencedirect.com/science/article/abs/pii/S0360319919302241) or presumably more efficient [dark fermentation](https://microbialcellfactories.biomedcentral.com/articles/10.1186/s12934-022-01893-3#Sec2), or even [wastewater](https://www.powertoprotein.eu/wp-content/uploads/resource-recovery-from-used-water_matassa_boon_verstraete_water-research.pdf), decreasing the dependence on chemical hydrogen production. Another scheme [here](https://openmicrobiologyjournal.com/VOLUME/16/ELOCATOR/e187428582207270/FULLTEXT/)
- there are numerous pathways to achieve that, and [numerous substrates to use](https://www.cell.com/joule/pdf/S2542-4351(20)30177-X.pdf)
- there are strains that [are endotoxin-free](https://pubs.acs.org/doi/10.1021/acsfoodscitech.0c00129) which is pretty important long-term (avoiding chronic inflammation and autoimmune diseases when medical support may be scarce is essential)

### Potential considerations
One of the potential strategies may involve [retrofitting flasks and controlling them](https://www.biorxiv.org/content/10.1101/729434v2.full) via a PC/PCB such as a Raspberry or ESP. However, it's not strictly sustainable long-term.

As a HOB reactor is [essentially a water reservoir being fed with $CO_2$ and water](https://www.sciencedirect.com/science/article/pii/S221191241830141X), later to be electrolyzed - we'd need:
- electricity (can be environmentally generated)
- basic nutrients
- separation machine (can [be modified manual](https://www.amazon.com/Dairy-Cream-Separator-Manual-METALL/dp/B01B68KPEK) if we're in need of a max low-tech solution)

One potential thing to consider is explosiveness of hydrogen, however this could be managed by keeping the concentration [below explosion limits (5-75%)](https://onlinelibrary.wiley.com/doi/10.1002/ceat.200403174).