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New solar farms use panels that can achieve light-to-electricity efficiency over 20% [1]. Electrolytic splitting of water to produce hydrogen is about 80% effic

New solar farms use panels that can achieve light-to-electricity efficiency over 20% [1]. Electrolytic splitting of water to produce hydrogen is about 80% efficient [2] for a combined efficiency of ~17%. Growing potatoes -- a calorie dense but not particularly protein rich crop -- converts only about 1.7% of sunlight to edible calories [3]. The intuition behind cultivating hydrogen oxidizing bacteria for single cell protein is that the coupled efficiency of solar photovoltaics plus electrolyzers can be an order of magnitude more productive per hectare for sunlight-to-protein than growing crops in fields. It doesn't require irrigation, weed control, pest control, tilling, or harvesters. It can use land that is too dry, rocky, hot, cold, or contaminated to grow crops. It's still an open question whether the output protein can be of a quality and price that it will out-compete e.g. conventionally grown soybeans, because despite all these advantages it is also much more capital intensive than growing beans. I recently wrote a longer comment about hydrogen oxidizing bacteria as protein source that you might find interesting: https://news.ycombinator.com/item?id=32288926 https://news.ycombinator.com/item?id=32288926 [1] from e.g. Longi https://cdn.enfsolar.com/z/pp/t8gzz7lxx769/L-Gi-LE-T-TMD-059-108-LR-5-72-HBD-530-550-M-35-30-and-15-V14.pdf https://cdn.enfsolar.com/z/pp/t8gzz7lxx769/L-Gi-LE-T-TMD-059... [2] https://www.quora.com/How-many-kWh-of-electricity-is-needed-to-produce-1kg-of-hydrogen-from-the-electrolysis-of-water https://www.quora.com/How-many-kWh-of-electricity-is-needed-... [3] https://onlinelibrary.wiley.com/doi/pdf/10.1002/fes3.348 https://onlinelibrary.wiley.com/doi/pdf/10.1002/fes3.348

gus_massa 4y ago
> can be an order of magnitude more productive per hectare for sunlight-to-protein than growing crops in fields. But what's the efficiency of converting Hydrogen (and CO2) to carbohydrates? Pulling number out of thin air, I'll be very happy if it's 10% or 20% [1]. So from solar to carbohydrates they get 20%*80%*¿20%?=3% that is the double of potatoes, not an order of magnitude better. And the conversion to proteins is even harder. They need a microorganism that can fixate Nitrogen from the air (that is very costly for the microorganism) or use a fertilizer like ammonia nitrate (that use a lot of energy in an industria plant). [1] For an easy, one step organic reaction in the lab, the efficiency is like 60%-70%. It varies a lot, but never expect something like 99%. In the lab, most reactions use a brute force approach like boiling it in acid, instead of using a specialized enzyme. On the other hand, the transformation form H2 and CO2 to carbohydrates has like 10 or 20 steps, and each step has a small lose. I'd be happy with a global 20% efficiency, but perhaps I'm too optimistic.
- sitkack 4y ago
  Would Alpha fold help genetically engineer new ways to efficiently process CHON into food-stuffs? https://alphafold.com/search/text/nitrogen https://alphafold.com/search/text/nitrogen I think the cool part of using solar panels to have an electrified process is that you can use non-farmland (Bill Gates is buying it all :), could use less water, also produces electricity. In the perfect future, we are all sucking on tubes of atmospheric liquid cheese product. From pipe to pipe.
- philipkglass 4y ago
  This report finds 10% as a lower bound and 60% as an upper bound for the energy efficiency of hydrogen oxidizing bacteria: "The energy efficiency of carbon dioxide fixation by a hydrogen-oxidizing bacterium" https://sci-hub.ru/10.1016/j.ijhydene.2013.04.153 https://sci-hub.ru/10.1016/j.ijhydene.2013.04.153 The authors found a tradeoff between efficiency and growth rates. The highest efficiency came with the slowest growth rate. But they concluded that 50% efficiency was achievable at practical growth rates. Keep in mind also that potatoes only contain about 10% protein by dry weight while the bacteria cultivated to make single cell protein can contain 50% protein by dry weight. Soybeans are about 40% protein.
ClumsyPilot 4y ago
> combined efficiency of ~17%. Growing potatoes -- a calorie dense but not particularly protein rich crop -- converts only about 1.7% Efficiency of light is not that important, because plants reach their maximum rate of photosynthesis at fairly low light levels. In reality yield is limited by low temperatures in winter, avaliability of water, etc. The process being proposed here requires much more investment of capital and resources than simply planting potato in the fields -> now we need solar panels, electrolysis, etc. But if you want to improve yield by throwing money at the problem, you build a greenhouse, invest in hydroponics, etc. and your yield will grow several times. So that would be a better point of comparison -> for a dollar or physical resources invested, does this approach give you more extra yield than a state of the art greenhouse would?

gus_massa 4y ago

> can be an order of magnitude more productive per hectare for sunlight-to-protein than growing crops in fields. But what's the efficiency of converting Hydrogen (and CO2) to carbohydrates? Pulling number out of thin air, I'll be very happy if it's 10% or 20% [1]. So from solar to carbohydrates they get 20%*80%*¿20%?=3% that is the double of potatoes, not an order of magnitude better. And the conversion to proteins is even harder. They need a microorganism that can fixate Nitrogen from the air (that is very costly for the microorganism) or use a fertilizer like ammonia nitrate (that use a lot of energy in an industria plant). [1] For an easy, one step organic reaction in the lab, the efficiency is like 60%-70%. It varies a lot, but never expect something like 99%. In the lab, most reactions use a brute force approach like boiling it in acid, instead of using a specialized enzyme. On the other hand, the transformation form H2 and CO2 to carbohydrates has like 10 or 20 steps, and each step has a small lose. I'd be happy with a global 20% efficiency, but perhaps I'm too optimistic.

sitkack 4y ago
Would Alpha fold help genetically engineer new ways to efficiently process CHON into food-stuffs? https://alphafold.com/search/text/nitrogen https://alphafold.com/search/text/nitrogen I think the cool part of using solar panels to have an electrified process is that you can use non-farmland (Bill Gates is buying it all :), could use less water, also produces electricity. In the perfect future, we are all sucking on tubes of atmospheric liquid cheese product. From pipe to pipe.
philipkglass 4y ago
This report finds 10% as a lower bound and 60% as an upper bound for the energy efficiency of hydrogen oxidizing bacteria: "The energy efficiency of carbon dioxide fixation by a hydrogen-oxidizing bacterium" https://sci-hub.ru/10.1016/j.ijhydene.2013.04.153 https://sci-hub.ru/10.1016/j.ijhydene.2013.04.153 The authors found a tradeoff between efficiency and growth rates. The highest efficiency came with the slowest growth rate. But they concluded that 50% efficiency was achievable at practical growth rates. Keep in mind also that potatoes only contain about 10% protein by dry weight while the bacteria cultivated to make single cell protein can contain 50% protein by dry weight. Soybeans are about 40% protein.

ClumsyPilot 4y ago

> combined efficiency of ~17%. Growing potatoes -- a calorie dense but not particularly protein rich crop -- converts only about 1.7% Efficiency of light is not that important, because plants reach their maximum rate of photosynthesis at fairly low light levels. In reality yield is limited by low temperatures in winter, avaliability of water, etc. The process being proposed here requires much more investment of capital and resources than simply planting potato in the fields -> now we need solar panels, electrolysis, etc. But if you want to improve yield by throwing money at the problem, you build a greenhouse, invest in hydroponics, etc. and your yield will grow several times. So that would be a better point of comparison -> for a dollar or physical resources invested, does this approach give you more extra yield than a state of the art greenhouse would?