Thread by @csmaje

I’m reposting my remarks on @GeorgeMonbiot’s energy data as an updated 🧵 after another read of his source. IMO this is important – I think George’s figure is wrong & this has implications for the feasibility of the ‘farm-free’ future he foretells in #Regenesis 1/16

George finally gave his source for his 16.7 kWh/kg bacterial protein claim as this paper (‘the Sillman study’): 2/16sciencedirect.com/science/articl…

So his figure isn’t in fact a real world one from Solar Foods as he previously claimed, but from an article (a “quantitative literature review”) involving estimates made using secondary data 3/16

I’ve already discussed this study & some of its limitations here: . More recent studies with more comprehensive energy inventories suggest much higher figures 4/16chrissmaje.com/wp-content/upl…

George’s 16.7 figure is based on 9.86kWh/kg biomass from the Sillman study, but this isn’t the full energy cost that’s specified in the study (Fig. 3) 5/16

Proper consideration needs to be given to other inputs & energy costs which I don't think are covered in George’s figure… 6/16

…like CO2 capture, bioreactor stirring heating & cooling, ammonia, post-processing, filtration to make it safe for human consumption etc. These are better specified in the more recent Leger et al study I used 7/16

The Leger et al study also used real-world efficiency data from actual PV farms, not a theoretical efficiency estimate as in the Sillman study 8/16

The Sillman study shows (Fig 3) that George’s energy figure of 9.86 kWh/kg would only provide, at best, a slurry of bacterial biomass at 2.5% concentration (presumably unsafe for humans to eat) 9/16

But this result could only occur if the CO2 input is provided with no energy cost, which I don’t think is the real world case for Solar Foods 10/16

So I think my 65kWh/kg protein calculated from the Leger study is a better estimate. Note that neither study includes full energy costs of building, maintaining & replacing infrastructure 11/16

Notwithstanding its low estimate, the Sillman study nevertheless remarks “The proposed protein production method is highly energy-intensive compared with conventional production practices in agriculture”, which is a key point I’ve been trying to emphasize 12/16

There are other techniques for producing microbial food. But they can’t just be invoked airily – their lifecycle energetics need specifying if we’re going to discuss their role. Using generated electricity instead of sunlight will always be a challenge energetically 13/16

TLDR: the Solar Foods pancake that George ate probably wasn’t “the beginning of the end of most agriculture” 14/16

George has stressed in his recent writing the importance of numbers. I agree the ones discussed here are important. So @GeorgeMonbiot will you retract your 16.7kWh/kg claim, or show what I’ve got wrong here? 15/16

More generally in this area, it's important not to confuse costs and efficiency.

See also comments by @alanwilliamz.
#NOtoFarmFree 16/16