Source
doi:10.7717/peerj.19229 — original publication (opens in a new tab; the file is not redistributed)
Context: thesis · empirical energy-intensity evidence for the vertical-farming exclusion in the strategic technology-options counterfactual
Summary
A controlled vertical-farm experiment (Shanghai Institute of Technology) measuring how eight supplemental-lighting intensities from 125 to 300 (micromol/m2/s PPFD, printed as “mmol/m2/s”) affect the growth, photosynthesis, yield, and per-unit electricity consumption of two hydroponic lettuce varieties (Lactuca sativa cv. ‘Spanish green’ and ‘Butterhead’) under a fixed red:blue = 4:1 spectrum and 16 h/8 h photoperiod. The authors first built an automated cart to measure and equalise PPFD uniformity (>80%) across each shelf, then grew plants on a four-layer rack (84 plants per layer) for 38-40 days. Fresh weight rose with light intensity for both varieties, but the marginal energy cost rose faster: the paper reports a production-efficiency ratio (grams fresh weight per kWh) and shows that pushing Spanish green from 200 to 300 (micromol/m2/s) buys only a 2.12% gain in that ratio while consuming 45% more electricity per day. For the Neobiome thesis this is primary evidence for why controlled-environment vertical farming is classed as energy-intensive and industrial, and therefore excluded from the community self-sufficiency technology set.
Key claims
- claim: "In vertical farming, major expenses include depreciation, labor, and electricity costs, with electricity often accounting for 20% to 30% of the total expenses [verified verbatim against the retrieved full text]"
source_location: "Introduction, p.2 (the paper attributes the 20-30% figure to Kozai & Japan Plant Factory Association, 2019)."
- claim: "This means that it requires more electricity consumption, and lighting electricity consumption in vertical agriculture is an important factor affecting its economy [verified verbatim against the retrieved full text]"
source_location: "Introduction, p.2 (citing Weidner, Yang & Hamm, 2021)."
- claim: "In terms of electricity consumption, the daily electricity consumption of P300 and P200 is 5.22 kWh and 3.6 kWh, respectively, P300 consumes 45% more energy per day than P200. [verified verbatim against the retrieved full text; P300/P200 = 300 and 200 micromol/m2/s treatments; power metered per single-layer treatment group (84 plants under 12 T8 tubes each), R:B=4:1, 16 h/d]"
source_location: "Results, 'Fresh weight, dry matter content, and production capacity ratio' / production-efficiency discussion, p.10."
- claim: "For Butterhead lettuce, under the P300 experimental condition, the production efficiency ratio reaches its maximum at 12.41 g/kwh, which is advantageous for Butterhead lettuce production ... For Spanish green lettuce, under the P300 and P200 experimental conditions, the production efficiency ratios are 12.53 and 12.27 g/kwh respectively, with the former being 2.12% higher than the latter. [verified verbatim against the retrieved full text; PER = grams fresh weight per kWh of lighting]"
source_location: "Results, production-efficiency ratio, p.10 (Fig. 7A, 7B)."
- claim: "At a light intensity of 125 mmol/m2/s, the fresh weights of Butterhead lettuce and Spanish green lettuce reach their lowest values, at 36.64 and 36.60 g. At a light intensity of 300 mmol/m2/s, both Butterhead lettuce and Spanish green lettuce reach their maximum fresh weights, at 64.80 and 65.40 g respectively [verified verbatim against the retrieved full text; source unit is micromol/m2/s, printed 'mmol/m2/s']"
source_location: "Results, 'Fresh weight, dry matter content, and production capacity ratio', p.9 (Figs. 6A, 6B)."
- claim: "This study suggests that in plant factories, Spanish green lettuce should be cultivated under a light intensity of 200 mmol/m2/s when the red-to-blue light ratio is R/B = 4, while Butterhead lettuce can be supplemented with a light intensity of 300 mmol/m2/s. [verified verbatim against the retrieved full text]"
source_location: "Conclusion, p.13."Thesis use
- Energy-intensity evidence for the exclusion. The strategic technology-options map classes “Vertical farming (controlled-environment)” as Excluded on the grounds that it is “energy + capex intensive; industrial”. This paper is a concrete, measured instance of that: real supplemental-lighting electricity draw (3.6-5.22 kWh/day per single-layer treatment group of 84 plants under 12 T8 tubes), electricity at 20-30% of operating expense, and a food-energy return of only ~12 g of lettuce per kWh of lighting.
- Diminishing returns argument. The 200-to-300 (micromol/m2/s) step buys a 2.12% production-efficiency gain for 45% more daily energy - a clean illustration that maximum yield and energy prudence diverge in controlled-environment agriculture, reinforcing why an off-grid, energy-constrained community would not adopt it.
- Scope caveat. Leafy salad only (two lettuce cultivars), lab-scale, Shanghai, grid-powered; the numbers are per single-layer treatment group under one fixed spectrum/photoperiod and are not a community-scale food-system model. Cite for the direction and order of magnitude of the energy burden, not for a transferable NZ coefficient.
NI relevance
None direct - by design. Vertical / controlled-environment farming is deliberately outside the Neobiome Intelligence technology set (part of the excluded counterfactual - alongside lab-grown / cellular agriculture and precision fermentation - that evidences the sustainable, self-contained selection philosophy). This source therefore feeds no SSI indicator or EDT domain calculation and carries no coefficient the engine consumes (feeds: []). Its role is thesis-side: primary evidence substantiating the energy-intensity rationale for keeping vertical farming excluded.
Research targets
No new research targets. This source is exclusion evidence for the food-technology counterfactual; it substantiates an existing classification rather than opening a quantitative gap.
Notes
Downloaded open-access from PeerJ (doi:10.7717/peerj.19229, CC-BY 4.0). All six quantitative claims checked verbatim against pdftotext -layout output. Unit artifact: the PDF’s micro (mu) glyph is dropped by pdftotext, so light-intensity and gas-exchange values render as “mmol/m2/s”; the standard and intended PPFD unit is micromol per m2 per s (300 mmol would be physically implausible for lettuce). Quotes are kept as extracted with the unit flagged in-line. Metering basis: the P300/P200 daily-kWh figures were metered per layer, and P300 and P200 are two distinct single-layer treatment groups (84 plants under 12 T8 tubes each), not one four-layer rack. Supplemental raw-measurement file not retrieved. Companion exclusion-evidence sources: cultured meat (Humbird 2021) and precision fermentation (LeverVC 2023).