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Page 8 of 13 Cheng et al. Carbon Footprints 2024;3:10 https://dx.doi.org/10.20517/cf.2023.53

Figure 3. Sensitivity analysis of life cycle models to identify these critical materials input to the GWP outcomes. (A) and (B) represent
greenhouse and plant factory cultivations, respectively.
plant factory cultivation, we clustered all the reviewed 64 China’s grid decarbonization pathways into 12
scenarios [Figure 4A].

All scenarios, belonging to the two high and low decarbonization levels, have the potential to decrease the
climate burden of plant factories compared with the baseline grid. For example, in the 2025-Low
decarbonization scenario (with power source composition: 53% coal, 4% natural gas, 10% solar, 10% wind,
7% nuclear, and 16% hydropower), one kilogram of lettuce produced in a plant factory emits 13.9 kgCO e
2
and 17.7 kgCO e of greenhouse gases at 100-year and 20-year scales, respectively, which is 7%-8% lower
2
than the baseline emissions (P ). If the coal-fired power was phased out in the 2050-High decarbonization
0
scenario, the GWP of plant-factory cultivations would decline by one order of magnitude. However, this
lower GWP is still five times higher than that of the greenhouse cultivations (G in Figure 2A). Notably,
0
under low and high levels of grid decarbonization, the 20-year GWP of the plant factory is 13%-27% higher
than the 100-year counterpart [Figure 4B].
Grid decarbonization decreases the TWP metrics over time, reflecting the rising relative climate
performance of the plant factory versus the greenhouse [Figure 4C]. However, the plant factory still fails to
show absolute climate advantage, although nitrous oxide emission further offsets the greenhouse’s
performance (TWP CH4+N2O < TWP ). This failure is reflected by the TWP range 5-66, much higher than the
CH4
crossover point at 1. Even when using solar, wind, and nuclear as alternative power sources, the production
of lettuce in plant factory still generates a larger climate impact than in traditional greenhouse. Only when
fully powered by hydropower did the plant factory perform better than the greenhouse.

Upstream methane and nitrous oxide emissions
Figure 5 shows the contrition of various greenhouse gasses to the total climate burdens of plant factory
cultivation. Under the varied grid decarbonization scenarios, carbon dioxide unsurprisingly dominates