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Page 2 of 13 Cheng et al. Carbon Footprints 2024;3:10 https://dx.doi.org/10.20517/cf.2023.53
if hydropower were fully deployed. Our findings add knowledge about climate-friendly and resilient vegetable
supplies under China’s grid decarbonization efforts.

Keywords: Climate resilience, plant factory, crystallinity of COF, sunlight greenhouse, global warming potential,
methane, nitrous oxide

INTRODUCTION
Plant factories, as indoor infrastructures for plants growing under a controlled environment, can increase
[1,2]
the climate resilience of vegetable production . However, the climatic performances of plant factories
differ from traditional sunlight greenhouses. Traditional greenhouses produce vegetables relying on
[3,4]
nitrogen fertilizers, with the corresponding nitrous oxide (N O) emissions , while plant factories primarily
2
rely on artificial illumination, consuming power , possibly with upstream methane (CH ) emissions. For
[1,2]
4
example, China’s upstream coal mining to generate power was recognized as a major global methane
[5,6]
emitter . Short-lived methane and nitrous oxide are more potent than carbon dioxide in heating climate
and have been responsible for a 0.5 and 0.1 °C warming in the past decade, respectively . Neglecting the
[7]
warming effect of the short-lived climate forcers may offset the intended benefits of shifting toward low-
carbon technologies . Thus, despite reducing fertilizer inputs, plant factory cultivations on coal-fired
[8,9]
power likely raise the climate burdens of vegetable production by replacing greenhouses.
Plant factories show significant promise in China since half of the world’s vegetables are grown there .
[3]
Recently, China released an Action Plan for Peaking Carbon Dioxide Emission before 2030, promoting
power-grid decarbonization by coal phase-out policy . Therefore, we ask: Can grid decarbonization
[10]
improve plant factory’s climate performance compared to greenhouses? This question is complicated by the
short-lived methane and nitrous oxide emissions. The reason is that the commonly used global warming
potential (GWP), like in prior Life Cycle Assessment (LCA)-based studies [11-13] , allows for comparing the
GHGs (or carbon footprint) between technologies at a fixed time horizon, but fails to evaluate the
dynamically cumulative radiative forcing of multiple GHGs due to the varied atmospheric lifetimes .
[14]
[14]
However, the technological warming potential (TWP) method overcomes this barrier .
Here, we applied the LCA-based TWP method [8,14] to compare the climate performances of producing
lettuce in a plant factory with artificial light and in a traditional sunlight greenhouse. Additionally, we
extensively reviewed China’s grid decarbonization pathways to set the scenarios and tested their effects on
the TWP metrics (see Methods and data). The novelty of this study lies in two aspects: For one thing,
compared with previous studies on the climate performance of plant factories, this paper uniquely considers
the contribution of non-CO gases to climate impacts from the temporal dimension; for another, this study
2
illustrates the climate feasibility of plant factories based on the context of electricity decarbonization in
China. Thus, this study fills the knowledge gap of the previously neglected effect of grid decarbonization on
the climate performance of newly soaring plant factories, especially when short-lived methane and nitrous
oxide were highlighted.

METHODS AND DATA
Life cycle assessment of lettuce cultivation
[15]
Referring to the ISO14040 (2006) , LCA method assesses the climate burdens of a product through four
steps, i.e., objective and system boundary definition, inventory analysis, environmental impact assessment,
and result interpretation. The attributional method (JRC-IEA, 2010) was selected in this study because
[16]
our comparison targeted the average impact instead of the marginal influence . The objective of the LCA
[17]
modeling was to quantitatively assess and compare the climate loads of two lettuce production technologies