Can CO2 enrichment be beneficial in conservation agriculture? Is the systematic production of CO2 enrichment in greenhouses, controlled environment systems, and vertical farms beneficial for the ozone layer?

CO2 enrichment in protected agriculture has been extensively studied as a strategy to enhance crop productivity, resource use efficiency, and climate resilience. This systematic review examines the scientific literature on CO2 enrichment in greenhouses, vertical farms, and controlled environment agriculture (CEA) systems, with a focus on its impact on crop physiology, photosynthesis, agricultural yield, modeling and simulation techniques, injection technologies, and sustainability challenges. A comprehensive bibliometric and systematic search was conducted in the Scopus database using key terms related to CO2 enrichment and sustainable protected agriculture, following the PRISMA methodology. From an initial set of 212 documents, 171 were selected after removing duplicates, inaccessible articles, and studies not directly relevant to this context. The findings indicate that CO2 enrichment can significantly improve photosynthetic efficiency, water use efficiency, and crop productivity, although its impact varies depending on species, environmental conditions, and application strategies. Computational models, such as CFD and machine learning, have optimized CO2 distribution in controlled environments, contributing to more precise and resource-efficient agricultural practices. However, environmental and economic concerns, particularly energy consumption, carbon footprint, and the sustainability of CO2 sources, remain critical challenges. To ensure the sustainable adoption of CO2 enrichment, it is essential to integrate renewable energy sources, carbon capture and reuse technologies, and advanced CO2 injection systems. This review provides a holistic assessment of current knowledge, identifying opportunities and barriers for the development of climate-smart protected agriculture systems that align with global sustainability goals and contribute to food security and environmental stewardship .Keywords: carbon footprint climate-smart agriculture; microclimate regulation; photosynthesis optimization; sustainable agricultural.

Accelerated population growth and economic development, along with the intensification of urbanization, have significantly increased pressure on infrastructure and natural resources to meet the global demand for food, water, and energy [1]. It is estimated that by the year 2050, global energy consumption will increase by 80%, while food demand will grow by 60% and water consumption will rise by 55% [2]. In this context, agriculture accounts for more than 70% of global freshwater withdrawals, highlighting the need to improve water resource use efficiency [3]. Greenhouses and Plant Factories With Artificial Lighting (PFAL) emerge as a key alternative to address these challenges, as they can achieve yields equivalent to traditional agriculture while using only 10% of the water required in open-field cultivation [3]. However, this type of infrastructure is among the highest energy consumers in the agricultural sector. In a protected production system, the interactions between water, energy, and food resources, known as the Water–Energy–Food (WEF) Nexus, are particularly evident [4]. This underscores the need for strategies to optimize the use of these inputs. To enhance the sustainability of greenhouse and PFAL production, it is imperative to develop innovative solutions that reduce high energy demand without compromising yield [5]. These strategies must take into account not only water consumption efficiency but also the provision of optimal environmental conditions for crop growth and development [6]. Within the context of microclimate management in these production technologies, carbon dioxide (CO2) enrichment has become a relevant strategy in protected agriculture due to its potential to enhance resource use efficiency and increase agricultural productivity [7]. The physiological response to CO2 varies depending on the species and cultivation conditions, influencing the photosynthetic rate, water use efficiency (WUE), and biomass partitioning [8]. In horticultural crops, such as tomato (Solanum lycopersicum), pepper (Capsicum annuum), and basil (Ocimum basilicum), elevated CO2 concentrations have increased biomass by up to 50%, promoting the development of both photosynthetic and reproductive organs [9]. In high-tech systems, such as Plant Factories With Artificial Lighting (PFAL), the combination of CO2 enrichment with artificial lighting and hydroponic techniques has enabled an increase in production density without compromising product quality.However, its efficiency depends on the precise control of multiple environmental variables, including CO2 concentration, light intensity and spectrum, temperature, humidity, and nutrient solution composition. These factors must be carefully managed to optimize photosynthesis, ensure proper plant development, and maximize resource use efficiency in controlled environments [10]. However, the implementation of CO2 enrichment requires advanced strategies to optimize its efficiency and minimize losses due to ventilation. The use of simulation models and computational fluid dynamics (CFD) has been fundamental in assessing gas distribution within greenhouses and improving its application [11,12]. Injection technologies, such as automated dosing, industrial emissions capture, and the use of renewable sources, have emerged as alternatives to reduce costs and enhance the sustainability of the process [13]. However, economic viability remains a critical factor, as operational costs must be justified by improvements in both productivity and crop quality [14]. Additionally, the efficiency of CO2 enrichment varies depending on the cultivated species, the phenological stage, and interactions with other climatic factors, requiring a comprehensive approach for its optimal application in different agricultural systems [15]. On the other hand, systematic reviews play a fundamental role in identifying and synthesizing existing evidence on CO2 enrichment in protected agriculture, enabling a rigorous assessment of its benefits and limitations [16]. This methodological approach enables the consolidation of information from previous studies using standardized criteria, facilitating the formulation of strategies based on scientific evidence [17]. Unlike narrative reviews, which provide a general overview without strict methodological criteria, systematic reviews follow a structured protocol to identify, select, analyze, and synthesize relevant information [18]. This will enable a quantitative and qualitative assessment of the impact of CO2 on different crops and production systems. Ultimately, this type of review provides a comprehensive perspective on current research trends, helping to identify opportunities and outstanding technical challenges [19]. Based on the above, this review article is structured around key questions that guide the analysis of the existing literature on the impact of CO2 enrichment in protected agricultural systems. Specifically, it aims to address the following questions. How does CO2 enrichment influence crop physiology and photosynthesis? What is the effect of CO2 enrichment on crop production and yield? What models and simulation techniques have been used to analyze CO2 distribution in controlled environments and its impact on plant development? What are the most efficient technologies for CO2 injection and enrichment in greenhouses? What role do Plant Factories with Artificial Lighting (PFAL) play in agricultural production with supplemental CO2? What are the economic benefits and energy challenges associated with this strategy? What environmental and sustainability implications are related to CO2 use in protected agriculture? Although CO2 enrichment has been extensively studied, the novelty of this review lies in its comprehensive and integrative approach, which combines experimental findings, modeling techniques, technological advancements, and economic–environmental assessments in a single framework. Unlike previous studies that focus primarily on physiological or agronomic responses, this review provides a multidimensional perspective, incorporating aspects like spatial CO2 distribution modeling, advanced injection technologies, and the role of emerging controlled environment agriculture systems (e.g., PFALs). By bridging these different dimensions, this study identifies critical knowledge gaps and proposes a roadmap for future research and the practical implementation of CO2 enrichment strategies in modern agricultural systems. The objective of this systematic review is to provide a comprehensive and up-to-date analysis of the impact of CO2 enrichment in protected agriculture. It aims to integrate findings from experimental and modeling studies, identifying trends, advantages, limitations, and challenges in its application. Additionally, economic, technological, and environmental aspects will be discussed to offer recommendations for the efficient implementation of CO2 enrichment strategies in various agricultural production systems. Finally, future research directions will be proposed to contribute to the sustainable development of more efficient and resilient agricultural systems in the face of climate change.