CO2 Enrichment In Greenhouses Research Articles

Zeolite enhances leaf photosynthesis and fruit quality in tomato through greenhouse CO2 enrichment

Elevated CO2 concentration has been widely acknowledged as a leading factor to global climate change, while deficient CO2 serves as a crucial limiting factor in modern greenhouse production. Harnessing the existing excessive CO2 to promote agriculture production is significant but filled with challenges. To this end, we proposed a concentration gradient-regulated CO2 enrichment system for capturing CO2 into greenhouses, which requires suitable CO2 sorbents with sufficient CO2 desorption capacity and high hydrophobicity at ambient temperature and pressure. Zeolites with different framework types and cations were detected by CO2 desorption and cyclic stability test under simulated agricultural production conditions. The results indicate that larger pore volume cooperated with higher Si/Al ratio and weaker alkali cations may be critical determinants for balancing high CO2 adsorption-desorption capacities and hydrophobicity in crop-cultivated environments. H-SSZ-13 zeolite is identified as the potential sorbents and exhibits exceptional CO2 release abilities and cyclic stability in tomato-grown environment. Long-term application of H-SSZ-13 zeolite to tomato plants significantly stimulated photosynthetic processes, particularly the Calvin-Benson cycle, culminating in notable improvements in plant growth, fruit yield and quality. This investigation provides a promising solution to develop a carbon-neutral CO2 enrichment system for both sustainable and productive greenhouse production.

Carbon capture from biomass flue gases for CO2 enrichment in greenhouses

Heating and CO2 enrichment systems can improve yields in intensive greenhouse agriculture Combining both techniques, which are currently applied commercially, can potentially enhance their effect. The CO2 must be separated from the other noxious gases present (such as CO, NOX, and SO2) to avoid them becoming part of the supply. The CO2 is then provided to the greenhouse on demand in the same way as the heating. In this work, we show that an improved food productivity of a pilot-scale greenhouse system combined with CO2 capture by adsorption using activated carbon and heating with alternative fuel. The proposed system's overall performance was evaluated and optimized. The best values were 46.7 g/kg of CO2 storage capacity on the adsorbent bed, 99.99 % removal rate harmful gases from the gas supplied to the greenhouse, CO2 levels of 1851.0 ± 262.8 mg/Nm3 of the CO2 levels in the greenhouse, and an enrichment time of 2.18 ± 0.92 h/day. The system's effective performance over extended periods (November–February) was confirmed and the productivity of a crop species (tomato) was compared to a control, showing an increment of 18 %. The results indicate that this is a valuable option for increasing the crop yield. By integrating this combined system with advanced climate control strategies, it is possible to maximize the CO2 provided per day, leading to higher yields. The system proved to be stable under real pilot-scale conditions over winter periods (four months).

Crop-localised CO2 enrichment improves the microclimate, photosynthetic distribution and energy utilisation efficiency in a greenhouse

In greenhouse cultivation, microclimate control is a highly energy-consuming process, and CO2 enrichment, which is a part of it, requires the direct consumption of fossil fuel energy. To achieve sustainable and economical greenhouse management, we must understand the performance and energy utilisation efficiency of CO2 enrichment in greenhouses. In this study, we conducted computational fluid dynamics (CFD) simulations for two CO2 enrichment methods in a strawberry greenhouse: (1) conventional overall greenhouse enrichment (‘Entire Enrichment’) and (2) crop-localised enrichment (‘Local Enrichment’). The spatial distribution of microclimate parameters was simulated using a CFD model; based on the results, the spatial distribution of the crop photosynthetic rate was also simulated using an environment–plant coupled model group. Furthermore, we quantitatively analysed the efficiency of CO2 enrichment (ECE) by calculating the changes in the photosynthetic carbon assimilation capacity of the crop canopy in relation to CO2 usage, which allowed us to propose a more efficient enrichment strategy. Compared with the Entire Enrichment method, the Local Enrichment method reduced the effects on greenhouse temperature and humidity but increased the average CO2 concentration inside the canopy by 264 μmol mol−1. As a result, Local Enrichment increased the average leaf photosynthetic rate inside the canopy by 1.48 μmol m−2 s−1. According to ECE analysis, Local Enrichment has huge advantages over Entire Enrichment; the mean ECE of Local Enrichment was approximately 4.4 times higher than that of Entire Enrichment (25.7 and 5.9 mmol mol−1, respectively). Moreover, scenario analysis indicated that the Local Enrichment system could be applied to larger greenhouses and improves ECE relative to that in a conventional system. Having compared the two enrichment methods comprehensively, we conclude that the Local Enrichment method could significantly improve the environmental parameters around the crop canopy in relation to photosynthesis and greatly enhance CO2 utilisation efficiency.

Agro-Industrial Symbiosis and Alternative Heating Systems for Decreasing the Global Warming Potential of Greenhouse Production

Greenhouses require large amounts of energy, which is the dominant factor making greenhouses more emission intensive than open-field cultivation. Alternative heating systems, such as combined heat and power (CHP), biogas, and industrial waste heat, are continuously being researched for reducing the environmental impacts of greenhouses. This paper assesses utilizing industrial waste heat and CO2 enrichment in greenhouses as an example to propose “agro-industrial symbiosis” (AIS), to refer to a symbiotic co-operation between agricultural and industrial partners. The global warming potentials (GWPs) of greenhouse production using different heating systems are inadequately compared in the literature, which is the research gap addressed herein. Additionally, potential emission reductions of greenhouse production with industrial waste heat are yet to be assessed via lifecycle assessment (LCA). A comparative LCA of Finnish greenhouse tomato and cucumber production using various heating systems was conducted. Naturally, replacing fossil fuels with bioenergy and renewables significantly decreases the GWP. CHP systems result in decreased GWP only when using biogas as the energy source. Additionally, utilizing industrial waste heat and CO2 resulted in a low GWP. These results are applicable worldwide to guide political decision-making and clean energy production in the horticultural sector.

Model predictive control of a Venlo-type greenhouse system considering electrical energy, water and carbon dioxide consumption

Greenhouse systems consume lots of energy, water and carbon dioxide (CO2) to provide a suitable growth environment for crops. Due to the problems of operation mode, some greenhouse systems are inefficient and need to be optimized. In this paper, four optimization strategies for improving the operation efficiency of greenhouse systems are studied. Strategy 1 minimizes the energy consumed for greenhouse heating, cooling, ventilation and irrigation. Strategy 2 minimizes the water consumed for irrigation. Strategy 3 minimizes the CO2 consumed for greenhouse CO2 enrichment. Strategy 4 minimizes the total cost of energy, water and CO2 consumed. These optimization strategies are based on a multi-input multi-output (MIMO) climate model and a modified evapotranspiration model. Moreover, a sensitivity analysis is conducted to study the influence of electricity price, water price, CO2 price and the range of system constraints on the optimization results. Finally, a model predictive controller (MPC) is designed to reject system disturbances and address model plant mismatch. The MPC controller is compared with a commonly used open loop controller. A performance index relative average deviation (RAD) is introduced to evaluate the tracking performance of the proposed MPC and the compared open loop control. Simulation results show that Strategy 4 reduce the total cost by 66.60 %, 92.68 % and 68.83% compared with Strategy 1, Strategy 2 and Strategy 3 respectively. Changes in electricity price have a greater impact on optimization results than changes in water price and CO2 price. Both temperature constraints and relative humidity constraints have a great influence on the optimization results. The controller designed is verified to be effective.

Analysis of leaf photosynthetic rates of hydroponically-grown paprika (Capsicum annuum L.) plants according to vertical position with multivariable photosynthesis models

The photosynthetic rates of leaves depend on the vertical position and cultivation conditions. However, few models have been proposed to express photosynthesis according to leaf position, and there was a lack of quantitative analysis between physiological indicators and model parameters. The objectives of this study were to analyze the leaf photosynthetic characteristics of paprika plants according to leaf vertical position using photosynthesis models, and to analyze the relationship between the total nitrogen content and the photosynthetic model parameters. Leaf photosynthetic rates at different vertical positions were measured under varying light intensities and CO2 concentrations in triplicate. Rectangular hyperbola and FvCB (Farquhar, von Caemmerer, and Berry) models were selected, calibrated, and validated as multivariable photosynthesis models. Total nitrogen contents and SPAD values were measured at each leaf position and the coefficients of the photosynthetic rate models were compared. The R2 values for the rectangular hyperbola and FvCB models were 0.86 and 0.91, and the RMSE values were 4.651 and 2.104, respectively. Total nitrogen content linearly increased with increasing vertical leaf position and it was linearly related to the maximum carboxylation capacity and maximum electron transport rate, estimated in the FvCB model. In this study, the FvCB model was considered more suitable for expressing the relationship between total nitrogen contents and plant’s physiological responses according to the vertical position of leaves. The vertical leaf photosynthetic rate models established in this study will contribute to determining optimal environmental conditions for maximizing crop photosynthesis and establish the criteria for precise CO2 enrichment in greenhouses.

Energy Gain in Passive Solar Greenhouses Due to CO2 Enrichment

The production cost of greenhouse cultivation depends mainly upon significant amounts of energy consumption in order to keep the optimum environmental condition for plant growth. Τhe expenditure on energy, either for heating or cooling, ranges between 30% to 60% of the total production costs, and any attempt to save energy will result in a positive effect on the potentiality of production accordingly, affecting the greenhouse product prices. Research has shown that CO2 enrichment in greenhouses significantly increases the yield of most indoor cultivation of plants of the C3 category. For these plants, when the CO2 concentration increases by three times above that of the atmosphere (380 ppm), the optimum plant growth temperature shifts higher by 5 °C to 10 °C reaching up to 30 °C to 32 °C. Therefore, huge amounts of solar energy can be captured inside the greenhouses, as the ventilation can be decreased. Alongside this, the use of a simple passive solar system consisting of plastic sleeves filled with water is considered to be an improved way to increase the energy inside greenhouses. In this work, three experimental trials were conducted to examine the benefit of the solar energy captured inside a greenhouse during CO2 enrichment at high temperatures. Finally, a modeling approach based on the heat loss equation was developed in order to establish the energy saving inside the greenhouses under the circumstances mentioned.

Low temperature water vapor pressure swing for the regeneration of adsorbents for CO2 enrichment in greenhouses via direct air capture

CO2 enrichment in greenhouses can be achieved by extracting CO2 from the outside air. For this purpose, adsorbents based on Na2CO3 or K2CO3 are promising for trapping and releasing atmospheric CO2. Even though the CO2 capture by these adsorbents has been studied before, there is not much information about their regeneration at low temperatures and using air as flushing gas. In this work an experimental design study has been performed to understand the effect of temperature, water vapor pressure and air flow rate on CO2 desorption. The results show that K-based adsorbents are a more attractive option given their higher CO2 capture capacity and lower energy consumption compared to the Na-based ones. The estimated amount of K-based adsorbent with a capture capacity of 0.1 mmol CO2/gads and regenerated at 50 °C with 90 mbar H2O would occupy only 2% of the total volume contained in a closed greenhouse, fulfilling its daily CO2 demand.

CO2 capture from ambient air using hydrated Na2CO3 supported on activated carbon honeycombs with application to CO2 enrichment in greenhouses

CO2 capture from ambient air is an interesting option for CO2 enrichment in greenhouses. In this study, adsorbents comprised of hydrated Na2CO3 supported over activated carbon honeycombs were prepared, characterized and tested for CO2 capture from air. The adsorption of H2O and the formation of the hydrates were studied by means of FT-IR spectroscopy. The inlet CO2 concentration showed to have a major influence on the conversion yield into NaHCO3, and the results fitted well to the Toth model. A statistical model of the CO2 capture capacity was obtained to get insight into the key parameters of the adsorption process. The air temperature and its moisture content showed to have the largest impact on the CO2 capture, while the flow rate had a minor influence. The chemical reaction path during the CO2 adsorption showed to be determined by the relative humidity conditions inside the reactor. Addition of more salt on the carrier showed to improve the CO2 capture capacity, but this is limited by the strength of the honeycomb carrier. Finally, a preliminary desorption test via a mild temperature and moisture swing was run to assess the feasibility of the process for application in greenhouses. The results showed that the required volume of adsorbent would be roughly 1/1000 of the total volume of a closed greenhouse assuming a target CO2 level of 1200 ppm.

A sustainable energy for greenhouses heating in Italy: wood biomass

More than 0.7 million ton of oil equivalent is the total requirement for thermal energy in the Italian greenhouse vegetable industry, derived mostly from fossil fuels, which corresponds to 2 Mt CO2 emissions. The technology of wood biomass system is a good candidate for heating greenhouses, since this resource is considered as 'greenhouse gas' (GHG) neutral when converted to heat, excluding the GHG generation during harvesting, transportation, and pre-processing of raw materials. Besides, the CO2 enrichment in greenhouses from the exhaust gas of a biomass heating system can bring benefits for greenhouse production, along with optimal management strategies to reduce fuel consumption. Unfortunately, CO2 enrichment from the exhaust gas of biomass boilers is still challenging and expensive, considering that wood biomass boilers generate a higher volume of particulate matters (PM) and ash emissions than other fossil fuels. However, wet scrubbers and other recent flue gas conditioning devices could help to reduce costs and make this process more feasible. In the Italian peninsula, the power energy load for greenhouses heating was estimated to be between 30 and 175 W m-2, while the thermal energy consumption varies between 21 to 546 kWh m-2 year-1 according with internal air temperature and climatic zones. In general, the total cost of a heating system with boiler, loading system, accumulator, control system and safety, installation, and heat delivering can vary from a maximum of 1400 € kW-1 for systems with power up to 100 kW, 600-800 € kW-1 for power over 100 kW, to a minimum of 400 € kW-1 for systems with power over 1000 kW. Thus, a techno-economic assessment is highly recommended to ascertain the economic feasibility of wood biomass boilers for the greenhouse industry, as related to the economic incentives by the National Decree of 28 December 2012, so-called “White Certifies”.

Universality of an improved photosynthesis prediction model based on PSO-SVM at all growth stages of tomato

CO2 concentration is an environmental factor affecting photosynthesis and consequently the yield and quality of tomatoes. In this study, a photosynthesis prediction model for the entire growth stage of tomatoes was constructed to elevate CO2 level on the basis of crop requirements and to evaluate the effect of CO2 elevation on leaf photosynthesis. The effect of CO2 enrichment on tomato photosynthesis was investigated using two CO2 enrichment treatments at the entire growth stage. A wireless sensor network-based environmental monitoring system was used for the real-time monitoring of environmental factors, and the LI-6400XT portable photosynthesis system was used to measure the net photosynthetic rate of tomato leaf. As input variables for the model, environmental factors were uniformly preprocessed using independent component analysis. Moreover, the photosynthesis prediction model for the entire growth stage was established on the basis of the support vector machine (SVM) model. Improved particle swarm optimization (PSO) was also used to search for the best parameters c and g of SVM. Furthermore, the relationship between CO2 concentration and photosynthetic rate under varying light intensities was predicted using the established model, which can determine CO2 saturation points at the various growth stages. The determination coefficients between the simulated and observed data sets for the three growth stages were 0.96, 0.96, and 0.94 with the improved PSO-SVM and 0.89, 0.87, and 0.86 with the original PSO-SVM. The results indicate that the improved PSO-SVM exhibits a high prediction accuracy. The study provides a basis for the precise regulation of CO2 enrichment in greenhouses. Keywords: photosynthesis, greenhouse, tomato, CO2 enrichment, photosynthesis prediction model, wireless sensor network, environmental monitoring system DOI: 10.3965/j.ijabe.20171002.2580 Citation: Li T, Ji Y H, Zhang M, Sha S, Li M Z. Universality of an improved photosynthesis prediction model based on PSO-SVM at all growth stages of tomato. Int J Agric & Biol Eng, 2017; 10(2): 63–73.

Carbon dioxide enrichment: a technique to mitigate the negative effects of salinity on the productivity of high value tomatoes

The present study was conducted to determine the mitigating influence of greenhouse CO2 enrichment on the negative effects of salinity in Mediterranean conditions. Hybrid Raf (cv. Delizia) tomato plants were exposed to two salinity levels of the nutrient solution (5 and 7 dS/m) obtained by adding NaCl, and two CO2 concentrations (350 and 800 μmol/mol) in which CO2 enrichment was applied during the daytime according to a strategy linked to ventilation. Increasing water salinity negatively affected the leaf area index (LAI), the specific leaf area (SLA), the water use efficiency (WUE), the radiation use efficiency (RUE) and dry weight (DW) accumulation resulting in lower marketable yield. The high salinity treatment (7 dS/m) increased fruit firmness (N), total soluble solids content (SSC) and titratable acidity (TA), whereas pH was reduced in the three ripening stages: mature green/breaker (G), turning (T), and pink/light red (P). Also, the increase in electrical conductivity of the nutrient solution led to a general change in intensity of the sensory characteristics of tomato fruits. On the other hand, CO2 enrichment did not affect LAI although SLA was reduced. RUE and DW accumulation were increased resulting in higher marketable yield, through positive effects on fruit number and their average weight. WUE was enhanced by CO2 supply mainly through increased growth and yield. Physical-chemical quality parameters such as fruit firmness, TA and pH were not affected by CO2 enrichment whereas SSC was enhanced. Greenhouse CO2 enrichment did mitigate the negative effect of saline conditions on productivity without compromising organoleptic and sensory fruit quality.

Wood Biomass as Sustainable Energy for Greenhouses Heating in Italy

The Italian greenhouse vegetable industry is an important sector that requires thermal energy as much as 0.74 Mtoe, derived mostly from fossil fuels, which corresponds to 2 MtCO2 emissions. The Energy Strategy 2020 of the European Commission calls for increased use of renewable resources in the energy system, thus pushing the technology of wood biomass system for space heating of the greenhouses, since this resource is considered as ‘greenhouse gas’ (GHG) neutral when converted to heat, excluding the GHG generation during harvesting, transportation, and pre-processing of raw materials. Taking into account the different climatic areas in the Italian peninsula, power energy load was estimated to be between 30 Wm-2 (in southern regions) and more than 175 Wm-2 (in northern regions), while the energy consumption was estimated in the range from 21 to 546 kWhthm-2year-1 according to different internal air temperatures. Moreover, the CO2 enrichment in greenhouses from the exhaust gas of a biomass heating system can bring benefits for greenhouse plant production, along with optimal management strategies to reduce fuel consumption. Unfortunately, CO2 enrichment from the exhaust gas of biomass boilers is still challenging and expensive, considering that wood biomass boilers generate a higher volume of particulate matters (PM) and ash emissions than other fossil fuels. However, wet scrubbers and other recent flue gas conditioning devices could help to reduce costs and make this process more feasible. Thus, a techno-economic assessment is highly recommended to ascertain the economic feasibility of wood biomass boilers for the greenhouse industry. Finally, some economic considerations are provided to make cost-effective use of the solid biomass in relation to the economic incentives by the National Decree of 28 December 2012, so-called “White Certifies”.

Modeling of CO2Emission from Soil in Greenhouse

Greenhouse industry has been growing in many countries due to both the advantage of stable year-round crop production and increased demand for fresh vegetables. In greenhouse cultivation, CO₂ concentration plays an essential role in the photosynthesis process of crops. Continuous and accurate monitoring of CO₂ level in the greenhouse would improve profitability and reduce environmental impact, through optimum control of greenhouse CO₂ enrichment and efficient crop production, as compared with the conventional management practices without monitoring and control of CO₂ level. In this study, a mathematical model was developed to estimate the CO₂ emission from soil as affected by environmental factors in greenhouses. Among various model types evaluated, a linear regression model provided the best coefficient of determination. Selected predictor variables were solar radiation and relative humidity and exponential transformation of both. As a response variable in the model, the difference between CO₂ concentrations at the soil surface and 5-㎝ depth showed are latively strong relationship with the predictor variables. Segmented regression analysis showed that better models were obtained when the entire daily dataset was divided into segments of shorter time ranges, and best models were obtained for segmented data where more variability in solar radiation and humidity were present (i.e., after sun-rise, before sun-set) than other segments. To consider time delay in the response of CO₂ concentration, concept of time lag was implemented in the regression analysis. As a result, there was an improvement in the performance of the models as the coefficients of determination were 0.93 and 0.87 with segmented time frames for sun-rise and sun-set periods, respectively. Validation tests of the models to predict CO₂ emission from soil showed that the developed empirical model would be applicable to real-time monitoring and diagnosis of significant factors for CO₂ enrichment in a soil-based greenhouse.

Greenhouse CO2 Enrichment Alternatives: Effects of Increasing Concentration or Duration of Enrichment on Cucumber Yields

Abstract Extended duration (delayed venting) and greater intensity were investigated as alternatives for CO2 enrichment of fall and spring greenhouse cucumber (Cucumis sativus L.) crops in North Carolina. The use of rockstorages allowed greenhouses to be enriched an average of 83% longer than was possible in conventionally ventilated greenhouses. Differences in daily enrichment times between rockstorage and conventionally ventilated houses were greatest during periods of high temperatures and high solar radiation levels in the early fall and late spring. In the rockstorage houses, enrichment increased fruit weights from 31–57%. Plants enriched to 600 μl·liter−1 yield as well or better than those enriched to 1000 or 1200 μ·liter−1 CO2. In the conventional houses, enrichment to 1000, 3000, and 5000 μl·liter−1 raised yields 18.5–34.5% in Fall 1983, Spring 1984, and Fall 1984. Cucumbers enriched to 1000 μl·liter−1 produced slightly less than the control plants in Spring 1983, however. In the conventionally vented houses, spring crops yielded best at the highest CO2 enrichment level, whereas for the fall crops the reverse was true.

Factors Affecting the Performance of Rockstorages as Solar Energy Collection/Storage Systems for Greenhouses

ABSTRACT DATA from 6 years operation were analyzed in order to identify important factors affecting the performance of rockstorages as devices for saving energy and enhancing CO2 enrichment in greenhouses. The data were taken from two similar rockstorages of slightly different design attached to two different size greenhouses. The data included seasons conducted with four different crops (lettuce, peas, tomatoes, and cucumbers), two different covers (single fiberglass and double polyethylene), with and without CO2 enrichment, systems of two sizes with similar wind exposures, and systems of the same size with different wind exposures. Fuel savings using the rockstorages ranged from a low of 54.8 MJ/m2 in the winter of 1981 to a high of 143.3 MJ/m2 in the spring of 1979. Percentage enrichment time ranged from 64.3% for the spring of 1984 to 100% in the winter of 1981, up to 45% more enrichment time than conventionally enriched treatments. Electrical energy debit, the additional electricity required to operate the rockstorages, ranged from 9.5 MJ/m^ to 34.6 MJ/m2 whereas collection efficiency varied from 8.0% to 19.3%. Equations for fuel savings, percentage enrichment time, electrical consumption increase, and collection efficiency were determined from the data and evaluated to provide a basis for comparing the effects of important seasonal differences. Fuel savings was found to be a non-linear function of average outside temperature and solar energy and to decrease with CO2 enrichment and increasing severity of wind exposure. Fuel savings under fiberglass was not significantly different from those under double polyethylene. No differences attributable to system size were found. Percentage enrichment time decreased linearly with increasing outside temperature and solar radiation and was found to be negatively affected by decreasing vent set point temperature but not by system size or severity of exposure. Electrical energy debit was found to increase linearly with increasing temperature and solar radiation as well as with CO2 enrichment, decreasing vent set point temperature, and system size. Collection efficiency was found to be a non-linear function of average outside temperature and to increase with CO2 enrichment; however, the increase was not beneficial. Peak efficiency was less under double polyethylene than under fiberglass and decreased with decreasing venting and heating set point temperature; however, the utilization of the energy was better under low temperature conditions so that total fuel savings increased.