Researchers have grown a farm of rooftop vegetables bathed in the CO2-rich exhaust air from city buildings—a somewhat dystopian idea which nevertheless boosted plant growth by an incredible 400%.
Their research turns building vents into an unlikely companion to food production. Many people will recognize these silver, mushroom-shaped structures that are visible on urban roofs: they form part of HVAC systems that pump out stale air and ventilate buildings with fresh air from outside. In buildings where lots of people live and work, the CO2 emissions from human respiration can reach surprisingly high levels, which is why these systems are needed to keep the air fresh and unpolluted.
But for the researchers on the new study, the thinking was, why let all that pent up CO2 vanish into thin air, when it’s a key ingredient in fertilizing plants and promoting their growth?
The majority of urban dwellers spend their time indoors—and so cities have a potentially huge and steady supply of CO2 that’s going untapped. These wasted emissions “can be used as a resource to create better growing conditions for plants,” says Sarabeth Buckley, plant scientist at the University of Cambridge and lead author on the study.
So between 2018 and 2019, Buckley and colleagues started their experiment on the roof of the Boston University campus in the United States, a building heavily populated by students during term time.
At each of the rooftop vents, the researchers planted neat rows of spinach and corn. Their vegetable patch was laid out in such a way that some plants were beside vents that emitted air from inside the building, while others were planted beside control vents that emitted regular atmospheric air. The plants were also exposed to more or less air power from the vents, to determine the impact of high winds on plants’ ability to use the CO2.
The researchers choose the two respective crops because on the one hand, spinach uses a metabolic pathway that is highly responsive to CO2, whereas corn uses another pathway that makes it less sensitive to elevated amounts of this gas—allowing the researchers to test the benefits of their system across different types of crops.
In addition to the rooftop vegetable planting, the researchers also installed CO2 monitors inside the rooms occupied by students, as well as beside the rooftop vents: this gave them a read on how much CO2 was available to plants when it was channeled out the building.
They found that when classes were in session, CO2 levels spiked noticeably—reaching above the recommended 1000 parts per million (ppm) for building interiors for 37% of the time that the classes were in session. This was also well above the 800 ppm of CO2 that plants need to receive a growth boost—so on the rooftop, this resulted in huge growth spurts for the veg.
This was most notable for the spinach, whose biomass increased fourfold beside CO2-emitting vents. Where spinach was grown beside vents that mimicked high wind speed, they still had double the biomass of spinach grown without the added dose of CO2. In fact in all cases where spinach was cultivated besides CO2-blasting vents, the plants were larger and had more leaves.
Even corn, despite being less sensitive to the growth boost of CO2, was between 2 and 3 times larger, and also greener, when planted beside the exhaust vents compared to the control vents. Because they’re less sensitive to CO2, this suggests that another factor like temperature might possibly be playing a role in the growth boost of this veg.
The researchers have questions remaining about whether this elevated CO2 affects nutrient levels in plants. But they also see huge potential benefits resulting from what they’ve found, which might collectively help build the case for urban farms.
Rooftops typically take up 20-30% of urban space, area that goes mostly unused. Looking at the available rooftop area for growing food in the city of Boston where the study was based, the researchers found that if we grew vegetables there and then added CO2 building exhaust to the mix (and assuming also that crops of different varieties would benefit similarly), the city could in fact produce enough food to satisfy 290% of its own vegetable demand.
Add to this the several general benefits of rooftop farms. Rooftop gardens can create insulation in winter and have a cooling effect in summer, saving on energy use and the associated emissions. The production of more local food also cuts back on the high transport and emissions cost of ferrying in food from far flung locations.
More research is needed before CO2-recycling urban gardens become a reality: “There is a lot that has to be figured out before a system can be developed that can be installed on rooftops,” Buckley says, adding that they hope to continue investigating the impact of building exhaust on crop growth at new study sites in the future.
But the findings so far may already have strengthened the case for urban farming. “This is only a taster of what is possible,” Buckley says.
Buckley et. al. “Enhancing crop growth in rooftop farms by repurposing CO2 from human respiration inside buildings.” Frontiers in Sustainable Food Systems. 2022.
Enhancing crop growth in rooftop farms by repurposing CO2 from human respiration inside buildings
Front. Sustain. Food Syst., 24 October 2022
Sec. Climate-Smart Food Systems
https://doi.org/10.3389/fsufs.2022.918027
- 1Earth and Environment Department, Boston University, Boston, MA, United States
- 2Systems Biology Department, Harvard University, Boston, MA, United States
- 3Sustainability Studio, Massachusetts College of Art and Design, Boston, MA, United States
Integrating cities with the surrounding environment by incorporating green spaces in creative ways would help counter climate change. We propose a rooftop farm system called BIG GRO where air enriched with carbon dioxide (CO2) produced through respiration from indoor spaces is applied through existing ventilation systems to produce a fertilization effect and increased plant growth. CO2 measurements were taken inside 20 classrooms and at two exhaust vents on a rooftop at Boston University in Boston, MA. Exhausted air was directed toward spinach and corn and plant biomass and leaf number were analyzed. High concentrations of CO2 persisted inside classrooms and at rooftop exhaust vents in correlation with expected human occupancy. CO2 levels averaged 1,070 and 830 parts per million (ppm), reaching a maximum of 4,470 and 1,300 ppm CO2 indoors and at exhaust vents, respectively. The biomass of spinach grown next to exhaust air increased fourfold compared to plants grown next to a control fan applying atmospheric air. High wind speed from fans decreased growth by approximately twofold. The biomass of corn, a C4 plant, experienced a two to threefold increase, indicating that alternative environmental factors, such as temperature, likely contribute to growth enhancement. Enhancing growth in rooftop farms using indoor air would help increase yield and help crops survive harsh conditions, which would make their installation in cities more feasible.
References
ACGIH American Conference of Governmental Industrial Hygienists (2011). TLVs and BEIs. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.
Ahmed, S., Buckley, S., Stratton, A. E., Asefaha, F., Butler, C., Reynolds, M., et al. (2017). Sedum groundcover variably enhances performance and phenolic concentrations of perennial culinary herbs in an urban edible green roof. Agroecol. Sustain. Food Syst. 41, 1–17. doi: 10.1080/21683565.2017.1279703
Ainsworth, E. A., Leakey, A. D., Ort, D. R., and Long, S. P. (2008). FACE-Ing the facts: inconsistencies and interdependence among field, chamber and modeling studies of elevated [CO2] impacts on crop yield and food supply. New Phytol. 179, 5–9. doi: 10.1111/j.1469-8137.2008.02500.x
Ainsworth, E. A., and Long, S. P. (2005). What have we learned from 15 years of free-air CO2 enrichment (FACE)? A meta-analytic review of the responses of photosynthesis, canopy properties and plant production to rising CO2. New Phytol. 165, 351–372. doi: 10.1111/j.1469-8137.2004.01224.x
Ainsworth, E. A., and Rogers, A. (2007). The response of photosynthesis and stomatal conductance to rising [CO2]: mechanisms and environmental interactions. Plant Cell Environ. 30, 258–270. doi: 10.1111/j.1365-3040.2007.01641.x
Allen, J. G., MacNaughton, P., Satish, U., Santanam, S., Vallarino, J., and Spengler, J. D. (2016). Associations of cognitive function scores with carbon dioxide, ventilation, and volatile organic compound exposures in office workers: a controlled exposure study of green and conventional office environments. Environ. Health Perspect.124, 805–812. doi: 10.1289/ehp.1510037
Apte, M. G., William, J. F., and Joan, M. D. (2000). Associations between indoor CO2 concentrations and sick building syndrome symptoms in US office buildings: an analysis of the 1994–1996 BASE study data. Indoor Air10, 246–257. doi: 10.1034/j.1600-0668.2000.010004246.x
ArrowStreet Architecture and Design. (2016). Addressing Campus Sustainability Through MIT’ s Roofscapes. Boston, MA: Massachusets Institute Technology.
Barrett, K. E., Barman, S. M., Boitano, S., and Brooks, H. L. (2012). “Respiration physiology,” in Ganong’s Review of Medical Physiology, 24th Edn (New York: McGraw-Hill Medical), 619–70.
Batchelor, J., Laurence, S. S., and Tina, S. H. (2009). Green Roof Planning Study. Boston, MA: ArrowStreet.
Boese, S. R., and Huner, N. P. (1990). Effect of growth temperature and temperature shifts on spinach leaf morphology and photosynthesis. Plant Physiol. 94, 1830–1836. doi: 10.1104/pp.94.4.1830
Briber, B. M., Hutyra, L. R., Reinmann, A. B., Raciti, S. M., Dearborn, V. K., Holden, C. E., et al. (2015). Tree productivity enhanced with conversion from forest to urban land covers. PLoS ONE 10, 1–19. doi: 10.1371/journal.pone.0136237
Buckley, S. (2020). Enhancing Plant Growth and Carbon Harvesting for Sustainable Agriculture (Dissertion). Boston University, Boston, MA, United States. Available online at: https://open.bu.edu/ds2/stream/?#/documents/390809/page/1
Buckley, S., Ahmed, S., Griffin, T., and Orians, C. (2021). Extreme precipitation enhances phenolic concentrations of Spinach 2 (S. Oleracea). J. Crop Improv. 34, 618–636. doi: 10.1080/15427528.2020.1750521
Bunea, A., Andjelkovic, M., Socaciu, C., Bobis, O., Neacsu, M., Verhé, R., et al. (2008). Total and individual carotenoids and phenolic acids content in fresh, refrigerated and processed spinach (S. Oleracea L.). Food Chem. 108, 649–656. doi: 10.1016/j.foodchem.2007.11.056
Cai, C., Yin, X., He, S., Jiang, W., Si, C., Struik, P. C., et al. (2016). Responses of wheat and rice to factorial combinations of ambient and elevated CO2 and temperature in FACE experiments. Global Change Biol. 22, 856–874. doi: 10.1111/gcb.13065
Calvert, A., and Slack, G. (1976). Effect of carbon dioxide enrichment on growth, development and yield of glasshouse tomatoes. II. The duration of daily periods of enrichment. J. Hortic. Sci. 51, 401–409.
Candlish, J. K., Gourley, L., and Lee, H. P. (1987). Dietary fiber and starch contents of some southeast Asian vegetables. J. Agric. Food Chem. 35, 319–321. doi: 10.1021/jf00075a008
Carter, T. L., and Rasmussen, T. C. (2007). Hydrologic behavior of vegetated roofs. J. Am. Water Resour. Assoc.42, 1261–1274. doi: 10.1111/j.1752-1688.2006.tb05611.x
Chakrabarti, B., Singh, S. D., Naresh Kumar, S., Aggarwal, P. K., Pathak, H., and Nagarajan, S. (2012). Low-cost facility for assessing impact of carbon dioxide on crops. Curr. Sci. 102, 1035–1040.
Coutts, E., Ito, K., Nardi, C., and Vuong, T. (2015). Planning Urban Heat Island Mitigation Planning Urban Heat Island Mitigation. Boston, MA: Trust for Public Land. doi: 10.1093/icesjms/fss088
Davies, Z. G., Edmondson, J. L., Heinemeyer, A., Leake, J. R., and Gaston, K. J. (2011). Mapping an urban ecosystem service: quantifying above-ground carbon storage at a city-wide scale. J. Appl. Ecol. 48, 1125–1134. doi: 10.1111/j.1365-2664.2011.02021.x
Decina, S. M., Hutyra, L. R., Gately, C. K., Getson, J. M., Reinmann, A. B., and Gianotti, A. G. S. (2016). Soil respiration contributes substantially to urban carbon fluxes in the greater Boston area. Environ. Pollut. 212, 433–439. doi: 10.1016/j.envpol.2016.01.012
Edwards, G. R., Clark, H., and Newton, P. C. D. (2001). The effects of elevated CO2 on seed production and seedling recruitment in a sheep-grazed pasture. Oecologia 127, 383–394. doi: 10.1007/s004420000602
Ellsworth, D. S., Oren, R., Huang, C., Phillips, N., and Hendrey, G. R. (1996). Erratum: leaf and canopy responses to elevated CO2 in a pine forest under free-air CO2 enrichment (Oecologia (1995) 104 (139–146)). Oecologia106, 416. doi: 10.1007/BF00328578
Fleisher, D. H., Timlin, D. J., and Reddy, V. R. (2008). Interactive effects of carbon dioxide and water stress on potato canopy growth and development. Agron. J. 100, 711–719. doi: 10.2134/agronj2007.0188
Garrison, N., Horowitz, C., and Lunghino, A. C. (2012). Looking up: how green roofs and cool roofs can reduce energy use, address climate change, and protect water resources in Southern California. NRDC Rep. R 12, 1–33. doi: 10.1109/TDC.2005.1547154
Getter, K. L., Rowe, D. B., Robertson, G. P., Cregg, B. M., and Andresen, J. A. (2009). Carbon sequestration potential of extensive green roofs. Sci. Technol. 43, 7564–7570. doi: 10.1021/es901539x
Guite, H. F., Clark, C., and Ackrill, G. (2006). The impact of the physical and urban environment on mental well-being. Public Health 120, 1117–1126. doi: 10.1016/j.puhe.2006.10.005
Halweil, B. (2002). Home Grown the Case for Local Food in a Global Market. Washington, DC: Worldwatch Institute.
Hanson, P. J., Edwards, N. T., Garten, C. T., and Andrews, J. A. (2000). Separating root and soil microbial contributions to soil respiration: a review of methods and observations. Biogeochemistry 48, 115–146. doi: 10.1023/A:1006244819642
Hatfield, J. L., Boote, K. J., Kimball, B. A., Ziska, L. H., and Izaurralde, R. C. (2011). Climate impacts on agriculture: implications for crop production. Agron. J. 103, 351–370. doi: 10.2134/agronj2010.0303
He, Y., Yu, H., Dong, N., and Ye, H. (2016). Thermal and energy performance assessment of extensive green roof in summer: a case study of a lightweight building in Shanghai. Energy Build. 127, 762–773. doi: 10.1016/j.enbuild.2016.06.016
Hendrey, G. R., Lewin, K. F., and Nagy, J. (1993). Free air carbon dioxide enrichment: development, progress, results. Vegetatio 104, 16–31.
Howard, L. R., Pandjaitan, N., Morelock, T., and Gil, M. I. (2005). Antioxidant capacity and phenolic content of spinach as affected by genetics and maturation. J. Agric. Food Chem. 53, 8618–8623. doi: 10.1021/jf052077i
Idso, S. B., and Idso, K. E. (2001). Effects of atmospheric CO(2) enrichment on plant constituents related to animal and human health. Environ. Exp. Bot. 45, 179–199. doi: 10.1016/S0098-8472(00)00091-5
Ismail, A., Samad, M. H. A., Rahman, A. M. A., and Yeok, F. S. (2012). Cooling potentials and CO2 uptake of ipomoea pes-caprae installed on the flat roof of a single storey residential building in Malaysia. Proc. Soc. Behav. Sci. 35, 361–368. doi: 10.1016/j.sbspro.2012.02.099
Jin, M., Bekiaris-Liberis, N., Weekly, K., Spanos, C., and Bayen, A. (2015). “Sensing by proxy: occupancy detection based on indoor CO2 concentration ming,” in UMBICOMM 2015: The Ninth International Conference on Mobile Ubiquitous Computing, Systems, Services and Technologies, Iaria, Nice, France, 1–10.
Johnson, B. S., Malecki, K. M., Peppard, P. E., and Beyer, K. M. (2018). Exposure to neighborhood green space and sleep: evidence from the survey of the health of Wisconsin. Sleep Health 4, 413–419. doi: 10.1016/j.sleh.2018.08.001
Kadam, K. L., and McMillan, J. D. (2003). Availability of corn stover as a sustainable feedstock for bioethanol production. Bioresour. Technol. 88, 17–25. doi: 10.1016/S0960-8524(02)00269-9
Kangasjärvi, J., Jaspers, P., and Kollist, H. (2005). Signalling and cell death in ozone-exposed plants. Plant Cell Environ. 28, 1021–1036. doi: 10.1111/j.1365-3040.2005.01325.x
Kimball, B. A., Kobayashi, K., and Bindi, M. (2002). Responses of agricultural crops to free-air CO2 enrichment. Adv. Agron. 77, 293–368. doi: 10.1016/S0065-2113(02)77017-X
Kimball, B. A., Pinter, P. J., Wall, G. W., Garcia, R. L., and LaMorte, R. L. (1997). Comparisons of responses of vegetation to elevated carbon dioxide in free air and open-top chamber facilities. Adv. Carbon Dioxide Effects Res. 61, 113–130. doi: 10.2134/asaspecpub61.c5
Kleerekoper, L., Van Esch, M., and Salcedo, T. B. (2012). How to make a city climate-proof, addressing the urban heat Island effect. Resour. Conserv. Recycl. 64, 30–38. doi: 10.1016/j.resconrec.2011.06.004
Kuti, J. O., and Konuru, H. B. (2004). Antioxidant capacity and phenolic content in leaf extracts of tree spinach (Cnidoscolus Spp.). J. Agric. Food Chem. 52, 117–121. doi: 10.1021/jf030246y
Leakey, A. D., Ainsworth, E. A., Bernacchi, C. J., Rogers, A., Long, S. P., and Ort, D. R. (2009). Elevated CO2 effects on plant carbon, nitrogen, and water relations: six important lessons from FACE. J. Exp. Bot. 60, 2859–2876. doi: 10.1093/jxb/erp096
Leakey, A. D., Bernacchi, C. J., Dohleman, F. G., Ort, D. R., and Long, S. P. (2004). Will photosynthesis of maize (Z. Mays) in the US corn belt increase in future [CO2] rich atmospheres? An analysis of diurnal courses of CO2uptake under free-air concentration enrichment (FACE). Global Change Biol. 10, 951–62. doi: 10.1111/j.1529-8817.2003.00767.x
Lee, S. C., and Chang, M. (1999). Indoor air quality investigations at five classrooms. Indoor Air 9, 134–138. doi: 10.1111/j.1600-0668.1999.t01-2-00008.x
Loladze, I. (2002). Rising atmospheric CO2 and human nutrition: toward globally imbalanced plant stoichiometry? Trends Ecol. Evolut. 17, 457–461. doi: 10.1016/S0169-5347(02)02587-9
Long, S. P., Ainsworth, E. A., Leakey, A. D., Nosberger, J., and Ort, D. R. (2006). Food for thought: lower-than-expected crop yield stimulation with rising CO2 concentrations. Science 312, 1918–1922. doi: 10.1126/science.1114722
Lower, E., and Restaurant, B. (2014). Case Study: economic viability of growing produce organically on-site at restaurants.
MADPH (2022). Appendix A: Carbon Dioxide and its Use in Evaluating Adequacy of Ventilation in Buildings.
McLeod, A. R., and Long, S. P. (1999). Free-air carbon dioxide enrichment (FACE) in global change research: a review. Adv. Ecol. Res. 28, 1–57.
Medek, D. E., Schwartz, J., and Myers, S. S. (2017). Estimated effects of future atmospheric CO2 concentrations on protein intake and the risk of protein deficiency by country and region. Environ. Health Perspect. 125, 1–8. doi: 10.1289/EHP41
Meier, A. K. (1990). Strategic landscaping and air-conditioning savings: a literature review. Energy Build. 15, 479–86. doi: 10.1016/0378-7788(90)90024-D
Miglietta, F., Lanini, M., Bindi, M., and Magliulo, V. (1997). Free air CO2 enrichment of potato (Solanum tuberosum, L.): design and performance of the CO2-fumigation system. Glob. Change Biol. 3, 417–427. doi: 10.1046/j.1365-2486.1997.00076.x
Min, K., Chen, K., and Arora, R. (2014). Effect of short-term versus prolonged freezing on freeze-thaw injury and post-thaw recovery in spinach: Importance in laboratory freeze-thaw protocols. Environ. Exp. Bot. 106, 124–131. doi: 10.1016/j.envexpbot.2014.01.009
Moore, B. D., Cheng, S., Sims, D., and Seemann, J. R. (1999). The biochemical and molecular basis for photosynthetic acclimation to elevated atmospheric CO2. Plant Cell Environ. 22, 567–582.
Myers, S. S., Zanobetti, A., Kloog, I., Huybers, P., Leakey, A. D., Bloom, A. J., et al. (2014). Increasing CO2threatens human nutrition. Nature 510, 139–42. doi: 10.1038/nature13179
Nadal, A., Alamús, R., Pipia, L., Ruiz, A., Corbera, J., Cuerva, E., et al. (2017a). Urban planning and agriculture. Methodology for assessing rooftop greenhouse potential of non-residential areas using airborne sensors. Sci. Total Environ. 601–602, 493–507. doi: 10.1016/j.scitotenv.2017.03.214
Nadal, A., Llorach-Massana, P., Cuerva, E., López-Capel, E., Montero, J. I., Josa, A., et al. (2017b). Building-integrated rooftop greenhouses: an energy and environmental assessment in the Mediterranean context. Appl. Energy 187, 338–351. doi: 10.1016/j.apenergy.2016.11.051
Nagase, A., and Dunnett, N. (2012). Amount of water runoff from different vegetation types on extensive green roofs: effects of plant species, diversity and plant structure. Landscape Urban Plan. 104, 356–63. doi: 10.1016/j.landurbplan.2011.11.001
Ng, C. W. W., Tasnim, R., and Wong, J. T. F. (2019). Coupled effects of atmospheric CO2 concentration and nutrients on plant-induced soil suction. Plant Soil 439, 393–404. doi: 10.1007/s11104-019-04047-4
Nijs, I., Ferris, R., Blum, H., Hendrey, G., and Impens, I. (1997). Stomatal regulation in a changing climate: a field study using free air temperature increase (FATI) and free air CO2 enrichment (FACE). Plant Cell Environ. 20, 1041–1050. doi: 10.1111/j.1365-3040.1997.tb00680.x
Nitsch Engineering (2016). Harvard Business School Stormwater Plan Update. Boston, MA: Harvard Business School.
Norby, R. J., De Kauwe, M. G., Domingues, T. F., Duursma, R. A., Ellsworth, D. S., Goll, D. S., et al. (2016). Viewpoints model-data synthesis for the next generation of forest free-air CO2 enrichment (FACE) experiments. New Phytol. 209, 17–28. doi: 10.1111/nph.13593
Norby, R. J., and Zak, D. R. (2011). Ecological lessons from free-air CO2 enrichment (FACE) experiments. Annu. Rev. Ecol. Evolut. Syst. 42, 181–203. doi: 10.1146/annurev-ecolsys-102209-144647
Nowak, R. S., Ellsworth, D. S., and Smith, S. D. (2004). Functional responses of plants to elevated atmospheric CO2–do photosynthetic and productivity data from FACE experiments support early predictions? New Phytol.162, 253–280. doi: 10.1111/j.1469-8137.2004.01033.x
Nuutila, A. M., Kammiovirta, K., and Oksman-Caldentey, K. -M. (2002). Comparison of methods for the hydrolysis of flavonoid and phenolic acids from onion and spinach for HPLC analysis. Food Chem. 76, 519–525. doi: 10.1016/S0308-8146(01)00305-3
Oberndorfer, E., Lundholm, J., Bass, B., Coffman, R. R., Doshi, H., Dunnett, N., et al. (2007). Green roofs as urban ecosystems: ecological structures, functions, and services. BioScience 57, 823–833. doi: 10.1641/B571005
Onoda, Y., and Anten, N. P. (2011). Challenges to understand plant responses to wind. Plant Signal. Behav. 6, 139–141. doi: 10.4161/psb.6.7.15635
Orsini, F., Gasperi, D., Marchetti, L., Piovene, C., Draghetti, S., Ramazzotti, S., et al. (2014). Exploring the production capacity of rooftop gardens (RTGs) in urban agriculture: the potential impact on food and nutrition security, biodiversity and other ecosystem services in the City of Bologna. Food Sec. 6, 781–792. doi: 10.1007/s12571-014-0389-6
Persily, A. (2020). “Quit blaming ASHRAE Standard 62.1 for 1000 ppm CO2,” in The 16th Conference of the International Society of Indoor Air Quality and Climate. p. 1-2.
Persily, A., and de Jonge, L. (2017). Carbon dioxide generation rates for building occupants. Indoor Air 27, 868–879. doi: 10.1111/ina.12383
Pirog, R., Van Pelt, T., Enshayan, K., and Cook, E. (2001). Food, fuel, and freeways: an iowa perspective on how far food travels, fuel usage, and greenhouse gas emissions. Leopold Center Sustain. Agric. 209, 1–37.
Pons, O., Nadal, A., Sanyé-Mengual, E., Llorach-Massana, P., Cuerva, E., Sanjuan-Delmàs, D., et al. (2015). Roofs of the future: rooftop greenhouses to improve buildings metabolism. Proced. Eng. 123, 441–448. doi: 10.1016/j.proeng.2015.10.084
Prajapati, S. K. (2012). Ecological effect of airborne particulate matter on plants. Environ. Skept. Crit. 1, 12–22.
Rao, P., Hutyra, L. R., Raciti, S. M., and Templer, P. H. (2014). Atmospheric nitrogen inputs and losses along an urbanization gradient from Boston to Harvard forest, MA. Biogeochemistry 121, 229–245. doi: 10.1007/s10533-013-9861-1
Reddy, M. T., Begum, H., Sunil, N., Rao, P. S., Sivaraj, N., and Kumar, S. (2014). Preliminary characterization and evaluation of landraces of indian spinach (basella spp. l.) for agro-economic and quality traits. Plant Breed. Biotechnol. 2, 48–63. doi: 10.9787/PBB.2014.2.1.048
Reece, C. F., Krupa, S. V., Jäger, H. J., Roberts, S. W., Hastings, S. J., and Oechel, W. C. (1995). Evaluating the effects of elevated levels of atmospheric trace gases on herbs and shrubs: a prototype dual array field exposure system. Environ. Pollut. 90, 25–31. doi: 10.1016/0269-7491(94)00095-U
Rice, S. A. (2004). “Human health risk assessment of CO2: survirors of accute high-level exposure and populations sensitive to prolonged low-level exposure,” in Third Annual Conference on Carbon Sequestration, Susan A. Rice and Associates Inc., Grass Valley, CA, 1–9.
Rogers, H. H., Runion, G. B., and Krupa, S. V. (1994). Plant reponses to atmospheric CO2 enrichment with emphasis on roots and the rhizosphere. Environ. Pollut. 83, 155–189. doi: 10.1016/0269-7491(94)90034-5
Rowe, D. B. (2011). Green roofs as a means of pollution abatement. Environ. Pollut. 159, 2100–2110. doi: 10.1016/j.envpol.2010.10.029
Saadatian, O., Sopian, K., Salleh, E., Lim, C. H., Riffat, S., and Saadatian, E. (2013). A review of energy aspects of green roofs. Renew. Sustain. Energy Rev. 23, 155–168. doi: 10.1016/j.rser.2013.02.022
Sanjuan-Delmás, D., Llorach-Massana, P., Nadal, A., Ercilla-Montserrat, M., Muñoz, P., Montero, J. I., et al. (2018a). Environmental assessment of an integrated rooftop greenhouse for food production in cities. J. Clean. Prod. 177, 326–337. doi: 10.1016/j.jclepro.2017.12.147
Sanjuan-Delmás, D., Llorach-Massana, P., Nadal, A., Sanyé-Mengual, E., Petit-Boix, A., Ercilla-Montserrat, M., et al. (2018b). “Improving the metabolism and sustainability of buildings and cities through integrated rooftop greenhouses (i-RTG),” in Urban Horticulture: Sustainability for the Future (Cham: Springer International Publishing), 53–72. doi: 10.1007/978-3-319-67017-1_3
Santamouris, M. (2014). Cooling the cities: a review of reflective and green roof mitigation technologies to fight heat Island and improve comfort in urban environments. Solar Energy 103, 682–703. doi: 10.1016/j.solener.2012.07.003
Sanyé-Mengual, E., Cerón-Palma, I., Oliver-Solà, J., Montero, J. I., and Rieradevall, J. (2015a). Integrating horticulture into cities: a guide for assessing the implementation potential of rooftop greenhouses (RTGs) in industrial and logistics parks. J. Urban Technol. 22, 87–111. doi: 10.1080/10630732.2014.942095
Sanyé-Mengual, E., Llorach-Massana, P., Sanjuan-Delmás, D., Oliver-Solà, J., Josa, A., Montero, J. I., et al. (2014). “The ICTA-ICP rooftop greenhouse lab (RTG-Lab): closing metabolic flows (energy, water, CO2) through integrated rooftop greenhouses,” in Finding Places for Productive Cities. Proceedings of 6th International AESOP Sustainable Food Planning Conference, VHL University of Applied Sciences, Barcelona, 693–701.
Sanyé-Mengual, E., Oliver-Solà, J., Montero, J. I., and Rieradevall, J. (2015b). An environmental and economic life cycle assessment of rooftop greenhouse (RTG) implementation in Barcelona, Spain. Assessing new forms of urban agriculture from the greenhouse structure to the final product level. Int. J. Life Cycle Assess. 20, 350–366. doi: 10.1007/s11367-014-0836-9
Satish, U., Mendell, M. J., Shekhar, K., Hotchi, T., Sullivan, D., Streufert, S., et al. (2012). Is CO2 an indoor pollutant? Direct effects of low-to-moderate CO2 concentrations on human decision-making performance. Environ. Health Perspect. 120, 1671–77. doi: 10.1289/ehp.1104789
Seppanen, O. A., Fisk, W. J., and Mendell, M. J. (1999). Association of ventilation rates and CO2 concentrations with health and other responses in commercial and institutional buildings. Indoor Air 9, 226–252. doi: 10.1111/j.1600-0668.1999.00003.x
Shafique, M., and Kim, R. (2017). Retrofitting the low impact development practices into developed urban areas including barriers and potential solution. Open Geosci. 9, 240–254. doi: 10.1515/geo-2017-0020
Shafique, M., Kim, R., and Kyung-Ho, K. (2018a). Green roof for stormwater management in a highly urbanized area: the case of Seoul, Korea. Sustainability 10, 584. doi: 10.3390/su10030584
Shafique, M., Kim, R., and Rafiq, M. (2018b). Green roof benefits, opportunities and challenges: a review. Renew. Sustain. Energy Rev. 90, 757–773. doi: 10.1016/j.rser.2018.04.006
Shafique, M., Xue, X., and Luo, X. (2020). An overview of carbon sequestration of green roofs in urban areas. Urban Forestry Urban Greening 47, 126515. doi: 10.1016/j.ufug.2019.126515
Sharkey, T. D. (1988). Estimating the rate of photorespiration in leaves. Plant Physiol. 73, 147–152.
Shohag, M. J. I., Wei, Y. Y., Yu, N., Zhang, J., Wang, K., Patring, J., et al. (2011). Natural variation of folate content and composition in spinach (S. Oleracea) germplasm. J. Agric. Food Chem. 59, 12520–12526. doi: 10.1021/jf203442h
Templer, P. H., Toll, J. W., Hutyra, L. R., and Raciti, S. M. (2015). Nitrogen and carbon export from urban areas through removal and export of litterfall. Environ. Pollut. 197, 256–261. doi: 10.1016/j.envpol.2014.11.016
Vadiee, A., and Martin, V. (2013). Thermal energy storage strategies for effective closed greenhouse design. Appl. Energy 109, 337–343. doi: 10.1016/j.apenergy.2012.12.065
van Beveren, P. J. M., Bontsema, J., van Straten, G., and van Henten, E. J. (2015). Optimal control of greenhouse climate using minimal energy and grower defined bounds. Appl. Energy 159, 509–519. doi: 10.1016/j.apenergy.2015.09.012
Vaughan, N. E., and Lenton, T. M. (2011). A review of climate geoengineering proposals. Clim. Change 109, 745–790. doi: 10.1007/s10584-011-0027-7
Warrington, I. J., and Kanemasu, E. T. (1983). Corn growth responses to temperature and photoperiod. II. Leaf initiation and leaf appearance rates. Agron. J. 75, 755–761.
Whittinghill, L. J., Rowe, D. B., Andresen, J. A., and Cregg, B. M. (2015). Comparison of stormwater runoff from sedum, native prairie, and vegetable producing green roofs. Urban Ecosyst. 18, 13–29. doi: 10.1007/s11252-014-0386-8
Whittinghill, L. J., Rowe, D. B., Schutzki, R., and Cregg, B. M. (2014). Quantifying carbon sequestration of various green roof and ornamental landscape systems. Landscape Urban Plan. 123, 41–48. doi: 10.1016/j.landurbplan.2013.11.015
Wong, N. H., Cheong, D. K. W., Yan, H., Soh, J., Ong, C. L., and Sia, A. (2003). The effects of rooftop garden on energy consumption of a commercial building in Singapore. Energy Build. 35, 353–364. doi: 10.1016/S0378-7788(02)00108-1
Yamori, W., Suzuki, K., Noguchi, K. O., Nakai, M., and Terashima, I. (2006). Effects of rubisco kinetics and rubisco activation state on the temperature dependence of the photosynthetic rate in spinach leaves from contrasting growth temperatures. Plant Cell Environ. 29, 1659–1670. doi: 10.1111/j.1365-3040.2006.01550.x
Zhang, X., Chen, X., and Zhang, X. (2018). The impact of exposure to air pollution on cognitive performance. Proc. Natl. Acad. Sci. 115, 9193–9197. doi: 10.1073/pnas.1809474115
“We MUST respect this earth - it is all we have
Claudio Dametto - South Australia
“I will always Vote to Preserve Our World.
Liam McGregor - Western Australia
“A simple message that even a politician can understand
Felicity Crombach - Victoria
“Please show you care about our future generations!!
Phil Harmer - New South Wales
“Save our world , Life & health before profits.
Kerry Lillian - New South Wales
“Close down all coal mines and Do not mine gas . Make these Companies
Daniel Johnson - New South Wales
“We want carbon free energy!
Edan Clarke - New South Wales
“Feels good to be taking a voter action step
Beaver Hudson - New South Wales
“Great Initiative. Let’s Hold elected officials Accountable to their bosses, us!
John Paul Posada - New South Wales
“We need actions not words we need honest democratic govt We need a pm
Bob Pearce - South Australia
“Thank you for this great resource. I was feeling helpless. Even this small step
Silvia Anderson - Victoria
“If political parties continue receiving political donations, we will rarely have politicians working for
Dan Chicos - New South Wales
“I only vote for people who will take urgent action to restore a safe
Susie Burke - Victoria
“Current government is not representing the opinion of the majority of Australian to meet
Neil Price - Tasmania
“We are fighting to rescue our kids' future from those who seek to steal
Vanessa Norimi - Queensland
“No time to waste Now or Never My vote is for NOW
Rosalie White - Victoria
“I am only 9 but I already care
Ava Bell - New South Wales
“From New Lambton Uniting Church - Caring for our world is a moral imperative.
Niall McKay - New South Wales
“Our federal govt is an International climate Embarrassment - its about time they stepped
Oriana Tolo - Victoria
“Vote earth this time!
Sue Cooke - Queensland
“We are in one on the wealthiest countries in the world. we have the
rowan huxtable - New South Wales
“The climate Emergency is the public health opportunity and urgent priority of the 21st
Mike Forrester - Victoria
“If they want my vote they better act now
Barbara McNiff - New South Wales
“We need to act locally now for the earth. Our only home. Vote Earth
Anne Miller - New South Wales
“I often look at the places I've known all my life and see how
Jim Baird - New South Wales
“Strike one For people power!!! Democracy might prevail outside the current cronyism that faces
Lorraine Bridger - New South Wales
“Our federal politicians Are Afraid to make action on climate change a major election
Jennifer Martin - New South Wales
“climate election, let's go!
Fahimah Badrulhisham - New South Wales
“Great to see this website that is a focus on action for climate change
Lynette Sinclair - New South Wales
“Let’s show politicians and the Murdoch media that climate change is by far the
Jane Aitken - Australian Capital Territory
“If you want to stay in power You need to take action to stop
Jane Bulter - New South Wales
“We are all that stands between terminal climate change and the vulnerable. We are
Carol Khan - Queensland
“We need a Government that Believes this is real and not taking money from
Ken Gray - New South Wales
“I'm voting for my childrens future
Anneliese Alexander - New South Wales