Frequently Asked Questions | Cityblooms

Frequently Asked Questions

A: Hydroponics is a method of growing plants using mineral nutrient solutions, in water, without soil. Terrestrial plants may be grown with their roots in the mineral nutrient solution only or in an inert medium that provides structure for root growth. Researchers discovered in the 18th century that plants absorb essential mineral nutrients as inorganic ions in water. In natural conditions, soil acts as a mineral nutrient reservoir but the soil itself is not essential to plant growth. When the mineral nutrients in the soil dissolve in water, plant roots are able to absorb them. When the required mineral nutrients are introduced into a plant's water supply artificially, soil is no longer required for the plant to thrive. A Cityblooms Micro-Farm utilizes a “closed-loop” hydroponic methodology that continually circulates and reconditions the nutrient solution being fed to the plants in order to achieve dramatic improvements in water resource efficiency.
A: Approximately 12,000 gallons.

Closed-loop irrigation systems have been shown to achieve significant increases in water resource efficiency. Commercial lettuce production guidelines published by the University of Hawaii, for example, suggest that optimal field irrigation rates for head and leafy lettuce varieties require the application of .6 gallons per ft2 per week (1 inch/acre/week) in humid climates.1 Closed-loop hydroponic systems growing lettuce crops have exhibited water use efficiency gains of 60% and greater as compared to irrigation rates of open field cultivation.2 Other crops have exhibited a range of efficiency gains when grown in closed-loop systems. A study conducted in Jordan on hydroponic production of forage crops (i.e. peas, barley, wheatgrass) resulted in efficiency gains of over 95%3 while an Australian study documented a 33% increase in water efficiency for hydroponic cucumber production.4

Closed-loop irrigation methods have also achieved large gains in fertilizer use efficiency. Commercial guidance published by the University of Arizona recommends the application of 175-200 lbs. of nitrogen per acre per season for lettuce crops as an example. However, that same guidance projects that as much as 50% of that nitrogen will be lost to run-off during the growing season.5 Comparatively, a scientific study examining nitrogen use in lettuce production utilizing closed loop techniques reported as much as a 75% gain in nitrogen use efficiency over field production methods.6

The actual gains in water and fertilizer gains that can be realized by a Cityblooms micro-farm are not yet known and we are looking forward to analyzing the data gathered during the trial. It is expected that resource efficiency gains realized will be in line with results documented by the scientific community. Using these metrics, a 16 unit Cityblooms micro-farm under lettuce production would realize an annual water savings of 12,160 gallons as compared to a similar area under field cultivation.
1. Valenzuela, Kratky, and Cho, Lettuce Production Guidelines for Hawaii, CTAHR, University of Hawaii.
2. Monaghan, Wood, and Hilton, Improved Efficiency of Nutrient and Water use for High Quality Field Vegetable Production using Fertigation. Acta Horticulture (2010), Vol.852 . pp. 145-152. ISSN 0567-7572
3. Al-Karaki and Al-Hashimi, Green Fodder Production and Water Use Efficiency of Some Forage Crops under Hydroponic Conditions, ISRN Agronomy (2012).
4. Grewal, Maheshwari, and Parks, Water and Nutrient Use Efficiency of a Low-Cost Hydroponic Greenhouse for a Cucumber Crop: An Australian Case Study, Journal of Agricultural Water Management, volume 98, issue 5 (March 2011).
6. See note 2.
A: One of the nutrients that dissipates most rapidly is Vitamin C; lettuce can lose up to 10% Ascorbic Acid content per day.

While scientific studies have shown that phenolic and carotenoid compounds in harvested produce can remain stable for sustained periods under optimal cold storage conditions, Vitamin C/Ascorbic Acid (AA) dissipates rapidly from fresh produce with the passage of time. For example, a 1944 study discovered that leafy vegetables held at 6°C lost 10% of their AA content in 6 days while those held at room temperature lost 20% in only 2 days.7

Cold storage temperatures appear to have the greatest influence on nutrient dissipation. In a 2006 study, AA dissipation in lettuce stored at 8 degrees Celsius progressed at 2.9 times the rate as compared to storage at 0 degrees Celsius.8 Similarly, green beans have exhibited a 92% decrease in AA after only 16 days of cold storage.9 Packaging choices, and their impact on post-harvest water retention, have also shown to have a significant impact in nutrient retention. In a study on broccoli florets, it was discovered that there was no AA loss in florets stored in a modified atmosphere package while florets packaged in perforated film lost between 75-85% of their AA after only six days of cold storage.10 Similarly, harvest and shipping methods impact nutrient retention as AA content has been found to be 15% lower in localized bruised tissue as compared to un-bruised tissue of the same specimen.11

Overall, the scientific data indicates that even with extraordinary care in the harvest process and immediate placement of harvested crops in optimal cold storage, fresh produce is subject to rapid loss of some beneficial nutrients with the passage of time. The reality is that crops often wait extended periods after harvest before entering cold storage and are subject to wide temperature fluctuations during transport. Furthermore, the inevitable jostling and bruising that is inflicted upon fresh produce as it moves through distribution only serves to accelerate nutrient loss.
7. Lee and Kader, Pre-harvest and postharvest factors influencing vitamin C content of horticultural crops, Journal of Postharvest Biology and Technology (2000).
8. Moreira et. al., Effects of abusive temperatures on the postharvest quality of lettuce leaves: ascorbic acid loss and microbial growth, Journal of Applied Horticulture (2006).
9. See note 8.
10. Kalt, Effects of Production and Processing Factors on Major Fruit and Vegetable Antioxidants, Journal of Food Science (2004).
11. See note 10.
A: By mitigating the scenarios that commonly lead to the majority of food loss.

An issue paper published by the NRDC in 2012 estimated that only 42% of the produce grown in North America is actually consumed. For fruits and vegetables, the largest losses occur in the production process, in distribution and retail, and at the consumer. These are areas in which a Cityblooms micro-farm placed in close proximity to the final consumer can make its largest gains. First, the automated controlled environment inside the cultivation units drastically reduces food loss during the growing process. Second, distribution and retail operations are virtually eliminated (creating further transportation energy efficiencies). Third, as crops are only harvested according to consumption demands, there should be very little waste in the kitchen. It is likely that a Cityblooms micro-farm can achieve food loss rates of less than 10%.

Food Losses in the Supply Chain
A: As the Cityblooms system has been developed for rooftop farming, we have searched for production methods that are as light-weight as possible. This search has naturally led us into hydroponic production. Over the last few years, the USDA has recognized that “organic" certification standards are only appropriate for evaluating crops grown in soil and as such have stopped issuing organic certification to hydroponic producers.

The main thrust of the confusion lies in the fertilizer options available to hydroponic growers. Organic farming methods rely on microbial life in soil to process organic material primarily sourced from animal products such as manure, blood meal, and fish guts into the basic elements plants need for nourishment. Alternatively, hydroponic growers are able to source those nutritional elements in a water-soluble state allowing for direct absorption by the plants. Isolating the nutritional minerals in a water-soluble state requires a refining process. This difference has no bearing on the quality or nutritional value of the final product. In fact, hydroponic production allows for an efficient and sterile growing environment with drastically reduced food safety risks. Plants don't care where the nitrogen comes from... its all the same molecule. The arguments against refined fertilizers lie in a history of soil farmers dumping vast amounts of fertilizer into their fields, of which their crops consume only a fraction. The rest of this wasted fertilizer "run-off" travels into rivers and groundwater systems causing secondary environmental damage. However, closed-loop hydroponic systems are designed to be vastly more water and nutrient efficient than traditional soil farming. There is consequently minimal fertilizer waste and no harmful run-off.

Aside from the nutrient inputs, the vast majority of Cityblooms operations, such as our choice of pest and fungus protection measures and other agricultural inputs utilize “certified” organic materials and methods.
A: Cityblooms uses non-GMO seeds whenever possible, mostly because GMO seeds do not make much sense for the Cityblooms style of farming. For example, in conducting selective breeding efforts to create GMO seeds, Scientists try to engineer crops so they can survive long shipping journeys and arrive at their location looking fresh, even though they are anything but fresh. Because our produce is consumed in an ultra-fresh state, Cityblooms is able to cultivate heirloom and other varieties selected for taste and nutritional value rather than appearance, shipping qualities, or pesticide resistance. This leads to a healthier lifestyle and a more interesting culinary experience than GMO crops can offer.
A: Micro greens are the young, nutritious, flavor packed shoots that are normally harvested before a plant starts to set its first true leafs. They contain not only high levels of protein and anti-oxidants compared to their seed counterparts, but also nutrients and beneficial compounds not always found in the adult plant of the same variety. Micro greens are different from sprouts because micro greens are harvested above the soil, leaving the root and seed hull (which carries the highest risk of contamination) behind.
A: It is common knowledge that produce eaten in a raw state carries a heightened degree of food safety risk. Furthermore, it is obviously impossible to design an agricultural process that completely eliminates the risk of bacterial or other contamination. As a threshold matter, enclosed hydroponic systems significantly reduce the risk of pathogen introduction over traditional field production methods. However, once a hydroponic system is contaminated, the constant water flow makes it easier for contamination to spread. In grossly simplified terms, an effective food safety plan begins with clean and sterile equipment and implements standard operating procedures (SOP) designed to minimize the risk of contamination during the growing process.

The Cityblooms system has features that significantly mitigate food safety risk. We do not use biologically active fertilizer so we are able to seek a sterile irrigation system by running ultraviolet filtration in the reservoir and dosing incoming water with hydrogen peroxide. Furthermore, the enclosed cultivation pods reduce the risk of system contamination from wild animals and airborne debris. As such, the largest single risk of contamination is from human operator interaction.

Cityblooms Micro-Farms can establish certification under the USDA harmonized Good Agricultural Practices Standards (GAP) for leafy green production. Conceptually, the standards encourage the creation of written manuals and employee training protocols covering a variety of food safety related topics. Cityblooms will conduct daily and weekly checks to ensure compliance with establish SOP and will also receive periodic third-party inspections by a USDA accredited inspector. While the USDA standards only require two third-party inspections per year (one scheduled and one surprise inspection) it is common within the industry for growers to implement a more rigorous independent audit schedule.
A: Like any type of agriculture, the answer depends upon the season, location, and cultivate under production. However, for point of reference, a cluster of 10 cultivation units (400 ft2 of growing area) can grow 50-60 lbs of fresh greens a week if an efficient crop such as green pea microgreens (“Pea Shoots”) are cultivated. Similarly, a cluster of 16 Cultivation Units can produce roughly 5 tons of lettuce per year.
A: As the produce is harvested from the system, the roots and growing medium are left behind. This leftover biomass can be composted to become excellent mulch for ornamental landscaping.