Hydroponic plants can enrich the lives of animals just as they do humans, and what better place to exhibit this than at a zoo. Paignton Zoo Environmental Park in Devon, UK, recently hosted the official opening of the Verticrop vertical hydroponic farming system, developed by Valcent EU. The idea of growing fresh food for the animals on-site originated from discussions between Kevin Frediani, curator of plants and gardens at Paignton Zoo, and Valcent Products (EU) Ltd., based in Launceston, who was developing a vertical hydroponic system for high intensity cropping. Space within the zoo was tight and at a premium, so options for on-site fresh food production were severely limited until the vertical cropping was introduced by Valcent. Within a small area in the middle of the zoo, which was formally a goat paddock, a 395 square foot greenhouse was erected in May 2009 and the system began installation in August. By the time of the opening on September 30, an impressive growth rate had ensured some sizeable lettuce was ready for viewing and for taste testing by the zoo occupants.
With an annual bill for animal feed currently in excess of $300,000 a year, it is the hope of management the high intensity Verticrop system will not only produce ultra fresh produce on-site, but also reduce both food miles and food costs for the zoo. Lettuce has been the initial trial crop for the Verticrop system, with many animals enjoying the fresh crunch of crispy green leaves. The zoo currently goes through 800 lettuce heads per week, $12,000 worth of fruit per month and also uses fresh herbs as enrichment for many species. Later on it’s planned that the hydroponic system will have more diversity of crops; currently small volumes of basil and other leafy greens are being trialed.
Each growing tray contains a nutrient feeding funnel.
The Verticrop system comprises 10 feet tall, multi-level growing trays, which are suspended from an overhead track. Each ‘rig’ consists of eight levels of growing channels or ‘trays’ of which there are two different sizes to accommodate various crops. Each growing tray, which has been purpose built for the Verticrop system, has a nutrient delivery funnel through which nutrients are dosed at the feeding station. The unique thing about this vertical system is that the rigs are suspended on a closed loop conveyor and in motion around the greenhouse track. Each circuit takes approximately 40 minutes with groups of rigs stopping at the dosing station on each round where nutrient solution is delivered via nozzles to the growing trays. The 395 square foot greenhouse has the capacity to grow 11,200 lettuce heads using the Verticrop system, compared to 4,332 in conventional systems.
Nutrient solution flows through the trays, past the plant roots and is channeled to the end were it is collected and drained away for recirculation. The movement of the stacks or rigs of trays, filled with lettuce plants, around the greenhouse to the nutrient delivery bay is a feature of the system which has great audience appeal as the many spectators who pass the greenhouse in the midst of the zoo grounds are testament to. The system features not only new technology in terms of rigs, conveyors, tray loading machinery and customized growing channels, but also incorporates high technology growing greenhouse equipment such as UV nutrient treatment, filters and automated nutrient and greenhouse control. A ‘touch-screen’ monitor linked to a Priva computer gives control over the nutrient dosing, greenhouse ventilation and the conveyor system. This system allows groups of growing trays to receive different irrigation programs so that young seedlings or different species can be dosed with fewer nutrients than those rigs containing larger plants. The Priva system also controls the under floor heating system. Another interesting feature of the Verticrop system is the custom made tray handler, which allows the growing trays to be loaded and unloaded from the rigs, four at a time; this should allow for commercial Verticrop systems to become fully automated.
Based upon technology originally developed in the Valcent Group’s research centre in El-Paso, Texas, much of the current success of the system can be attributed to Valcent’s UK team led by horticultural development manager Grahame Dunling, who with many years of experience as a grower and manager was fully aware of the challenges involved in designing high intensity solution culture systems. Grahame’s knowledge and expertise saw the development of customized growing trays, which are a unique feature of the system and has made the many modifications and improvements required to get the Verticrop system fully operational. Along with customized growing trays, the system will incorporate the use of the latest technology in soilless growing media. Because the final product is destined to be fed, roots and all, to the animals, the media used to raise and support the seedlings needs to be suitable for this purpose. Rockwool has been avoided for this reason, and it is intended that hydroponic seedling media made from a cellulose fiber derived from wood is to be used, which can be fed to the animals once the crop is harvested.
“Manipulations of the nutrient solution and environment could enhance the fiber, vitamin and beneficial nutrient levels and phytonutrients in the fresh greens.”
While growth through summer in the multi-level system has been rapid, it is planned to trial LED supplemental lighting as the season progresses into the shorter days and lower light levels of the UK winter. Valcent has been working in association with Philips to trial new LED technology, which is hoped will lead to the development of a commercially viable lighting arrangement for the Verticrop system.
Initially several varieties of butterhead and loose leaf lettuce were trialed to determine which would produce the best `fodder crop’ for the zoo animals. While hydroponic lettuce destined for supermarkets and consumers needs to meet specific qualities of long shelf life, compact heads and acceptable weight, fresh produce for the animals is a little different. The vegetables, herbs and other produce grown on-site can be harvested and fed out immediately, guaranteeing the animals have salads fresher than most zoo-goers will ever experience. While there might be less of a concern over extended shelf life and compact heads, there is interest from zoo staff and researchers in using the system to not only enrich the lives of the animals with fresh produce, but also to manipulate the nutritional quality of the vegetables being grown in the Verticrop system. With hydroponics and protected growing environments, there is much more control over plant nutrition than there is with soil grown crops. Starting with a base of good quality water, the nutrient solution can be manipulated to influence the compositional quality of the hydroponic crop and whether this is for animals or for improving human nutrition it is an idea which has increasing appeal to many.
Kevin Frediani, curator of plants and gardens at Paignton Zoo is particularly interested in the nutritional quality of fresh fodder and is hoping that the Verticrop system can be used to address problems such as `hemosiderosis’ in zoo animals. Hemosiderosis is a worldwide problem in zoos where certain animals, who are no longer dining on the food of their native habitats, end up consuming too much iron, which ends up stored in body tissues. This iron builds up in organs such as the liver where it stays permanently and causes severe tissue damage over time. While zoo animals can be fed commercial premixes low in iron, the fresh fruits and vegetables fed to many animals as part or all of their diet typically contain more iron than is needed. With fruit, vegetables and herbs being an important part of not only captive animals diets, but as part of the enrichment and activity programs, the issue of iron levels and hemosiderosis can become widespread in some species. This problem is further compounded at Paignton Zoo as vegetables grown locally in the deep red, iron rich soils of Devon are higher than normal in iron, and in general commercially-grown vegetables worldwide produced with soil fertilizer additions would be expected to have higher iron contents than the vegetation many zoo animals consumed in their native environments. With hydroponic systems and starting with RO, distilled or rainwater (free from naturally occurring iron in the water supply) it is relatively simple to lower iron in the solution to levels where plant iron deficiency and growth reductions are limited, but the resulting tissue has minimal iron levels, making it more suitable to animals prone to development hemosiderosis. Further manipulations of the nutrient solution and environment could see improvements in dry weight, fiber, vitamin and beneficial nutrient levels, phytonutrients, chlorophyll and other health related factors in the fresh greens that are difficult or impossible to achieve with commercially prepared dried animal feeds.
One of the most exciting aspects of the Verticrop system installed at Paignton Zoo is that is it is effectively `taking hydroponics to the people,’ zoo-goers can walk around the outside of the greenhouse and view the plants moving and growing in situ. This is particularly relevant to Paignton Zoo which is also a botanic garden keen to education people about all aspects of horticulture and the impact on our environment of crop production. Public viewings of large scale hydroponics are rare and while many people are aware of soilless culture, few have the option of seeing high intensity crops growing in real life. At a later date, a web cam installed on the greenhouse ceiling will provide a live feed on the zoo’s website, allowing visitors ongoing viewing of plant progress. Good publicity regarding hydroponics is always a bonus and at Paignton Zoo; healthy lettuce at all stages of development can be seen and the story of how the animal’s lives are enriched by on-site fresh produce is told. The fact that the Verticrop system is the first high intensity vertical hydroponic system of its kind installed in a zoo anywhere in the world makes it a great addition to Paignton Zoo’s attractions.
If you understand how hydroponic systems work–which is not difficult–you should have no problem building and maintaining the home unit I describe below. Most hydroponic systems employ some type of media, like rockwool, expanded clay pellets or perlite, to support plants and hold nutrient solution in their root zone between watering cycles. In medialess systems (often referred to as “water culture”), a continuous supply of nutrients is provided to plant roots either in a fine mist (aeroponics) or flow, in which the root tips hang (Nutrient Film or Flow Technique). A combination system, called aerohydroponics, employs both the flow of nutrient and the fine mist for the best of both worlds. Another water culture system is the float system, which many of you have probably read about in other articles I’ve written for The Growing EDGE. This type of system works by placing plants in a foam board so their roots hang through it, and floating the board so their roots hang through it, and floating the board on the surface of the nutrient solution in a tray or pan. There’s no doubt that all of these systems work very well, but they do have some drawbacks for home applications.
To make the stand, you can use regular Schedule 40 three-quarter-inch PVC pipe, and fittings to connect the pipes together. It is essential for you to create a one-inch slope from one end of the stand to the other for nutrient drainage to occur. The diagram below shows the construction of the stand and its slope for a single bed. You’ll want to build your stand according to how big your growing area is. My home system, as you can see in the photos, is a double-long bed. To start off, you may want to just make a system with only one growing bed (roof pan).
Once the stand is ready, the trays just get pop-riveted to it, using a silicone sealant to caulk around the rivets. Then you drill two half-inch holes in the lower end of each sloped tray and screw a male half-inch PVC adapter into each; don’t forget to caulk around them with silicone to protect against leaks. Connect equal lengths of half-inch PVC pipe to each adapter, using elbows and a T-fitting to create a cross-bar between the two that will join them into a single drain line to the nutrient tank, which should be situated directly beneath the drainage holes. Refer to the diagram below for a better idea of how this should look. In the systems I built, I fitted each of the drain holes in the end of the growing beds with a three-inch tube of window screening to prevent perlite from entering the nutrient tank.
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