The Weihenstephan-Triesdorf University of Applied Sciences received a growtainer at the beginning of the year, intended for research and teaching purposes. The "Gemüsering Thüringen" company is financing the mobile greenhouse for a period of ten years. This is a fully insulated container that has been specially modified to create optimal production conditions for vertical planting systems, regardless of the environment and climate.

Since that time, the growtainer has been put into operation and is now used in particular for research projects in the field of "urban farming". Prof. Dr. Heike Mempel heads the project group of the same name, dealing with scientific questions on possible advantages and disadvantages of a closed indoor farm without sunlight.

Horticultural engineer Ivonne Jüttner is involved in the project "Product Quality and Resource Efficiency in Plant Production in Indoor Farming Systems" with an economically and ecologically meaningful cultural selection and the development and optimization of the associated procedures in a completely closed culture area. It compiles input/output balances of all material and energy flows, evaluates them with regard to sustainability and with the overriding goal of resource conservation. The project is funded by the Bavarian Ministry of Food, Agriculture and Forestry.

Another experimental setup examines the transpirational behavior of the growing plant. In the closed environment of the container, this parameter plays a key role. The transpiration flow through the plant is the driving force for nutrient and water uptake by the roots and it affects plant growth. At the same time, perspiration leads to increased humidity in the enclosed culture area. This must be removed by technical means, after which it is returned to the irrigation system in order to maintain the water cycle. This in turn results in an important advantage of indoor farming systems: water consumption is reduced enormously. The water absorption of the plant also influences the consequent dry matter of the products and thus their quality. Ivonne Jüttner is currently working on recording and visualizing the temperature and humidity distributions, as well as the air movement caused by the two incorporated fans.

LED lighting
The culture system and the design of the container significantly affect the climate in Growtainer. The homogeneous and exactly controllable culture guidance in closed systems with LED exposure in particular is a decisive advantage over conventional culture systems. The ability to precisely adjust the climate and growth conditions influences growth and ingredients in a targeted manner. These freely adjustable conditions allow a year-round and consistent production on site. In the coming year, a scientific assessment of the functionality of the Growtainers will be created. As soon as any weak points have been identified, the technical equipment can be optimized as the project progresses.

Using modern measuring and sensor technology, data on resource consumption and plant growth are recorded over the entire project period. Despite the use of energy-saving LEDs and good insulation of indoor farms, scientific studies show that energy use is the most critical factor compared to traditional culture methods. Nevertheless, the entire resource efficiency is mainly due to a reduced use of water and pesticides as the major advantage of indoor production. A comprehensive scientific analysis of the possible uses and limitations of closed indoor farming concepts using the example Growtainer, with subsequent practical evaluation of the results, in any case will be an important prerequisite for opening up application areas and fields of activity for horticulture in this innovative segment.

Smart Greenhouse Management System
The combination of the findings from the "Process Simulation based on Plant Response (Prosibor)" project, with project results from the Growtainer trials, will make it possible to compare indoor systems against conventional greenhouse production. Through the "Prosibor" project, a sensor-based intelligent greenhouse management system will be developed in cooperation with the Humboldt University of Berlin and the company RAM from Herrsching. Ivonne Jüttner will also develop a comprehensive analysis of potential plants that could be of interest for cultivation in pure artificial light systems. A special focus will lie on the potential added value that cultivation with artificial lighting systems could offer over cultivation under glass.

The added value can be a result of the increase in desired ingredients, the year-round production of, for example, flowers or fruits, production without the use of pesticides, or other criteria. As part of the study "Substance Use of Crops for the Chemical Industry", the HSWT, together with the State Research Center for Agriculture and other project partners, had already analyzed potentials for regional cultivation of medicinal and aromatic plants and evaluated initial approaches to indoor production.

In one of the two compartments of the Growtainers, students of the 5th Horticulture semester will carry out the first plant experiments in the greenhouse module. For example, they are investigating the suitability of different LED lights for the culture of Asian lettuces. The plants are hydroponically cultivated on several layers, one above the other. The energy required for the photosynthesis of plants is provided via LED modules at each shelf level. These immerse the interior of the Growtainer in a purple light; a combination of the blue and red spectral ranges. This light combination is used very efficiently for photosynthesis by the plants. To the human eye, however, it is rather uncomfortable, which is why any activity within the Growtainer is restricted to the use of safety goggles or with the LEDs switched off. In this exposure, the leaf colors of the plants might also not be judged correctly, which complicates an assessment of the nutritional status of the plants.

Findings from the already completed project "Energy Saving and Increased Efficiency in Horticultural Production with LED Exposure Systems" also show that for most plants an even broader spectrum of light, in addition to blue and red, optimizes the product quality: a supplement of yellow and green light, for example. This spectrum then appears white to the human eye, and the plants growing under the LED lights will have a natural green color, which facilitates not only positive growth effects but also the necessary work being done in the Growtainer. The determination of the ideal light spectrum for different plant species and their stages of growth is also an important issue in the research of the Growtainer.

For more information:
Hochschule Weihenstephan-Triesdorf 
Am Hofgarten 4, 85354 Freising
Tel: +49 (0)8161 71-3416 
Fax: +49 (0)8161 71-4402