Growing Green

Many companies struggle to find the right balance between reducing costs and growing their business.

For some, it seems like an impossible equation, for others it looks like a great challenge.

Students and researchers are in a constant search for more efficient and less consumption tools and equipment to enhance the quality and quantity of products.

Ibtihal al Mandhari, in her master’s thesis in Agricultural Engineering, SQU, suggests substituting use of evaporative cooling system with the refrigeration system with air-conditioners in greenhouses.

This, she feels, will save water and electricity and increase production.

“Greenhouses is one of the most important technologies aimed at enhancing crop production in terms of quality and quantity. The evaporative cooling system is usually used to reduce high temperatures and humidity inside the greenhouse in Oman. However, due to the high consumption of water and electricity in the evaporative cooling system, the refrigeration system with air- conditioners can be used as an alternative to cooling in warm and humid areas,” says Ibtihal.

technical and

financial aspects

Her study aims to evaluate the technical and financial aspects of the greenhouse cooling system using AC cooler. A single Quenset AC-cooled greenhouse (6 metre in length and 3 metre in width) was built at the Agricultural Experiments Station at Sultan Qaboos University (SQU) and was covered with a layer of rock wool for preventing the entry of sunlight, which is the main source of heat inside the greenhouse, and as an alternative to sunlight, artificial lighting (LED) was used, she explains. Three types of high-value lettuce were cultivated in the hydroponic system.

In order to assess the technical efficiency and performance of the greenhouse, several criteria were used such as land use efficiency, water use, gross water use and energy use efficiency. Also, crop performance was evaluated by measuring the fresh and dry weight, the number of lettuce leaves, the head area of lettuce, chlorophyll content, the colour of lettuce, micro and macro nutrients and sensory evaluation.

The financial analysis was used to determine the budget and net retune.

AC-cooled greenhouse

The results showed in the summer that the efficiency of the land for the AC-cooled greenhouse reaches 6.8 kg per square metre, and the efficiency of gross water use reached 48 kg per cubic metre, which is 99 per cent higher compared to the evaporative cooled greenhouse.

As for the lettuce performance, it was found that the fresh weight, head lettuce area and chlorophyll content were affected by the level of artificial lighting.

Likewise, the amount of macro and micro nutrients in lettuce was greater compared to nutrients in lettuce grown in the evaporated greenhouse.

The results revealed in the sensory evaluation that people prefer the taste, appearance, and size of the lettuce grown in the AC-cooled greenhouse.

The results indicate that the internal rate of return IRR within 20 years will be 63 per cent and that net profits start from the second year of planting the lettuce crop in the greenhouse.

By analysing the sensitivity of profitability to some factors, the results showed that investing in lettuce cultivation in greenhouses was highly influenced by the selling price and net weight, Ibtihal mentions.