COST OF ONE-HECTARE GREENHOUSES IN KENYA
The construction of greenhouses makes it easier to control the growing environment of the crops. Moreover, high-value crops are primarily grown in greenhouses to minimize the risk of losses. In the greenhouse, it is possible to control the temperature, humidity, light penetration, pests and insects, water supply and nutrient supply. Most commercial farmers of high-value crops set up big greenhouses which can cover up to one hectare of land. The cost of one-hectare greenhouses is fairly high. Hence, a lot of care and precision must go into construction.
Cost of different sizes of greenhouses
Greenhouses come in various sizes and materials. The construction costs mainly determine the type of greenhouse to choose. We can group greenhouses into two according to the materials used for the frame. These two groups are wooden and metallic greenhouses. Wooden greenhouses need to be treated first before use to avoid damage by termites or rotting. Nails and barbed wire hold the greenhouse polythene in place in wooden greenhouses. We can’t use a wooden framework in large greenhouses due to the weight of the structure. This means that the farmer cannot evade the cost of one-hectare greenhouses by going for cheaper materials. Metallic greenhouses use of galvanised steel, iron or aluminum to support the structure. Galvanised steel and aluminum have the advantage of rust resistance, and tapping screws, profiles, and wires hold the greenhouse polythene in place. At Eunidrip irrigation systems, we have professionals skilled at building quality wooden and metallic greenhouses. The costs of greenhouses we offer cater for the; structure, materials, drip irrigation system and installation labour. The charges for building different sizes of greenhouses are displayed below.
| Greenhouse construction costs | |
| Size | Metallic greenhouses |
| 8 m × 15 m | KES 200,000 |
| 8 m × 20 m | KES 235,000 |
| 8 m × 24 m | KES 255,000 |
| 8 m × 30 m | KES 300,000 |
| 8 m × 40 m | KES 480,000 |
| 8 m × 48 m | KES 500,000 |
| 16 m × 24 m | KES 500,000 |
| 16 m × 30 m | KES 550,000 |
| 16 m × 40 m | KES 890,000 |
Wooden greenhouses are generally cheaper than metallic greenhouses because of the high cost of galvanised steel, iron and aluminum. However, metallic greenhouses have a much longer life span.
Greenhouse dimensions
Greenhouses come in all shapes and sizes. The main factors determining the size of the greenhouse to be chosen are the available land and the construction cost. We can group greenhouses in Kenya into three classes depending on the size. These three classes are;
| Greenhouse dimensions | ||
| Small greenhouses | Medium greenhouses | Large greenhouses |
| 8 m × 48 m | >16 m × 40 m. |
| 6 m x 10 m | 16 m × 30 m | |
| 6 m x 12 m | 16 m × 40 m | |
| 6 m x 15 m | ||
| 8 m x 15 m | ||
| 8 m x 25 m | ||
| 8 m x 30 m, | ||
| 8 m x 45 m | ||
| 8 m x 48 m | ||
Cost of automated greenhouses Automated greenhouses are those whose internal environment can be controlled by a computer. The computer uses sensors to determine the correct times to irrigate or start and close the air conditioning system. The system also enables remote monitoring of the greenhouse. Automation of large commercial greenhouses is costly. The average cost of a fully automated greenhouse ranges from KES 3030 to KES 5303 per m2. This means that the average cost of a one-hectare greenhouse, which is fully automatic, will cost 30 million to 53 million Kenya shillings. Greenhouse owners choose to automate the greenhouses or partially automate them fully. Factors that affect the cost of automated greenhouses are:
- Required area- the larger the required area, the more construction cost.
- Construction materials – The type of chosen materials affect the lifespan and maintenance costs. Durable materials are more costly than poor quality materials, but they will save on maintenance and repair costs.
- Framing – the chosen material should be strong enough to support the whole structure. Large one-hectare greenhouses can only use metals as the framing materials. Galvanised steel, iron and aluminum costs much more than wood or PVC plastic pipes.
- Environmental control
Cost of one-hectare greenhouse environment control
As we have seen, setting up a fully automated greenhouse is very costly. Many farmers choose to automate only parts of the greenhouse. A Heating, ventilation and Air Conditioning (HVAC) system is a fully automated system that controls heating and air circulation in the greenhouse. It can come as one unit or separated units. The HVAC system can cost up to KES. 574,000 or more depending on the features of the system. The usage of this system increases the overall cost of one-hectare greenhouses. Alternatives to using this are system boilers and small Horizontal Airflow (HAF) fans. The boilers assist in heating the greenhouse, and the operating cost depends on the fuel costs. HAF fans assist in the ventilation of the greenhouse, and the price ranges from KES 11,000 to KES 18,000.
Glowing lights come in various sizes and prices depending on the wattage and power generated. The average cost of lights ranges from KES 2,300 to KES 14,000. Thermostats and sensors are used to monitor the internal environment of the greenhouse. They can be used together with the heating and cooling systems to control the air temperature of the greenhouse automatically. The cost of thermostats varies depending on the features. The price ranges from KES 68,000 to KES 170,000.
Importance of automation on big greenhouses
Automation of one-hectare greenhouses has helped commercial farmers be more confident in their practices. Here are some of the importance of automated greenhouses.
- Creation and maintenance of an ideal climate – these greenhouses use sensors to detect changes and correct them in the greenhouse. The parameters managed by the computerised system are; heat, humidity, light levels, ventilation, soil nutrient levels, pests and soil moisture levels.
- Reduction of energy costs – automated systems monitor the soil water levels. When the levels are below the required amounts, the system turns on the irrigation and supplies only the required quantity. This saves on water and energy use in the greenhouse.
- Remote real-time monitoring – by linking the computer to a mobile device or laptop, a farmer can monitor the conditions of the crops in the greenhouse.
- Reduced labour costs – the cost of one-hectare greenhouse is high. By using automated systems, a farmer can cut down on labour costs.
- Analysis of plants’ growing data – Data collected with the computer are; the plant cycles, soil data, nutrient intake data and climate control report. This information will help the farmer know the best growing conditions and how to achieve that.
- Improved plant health and quality – sensors inside the greenhouse help detect pests and diseases early on. The farmer can control the disease by ensuring high quality and quantity yields.
Project management during greenhouse construction
Project management involves starting up, planning, executing and closing a task, meeting the client’s demands at the right time. The steps involved in greenhouse construction project management are:
- Designing and feasibility studies
- Solution planning and detailed designing
- Building and execution
- Training and after-sale report
Designing and feasibility studies
This is the first step in any greenhouse construction project. At this stage, the client comes to us to build a greenhouse. The steps involved in this stage are;
- Greenhouse feasibility study – this is done to check whether the location of the greenhouse will be suitable.
- Crop and climate assessment – climate and crop assessment will determine the design of the greenhouse.
- Financial requirements planning – done to determine the overall costs of the project
- Initial greenhouse technical design. The factors to be considered during the designing phase are:
- The climate of the area – the area climate determines the type of equipment to be prioritised in the greenhouse.
- Greenhouse size to be constructed – whether is for a small scale farmer or commercial farmer
- Crops grown in the greenhouse
- Greenhouse materials availability
- The topography of the land
- Government policies
- Maximum light transmission required
- The expected lifetime of the greenhouse
Detailed design and solution planning
This stage comes next after the client has paid the full cost of a one-hectare greenhouse. This stage involves engineering works and planning, designing the structure, heating and cooling system design, irrigation control, and greenhouse construction schedule.
Execution and building
The execution phase involves the construction of the greenhouse on the site. It should be done according to the schedule to be completed at the right time. The stages involved are;
- Project scheduling – involves planning the work to be done on the available days.
- Logistics – transportation of the required materials to the site.
- Subcontractors management
- Supervision of the whole project.
Training and after-sales report.
This stage comes after the project is completed. The project is handed over back to the client, and training is done. If any technical or operational support is required, it is done during this stage. Training done at this stage can be how to start and stop the equipment, how to operate the systems in the greenhouse and maintenance practices. Technical support and operational support offered are repair and maintenance services etc.
Availability of materials for greenhouse construction.
The type of greenhouse to be constructed determines the kind of materials to be used. At Eunidrip irrigation systems, we have a variety of materials that you will need for your greenhouse. These materials are reasonably priced and can be purchased through our online shop. We can deliver the materials to any place in Kenya from Nakuru. Common materials used for greenhouse construction are;
- Wood – used mainly in wooden greenhouses for the pillars, supports and reinforcements.
- Galvanised steel – these are used in metallic greenhouses as pillars, supports, reinforcements, arches, beams and straps, canals and crop wires
- Aluminum – aluminum is used for pillars, supports, reinforcements, arches, beams and straps, canals and crop wires.
- Iron – iron is used to make the support structure of the greenhouse. It is used in beams, pillars and straps.
- Concrete – for making foundation supports
- Nails – used to hold the polythene in place in wooden greenhouses
- Tapping screws – they make use of a drill to secure the profiles in place
- Profiles and wires – these two are used together in metallic greenhouses to hold the greenhouse polythene
- Insect nets – usually are placed on the sides of the greenhouse to allow air inside while still protecting against insects.
- Covering materials – greenhouse cover materials can be plastic films, glass or rigid plastics. These materials protect the greenhouse against external factors while allowing light to pass through. Examples of plastic films are polyethylene copolímeto ethylene vinyl acetate, polyvinyl chloride plastics, and multilayer. Rigid plastics used include methyl polymethacrylate, polycarbonate and polyester
Factors to consider when setting up a Greenhouse
Before setting up the greenhouse, there are several factors to consider. Considerations during site selection are essential. The following factors affect the location of the greenhouse site.
- The water and electricity supply – greenhouses use drip irrigation systems to supply water to the crops, and automated greenhouses require electricity to operate. It is crucial to ensure the greenhouse is located where these two things are to ensure an efficient system.
- The micro-climate conditions – micro-climate conditions refer to weather conditions that are present only in a specific location, e.g., fogging during certain times of the day.
- Road network – if the greenhouses are going to be used for commercial farming, it is essential to have a good road network. A good road network will ensure the product gets to the market at the right time
- The orientation of the greenhouse – the greenhouse should be oriented in a direction that ensures maximum light penetration during the day
- Presence of trees – trees near greenhouses will form shades reducing light penetration into the greenhouse.
- Soil at the site – the soil should provide adequate drainage to avoid cases of water accumulation in the greenhouse.
- Topography – a slope of about 1% is desired so that water can drain away from the greenhouse site.
- Wind velocities – if the wind velocities are high, it is easy for the greenhouse to be damaged. The planting of windbreakers can assist with this problem.
- Labour availability – large greenhouse projects will require more labour than small projects.
Greenhouse foundation
A greenhouse foundation should be solid and stable enough to support the whole structure. The first step in foundation construction is deciding on the depth and width to dig. The depth to be dug depends on the soil’s bearing capacity, the depth of shrinkage and swelling for clay soils, minimum practical foundation depth, and the groundwater table. Level ground is vital in the stability of a foundation. Levelling of the floor is usually done in areas with very steep slopes. A level ground ensures;
- Greenhouse stability during storms
- Durability of the greenhouse materials
- Repair and maintenance cost savings
- Neatness because there are no puddles of water in the greenhouse.
The foundation of a greenhouse should meet the following requirements
- Able to safely contain and distribute the weight of the greenhouse.
- The foundation footing should rest on undisturbed soil and at a 50 -60 cm depth.
One hectare greenhouse construction for roses
Roses are high-value crops that are primarily grown in greenhouses to ensure maximum yield. One-hectare greenhouses for roses come in dimensions of 120 m by 80 m. They are built using galvanised steel or aluminum to provide adequate support for the whole structure. The cost of one-hectare greenhouses is above KES 23 million. The metalwork done on one of these greenhouses costs about KES 12 million.
One hectare greenhouse construction procedure
- The first step in any greenhouse construction is to mark out the support points on the ground.
- Foundation digging for the supports is done next.
- Metal painting to avoid rust
- After digging, metals for support are placed in the ground, and the base is reinforced with concrete.
- Arch making and mounting on the greenhouses
- Front porch construction
- Insect net placement on the sides
- Greenhouse polythene mounting
- Drip irrigation set up in the greenhouse – main lines (160 mm), submain lines (90 mm) and laterals (40 mm) are used in the drip system.
Effects of climate on large greenhouse projects
To build large greenhouses, a farmer must clear vast areas of land. The reduction in trees in an area directly impacts the rainfall received in an area. Trees act as windbreakers resulting in rainfall formation and soil erosion control. Large greenhouses construction will increase soil erosion and dry conditions in an area.
In most greenhouses, pesticides and fungicides are used to control pests. The pesticides and fungicides used, end up contaminating the air. This is especially true in large greenhouses, which make use of a lot of pesticides. This problem can be controlled by encouraging farmers to use natural ways to control the pests, e.g., using ladybugs to feed on the pests.
The construction of large greenhouses will require heavy machinery. These types of machinery use fossil fuels that, when burnt, release emissions toxic to the environment. Large greenhouses projects produce many products that need vehicles to move the produce to the market. These vehicles also use up fossil fuels, releasing emissions toxic to the environment. We can solve this problem using electric cars.
Large greenhouse projects require large volumes of water. This is why most of them are located near sources of water. This can negatively impact the environment, especially during the dry seasons when the water level goes down. The fish will be affected, leading to the migration of the fish in the area.
Returns on investment cost of one-hectare greenhouses
As much as the cost of one-hectare greenhouses is high, the returns on the investments are worth it. Large greenhouses mean more produce can be grown in ideal conditions, maximising profits. Most of the systems in the greenhouses are automated, ensuring production efficiency. Automation helps in reducing labour costs, energy use and water use. This, in turn, saves on production costs. Kenya being a country dependent on agriculture for its economy, an ample supply of agricultural produce can assure a farmer of high returns.