Reuse is an important aspect of our sustainability strategy. In our greenhouse, it mainly relates to the reuse of water and the circular use of CO2.
It goes without saying that water is important for plant growth. We do not use drinking water but, instead, the rainwater that falls on our greenhouse. This water is collected in a large water tank.
Before we use the rainwater to water our plants, we take samples from both our plants and the rainwater. Each week, we analyse how much food, and what type, our plants need and look at which nutrients we need to add to the water.
By nature, rainwater only contains a certain salinity and acidity level but does not contain any nutrients such as iron, phosphoric acid, ammonium nitrate, or calcium. However, we also reuse water from our greenhouses, which does contain nutrients. We always take samples from the reused water to calculate whether we need to add nutrients to the rainwater and reused feed water mix, and in what quantities, in order to achieve an optimum nutritional value once again.
We collect surplus water from the watering process, as well as from our DryGair dehumidification system, via gutters and take it to a central silo. The polluted water is first passed through a heat disinfector and is cleaned of any viruses and bacteria. Afterwards, it is transferred to the clean water silo and then combined with the rainwater from the water tank to be reused as feed water for our plants.
In this way, we can reuse more than 140,000 litres of water every day.
Besides water, our plants also need CO2 to grow. Without a sufficient amount of CO2, they would not grow as fast and not turn out as strong and beautiful. They would soon start to droop in the vase and be less resistant to diseases and fungi. The optimum amount of CO2 they need depends on the light. The more light there is, the more CO2 the plants will absorb. Roughly speaking, we have twice the amount of CO2 in our greenhouses as in the outside air.
We can produce CO2 ourselves using our CHP (Combined Heat and Power system), but we also obtain CO2 from other sources. In many sectors, such as the manufacturing industry, CO2 is a problem. Current levels of CO2 emissions are harmful to the environment and exacerbate the greenhouse effect. The good thing is that our plants absorb CO2 and emit oxygen, which is good for the environment. Our sector can therefore eliminate some of the problem. And that is what we do.
The Dutch horticultural sector and the manufacturing industry are working together to reuse CO2 released during factory processes for use in greenhouses. Shell has a pipe running from the Botlek in Pernis to the main horticultural areas in the Netherlands, including De Zuidplas nursery. Together, we can prevent the harmful emission of several megatonnes of CO2 each year and produce oxygen in return.
Since we obtain CO2 from the manufacturing industry, we don’t have to burn as much natural gas with our CHP in order to produce CO2. This is a double benefit for the environment.