Nick van den Berg, Bunnik Plants

NL: How to become a recognized zero drainer

Bunnik Plants in Bleiswijk, the Netherlands, is recognized as zero drainer. In the talks with DCMR Milieudienst Rijnmond, the Waterschap Schieland and Krimpenerwaard, the pot plant companies have been able to demonstrate they are not draining waste water. Nick van der Berg, cultivation specialist at Bunnik Plants, is closely involved in all talks: "The authorities have let us know in writing that it is credible that we do not drain waste water. We are happy with this recognition as zero drainer." By zero draining, the company wants to spare the environment completely, and it fits the ambition to grow without artificial fertilizer and insecticide, but with more resistance in 2020.

Weekly 700,000 plants are grown sustainably on average on more than 25 hectare. The assortment consists of 50 different kinds of indoor plants, mainly green plants but also flowering ones. Of the six growth locations, three are equipped with roll containers and three with concrete floors, but all have a low/high tide system to provide water. The return water is filtered because of organic pollution by a sieve bend.

Underground water storage
The irrigation water is 100% rainwater, which is collected in basins inside and outside. At three locations, the residue water is stored underground. The underground water storage happens at four depths: 10, 20, 30, 40 meter. The growth specialist: "In case of water shortage, we first pump water from the deepest layer. When the pumped up water gets too much salt concentrations, we switch to a higher lever." The pumped up water is UV disinfected, and is stored in the rain water basin.

"We aerate both the rain water and the low/high tide return water. Because of the higher oxygen content, there are less pathogens, nutrients bind better to the water, and algae growth is countered."

No large adjustments
Van den Berg: "Because multiple locations were already closed because of the low/high tide system, zero draining was achievable with a few adjustments. Because of the system, we did not have to do large adjustments. The most important adjustment was the filter system of the washer for the roll containers. Because of the crop protection agents used in the growth, the rinse water of the container washer has to be filtered finer to be reused. The sieve bend for the organic pollution has been replaced by a vibrating screen, which can filter up to 20 micron. 

Another adjustment was the collection of the condensed water of the greenhouses. The growth specialist: "Before, the condensed water was collected in the silo for the return water, but now it is stored in an separate silo, making it traceable". A few tubes, which run to the ditch, and served for the overflow of basins, have been glued shut. The overflow now goes to a silo that was not in use.

Putting everything in writing
Bunnik Plants has chosen to keep reporting in their own management and not hire a consultancy agency, to get an even better insight in the water streams at the various locations. Per location, the cultivation specialist has had to compile an entire book for the authorities, containing everything on zero draining. "They kept going on the maintenance plan. You have to answer questions, what do you do with leaking containers or drain gutters? Has the personnel been instructed? You have to describe that you first alert your own technical service, and only then an external company"

Growing sustainable
At Bunnik Plants they believe in sustainable and environmentally responsible growing. To meet their energy requirements, they use more than 9,000 sun collectors, mostly attached to the company buildings. Together with their own biomass plant, which burns wood chips and pruned cuttings, the generated electricity is sufficient for 4,000 households. The waste heat from this, and from the RoCa-plant, heats the greenhouses.

The growth specialist concludes: "In the coming time we are going to grow more resistance, so we can do without artificial fertilizer and insecticides. We still have to take a few more steps next year to see if it is manageable."

Source: Glastuinbouw Waterproof

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