The Greenport greenhouse in Venlo is a benchmark in greenhouse cultivation. Tomato grower, Joep Raemakers, achieves 10 percent higher productivity and a savings of 35 percent in energy costs with this semi-closed greenhouse. The nearby Health Centre, and the Mytyl School can also rack up large energy savings by using the surplus heat from the Greenport greenhouse

Verkerke, W.

English

Wageningen Yield 

 14 < syscope > 15 
Raemakers is the driving force. Without him there would be no 
Greenport greenhouse. How did it all begin? He emphasizes that  
he is first and foremost a tomato grower. He is not a philanthropic 
institution but is interested in making a business profit just like every 
other entrepreneur. The initiative for the Greenport greenhouse was 
derived from his drive to be an expert in his field. ‘For years the pro-
ductivity increased about 5 to 8 percent per year, but the last few 
years the growth in productivity tapered off. We had reached the 
limit. Every year you have a number of days in which there is too  
little light, there is too much heat or there is either too little or too 
much damp.’ What can you do about that? The tomato grower con-
cluded: ‘You have to be able to de-humidify, to cool and to dampen.’
Joep Raemakers briefs the consultation group in his semi-closed greenhouse.
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Greenport greenhouse as  
a source of inspiration
The Greenport greenhouse in Venlo is a benchmark in greenhouse cultivation. Tomato grower, Joep Raemakers, 
achieves 10 percent higher productivity and a savings of 35 percent in energy costs with this semi-closed 
greenhouse. The nearby Health Centre, and the Mytyl School can also rack up large energy savings by using  
the surplus heat from the Greenport greenhouse.
plant temperature measurement. A permanent supervisor, Wouter 
Verkerke, comes by every week to discuss the data and to hear 
about possible problems. Verkerke knows his way around the 
research world and knows which researcher to consult for each  
cultivation problem they come across. The other activities whereby 
the supervisor assists are just as important. Raemakers: ‘In  
projects like this, it’s all about working well together with all parties, 
so that you form a team. Wouter and I spend a lot of time on  
motivating people so that everyone is heading for the same goal.’
>> Shining example
Up until now, this has been successful. All the parties who took 
part at the beginning are still involved (Verkerke and Vermeulen, 
2008). This can be attributed to the approach taken by the  
project (Raaphorst et al., 2010). Priority has been given to 
transfer of knowledge within the sector. To this end, the website 
www.greenportkas.nl offers detailed information about what is hap-
pening in the greenhouse. On a restricted page, the consultation 
group can continuously access the data. This group is comprised 
of pioneering greenhouse growers from the region, and from  
various crop sectors. They consider and discuss the results. There  
are regular visits by other growers in the whole country who take 
over ideas and parts of the greenhouse design. Two growers from 
the consultation group – a strawberry grower and a chamomile  
cultivator – both want to get going with a similar project. Every 
business that is in some way connected to this initiative is proud  
to be associated with the environmentally friendly aspects of this 
greenhouse. The Horticultural Trade Board does as well. In its  
New Year’s speech, the greenhouse cultivation sector was praised 
for the socially responsible action of providing heating for the 
Health sector. In this way, the project is a shining example of how 
an innovative idea in the field can become a source of inspiration 
for the entire sector.
>> Developments continue
In the meantime, the innovative ideas continue to develop. 
Raemakers is not prepared to publicize all his ideas, but the con-
cept of a new type of glass is already public. A test is about to be 
set up using double-glazing to reduce energy consumption without 
compromising the amount of light that passes through it. In this 
way, the project is the centre point of new developments which in 
the end are beneficial to the entire greenhouse horticultural sector.
In this way, Raemakers came up with the semi-closed greenhouse, 
which made de-humidifying and cooling possible, with an additional 
misting installation and assimilation lighting. This had one disadvan-
tage: more heat in the greenhouse. But he figured out a solution 
for that too: heat storage in underground water at a depth of  
90 metres and pumping it to the surface when needed. He was 
prepared to supply the surplus heat to his neighbours: a Health 
Centre and the Mytyl School. 
In this way, Raemakers linked his own interest to that of others.  
His aim was to increase production by 20 percent and to halve his 
energy bill. He was prepared to share the energy savings with his 
neighbours at the same time. With this energy saving, he addressed 
a community goal: reduction of the greenhouse gas, CO2. 
>> Never seen before
Raemakers saw that his idea carried little risk. ‘The techniques had 
been available for some time in the functional building sphere. The 
only thing was they had never been applied in horticulture before.’ 
Not everyone shared Raemaker’s confidence. For example, his 
neighbours with whom he wanted to share his energy surplus.  
To be dependent on a tomato grower for your energy requirements 
had no precedent. What would happen if the tomato grower went 
bankrupt? The neighbours were reluctant. 
It was a good thing that Raemakers had chosen a crucial first part-
ner for this process: the technical installation firm Thissen who was 
responsible for the energy supply for the whole Health Centre 
Group. Together with Thissen, Raemakers did the calculations for 
the entire project and they came to the conclusion that energy  
supplied from a horticultural business was quite a feasible option. 
With Thissen’s encouragement, the Health Centre agreed. In the 
end, the grower won over all the institutions and partners involved 
(Vermeulen et al., 2010). Obstacles are never insurmountable: 
‘You only need to take the time to achieve what you set out to do.’
>> Support for cultivation
As a result of his determination, Raemakers has succeeded in get-
ting a whole network of organisations and enthusiastic people to 
stand behind him. He received a subsidy from SenterNovem to 
build the greenhouse and, as well as that, a subsidy from the then 
Ministry of Agriculture for three years of support by researchers 
from Wageningen UR. They assist him with cultivation issues, 
because cultivation in a semi-closed greenhouse requires a differ-
ent method of growing than in traditional greenhouses. Data is  
continually collected and monitored from the greenhouse, like  
For more information: Wouter Verkerke, t +31 317 478905, e wouter.verkerke@wur.nl


Greenport greenhouse as a source of inspiration

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