Greenhouse as source of energy - Energiek2020

Greenhouse as source of energy
towards a powerful and climate-neutral greenhouse
horticulture sector
In the Netherlands, we eat tomatoes, sweet
peppers and cucumbers all year round. We also
enjoy having flowers on the table, pot plants in our
rooms and bedding plants in the garden. Dutch
growers produce these top quality products in
greenhouses. To do this the greenhouses have to
be heated in winter and in some cases lit as well.
In the summer, the greenhouses sometimes have
to be cooled. All this requires energy.
In the past growers were able to make use of the
generous Dutch natural gas reserves. This gas from
Dutch soil is gradually being used up and therefore
becoming increasingly more expensive. In addition, over
the past decades, there has been a growing awareness
that the emission of CO 2
from burning natural gas is
harmful to the atmosphere.
The Dutch growers are, therefore, taking measures to be
less dependent on fossil fuels such as natural gas. They
are actively looking for growing systems with low energy
consumption and alternative energy sources.
Aims
The horticulture industry has been working on reducing
energy consumption for some decades now and from 2000
also on the development of sustainable, thus non-fossil fuel,
energy. Together with government, the ambition has been
formulated that all greenhouses constructed after 2020 are
to be near-independent of fossil fuel. Growing in these
green houses will be sustainable and cost-effective.
Moreover, the aim for these new greenhouses is to supply
sustainable heat and electricity.
The industry however, is proceeding beyond just formulating
an ambition. Hard work is taking place on a number of
concrete objectives for the year 2020.
• CO 2
emissions will have been reduced by more than half
compared with 1990,
• Every year, 2% less energy will be used per unit product,
• As a result of which 20% of the energy consumed in Dutch
greenhouses will come from sustainable energy sources.
The Greenhouse as source of energy programme was
launched in 2005 in order to achieve this. Growers,
organisations, researchers and industry work together in
this action and innovation programme on innovations that
will make it possible to grow crops in greenhouses while
using less, and in the future no, natural gas.
Well on the way
The horticulture industry has achieved many fine
results in reducing the consumption of natural gas.
An intermediate audit carried out by order of the
Government has shown that the industry is well on
course. Since the reference year 1990, the use of
fossil fuel per unit product has decreased by 50% and
the total emission of CO 2
has been reduced by 23%.

Trias Energetica
The principle of the Greenhouse as source of energy
programme is the so-called Trias Energetica. According
to this principle, the energy consumption can be
reduced in three steps:
Step 1:
As much energy as possible is saved while growing, for
example by better insulation of the greenhouse or by a
different growing strategy.
Step 2:
The energy still needed is obtained, as much as
possible, from sustainable, non-fossil, energy sources,
such as geothermal energy or solar energy.
Step 3:
If steps 1 and 2 are not sufficient, fossil fuel is used as
intelligently and economically as possible.
Seven so-called transitional paths have been identified
in the Greenhouse as source of energy programme
that can contribute to achieving the Trias Energetica
approach. Elements from these paths will lead to a
comprehensive package of measures with which every
company, whether growing vegetables, flowers or
plants, can operate in an energetically sustainable and
cost-effective manner.
Growing strategy
Growers, researchers and consultants have designed a
package of measures that restrict the demand for energy in
greenhouses. The name next generation cultivation has been
given to carrying this out in practice. The crop is central in this
new approach; the temperature, the moisture content and the
CO 2
concentrations are all geared to the needs of the plant.
A number of growers have been working in this way since 2009
and they are achieving good results.
Hans Vereijken, tomato grower:
“Saving energy doesn’t have to be difficult. We built a new
greenhouse in 2009 with a new type of installation to keep
the greenhouse dry. The principle is simple and because of
this we can keep the screens closed for longer. This results
in less loss of heat from the greenhouse and we can save
on energy without loss of yield or quality.”
Marc Grootscholten, director of the trial
and implementation company GreenQ
Improvement Center:
“We are in our third year of testing LED lighting for tomatoes.
It appears that using LED lamps between the tomato plants
can save around 15 to 20% electricity in comparison with
the lighting usually used in tomato growing. By combining
the use of LED lamps with the new growing strategy, we
can even save up to 30% on electricity and heat compared
with what is common in practice.”
Light
Growers can achieve higher production with the same amount
of light. Natural light can be used more efficiently with new
greenhouse materials. These materials let more light through or
retain the heat better. Artificial light can be used more efficiently
by using new and better lamps, such as LED lamps, in
combination with the lamps in common use.
G r e e n h o u s e a s s o u r c e o f e n e r g y

Biofuels
Residual wood from forests and crop and manure
residues are very likely to be successful as biofuels for
use as sustainable energy sources in horticulture.
Geothermal energy
There is ample geothermal energy available in the Netherlands.
Research has shown that there are hundreds of hot water wells
at great depth that can be used as sustainable energy sources.
A study carried out by the Greenhouse horticulture department
of the University of Wageningen in 2007 showed that the
industry can save at least 10% of the use of fossil fuel by
pumping up geothermal energy.
Ad Wouters, bedding plants grower:
“The high demand for heat in our company in the
winter can be met well by burning wood. There is a
supplier near to us who can supply us with sufficient
wood. We agree a fixed price with him and that is a
big advantage compared to gas, where the price
varies a great deal. We do notice, though, that wood
is becoming scarcer of late due to the big demand
for this fuel in Germany.”
Menno Ammerlaan, pot plant grower:
“Geothermal energy is a sustainable alternative for natural
gas. As well as this, using geothermal energy, in contrast to
natural gas, means that the price of energy is stable and
affordable. In recent years the gas price has fluctuated
sharply both up and down, and this makes a normal
commercial operation impossible. The capacity of our
source is greater than the energy need of our own company.
Therefore, we also supply energy to a swimming pool, a
sports complex, a school and two other greenhouse
companies. We want to heat as many companies as possible
from our own source.”
Feije de Zwart, researcher:
“We are working on a greenhouse that produces electricity,
the Daylight greenhouse. A sophisticated system has been
installed at the top of the greenhouse where solar energy
in the form of heat and electricity is collected. At the same
time, the installation catches the direct sunlight before it
enters the greenhouse. This greenhouse is therefore very
suitable for pot plants, because these often prefer to be
away from direct sunlight. The heat and electricity that is
generated can then be used as sustainable energy in the
company.”
Solar energy
The sun provides free energy. This energy can be used to heat the
greenhouse or to generate electricity. Heat can be collected and
stored in the summer in a semi-closed greenhouse and then used
in the winter for heating. Another way of using solar energy is to
generate electricity using solar cells in the top of the greenhouse.
G r e e n h o u s e a s s o u r c e o f e n e r g y

Sustainable Electricity
A horticultural company with a combined heat and power
system (CHP) can produce electricity as well as heat from a
cubic metre of natural gas. Generating power in a CHP is much
more efficient than what is normal in most large power
stations. Growers supply their excess electricity to the public
network and in this way horticultural companies become local
energy producers. The horticulture industry already produces
15% of the household electricity used in the Netherlands.
Sustainable with CO 2
CO 2
that is emitted in industry can be used by growers in their
greenhouses to stimulate growth. A pipe has already been
laid between the Botlek area to greenhouses in the Westland
and other areas for this purpose. Furthermore, growers use
the CO 2
that is emitted from their own CHPs and heating
boilers as much as possible.
2011 and onwards
The horticulture industry will continue to invest time and
money in the development of greenhouses with low energy
consumption and new growing strategies in the coming
years. Researchers, greenhouse constructors and computer
experts test new technologies and ideas on a semi-practical
scale at the Innovation and Demonstration Centre of the
Greenhouse Horticulture department of the University of
Wageningen in Bleiswijk. Research is not only carried out in
the research centres. Growers are also busy with the
development of new strategies in the horticultural companies
themselves.
There will be a great deal of attention paid to CO 2
in the
coming years. If less natural gas is used there will be less
CO 2
available for the growth of the crops. Therefore,
research is being carried out into how crops can supply a
comparable yield with a lower CO 2
dose. There is also an
increasing interest in the carbon footprint of horticultural
products. The industry is therefore working on a protocol for
an objective determination of the carbon footprint.
The Greenhouse as source of energy programme is aimed in
the first place at Dutch growers. Because of the good
cooperation between businesses, knowledge institutes,
suppliers and government, the Dutch horticulture industry is
developing into the global market leader in saving energy,
the use of sustainable energy and greenhouse climate
management. The whole horticultural cluster benefits from
this unique programme, which is co-financed by industry and
government.
The Greenhouse as source of energy
programme (Kas als Energiebron) is
the innovation and action programme
towards a powerful and climate-neutral
greenhouse horticulture sector in 2020
by the Productschap Tuinbouw,
ministry of EL&I en LTO Glaskracht
Nederland.
Would you like to know more?
www.kasalsenergiebron.nl
www.energiek2020.nu (in Dutch)
Contact the programme managers as spokesperson:
Piet Broekharst, Horticultural Product Board (Productschap
Tuinbouw).; p.broekharst@tuinbouw.nl
Jolanda Mourits, Ministry of Economic Affairs, Agriculture and
Innovation (EL&I); j.a.m.mourits@minlnv.nl
Luc Goedhart, LTO Glaskracht Nederland; luc.goedhart@zlto.nl
December 2011