It’s time to recognise Maurice van der Hoorn as a sustainability pioneer

In 2006, Dutch Phalaenopsis grower Maurice van der Hoorn opened the coutry’s first gas-free greenhouse. Back then, the notion of a ‘Kas Zonder Gas’ (greenhouse without gas) was unimaginable. Today, amid increasing concerns about energy supply, Maurice’s pioneering achievement is beginning to make its mark in the horticultural world.

“As lower temperatures trigger Phalaenopsis to start the flowering process, they therefore require a cooling system. “Cooling a greenhouse had seemed so unnatural and wasteful to me. Not to think about the tons of energy used to heat the greenhouse in winter and then to lose this energy in the summer by throwing open the windows to keep it cool is a situation that  now makes me feel quite uncomfortable.” says generation orchid grower Maurice van der Hoorn when thinking about the time he was growing his plants while being connected to the gas grid.


Customised integrated energy system

Contrary to all other conventional Phalaenopsis greenhouses – which cover a total area of around 200 ha in the Netherlands -Van der Hoorn Sustainable Orchid Nurseries (trading under the Amore Mio brand), does not rely on natural gas as a source of heat. Instead, they use a customised, integrated energy system based on a high-efficiency Grasso heat pump that works by recovering heat stored naturally in groundwater or aquifers. The ammonia heat pump runs during the winter months, generating both warm (50°C) and cold (6°C) water. The heat produced is used directly for the warming of the greenhouse, while the cold water is stored in two aquifers which have a capacity of 180m3/hour and sit one hundred metres deep. In summer, the greenhouse is cooled exclusively with the cold water from the aquifers allowing the heat pump to be turned off entirely.

The biggest challenge Van der Hoorn and his horticultural engineering company Bosman Van Zaal faced was to achieve optimal utilisation of the available low-grade heat. For that they used a heat exchanger in combination with a convection system. Floor-based convectors, over the full length of the greenhouse and in between the bays, are covered with a grid. Water goes to small tubes at the bottom of the appliance which can provide both heat or cooling. Fans draw in air through the grids and direct it along the tubes before distributing air masses equally under the rolling benches.


Off-peak hour electricity

The 15,000 m2 greenhouse has entirely shifted away from natural gas but cannot operate without electricity (3.5 million kWh/year) . However, the large water buffer tank (400m3) allows the tropical plant nursery to benefit from lower electricity rates during off-peak hours. Van der Hoorn agrees it can be addictive and time-consuming to constantly shop around for deals but stresses that he is not pulled from his bed at night to spend hours in front of his screen. “I am an avid market watcher, checking a few times per week but it has not become my sole focus as a grower. Off-peak hours are usually at night time and that’s when the heat pumps are on. The old 6,500m2  greenhouses were consuming 400,000 cu per year, today gas consumption is zero. As such, the groundwater pump system claims a 40% energy saving per year but this doesn’t mean you save 40% on your electricity bill. Naturally we buy carbon-free electricity and operate a climate-neutral plant nursery.”


Amore Mio is the candy store among Phalaenopsis as the brand represents over 20 different colours.









Fluctuating prices

Van der Hoorn adds that electricity prices fluctuate strongly. “Between 2006 and 2007, they were relatively low, 2008 was an expensive year followed by significant price drops. Today, electricity prices are high so growers who purchase gas to generate electricity are clearly benefiting. But we have had times when running a co-generation plant was not profitable. In Dutch greenhouse horticulture it is an extremely delicate subject. Gas for greenhouse growing has always been subsidised in terms greenhouse growers pay less energy tax. That’s the advantage I am currently missing out on. Thinking about my fellow growers, I am of course not advocating for a higher gas price. Though the reality is that break-even for an aquifer system is at a gas price of about 25 to 28 cents per cu m but gas is currently costing 20 to 22 cents,” he says.

In a world where it often seems people only have time to listen to those who shout the loudest, 30-year old Van der Hoorn is a modest horticultural entrepreneur, avoiding trumpeting his accomplishments. Perhaps too modest when considering the amount of risk taking when he built his Kas Zonder Gas. That is, in 2006, before Dutch greenhouse builders launched a variety of closed and semi-closed  greenhouses (branded as, for example, Sunergy, Sunwind, Flowdeck, Daylight) all of which delivered significant increases in energy efficiency albeit still connected to the gas grid.









Careful packing of plants


Sustainability sells badly

At the time, the Kas Zonder Gas created a lot of buzz in the media, giving Van der Hoorn’s Amore Mio-branded orchids unprecedented attention. In 2008, the orchid grower was presented the Encouragement Award at the annual Dutch Horticultural Entrepreneur of the Year Awards, but when the media’s fascination faded, selling sustainability was, and still is, very hard. “It might be that my voice is not strong enough. Don’t get me wrong; I warmly welcome the fact that other horticultural companies do their bit to help the sector act responsibly towards the environment but I don’t have the financial means larger companies have. I tried to include the gas-free message on our plant labels, that ours is a plant nursery which is truly without gas and, thus, without the smoking chimney of a cogeneration plant. However, there’s an ocean of eco labels and sustainability claims that rather confuse than reassure consumers. At the wholesale level, I receive lots of praise from my customers for my sustainability efforts but at the end of the day it’s all about money and cheap prices.”

What Van der Hoorn really regrets is that he has not been given the opportunity to promote sustainably-grown plants upstream on the supply chain, for example by teaming up with the customers of his customers – the large garden centre chains. He is also not hiding his frustration that an individual approach like his is sometimes sneered at. “We are one of the first orchid companies which has measured its ecological footprint. We produce around 0.8 kg/CO2/per plant. Our total annual production amounts to 1 million plants which is 800,000 kg CO2. One Phalaenopsis with a 0.8kg/CO2 is said to be equivalent to an 8km drive by car, acknowledging that  a new car has an average carbon footprint of 100gr/km. 0.8 kg CO2 also equal to 48 grams of grounded beef (1 kg grounded beef produces 16.8 kg CO2).

However, at business networking events of large floral wholesalers they don’t even listen to you, to understand that sustainability only needs a sector-wide approach such as Floriculture Sustainability Initiative (FSI). Though individual ranking of floricultural companies based on their footprint would truly spur more and more companies to set goals for reducing their CO2 emissions and help them to differentiate themselves in the market place. To date, neither Benefits of Nature, FSI nor MPS provide such a ranking system.”


Earthquakes in the Netherlands

Van der Hoorn’s advocacy has had limited ripple effects beyond the glasshouse walls of his plant nursery. Until now. Recent events in the Netherlands have seen a resurgence of interest in his Greenhouse Without Gas. Earthquakes began damaging homes in the northern province of Groningen, where the Dutch discovered the largest gas field in Europe back in 1959. Gas-free housings and companies all of a sudden became high on the Dutch government’s agenda with phasing out of Groningen gas seeming inevitable in the long run. “It’s rather funny to see that new, large-scale energy saving greenhouses are now making the headlines while still not being completely switched off the gas grid. I had already done that thirteen years ago so for me it was nothing new. Due to the seismic activity in Groningen, my carbon-neutral greenhouse is currently drawing renewed attention from the horticultural community with Bosman Van Zaal regularly bringing in growers and other horticultural professionals from home and abroad,” says Van der Hoorn adding he still takes great pleasure in showing fellow growers around.


The Kas Zonder Gas created a lot of buzz in the media, giving Van der Hoorn’s Amore Mio-branded orchids unprecedented attention.

Floor-based convectors, over the full length of the greenhouse and in between the bays, are covered with a grid. Fans draw in air through the grids, direct it along the tubes before  distributing air masses equally under the rolling benches.


Not a success for everyone

Meanwhile, he is perfectly aware that a Greenhouse Without Gas is not a success story for everyone. “The benefits depend on the energy needs of the crop. In Phalaenopsis, half of the greenhouse requires cooling (20°C) while the other requires heating (28°C) which makes a heat pump ideal to use as heating and cooling are provided through the same investment. Many a tropical plant grower uses a cogen plant generating both electricity, usable heat and carbon dioxide, forcing them to generate cooling separately which is a costly exercise. In my case, cooling provided by the heat pump is a kind of waste product which allows me to cool my greenhouses in summer partly for free,” says Van der Hoorn adding that operating a gas-free greenhouse requires an entirely different mindset than using conventional heating and cooling systems. “Dutch growers are typically used to literally feeling 50°C to 60°C heat when touching greenhouse heating tubes. With low-grade heat, the water is around 32°C upon entering the greenhouse whilst we are able to maintain it around 28°C by catering for a proper air distribution system. In the old greenhouse we worked with a conventional cooling system using 200 watts per m2, which is a lot of energy in summertime.”



Successful change starts with personal courage and…perseverance. Van der Hoorn: “To optimise the new system’s chance of success we carried out the necessary testing with air heating. Bosman Van Zaal did the maths, then we jointly committed and implemented. The fact is that you need a new-build. Adapting an existing greenhouse would have been impossible.”

Though along the way much acknowledge has been acquired, the Greenhouse Without Gas is still waiting for perfection. “You only know what needs to change when you see how the system is working,” the sustainability pioneer says. Using new insights provided by the Dutch horticultural education cluster Het Nieuwe Telen (Next Growing) – which focuses on sustainable growing practices – he continually tweaks things. In the beginning, Stechdoppel polycarbonate roofing for super insulation and double energy screens caused humidity levels to rise. “Meanwhile, I have learnt how to fine-tune venting and air circulation. Speaking of polycarbonate roofing and its drawbacks, one is that fireworks on New Year’s Eve keep you awake at night due to possible fire hazards,” comments Van der Hoorn.

Working with convection heating also means air currents can lead to substrates becoming dry more quickly. “Using a more fine grade of bark allows me to have 5 to 10% more humidity in the pots which eventually translates into better branching and more buds with bolder colours. Customers tell us that we are the candy store among Phalaenopsis growers as we grow over 20 different colours. Amore Mio orchids also differentiate themselves by their smaller 12 cm pot size,” explains Van der Hoorn.



The large water buffer tank (400m3) allows the tropical plant nursery to benefit from lower electricity rates during off-peak hours.






Making history

The Greenhouse Without Gas has made history by being one of the first intelligent ways to sustainably satisfy different energy needs in Dutch greenhouse orchid production and it is still the first of its kind in the horticultural world. It will continue to change the way greenhouse horticulture thinks about energy production. Questioned about his inner drive for sustainability, Van der Hoorn stresses that he sincerely cares for people and the planet, especially when thinking about future generations. And even though sustainability is hard to sell, the Kas Zonder Gas had led to an overall positive recognition of the Amore Mio brand which in turn has helped anticipate regulatory trends and policies. But he is honest enough to admit that profit is also one of the major drivers of sustainability. “Back in 2006, it was not  my primary goal to become a world changer. Only in a perfect world would companies be angelic. But we’re a business and we need to provide returns to cover our operating costs. At the end of the day, all horticultural entrepreneurs consider the financial aspects first.”


Grasso heat pump

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