The UK’s fresh produce industry may be ahead of most others in the field of agritech, but when it comes to glasshouse technology, it’s no secret that the Dutch sit top of the pile as an example for the rest of Europe to follow.
While the Netherlands is at the cutting edge of efficient and sustainable technologies in glasshouse growing, most UK producers are only just beginning to adopt some of the techniques that were introduced in the Netherlands years ago. One important reason for this is government investment, with the Dutch industry far more heavily subsidised than its British counterpart.
Technologies such as combined heat and power systems, biomass boilers and LEDs are still the exception rather than the rule in the UK, with investment requirements and ageing glasshouse infrastructure proving an obstacle to development in the UK. Not all investments are so costly, however, and an AHDB sustainability initiative, which gives growers information on how to save energy at commercial nurseries, recently completed a study group on a glasshouse production philosophy known as Next Generation Growing.
Pioneered in the Netherlands, NGG encourages growers to carefully analyse the plant’s needs and control conditions in the greenhouse accordingly – namely CO2 levels, humidity and temperature – to keep the plant in balance and maximise photosynthesis. While the focus is on plant physics, many of the methods used to optimise growth have also proven useful in saving energy and making glasshouse production more sustainable.
“It’s about keeping the plant in balance by giving it what it needs when it needs it, whether that’s light, CO2, water or whatever,” explains Ed Hardy who heads up the AHDB’s GrowSave project. “It’s as much about disease risk and keeping the plant healthy as it is about energy saving. But the two go hand in hand.”
The project, led by Dutch horticultural consultant Mark van der Werf, has highlighted to growers (of cucumbers, tomatoes, peppers and herbs) the importance of achieving an even climate throughout the glasshouse by using sensors to monitor different areas. And while UK growers will likely take more persuading to adopt NGG, Hardy believes the study group is a step in the right direction.
“Companies have done what they’ve felt comfortable with and they’ve seen mixed results depending on how much they’ve committed to what they’ve been shown,” he says. “They’re probably among the first in the UK to really adopt these principles. It does challenge some of the traditional methods used in UK glasshouses and I think people are a little bit reluctant because it’s a bit alien to them, but it’s proven itself as an effective way of growing in Holland and we’re trying to encourage it in the UK too.”
Another development that has been slow to catch on in the UK is LED lighting. And despite its benefits in boosting product quality and driving down energy costs, the huge initial investment needed to replace existing sodium lamps with LEDs has put off most growers, says Hardy. “In the UK we’ve got guys with 30-40-year-old greenhouses and when you’ve got an old structure it’s difficult to justify retrofitting new solutions,” he explains. “Putting in LEDs is probably not worth doing when you’ve already got sodium lamps set up. In terms of the more advanced glasshouse technology we’re just not at the same level as the Dutch.”
By contrast, CHPs are more straightforward to install, and their uptake has been promoted by the British government through incentives for CHP schemes over the past decade. This has encouraged some UK growers to install them, but from a sustainability perspective, Hardy believes it is perhaps preferable for growers to buy in excess carbon dioxide from other industries rather than producing more of the greenhouse gas themselves. As energy prices rise in the UK, there is also a growing financial argument for sourcing the gas from the external market – so long as the CO2 shortages seen this summer don’t persist.
“CHPs are a reasonable option for those needing heat and electricity but many growers still run gas boilers for CO2,” says Hardy. “For those with large heat stores, heat can be used later as required, but otherwise it is lost. There is an ongoing debate as to which is cheaper: running a gas boiler and wasting at least some of the heat, or buying pure CO2 from the external market. From a sustainability perspective, buying in waste CO2 should be favourable; it’s an unwanted by-product for many industries, but a desirable commodity for horticulture, where there is big demand for it.”
In future, Hardy would like to see industries that produce unwanted carbon dioxide being set up next to greenhouses to reduce CO2 waste and provide growers with a ready supply of the gas. “Maybe that’s where things will go in the future,” he says. “One man’s waste is another man’s resource.”
An alternative system – and one that has been pushed by government in recent years through the Renewable Heat Incentive (RHI) – is biomass, however Hardy stresses that it could become difficult to source enough biomass fuel, which often comes in the form of wood chips and biomass wood pellets.
“Large biomass boilers require a lot of fuel and if we suddenly get lots of growers installing them in the UK, it could become problematic. We have to ask ourselves: are we using fuel at a greater rate than we can supply it ourselves, and if so, will it necessarily be possible to import enough from elsewhere as uptake of biomass boilers grows internationally?”
The most sustainable and reliable way to heat a greenhouse, in Hardy’s opinion, is to install a ground source heat pump. “None of the systems are perfect, and some are more sustainable and economical than others,” he says, “but heat source pumps are probably the best option.” Harnessing natural heat from the ground by pumping water through it in pipes, the heat pump then increases the water’s temperature, and the heat is used to warm the glasshouse. The system still needs electricity to run, but the idea is that it uses less energy than the heat it generates.
As with other options, it requires a big initial investment, but government support is at hand – and more so than for any other system. “Installing a ground source heat pump relies on the grower having a large open area where they can install enough pipework to extract the heat, or you drill down 200m and have an expensive borehole put in,” Hardy says.
“It’s not cheap technology but at the moment heat pumps are the best supported of the renewable technologies through the RHI.”
Unfortunately, there’s not been as much uptake of the technology as one might have expected. “Growers are more familiar with boilers, so replacing an oil boiler with a biomass one is perhaps less daunting. Heat pumps, however, can be seen as this dark art that nobody really understands. Actually, it’s not that complex – it’s just more of an unknown quantity.”
Ultimately, the uptake of renewable technologies in UK glasshouses will take time – and better financial support from government – but the ball is now rolling. And the Netherlands is proving a useful example to follow.
CASE STUDY: Green future-proofing at Hugh Lowe Farms
One UK glasshouse grower that is ahead of the sustainability curve is Hugh Lowe Farms, writes Ed Leahy. The soft-fruit producer’s new glasshouse near Hadlow in Kent aims to bolster capacity while using the latest efficiency measures to keep energy and water use to a minimum.
“We’ve tried to future-proof our whole production and by building the glasshouse we’re extending our season,” says managing director Marion Regan. The recently constructed glasshouse already boasts an array of mod-cons, including a computer-controlled atmosphere, and ground-rails that could one day be used by robots.
With water increasingly topical after this summer’s record dry spell, the glasshouse is fully self-sufficient, capturing its own water from rainfall. “Unless it’s exceptionally dry, we’re 100 per cent self-sufficient. All the water gets stored after being captured from the roofs and we filter that back into the glasshouse. It’s a great source of fresh water,” says Lance Mansell, glasshouse and cane fruit manager at Hugh Lowe Farms.
The water is fed through a drip irrigation system that uses sensors to monitor moisture levels in the soil, with data stored on a ‘climate computer’, which is then used to control an optimum atmosphere in the glasshouse. “It’s precision farming,” says Mansell.
In addition, thermal screens that act like curtains can also be deployed to help capture heat, saving 20 to 30 per cent of energy consumption.
