In Flanders, greenhouse growers have been contributing to the environment for more than ten years by saving energy and producing heat as efficiently as possible, using co-generation.
The cooperation Verenigde Groentetuinders (VGT) from Rijkevorsel built their first 7 ha greenhouse in 2003. In 2006, a second greenhouse of 8 ha was added. On those 15 ha, VGT grows bell peppers, and for heating they immediately opted for co-generation.
Koen Neyens, one of the founders of VGT, says they worked with Electrabel in the beginning: "They invested in an engine. We purchased the heat. In 2007, we expanded the co-generation and took over the installation from Electrabel."
Feeding residual electricity to the grid
Because bell peppers are unlighted, VGT only uses 2% of the electricity generated. The rest is fed to the grid. "In a normal gas boiler, the energy content of the gas is only converted to hot water. In co-generation, 43 to 45% of the energy is converted to electricity, but the released heat is used to heat water, and we are achieving 100% efficiency.
"By condensing the smoke fumes, we can also recuperate heat, and even achieve efficiency of more than 100%. The latest electricity plants achieve a maximum efficiency of 55%. In bell pepper cultivation, we also invest in single or even double energy screens. We are still trying to grow with as little energy as possible."
Decentralized electricity production
According to Koen, co-generation and greenhouse horticulture go very well together. In recent years, a black-out could have occurred in the winter. When all energy is produced in one spot, the chance of a large-scale blackout increases. "We produce electricity decentralized. Last year, for example, we received a request from electricity company Eandis to help support the grid when they had to repair a mains supply after a fire, and it had to be disconnected for some days. We can play a role in society."
Co-generation can run during the day, when energy use is often high. The warm water is stored in buffer tanks and is pumped into the greenhouse when it cools at night. "Running during the day has the added advantage that we can recuperate CO2 from smoke fumes to supply as 'fertilizer' to plants. This increases the production in the greenhouse and the plants release oxygen.
"Our co-generation has been adjusted to the heat requirements of our company in winter. During a part of summer we pause our activities, but we are running during the day, when the energy requirement is the highest. We only have to heat our greenhouse in the morning, to prevent condensation on the plants."
Cooperative on the market
VGT has been associated with WOM (co-generation support company). This is a cooperation of growers using co-generation, which takes care of the sale of electricity, but also negotiates the purchase of gas. "We joined because we have a cooperative nature, because we believe we are stronger by joining forces. Through WOM, we are an interesting party to buy electricity from, or sell gas to. Moreover, it represents our interests in interactions with the government."
Herman Mariën, teacher at the Thomas More Campus Geel and responsible for WOM: "WOM was founded by five growers in 2006. As a result of the energy crisis at that moment, every grower was looking for energy saving techniques to keep the heating costs within limits. The motivation was to further lower the heating costs by optimizing the yield and the costs of co-generation. The college quickly exempted me to lead WOM and guide its members.
"Through WOM, growers can jointly purchase gas against better rates. We do the same for selling electricity. At the moment, we represent 130 growers and we are no longer seen as a small player on the energy market. WOM is a cooperative co-generation support company, but the co-generation is managed by the growers themselves. We do not control their engine. The growers decide how they will sell their energy, but we support them with education."
The goal is 400 megawatt
Mariën: "In the fall, we determined that the disengagement plan mentioned that we should first look at where our co-generation could supply people with electricity. We have an important role in the decentralized production. Distributed over Flanders, we're the equivalent of a small nuclear plant. The goal is 400 megawatt. Our cooperation has a bit more than 300 megawatt of power.
"In the provinces of Antwerp, East and West Flanders, we can make sure that electricity is produced at moments the users are active, and we realize 30% reduction of CO2 emissions. By applying co-generation in greenhouse horticulture since 2007, we have been active for more than 10 years in reducing the CO2 emissions. Our society demands electricity. We can supply it in a sustainable manner."
Pieter Timmermans, adviser at Boerenbond: "Greenhouse horticulture has become much more sustainable in the last 15 years. Oil was replaced by gas as main fuel, which has much lower CO2 emissions per MWh fuel. The use of gas also made the introduction of co-generation in the sector possible, which is at the moment able to supply 500,000 Belgian families with electricity.
"The emissions from co-generation are, however, completely included in the figures of the horticulture sector, while it seems more logical to partly ascribe those to the energy sector. If the electricity production for families is taken into account, greenhouse horticulture reduced its energy use with 45% between 2005 and 2016."