References Agriculture

In order for domestic greenhouse cultivation to continue in Finland, it will be necessary to find growing media to replace horticultural peat in the next few years. Luke’s study for the Finnish Glasshouse Growers’ Association shows that development work is producing results, but a transition period is needed.

If the use of peat-based growing media were stopped today, about 90 percent of Finnish greenhouse companies would collapse. Domestic tomatoes, cucumbers and potted salad greens would disappear from Finnish dining tables and flowers from balconies. This is how the members of the Finnish Glasshouse Growers’ Association assessed the situation just over a year ago. An alternative to horticultural peat was already being sought at that time. In fact, it has been sought after for years.

“About 10 percent of the peat extracted in Finland is horticultural peat, and it is obtained as a by-product of energy peat from the surface layers of the bog. When the extraction of energy peat ends, the availability of horticultural peat is also likely to decline,” says Niko Silvan, a researcher at Luke. According to him, scientists and growers are prepared for a transition period of a few decades, during which horticultural peat would be raised from pre-drained bogs and less year by year. However, the regulation envisaged by the EU, the EU Sustainable Finance Taxonomy, could radically change the situation even sooner.

“If horticultural peat is classified as very harmful, it will be impossible for greenhouse entrepreneurs to get loans and subsidies, for example,” says Silvan. Sustainable alternatives must therefore be found already in the coming years.

Uniform quality – affordably and sufficiently

The Finnish Glasshouse Growers’ Association wanted an accurate picture of the global use and availability of horticultural peat and growing media that could replace all or part of the horticultural peat. The study was commissioned by the association in the spring of 2021, and Luke completed it in October.

“In addition to serving as a growing medium, the material must be sufficiently available and affordable and of uniform quality to enable growers to prepare for a certain crop yield. Retail chains make sure that the decline in yields cannot be passed on to prices. If the crop yield drops by five per cent, for example, every other greenhouse company will make losses,” says Jyrki Jalkanen, Executive Director of the Finnish Glasshouse Growers’ Association.

Renewable and recyclable wood fiber

According to Silvan, more than 90 per cent of Finnish greenhouse vegetables and flowers are grown on horticultural peat, while in Central Europe the share is 50–80 per cent. This is by no means to say that the problem with growing media has been solved in Central Europe. There is, for example, a lot of stone wool in use, which is also favored by many Finnish cucumber growers.

“Making stone wool, however, requires a lot of energy and it cannot be recycled. Our clear starting point was that growing media must be made of renewable and recyclable materials,” says Jalkanen.

In Luke’s study, the most promising new growing medium was wood fiber, which is readily available in large quantities and can be ground into small sticks or even fluff as needed. Industrial production can be expected at least from the Finnish company Biolan, which plans to start up its biofibre plant in the autumn of 2022. However, wood fiber requires other raw materials to support it in order to act as a growing medium.

“Wood fiber could be used by priming, that is, improving it, with horticultural peat in the transition phase and later with other raw materials such as peat moss,” says Silvan. According to him, peat moss growing in bogs would be a suitable growing medium on its own, but its large-scale harvesting is not considered a sustainable option, even if it is renewed in decades.

According to the study, lake reed and reed canary grass are also promising alternatives, and so is digestate from biogas production when it is of uniform quality.

We worked closely with Luke’s researchers throughout the study. In this way, the daily work of growers and scientific research complement each other in the best possible way.”

– Jyrki Jalkanen, Executive Director, Finnish Glasshouse Growers’ Association

Growers and researchers work closely together

Silvan emphasizes that every new growing medium requires changes in cultivation. Cultivation must therefore be researched and developed alongside growing media. Jalkanen and Silvan consider the feasibility study a good basis for further research and the search for research funding. It also serves as a good example of how researchers and research clients can collaborate.

“Our team met Luke’s team through Teams a dozen times in a few months. We were able to easily pass on all the information we heard from growers and growing medium producers, and Luke’s experts, in turn, evaluated from a scientific perspective what to do with these tips. I recommend this approach also to other research clients,” says Jalkanen.