Why mushrooms have what it takes to be a meat substitute - and can save the world at the same time

Bizarre and mysterious: the largest organism on the planet pulsates beneath our shoe soles. The fungal mycelium takes on functions in our ecosystems of biblical proportions: it mills through the earth's soil for several kilometres and thus accounts for 70 percent of the biological carbon in it. We have known this at least since the Netflix documentary "Fantastic Fungi", which gives us an insight into the fascinating world of fungal mycelium and its gigantic underground network. One thing becomes clear: there is far more to know about mushroom mycelium than we previously suspected.

Which is no wonder, after all, the mysterious mycelium is only visible above ground through its fruiting body, the mushroom. This settles on tree trunks, sprouts from forest soils - or grows in the laboratory. In the mushroom cultivation "Hut und Stiel" on the outskirts of Vienna, it even grows on old coffee grounds. Why coffee of all things? "Coffee is available in unlimited quantities in Vienna with its coffee house culture," says Thomas Fahrnberger, a staff member and mushroom expert. And the waste in the form of brew holds previously untapped potential. This business idea of a special kind came about when agricultural science student Florian Hofer heard about it for the first time at a lecture at the University of Natural Resources and Applied Life Sciences in Vienna: old coffee brew as a mushroom substrate. Enthusiastic about the idea, he and agronomist Manuel Bornbaum started their first experiments. Together they founded the start-up "Hut und Stiel" in 2015.

Competing mushroom farming? Industrial factory farming

Today, seven years later, the company has numerous cooperation agreements with coffee houses, restaurants, banks and retirement homes across Vienna. Thomas Fahrnberger has been part of the team since 2019. The career changer actually comes from the metal industry: "I no longer found any sense in working in a company with over a thousand employees." The reorientation at that time also brings him to the topic of meat-free nutrition - after all, an interview of the "Hut und Stiel" founders Hofer and Bornbaum catches his attention: "They said that there are no competing farms in mushroom farming. That only industrial factory farming is the competition." To counter meat with a competing food, a substitute product that can be produced much more sustainably and thus protects farm animals and the environment? Inspired by this potential, the Lower Austrian quits his job and moves to Vienna to join the vision of the two founders.

While we are now walking in the glistening sunshine with mushroom aficionado Thomas across the community farm, where apart from the mushroom farm 19 other initiatives are responsible for growing vegetables, he tells us why the farm is not as bustling as usual at the moment: Many restaurants have fewer customers or close down completely during the summer months, so "Hut und Stiel" also produces less at this time. "At peak times, we produce 1.5 tonnes of substrate a day and harvest three times a week". One cooperation partner even drinks a particularly large amount of coffee: there, between ten and fifteen boxes of coffee grounds, each weighing 25 kilograms, are collected per week and processed into mushroom substrate - the nutrient medium that mushrooms need to grow. In nature they grow on tree trunks or forest soils - in a cultivation you have to get inventive and make the substrate yourself.

Thank you, coffee: a waste product with potential

Sawdust or straw are good for offering the fungus and its mycelium an alternative living space. Actually, even better than coffee brew: "Both have a much higher bioefficiency - so there is more yield per kilogram of substrate," says expert Fahrnberger. But part of the young entrepreneurs' vision is the idea of recycling: unlike straw and shavings, coffee brew is available en masse, as a large part of the bean is usually simply thrown away as a waste product of coffee brewing. "Hut und Stiel" uses this resource and turns the old coffee grounds into a mushroom substrate. Through several experiments it quickly becomes clear: the oyster mushroom grows best here. "Depending on the substrate, it takes between ten days and four weeks until the mushroom is ready for harvesting.

For the optimum moisture content of 50 per cent, the moist coffee brew is mixed with straw. If the substrate is too moist, mould will also nest very quickly. "This is quite common in mushroom cultivation," Fahrnberger knows. "Mould spores are much more resistant and faster than edible fungus spores." This happens again and again, especially in so-called "LowTec farms", as hers is one. There, the substrate is not sterilised, but merely pasteurised, which makes it easier for the mould to settle. The substrate must therefore be packed in an environment that is as sterile as possible, and affected bags must be sorted out directly if in doubt.

From coffee substrate to harvestable fungus in one month

The sterile production room is very sporadically furnished, with only a table and a mixing machine awaiting us. In the machine, the substrates are mixed into a mass: 60 per cent straw, 40 per cent coffee grounds and the mushroom mycelium. Afterwards, the finished substrate is sealed in black plastic bags and taken to the incubation room.

There, in the windowless room, it is uncomfortable: a cool 20 degrees ensures that the mycelium does not die, loudly rushing exhaust pipes control the CO2 content in the air. The bags are stored in the incubation room for a month until the mycelium has eaten its way through the substrate sufficiently and the plastic can be cut into the sides. After this phase, the bags are moved to the fruiting room: oxygen and light reach the substrate and the mycelium forms fruiting bodies. Experts call it the fruiting phase: within a week, hand-sized oyster mushrooms sprout here until they are packed freshly harvested and delivered to customers on the same day.

In the fruiting room it is still a little cooler: we look over Fahrnberger's shoulder as he carefully checks the room temperature and humidity. All the settings have to be right for growth: 12 to 18°C and up to 90 per cent humidity prevail here. In five shelves of eight tiers each, the cut substrate sacks lie next to and on top of each other. Because production has been shut down due to the summer slump, the room is relatively empty: we can walk through the rows and see the coffee brew with the thick layer of white mycelial threads in the sacks. Here and there the fruiting bodies sprout from the sacks, in two days it will be harvest time. The coffee grounds, by the way, go on the farm compost after harvesting and can later be used as fertiliser.

Fascination mushroom: the future of our food?

The fungus is fascinating not least because it is neither animal nor plant. In fact, it shares more DNA sequences with us humans than with plants. Nevertheless, the fungus is advancing to become a sustainable alternative for foods that are considered particularly resource-intensive. "Mushrooms are a very exciting topic with a lot of future," says Fahrnberger. He is particularly enthusiastic about their potential to at least partially replace foods like meat. According to the Food and Agriculture Organisation of the United Nations (FAO), industrial factory farming is responsible for 18 percent of global greenhouse gas emissions. That is more than global transport emits combined. In addition, the production of meat and milk requires 77 per cent of global agricultural land, even though animal proteins provide only 17 per cent of humanity's caloric needs.

"Mushrooms are very sustainable when you consider how much we can harvest from this small area and how much land would be needed for the same amount of beef. They grow faster and require fewer resources than almost any other food."

According to the expert, sawdust has a biological efficiency of 1:1, meaning that one kilogram of substrate yields one kilogram of freshly harvested mushroom. "That is incredibly efficient and space-saving." A lot of yield on a small area: a successful model for urban farming projects worldwide - and a future topic for urban food security.

Umami and texture: meat substitutes made from mushrooms

As a meat alternative, mushrooms, unlike soy and seitan for example, are less controversial and not only popular with vegans. Around half of the yield at "Hut und Stiel" therefore goes to processing companies. The rest is bought by private customers at the farm - or they get the mushrooms from "Hut und Stiel" delivered to their homes by e-car. Thomas Farhnberger looks at his watch, he still has one more delivery to make this afternoon. Vegetarian pestos, sauces, mushroom goulash or mushroom sausages: all this can be made from oyster mushrooms. But why are mushrooms so good as a meat substitute?

"On the one hand, it's because of the texture. It's very stringy, like meat," he says. In addition, mushrooms have a classic umami taste: spicy, savoury and also meaty. The umami taste is also the reason why mushrooms are so often used in Asian cuisine as a seasoning for sauces or soups.

Whether above or below ground, the mushroom has potential, that much is certain. Anyone who has seen the documentary "Fantastic Fungi" knows that it can even decompose plastic or help to cope with oil crises - and revolutionise our diet. Will the fungus, to put it exaggeratedly, save the world? "In my eyes, it can definitely make the world a better place," says Fahrnberger.