Why do Mushrooms Grow in Coffee Grounds? Complete Guide

Mushrooms contain macronutrients that are essential to supporting a thriving immune system, the nutrients we need in bulk that provide us energy. 90% of a Coffee beans biomass is wasted every time a cup of coffee is made. How can they help each other? 

Mushrooms thrive on almost any kind of lignocellulosic biomass, which coffee has a high concentration of. This is a renewable biomaterial composed of nutrients that are able to be reused and can be metabolised and broken up into various compounds by fungi.

Mushrooms are similar to plants in many ways, but they lack chlorophyll and need to retrieve nutrients from other materials. They are essential to the balance between humans and nature making it not so surprising that they can be used to hold off another huge amount of human waste by simply recycling and reproducing.

Furthermore, certain mushrooms have higher price ranges than others due to a myriad of reasons meaning they’re not the only living things that are picky when it comes to their growing conditions. 

Does Coffee Grow Mushrooms? 

Simply putting it, coffee does grow mushrooms. More specifically, coffee grounds – the ones you discard after making your coffee – are prime breeding grounds for many bacteria and fungi, mushrooms included.

Coffee’s lignocellulosic biomass and the preparation of the coffee to the discarded coffee grounds prepare themselves perfectly for mushrooms to thrive as the substrate would already be pasteurised and sterile while the biomass would provide the mushrooms what they would need to grow and reproduce. 

What Mushrooms Grow Well on Coffee Grounds? 

Oyster mushrooms and Shiitake mushrooms are known for being the best of the species to grow on Coffee grounds. The secret is that Mushrooms can be trained to like and grow on certain substrates, but some adapt easily and some do not. Oyster mushrooms adapt easier because of an immense creation of enzymes for consuming cellulose. 

Shiitake mushrooms pair well with coffee grounds due to the range and amount of nutrients packed into them. Despite this, the coffee grounds are also too acidic for the shiitake mushrooms and, unlike the Oyster mushrooms, need to be paired with saw dust, hard wood pellets, or straw. Those three are the recommended substrates when it comes to this pickier mushroom. 

How Do You Grow Fungi on Coffee Grounds? 

You would need to get fresh coffee grounds first. You must use the coffee grounds and complete the manual part of this process less than 24 hours after the preparation of the coffee as other bacteria and mould can start to grow, affecting your cultivation. 

To start with, the method you would use to grow mushrooms with coffee grounds depends on the type of Mushroom. Oyster mushrooms can grow in coffee alone as they can adapt to the conditions presented but it is recommended that you add another substrate such as pasteurised straw, hydrated sawdust pellets, or hardwood pellets to improve the air exchange in the substrate. 

Weigh your substrates and spawn before mixing them together, ensuring that the balance is correct. The spawn that has been recommended to use are blue and white Oyster mushrooms as they are more stalwart than other types. 

Fill your medium of growing such as a grow bag and seal it well, leaving it to sit in a dark space for 2–3  weeks at room temperature. 

Once 2–3  weeks are up there should be white mycelium growing across the top of your grounds, your grounds are now colonized and ready to be placed in fruiting conditions. It is essential to know how you want to fruit your mushrooms as different conditions provide different outcomes for your cultivation. 

When using a grow bag you can cut 2-3 cm holes in it and place it in a location that has indirect sunlight around it. You can also start spraying it with water everyday and within a week you will see the fruition of your work. Continue spraying for another week so your cultivation may grow. 

You will notice the top of your cultivation flattening out as Oyster mushrooms do and that is when you know that they are ready to be harvested. There is more than one way of cultivating but the easiest would be to cut the mushrooms off or twist them from the base. 

Read more: How Difficult Is It To Grow Mushrooms? 7 Easy Steps

How Does Caffeine Affect Mushroom Growth? 

Mushrooms grow very well on coffee. The reason is that caffeine when given to mushrooms has the effect of boosting their growth and accelerating the time a culture needs to become fruitful.

These results are shown when the inoculation process, from the mushrooms and coffee grounds being measured to them being mixed together and cared for, are done right and in the right conditions. 

Studies on Spent Coffee Grounds (SCG) and caffeine on the growth of mushrooms in liquid, solid, and a commercial scale show different results when different circumstances are presented. On agar and in liquid cultures in the laboratory, caffeine hindered mycelial growth.

Higher levels of SCG in sawdust and SCG substrates were seen delaying and preventing fruiting from occurring. In spite of the growth inhibition, Xanthine that is present in Oyster mushrooms partially degraded the caffeine present in the SCG. This was seen in all the SCG substrate mixtures. 

The caffeine was mostly degraded by the successive N-demethylation to theophylline (1,3-dimethylxanthine) and 3-methylxanthine, however, paraxanthine and theobromine also accumulated in the substrate.

It is still unclear if caffeine metabolism took place in the fruiting bodies themselves or whether caffeine metabolites were transported there from the mycelium since caffeine and its demethylated metabolites were also found in the fruiting bodies.

Now based on the studies of caffeine effects on the growth of mushrooms, it would be necessary to eat 250 kg of Oyster mushrooms to consume the same amount of coffee that one expresso would have.

Indicating that the health impact of caffeine in mushrooms is not consequential at all. The studies also give us hope as recycling coffee grounds to grow mushrooms has potential to aid in the detoxification of coffee waste.