‘Shrooms & char

Muschrooms & Biochar

Yesterday I visited Main Street Farms (MSF), a highly sustainable aquaponics operation that also includes high tunnels and mushroom production.  They are also hard at work learning how best to put worms & insects to work and have created an admirable agro-ecosystem which could provide a successful model for local food production in the Northeast and beyond.

What made the tour even more interesting were the folks there with me, two employees from a ‘combined heat & biochar’ (CHAB) equipment manufacturer and a very knowledgeable horticulturalist from Cornell. Our hosts graciously toured us around their facilities and showed us all of the different research projects they’ve been conducting over the past few years in an effort to become as sustainable as possible. Inspiring stuff to say the least. We are hoping to start a project using biochar production technology on-site which would enable them to become even more sustainable.

My role on the team is to uncover and quantify opportunities for possible biochar ‘interventions’, one of my favorite things to do! I had a number of different thoughts on how biochar could benefit this kind of operation but for today I’ll focus on the fungi! As I’m always on the hunt for underutilized biomass, I was delighted to see up close for the first time some spent mushroom substrate (SMS) from their oyster mushroom production. They had at least two different flavors; some made from sawdust & some from coffee grounds. I immediately asked for samples to test for biochar thinking I’d uncovered a novel new feedstock. When I had time for a quick tete-a-tete with Master Google I soon found out that my novel idea wasn’t so novel after all, others are on the case!

Turns out for every pound of delicious fungi produced, five pounds of substrate are needed, so there is a growing amount of this stuff around looking for appropriate end uses. The moisture content is pretty high (>60%) which can be a challenge for charring, but a CHAB unit could help with that.

After a mushroom flush (think harvest not toilet!) sometimes the substrate can be ‘dunked’ or rewetted to grow another flush. Apparently after dunking some growers ‘roll’ the substrate in vermiculite to increase water holding capacity. So another interesting possibility for biochar would be to roll the mushroom growing medium in biochar and get rid of the not very eco-friendly, vermiculite. Within an aquaponics system, I’m wondering if by dunking the substrate in the nutrient rich fish water, sufficient nutrients would be added back in to the substrate to provide for more flushes. Alas this is completely outside of my area of focus but still interesting to put out there for someone else to answer or research.

From a quick scan I also learned that SMS needs to be heat treated before it leaves the grow room to eliminate any pathogens before being added to compost or land applied. With a CHAB unit in the greenhouse, the heat could most likely be used for this purpose.

What I’m really wondering though, is whether biochar or a biochar blend could be used as a mushroom substrate. Surprisingly Master Google failed to deliver any interesting research or projects on this topic. If anyone has knowledge on this, I’d love to know!

Next up I’ll be casting about for biochar synergies for aquaculture!

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