Research Update — Acorns and Mushrooms

Two of our current projects moved along today. Here are the data and impressions.

Acorn Processing

Acorns are a decent-value nut found widely across the temperate world. The common thought is that a person could collect many times more calories than he or she expended while gathering acorns. I am gathering data on the caloric investment and payoff from processing acorns from tree to meal.


Scott and Casey gathering acorns in the park.

I spent an hour gathering 1.6 kg (3.5 lb) of acorns from Tower Grove Park in St. Louis (with the permission of the park authorities, of course). In that hour, I covered 140 m2 (1507 ft2), measured by collecting in 2-m-wide swaths marked by pin flags. I believe this is a minimum amount of acorns per time and space because more than half of the nuts were already half eaten by squirrels. I have certainly been in locations with much denser acorn concentrations.

I burned about 136 calories in that hour (I estimate this to be equivalent to picking fruit or vegetables). It was a 6.4-km (4-mi) round trip, which burned 208 calories. Total calories burned in gathering acorns: 344. That is 215 calories per kg (98 calories per lb), but that could be lowered by gathering more acorns in a single trip.

Casey inspecting the acorns.

Next will come processing, including washing, shelling, soaking, and grinding.

Anecdotal Observations

These are really sweet acorns. To test, I split the acorn open and chewed on the meat. It took 10 seconds before I tasted any bitterness. This is unusually sweet. Many acorns will give a bitter taste in 1-3 seconds of light chewing. This is due to tannins, which will be removed by soaking.

Also, apparently it is unusual to see an adult man crawling on his hands and knees across the park, picking up acorns. I got quite a few curious looks. The pin flags and notebook at least gave me some semblance of “official science going on here.” Now who’s the nut?

Growing Mushrooms

I am following the process outlined in Falconer’s 1901 mushroom growing manual outlined in yesterday’s blog post. Step one was finding a whole load of horse manure. Luckily, Ride On St. Louis (a riding school and horse therapy place) offers free manure for the taking.


Back when I was an archaeologist, this was called a shovel toss.

Not much data to report here. It took me about 30 minutes to shovel about a ton of manure mixed with straw and wood shavings. I tried to avoid the white manure which has composted too hot and burned. There were so many shavings that I had to figure out how to separate the horse droppings from the shavings. I found that by tossing the mixed stuff up in a steep pile, the horse apples rolled off and the shavings piled up. Then I could shovel up the manure, leaving much of the shavings.

Horse manure in the garage.

Once at home, the manure was piled onto the floor of the garage to ferment. It should heat up over 54°C (130°F), which kills a lot of bacteria and conditions the droppings into mushroom substrate. It will be turned every 3-5 days to ensure even heating.

Next I’ll be building the mushroom beds out of scrap lumber and looking for spawn. More on this as things develop.

Anecdotal Observations

Horse droppings don’t smell bad. They are sweet and musty.

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