Here is the beginning of this year’s harvest of rose petals. Last year I made Cactus Rose Wine out of prickly pear fruit syrup and rose petals.

Hmmm, I thought. I have been trying to economize, partly just to do the right thing, and partly because I’d like to attend the Fourth Advanced International Colloquium on Building the Scientific Mind to be held at the Sustainability Institute in South Africa in March. In order to go, I have to really scrimp and save. So, I haven’t turned on any heat in my house. I built the windowbox heater, and now talking with Linda gave me another idea.

When I lived in Japan, I became familiar with an item of furniture that is common in Japanese homes called a kotatsu. Most Japanese homes that I experienced did not have central heating. Instead, people used space heaters (often kerosene) and the ingenious kotatsu. The kotatsu is a low table with a heating element attached underneath the tabletop. The table is covered with a quilt that reaches to the floor on all sides, and then covered with another tabletop. People sit around the table on cushions with their legs and feet in the warmth under the table.

Since a compost of coffee grounds and sawdust is bound to smell good (or, at the very least, not smell bad) as it heats up, I thought: Why not build such a compost bin inside the house? When it gets cold, I could siphon off some of the heat.

But I couldn’t build a large compost bin inside the house! Where would I put it? (My house is rather small.) And I certainly couldn’t build one large enough to heat my entire main room.

But I did have an old round tub outside, and I did have an old umbrella table–without the umbrella, but with a solid wood tabletop. It seemed to me that a small compost bin, if it did successfully heat up, might generate enough heat to take the chill off underneath the table.

Hmmmm. Why not give it a try?

Linda came over and helped me build the compost kotatsu.

We put the tub underneath the table and then built a bin of 1/2″ poultry netting.

Then we lined the bin with burlap.

For the compost, we used free coffee grounds collected by ourselves & friends, from coffeeshops and our own kitchens. Linda got free sawdust from her neighbor who does woodworking. Linda also donated some starter compost from her own bin.

We added enough water to make it the right consistency.

Then we filled the bin.

Here’s how the assembled compost kotatsu looks,

from underneath . . .

and with the table assembled . . .

When it gets cold, I’ll put a longer tablecloth on the table to trap the heat.

Within three days the interior had reached 115 degrees. It has been rather warm here, so I haven’t needed to siphon off any heat yet. When I do, I plan to use a simple tube inserted into the compost bin at an angle to perform the heat transfer–an idea similar to that of the windowbox heater. Then I’ll have to observe whether that causes the compost to cool off too much or not.

The best case scenario: free heat + free compost for the garden

The worst case scenario: free compost for the garden

What’s not to like about an experiment like that?

I’m no carpenter, but I built a simplified version of the heater for my house this year. It cost me $28 for supplies, and friends donated scrap lumber to help me out. Here’s what it looks like:

Next year I plan to make it longer and to set it at a steeper angle for greater efficiency.

First, make two deep cuts in each olive–all the way to the pit. I made my cuts one on each side.

Soak them in a brine of 1/4 cup salt to two cups of water.

IMPORTANT: Use kosher salt, pickling salt or sea salt. Don’t use iodized or plain salt.

Make sure the olives are completely covered with brine.

Stir a little bit each day.

Change the brine every week.

Taste after three weeks to see if the bitterness is gone. This time I soaked mine for four weeks.

When the bitterness is gone, rinse the olives in water and pack in jars. The recipe my friend gave me called for packing them with garlic, lemon, and spices, but I like the beautiful olive taste so I didn’t add these. I used about a tablespoon of salt, one part water and one part vinegar per jar. I think next time I’ll use a little less vinegar, although as the olives age, the vinegar taste mellows a bit.

Top each jar with about 1/2 inch of olive oil. Turn the jars upside down.

After a week, turn them right side up.

Try not to eat them all in one sitting. (It’s hard!)

(Quick update on the olive recipe–I found that adding an additional tablespoon of salt and the juice of half a lemon to each jar improved the taste immeasurably. And to be honest, there aren’t many left