To get to the roof, you have to climb up 103 stairs. It's one more reason to try to use everything there is and not have to bring down dead plants or exhausted dirt, or to carry up fertilizers, compost and new dirt. But the garden is a dynamic project, a microcosm of the cycle of life and there's always something dying, leaves falling, and new things to plant.

That's why I've had two compost piles for a long time: one with composting worms and the other more traditional, a slow compost pile full of dry leaves, little branches, dead plants... basically things the worms would rather not eat.

The worms, like I explained, get vegetables scraps from the kitchen, minus onions and citrics. And they love recycled paper. They're pretty happy, but plodding. They have a quiet life :)

The other pile is even mellower. Maybe it takes a year for the dry leaves and dead branches to decompose, and there are always more bits left behind. And I can't put weeds in there because with cold composting, the seeds remain viable. And I have more volunteer tomatoes than I can shake a stick at.

I've been wanting to try 'hot composting' for a while. Normally, you can't do that on a roof. I don't have enough material and I don't have enough space even if I did. Hot composting, that requires a certain proportion of 'greens' (material with high levels of nitrogen) and 'browns' (materials high in carbon), can get up to 60°C in a couple of days, decomposing everything that you put in there, killing weed seeds and fungus along the way. It's great. In Massachusetts, we had a huge pile and it was so hot that once we put a dead sheep in there and she decomposed right away, giving away no odor, without a trace left behind.

I'm not planning on composting sheep on the roof! But I do want to do hot composting. But I have those two problems. First, everyone says you have to have a minimum volume of 1 cubic meter (more or less a cubic yard). My compost bins measure 60 x 60 x 80cm which is a bit less than a third of a cubic meter (288 liters) and that's when they're full to the top. Second, with my paltry amount of dead branches and leaves, the pile is too cold. It decomposes, but it takes its sweet time about it.

The folks at the University Cornell who have an entire Compost Physics website say that you can make hot compost with just 40 liters of material. I decided to try it, my own way. I'm a little nervous about showing you what I'm doing before I know if it works, maybe it will fail? But I decided to show you as I go, and we can discover any problems together, and maybe you've got suggestions!

First, I went to the market, and asked at the stand where I buy my veggies if they would save the bits of vegetables that they don't sell: the leaves they cut off the cabbages, the old escaroles, the wilted chard, and so on. And they give me bags full! I leave them one of those huge grocery bags and every day they fill it up, and I go pick it up and leave them an empty one. I've asked them several times if it's too much of a pain, but they promise it's not. The internet says that it's very important that everything be in small chunks, so I bring up a cutting board and cut it all up with a big knife before I throw it in. For the 'browns' I'm going to use recycled cardboard like always, since it's something that there's plenty of in the city.

I just started this past week. The day before yesterday I added 8 big bags to the pile, right on top of the dead plants and branches and things that were already in there. Today I went to look and if I dig in a couple of inches, I can already feel the heat! Today I put a couple of cardboard boxes in water to soften them up and I'll rip them up later and put them in. There is supposed to be 2 bags of green (market waste) for every bag of brown (cardboard).

The challenge? Making a lot of clean, weed and fungus-free compost in three weeks out of free stuff that would otherwise go to the dump. Maybe with my small scale it'll take six weeks, but that's still way better than the long year it's been taking me up til now. I'll keep you posted!

And did I mention the hardenbergia are blooming?! I first discoverd them at a plant workshop at the Laberint d'Horta and I love them. They remind me off little minions or mini Yosemite Sams.

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