Hot composting and humanure

Having done a survey of the soil in our garden, one of my main aims has been to increase the biological and fungal activity in the soil. For this we will need loads, and loads of compost!

Hot composting

After some research, I decided that the quickest way of doing this would be to make a hot compost pile. Basically this involves making a normal compost heap, with lots of layers of high-nitrogen materials, mixed with high-carbon materials, then turning the heap every two days. This mixes the materials thoroughly, and aerates the pile, providing oxygen to the bacteria and helping to spread the fungal growth. Using this method, it should be possible to make a rough compost in 18 days.

My first heap was a great success. I used old sheep bedding, which has a high nitrogen content from all the urine, as well as some straw and poo. I mixed this with cut weeds from the garden, of which we have lots! I turned it regularly, watering it with urine if it dried out. The internal temperature rose rapidly to about 50ºC, then died off after a few days. The heat is a good indicator that there is lots of biological activity going on, and you can see the fungal growth in white strands passing through the heap. It was quite amazing, the heat from the compost was incredible, so hot you could barely touch it!

The pile did not decrease in volume at all, unlike a traditional compost heap, so we got a huge amount, about 2m², of rough compost. We used this mix to feed the garden and trees. One thing we noticed, was that where previously we’ve had a problem with ants climbing the trees and eating the fruit, the compost seems to have given the ants plenty to use at ground level, so they don’t seem to be bothering the trees so much.

Humanure

We’ve been storing our own poo, or humanure, for about a year now, so it’s worth reporting on what has happened with that. The humanure has been kept in plastic barrels, with a fine mesh on to keep thee flies out, and a loose lid to allow for air to enter. I’ve rolled the barrels regularly to mix up the contents.

Humanure barrel maturing
Humanure barrel maturing

After only a couple of months the humanure looked nice and decomposed, with no odour in the main body. However, after tipping some out to have a look, it seems that rolling the barrels hasn’t been sufficient to mix it up properly. While we’ve tried to separate out the urine into a separate container, some has gotten into the barrel and mixed with the soil at the bottom. This has created an evil–smelling lump of soggy soil at the bottom of the barrel. To get round this we will use straw at the bottom of the barrel instead of soil. We had also overfilled the barrels, making it harder to aerate the contents properly.

We’ve also had an issue with toilet paper – to add it to the barrel or not. While the paper will eventually decompose, it takes a lot longer. We’ve decided not to allow paper in the barrel, as when the barrel gets emptied out onto the compost heap it will be visible, and may lead to awkward questions from our Bulgarian neighbours, who already think we’re completely mad, what with our reed beds and mulching! Leaving the paper out makes it all a bit more discreet.

We’ve decided to mix our humanure with other materials in a hot compost pile. The high internal temperatures reached in these piles will ensure any pathogens are completely destroyed, and the resulting compost will be safe to use on all the garden.

Putting it all together

For my second hot compost heap I’ve gathered a lot more materials. I’ve got a pile of horse bedding from a friend’s stable, there’s still plenty of sheep manure to use, loads of weeds from the garden, straw and sawdust from the chickens, and our humanure. Having mixed this lot together I now have about 4m² of compost, with an internal temperature of about 65ºC. I’m not mixing this heap up as much, mainly because we don’t need in until later in the year, but also because I’ve hurt my elbow turning the first lot.

Hot compost pile
Hot compost pile

I am able to use the temperature and look of the pile to gauge what extra ingredients to add; if it’s too hot, add more carbon materials like straw or sawdust to reduce the nitrogen ratio. If it’s not hot enough, pee on it. The pile needs to be covered, both to prevent it drying out, and to stop it getting too wet from the rain. If it’s too wet the bacteria can’t breathe.

So, we now have 6m² of compost which we can use in the autumn to prepare the ground for next year’s plantings. We’ve been able to use materials which would normally take much longer to decompose, and we’ve got compost that has a huge amount of bacterial activity and fungal growth, which is ideal for trees and other plants around the garden. Early tests on our potato bed shows that adding the compost as a mulch has led to potato plants about 50% bigger than the ones without, but we’ve not yet assessed the crop yield from those beds.

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