Calcium carbonate: burning eggshells and mussel shells; bones?

[TallGirl]

Ok, I hope this isn't too macabre...

Eggshells and mussel shells take ages to break down in the compost, or basically don't. So I thought maybe I could burn them to break them up faster, and the lime would go onto the brassica/onion bed of the year at the same time as the wood ash that it ends up in.

Would that work? So far I haven't seen eggshells in the ash when I'm emptying the stove, so it looks like they're at least breaking down. Will the lime make it into the ash or does it all go up the chimney? What else am I losing by burning rather than composting?

And what about bones? Is it worth cremating the final remains of a roast-chicken carcass?

[Capsid]

You will need quite a high temperature to make the lime, but this makes quicklime (calcium oxide) when all you want for the garden is calcium carbonate. So I think all you need to do is crush the eggshells up and mix in with the compost and let nature do the rest.

Same for bones, just smash them up into small pieces.

[TallGirl]

Thanks Mark! Does the garden get the calcium carbonate in any reasonable timescale if you put shells and bones on in recognisable pieces?

Just found this - you got me looking for quicklime and slaked lime: BBC - GCSE Bitesize: Uses of limestone "Limestone, quicklime and slaked lime are all used to neutralise excess acidity - which may be caused by acid rain - in lakes and in soils. "

[dod]

Limestone (CaCO3) is useful for buffering acidity, quicklime (CaO), which makes slaked lime (Ca(OH)2) when dissolved in water, would probably affect the pH of the soil rather more than your plants might wish to stand (albeit for a relatively brief period). I expect that having limestone present in the soil will mean that should the plants need it they would be able to get it.

[Potstubsdustbins]

Fortunately you will not be able to produce the heat require to produce quicklime. Quicklime can be highly volatile when mixed with water the reaction gives of loads of heat. In a dry dust form it can again be very dangerous especially if inhaled. It will mix with bodily fluids and the reaction will take place within the body.

Best stick to gardening/hydrated lime its much safer.

Colin

[Two_Sheds]

Whole eggshells don't rot down in the compost heap, but crushed ones do better ~ I turn my heaps every couple of months and don't find any remains of eggshell in them

Bones do linger, but I just keep chucking them back in

[TallGirl]

Fortunately you will not be able to produce the heat require to produce quicklime. Quicklime can be highly volatile when mixed with water the reaction gives of loads of heat. In a dry dust form it can again be very dangerous especially if inhaled. It will mix with bodily fluids and the reaction will take place within the body.
Colin

O....k.... probably just as well - thanks!

[BUFFS]

put the eggshells into the oven when you are baking/roasting for 10/15 mins,then they break up easy in your hand and then thrown on compost heap,to break down fast..

[planetologist]

Bones are calcium phosphate, though. Apparently it's less effective at increasing pH.

Wikipedia says the calcining temperature of CaCO3 is 848 C, which you can just about get to in the hottest part of a woodstove.

[solway cropper]

Bones are calcium phosphate, though. Apparently it's less effective at increasing pH.

But it's what bone meal is made from so very useful as a source of phosphorous. I wouldn't want to be working with unsterilized crushed bone dust myself although if it was burned it should be OK. It's tempting to try and recycle everything but sometimes it's more trouble than it's worth. I have access to heaps of commercially harvested sea shells and have wondered for years about trying to use them in the garden but there are easier ways to get nutrients into your soil. On a similar note we get lots of dead jellyfish washed up each year and I have thought about collecting them in a bucket and adding them to the compost heaps but I suspect the neighbours might complain!