I started this discussion
over on the discussion board - I have a calculation to put together hence bringing it back to my blog. It's demonstrated that worms fix carbon
. Do they fix enough to make a serious difference to the "overflow" of the carbon bathtub
? Please do check my calculations, this is important stuff and I've not had a complete night's sleep in two years (toddler daughter, bless her.)
A worm can fix 21- 63 mg/week per worm, according to this paper
So we could say somewhere between 1000 and 3000 mg per year - call it 2g of carbon fixed per worm per year?
So in order to fix 4.1 Gt of carbon, the current overflow:
4.1*10^9 *10^3kg per year / 2*10^-3 kg per worm per year
= 2.05*10^15 worms would do the job.
Numbers can reach one to two million per acre in good farmland; in intensive cultivation somewhere around 3 000 per cubic foot
. Another source has the same order of magnitude
. Let's convert that to SI units - since 1 cubic metre = 35.3146667 cubic foot,
3000 worms per cubic foot = 105 944 worms per cubic metre (we'll tidy up the number of significant figures at the end as usual) and this equates to around a thousand million worms per Hectare-metre - (a metre deep).
So the volume of intensive worm cultivation we need is approximately
2.05*10^15 worms / 105 944 worms per cubic metre
= 19 349 845 200 cubic metres
1 hectare = 10 000 square metres so assuming we can cultivate the worms a metre deep, we can split cubic metres into (square metres multiplied by metres), this means the area we need for worm cultivation is about
19 349 845 200 cubic metres / (10 000 * 1 metre)
= 1 934 984.52 hectares
Let's call it around two million hectares of worm cultivation. Is that doable? We would need to find two million hectares of land that is not being used for food production (we cannot afford to further endanger the food supply by competing for land use.) Could we do worm farms on boats, moving around to unload the products at different places? I think my imagination is starting to run away with me.
It is necessary to factor in the other climate-affecting outputs of the worms - they apparently emit nitrous oxide
, which is a gas with a more powerful global warming effect than carbon dioxide. We need to know how much nitrous oxide they emit, and whether it could perhaps be harvested and broken down another way, before this proposal can go further.
What else would we need to know to hack out a proposal for a field trial? How do we demonstrate the carbon fixed by the worms over a time period? Would it be possible to separate out the CaCO3 crystals for example by washing a weigh them? Sample the input and output - compare the fixed carbon in both?
I can see it could be possible to run a social enterprise fixing carbon with worms, if we can prove the carbon fixing scales properly and isn't blasted out by the nitrous oxide emissions from the worms. Since there is already a carbon offset trade for flying, perhaps this could be a replacement for that. This has a better claim to be genuinely fixing carbon than planting trees does.
Inputs required: containers, labour, food for worms (inedible organic matter), enough water to run a worm farm (we should be able to find an estimate from current worm farmers), starting stock for worm-breeding.
Outputs to distribute: finished worm compost (good planting medium), including fixed carbon (highly valuable!), worm juice (depending on cultivation style - useable for hydroponics).
I started sketching out some plans
in another post.
Note: several folks have pointed out that conversion to worm-friendly farming would go a long way to fixing the carbon - but we have yet to show that it would fix the N2O part of the problem. The N2O given off would still be a big - possibly bigger - problem. Intensive cultivation with N2O trapping as I'm proposing has the potential to stop the warming effect.
It may be that organic farming also fix the N2O problem if it can be demonstrated that cultivation practices enough denitrifying bacteria. Nitrates are discouraging to denitrifiers - nitrates which are the backbone of the NPK 'green revolution' artifical fertilizers. So in conventional +NPK cultivation, fixing any of the N2O from these extra (O)10^15 worms is unlikely.