The C/N ratio of the sludge is around 6. But the levels of %C is quite high, I modelled the process mixing the sludge with the straw but the amounts of straw needed are too high because instead, a there is a residue with high C content. I think I need a residue higher in N.
Timber-industry wastes are the most suitable and most abundant. These can have C:N ratios ranging from 50;1 to 200:1, so you will need to check the actual ratio in any waste that is available. Some worm species such as the Tiger Worm would successfully turn sludge/wood-waste mixes into compost.
The C / N ratio of a compound determines whether there will be immobilization (I) or mineralization (M). The main purpose when using a compound in which there is soil M to plants using the nutrients available. C / N ratio between 10/1 and 17/1 has the tendency to equilibrium with M = I; between 17/1 and 33/1 is changing balance for M = II. It is important to take into account also the C / S and C / P ratio. In lean mixtures lead to the S and P I. If it is necessary to increase the C / N ratio more than 20/1 to poor grass straw N- or wood chips with relative high C / N can be used (> 100/1 ). Will need to calculate the amount to be merged, considering the goal.
Other than sawdust and wood shavings, organic wastes of leguminous crops will also help in improving C / N ratio of heap
You may refer to this publication and use the formula, I think that in addition to all the raw materiel colleagues have mentionned, you can use also tomato endcycle plants they have more than 47 in their C/N. Woody municipal greenwaste generaly have also a higher C/N.
Conference Paper Dynamic composting optimization through CN ratio variation a...
Residues with high N content: different manures (poultry for example), meals (animal origin - feather, bone, horn shavings) and legum-residues (oil cakes). Attached please find additional specifications (txt & tables).
http://www.uky.edu/Ag/CCD/manures.htm
Dear Yago,
The C/N of your WWTP is about 7.5, You need to add a C, and woody waste is often used since it is cheap. In Spain, you could try to find:
Olive husks
Bark-hardwoods
Paper mill sludge (with less than 65% water content)
Sawdust
Wood shavings
Shurb or tree trimmings
Good luck,
Do not add saw dust, wood chip and alike. These compounds are degraded very very slowly (half life a few uears in compost pile). By adding this you add inhert carbon.
Add straw, grass, leaves - residues that contain C mostly as cellulose.
You can accelerate the process greatly (and therefore use more fiber) by adding 'tiger' worms. Check out a website 'mynoke worms New Zealand'. These worms specialise in composting higher-lignin wastes.
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