Tuesday, August 27, 2013

Commercial compost: low nitrate levels. Experiments in holding pattern.

After the < 5mg/L reading I got from an earlier test, I ran the reference test, which ran correctly. Not that that's much more than a sanity check.

I wondered if I might have the wrong thing in the bag.

A first-level Agromin support person gave me values of nitrate as 2-8.6 milligrams per kilo dry weight of EcoScraps compost mix. That's less than 1/1000 of what I expected! I asked for someone else to call me back. No call so far today.

Further data from EcoScraps directly shows 0.001% dry weight as nitrates. So a kilogram of dry compost (is there such a thing?) would still contain on the order of 10mg of nitrate... right along with the Agromin folks and my tests.

It would appear that this compost is not suitable for LaConte style recoveries.

I now have the name of someone else to contact who may have more  comprehensive information on the subject of compost nitrate composition. I will call him tomorrow.

Compost experiments 2 and 3 halted for now.

Nitrates from commercial compost 3

I bought more equipment. This is a weakness. I must resist. I have two scales and a nitrate/nitrite test kit. I am continuing the previous experiment while moving on with this one.


  • Leaching may extract more (or less) nitrate over time.
    Check at 1 and 24 hours.
  • According to the literature, the evaporite is going to be a mix of [Na,K,Ca,Mg][CO3,NO2] with either the Ca or the CO3 at zero. Fe and Cl may be present as well.
    We will presume it is the CO3 species that is absent.
  • Potassium carbonate has the highest molecular weight of the various components of potash: 138g/mol.
  • Calcium Nitrate has the highest molecular weight of the various potential components of raw saltpeter: 236g/mol.
  • Suppose we have N grams of a CaCO3 precipitate. To calculate the amount of potash required to provide that much carbonate, divide by the molar mass of CaCO3 (100g) and multiply by the molar mass of potassium carbonate (138g) for a net mass multiplier of 1.38.
    1.38 times the Mass(CaCO3) is the max Mass(potash) to be used.
  • Suppose we have N grams of a Ca(NO3)2.4H2O evaporite. The mass divided by 236g is the number of moles of calcium nitrate. Calcium nitrate mixed 1:1 molar with potash results in 1 mole of calcium carbonate and 2 moles of alkaline nitrate. 138/236 =  0.58, thus:
    0.58 times the Mass(Ca(NO3)2) is the max Mass(potash) to be used.


    Part 1, 1 hour

  1. Place 1kg of compost in a stainless pot
  2. Add 2 liters of distilled water
    Checked: Total mass: 3kg 
  3. Let stand for 1 hour
  4. Filter (seive and paper towels, as above)
  5. Measure 1 liter of fluid
  6. Get mass of solution to estimate dissolved salts, and verify by checking weight of remainder of fluid and soil
    1003g (about 3g, estimate 6g in 1kg of compost)
    Remainder: 1997g
  7. Perform Nitrate test
    Nitrates: < 5mg/L (Well THAT sucks. Maybe it's wrong?)
  8. Return the fluid to the mass

    Part 2, 24 hours

  9. Let stand for 23 hours
  10. Repeat mass measurements

  11. Test for nitrate
  12. Was it worth waiting the 23 hours

    Part 3, Analysis

  13. Extract all the solution
  14. Filter the solution
  15. Evaporate with minimal heat
  16. Weigh evaporite
  17. Calculate the maximum potash required:
    0.58 * mass(evaporite):
  18. Gather the potash
  19. Dissolve the evaporite in a minimum of distilled water
  20. Divide the solution into two halves (S1 and S2)
  21. Divide the potash into two halves (P1 and P2)
  22. Add one tenth of P1 to S1
  23. Observe a precipitate (hopefully)
  24. Add more of P1 to S1 very slowly until no more precipitate is formed
  25. Weigh the dry remainder of P1
  26. Dry and weigh the precipitate from S1
    S1 Precipitate: 
  27. Recalculate the maximum potash required:
    1.38 * mass(precipitate)
  28. If this new "maximum potash" value is lower than the mass of P2, reduce the mass of P2 to the lower maximum.
  29. Add  the (possibly reduced amount of) P2 to S2
    Hopefully this achieves a zero value for both calcium and carbonate, leaving only nitrates in the wake
  30. Dry and weigh the precipitate from S2
    S2 Precipitate
  31. Compare the masses of the precipitates. They should be equal.

The pictures here are very low res because my regular digital camera has been lost, and I am taking stills with a videocamera instead. :P

Nitrates from commercial compost 2

Ala laConte, I try to get the nitrates to effloresce.

General Process

  1. Place 2 gallons (compacted) of compost in a 5 gal painter's bucket
  2. Add 1 gallon of distilled water
  3. Let stand in warm dry conditions
  4. Add more water
  5. Repeat steps 3 and 4
  6. Observe (or not) efflorescence

Actual process

24-Aug-2013: Steps 1-4 complete
27-Aug-2013: After three warm dry days, the compacted soil was still damp-verging-on-wet. I roughed the surface up to give more surface area for evaporation.

Tuesday, August 13, 2013

Nitrates from commercial compost 1


  1. Place 2 liters (uncompacted) of compost in a stainless steel vessel
  2. Add 1 gallon of distilled water.
  3. Wait an hour
  4. Filter the solution through metal sieves until all the large particles were removed.
  5. Pour it through paper towels (poor man's filter paper for large quantity jobs)

A not-very-clear solution remained. It looked a lot like a cross between tea and black coffee. The humus is composted from local waste vegetable material, presumably including things like coffee grounds, tea leaves, and tree bark, all of which could give a soluble brown tincture.

I elected to try and precipitate it out using a base (assuming tannic acid and its ilk were the colorants) so I tried chalk, then sodium hydroxide. Neither changed the color significantly.


Given a dark and now contaminated sample, I tossed it down the drain.

Sunday, August 11, 2013

Nitrates from commercial compost

This pursuit of nitrates has led me up several blind alleys, but they are an essential material for a variety of other early chemistry experiments. I really don't want to try the Chamber Process without at least some nitrate catalyst. I am torn.

The core problem


Modern industrial production of nitrates starts with nitric acid.

Nitric acid is produced from ammonia through the high pressure high speed platinum-catalyzed Ostwald Process.

Modern production of ammonia starts with high pressure high speed osmium catalyzed fusing of hydrogen and nitrogen: the Haber Process.
Obtaining nitrates is trivial in the modern world, and very complicated in a primitive environment

It would be easy to buy a cold pack or some fertilizer with ammonium nitrate in it, dissolve it, mix in some potash, et voilĂ ! Saltpeter! Likewise neutralizing nitric acid with lye. But the thing is, there is essentially no natural source of ammonium nitrate or nitric acid and this is supposed to be a primitive chemistry blog.

As usual, space and time are the limiting inputs. If I had a large yard and a twelve to eighteen month timeframe, I could do all this "the right way" and not need to shortcut the system. I was pondering actually switching from renting an apartment to renting a house with a yard when something strange happened: I had an idea.

Someone else do the primitive "hard part"

There are various estimates of nitrate per ton of compost, but a consensus figure seems to hover around 1%. Thus 1kg of compost might contain 10g of nitrates.

This being southern California, there are a lot of community based composting services, because only the very rich can know that everything should be totally natural and completely free. :)

Simply buying a bag of "certified organic compost" and leaching it for nitrates would confirm whether or not the basic process worked like all the old texts say it does. So long as there were no high tech steps taken in the composting process and no external additives (neither likely in "organic" compost) it should be valid. There are even a couple of local places I could visit and see what actually went into producing the compost.

After a phone call to Agromin to make sure I was buying 100% unadulterated compost, I purchased their (rebranded) EcoScraps compost at a local hardware store.

Friday, August 9, 2013

Aerobic Vegetable Composting 1

After the disheartening math on nitrate production from liquid mammal waste, I decided to do a regular compost based on food scraps.  Whether this makes sense or not, I avoided garden clippings in this run because the measured goal is nitrate production. Any fertilizer remaining on the garden clippings would skew the results, showing a false success.

With that in mind, I am composting things that humans would eat, not simply vegetation. I expect I'll do a vegetation one as well, and perhaps both varieties supplemented with other materials, but for now I'm just taking the simple route.

Tools and Materials

Organic matter

I got the material from several local chain restaurants. I walked in, asked to speak with the manager, and asked if I could get a day's worth of produce scraps from their counter/prep area. Some did prep in the morning, and asked me to come back the next day. Others gathered their scraps all day and asked if I could come back later in the evening. Everyone was quite willing to help.

Here's what I ended up with:
  • Lettuce
  • Mix of lettuce & other vegetable matter
  • Meat scraps

The Composter

I just used a rolling trash bin I bought at the hardware store. I cut holes in the sides to allow aeration. I considered buying a "real" composter with a horizontally mounted cylindrical drum and a crank on the side, but for my first run I figured something less sophisticated would do. The bottom of the bin was watertight, to prevent solubles from escaping during the composting process.


The pile

Lettuce, cabbage, tomato, and other vegetable scraps have a C:N of about 12, so in order to get out to 20 or 25, I needed some carbon added. I bought a bale of straw from a local pet supply, weighed out Nkg and added it in in layers with the vegetable matter. This was a single-batch process. Everything was added at the same time.

The Weather

August in southern California is sunny, not particularly humid nor arid, and stayed in the 70s and 80s for the entire period.


Catastrophic failure, experiment terminated early. Apparently there was too much animal protein in the mix. By day six the rotting smell was overwhelming and I terminated it. I shall fall back and consider other alternatives, certainly including no animal matter in the next incarnation.