From your description, it sounds as if the vermicompost was very wet.  You may not have had enough carbon sources making your C:N ratio off.

It had a higher nutrient content (percentage I assume, not mass) across the board for all nutrients?  Coffee is very acidic, and along with the development of carbonic acids your mixture was probably at a low pH, which would aid in the mobility of some macro nutrients, but possibly help the retention of cations.  Seems like you should have some mixed results.  

If the nutrient concentrations are going down you are either (1) leaching nutrients out of the compost during the process or (2) adding large amounts of carbon through biological pathways to dilute the nutrients in the final compost.  Most likely it is the first.  

It's likely due to the fact the percentage of fresh matter is very low since you use in majority (I guess), ground coffee. Try to put more fresh kitchen waste (70% w/w)and a little bit of ground coffee (20% w/w) in addition to sawdust or straw (10% w/w). The last one will absorb the excessof moisture in fresh kitchen waste.

       Sir

I do agree with the Khalid Azim

Refer  PDF] Effect of Drying on Vermicompost Macronutrient Composit

My review onynamics of  Earthworm soil plant relationship

Dear Sr. 

I am agree with Khalid Azim.

And also It is very important have good moisture.  When ants appear, it is because your compost is dry.  Becarefull with moisture.  In the other hand, coffe waste is acid and  it have another elements that you need wash before use.

Hi Jason,

Vermicomposting is a complex ecoystem - even in 'simple' trials such as yours, considering only two waste streams / organic resources. I often find it more even more difficulty to be limited to only two resources as the optimum ratio of the two resources may not be the optimum for successful vermicomposting. Understanding that vermicomposting can have different desired outcomes, depending on what your primarily goal is, e.g. organic waste reduction at lowest costs, best quality vermicast, minimum effect on the environment during vermicomposting, or a focus on breeding earthworms.

All colleagues above mentioned potential or most likely reasons for not meeting your desired outcome, which I asume from your introduction is vermicomposting for  concentration of nutrient content in the solid product. We all know that parameters  such as pH, moisture (too wet or dry) C/N ratio, structure, oxygen supply, and there will be few more to consider, will effect your outcome. We all could advise you in more detail if you would share a few more details. You mentioned some analysis you have conducted already. Maybe you can provide pH, moisture content, C/N ratio, mixing ratio, nutrient content etc. Do you have produced any leachate in your reactors? Have you analyzed it and calculated the nutrient budget in the solid and liquid fraction? Did you loose any e.g. N? Nitrogen and potassium are washed out easily.

I would like to encourage you to carry on with your trial - understanding why a system is not working is the key to find the successful system. You will find that some combinations of organic resources will not work in the lab (small reactors), but will  succeed at large scale in the field. As well you will find that successful trials at small scale do not work in the field at full scale. For example I can force compost worms to feed on certain organic wastes if they can't escape the reactor. Once there are no borders, the worms will just leave or stay out of your mix and search for better feedstock sources.

The total nutrient content of the vermicast might be seen as the most important aspect for marketing, as this is number you can easily put a value to, when comparing with mineral fertilizer prices. The true market value - at least here in New Zealand - is in the humus and the biological functions of the vermicast. We are marketing close to 50,000 tonnes of various vermicast products this year and often customers prefer the vermicast with a wider C/N ratio and lower total N content of 1% over the nutrient-richer vermicast with a nitrogen content of close to 2%.

I am looking forward to some more details from you to help solving your 'mystery'.

Keep up your interesting vermicomposting research.

Warm regards,

Michael

Ground coffee (acidic) mixing with raw salad from supermarket makes the mixture marshy and the moisture percentage becomes high with raising temperature during the process in the reactor. For excessive moisture with acidic condition some earthworms died. And as the fermentation process was still continuing (not finished) in the reactor during the little span of time some macro nutrient may be shown as reduce.