Accurate carbon accounting is dependent on using the correct values of char dry bulk density and carbon content for all the biochar that we make.
Furthermore these values need to be verifiable by an independent third party if we are to achieve credibility as a producer of voluntary biochar carbon credits.
Therefore we use established international standards for sampling, measuring and calculating the values of dry bulk density and carbon content.
The following techniques are involved:
Sampling: At least 15 small samples are taken from a batch of biochar to make up a representative sample from which to measure the dry bulk density and carbon content.
Moisture content: The moisture content of the biochar sample is determined by comparing the weight of the sample before and after it is heated at 100 C for sufficient time to remove all moisture from the sample.
Dry bulk density: A volume of at least 1 litre of the representative sample is used so that the accuracy of weighing is not compromised or made more difficult than necessary.
The dry bulk density is a measure of bulk density with zero moisture content.
Carbon content: The size of the sample used for the analysis will depend on the accuracy of the weighing instrument used. If the same sample is used as is used for measuring dry bulk density then the sample will be dry at the start.
Heating is carried out to drive off all volatiles but without burning any carbon. The loss in weight is the weight of the volatile content of the char.
Then further heating is carried out to burn off all the carbon until only ash remains. The loss in weight is the weight of the carbon content of the char.
The weight of the residual ash is the weight of the ash content of the char.
The results of the analysis of our biochar by Bygen Pty Ltd are summarised below:
Report Date: 19 April 2020
Moisture content: 51% (as received).
After moisture removal:
Carbon content: 79.4%
Ash content: 12.18%
Volatiles content: 8.42%
Calcium 18300 mg/kg
Potassium 2520 mg/kg
Iron 2370 mg/kg
Magnesium 2030 mg/kg
Aluminium 1120 mg/kg
Sodium 716.87 mg/kg
Phosphorous 693.87 mg/kg
Manganese 243.5 mg/kg
Sulfur 232.25 mg/kg
Zinc 30.21 mg/kg
Boron 10.71 mg/kg
There were no measurable amounts of heavy metals in our biochar.
PAH analysis: The analysis of 27 different types of polycyclic aromatic hydrocarbons (PAH's) revealed no measurable amounts present in our biochar.