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 offsets.
Therefore we propose to 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 should be taken from a batch of biochar to make up a representative sample from which to measure the dry bulk density and carbon content.
Dry bulk density: A volume of at least 1 litre of the representative sample should be used so that the accuracy of weighing is not compromised or made more difficult than necessary.
Ideally dry bulk density is a measure of bulk density with zero moisture content.
Carbon content: A volume of at least 1 litre of the sample should be used for the same reasons as above.
If the same sample is used as is used for measuring dry bulk density then the sample will be dry at the start.
Then 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.