Sampling and measurements

The following indicators shall be measured for each production batch:

• $H/C_{\text{org}}$

• Carbon content (organic and/or total)

• moisture content

• random reflectance and residual organic carbon (only if applying for 1000-year permanence)

Measurements shall be performed by laboratories with at least one quality assurance accreditation, such as:

• ISO/IEC 17025

• CEN/TS 17225-1

• ISO 10694

Unaccredited laboratories from academic settings shall be evaluated on a case by case basis by the VVB and the Rainbow Certification Team.

The sampling procedure detailed in sections below and summarized in Figure 1 is the recommended approach for representative sampling. However, Project Developers may implement their own approach if it is detailed in the PDD and in Sampling Records; ensures one representative sample per production batch; addresses samples and composite samples amount and frequency; and ensures homogenization. The VVB and the Rainbow Certification team must validate the rigor and representativeness of the proposed sampling approach.

The recommended approach sampling requirements are based on the following sources:

• EU Fertilising Products Regulation (EU) 2019/1009

• European Biochar Certificate Guidelines Annex 4 Representative Sampling

Figure 1: The Rainbow recommended sampling approach is summarized here, and detailed in the text in following sections.

Representative sampling

One representative sample per Production Batch shall be created and sent for laboratory testing. This sample ensures that any within-batch variability is captured in the measurements.

Table 1 details the number of composite samples that shall be taken per Production Batch to obtain one representative sample, based on the EU Fertilising Products Regulation (EU) 2019/1009.

The representative sample size should be be 24 liters * the n number of composite samples per Production Batch detailed in Table 1.

Table 1 Recommendations for the number of composite samples of biochar to take, based on the site's annual biochar production output.

Annual output (tonnes)	Composite samples per Production Batch (n)
≤ 3 000	4
3 001 – 10 000	8
10 001 – 20 000	12
20 001 – 40 000	16
40 001 – 60 000	20
60 001 – 80 000	24
80 001 – 100 000	28

The European Biochar Certificate Guidelines Annex 4 Representative Sampling should be followed for taking composite samples. Those requirements are summarized below.

Continuous production

• The first sample must be taken within 7 days of the start of the Production Batch.

• To prepare one sample, 8 sub-samples of 3 liters each are taken at intervals of at least one hour directly at the discharge of the freshly produced material. This shall be repeated for three consecutive days.

• The 24 samples are combined to form one composite sample.

Non-continuous production

Homogenization

The representative sample shall be homogenized by the Project Developer or by the laboratory that performs testing. The biochar shall be ground to a size of <3 mm.

The ground sample is mixed by shoveling the pile three times from one pile to another.

A sub-sample of 1.5 liters shall be taken from 15 spots in the mixed pile.

The 15 sub-samples are re-combined, and then mixed by shoveling the pile three times from one pile to another.

From the mixed pile of the combined sub-samples, 15 subsamples of 150 ml each should be taken at 15 different spots in the pile and combined. This combined homogenized representative cross sample is used for laboratory testing.

Retention samples

A one-liter retention sample shall be collected each day that biochar is produced. These samples should be combined for storage over the calendar month. Retention samples must be stored for a minimum of two years.

Sampling records

For each Production Batch, Project Developers shall submit a Sampling Record for verification to prove their adherence to the requirements above. Sampling Records shall include the following information for each sample taken:

• Date of sampling

• Amount of biochar sampled

• Description of representative sampling process (either followed the recommended approach, or describe the individual approach)

• Sample ID

• Visual description and observation of biochar

• Description of any potential anomalies

• Proof of retention sampling (if performed for that Production Batch)

• Photos showing the date, sample ID, and amount of biochar that is included in the present Sampling Record