Pre-existing biomass in Samana

Mesure de biomasse préexistante

In Samana, we also need to measure the pre-existing biomass (baseline) on a sample, as was done in Damaro in 2025. We should have taken these measurements in 2024, the year the plots were seeded. Measuring these trees two years too late means that their biomass will contain two years of growth and therefore two years of carbon that belongs to the project but that we will have to deduct (since, as we remember, the project cannot account for pre-existing carbon on the land prior to project activities).

Measuring pre-existing biomass requires several steps:

  • EcoAct calculates the sample size, performs stratification, and randomly identifies the sample plots and GPS coordinates of the measurement point on each plot.
  • We update the standard operating procedure and train GUIDRE
  • For each of the 40 plots, GUIDRE’s measurement teams must
    • find the plot in the given village
    • mark the perimeter of the 600 m² circular plot with barrier tape
    • identify all existing trees, measure their diameter at breast height and height, and identify the species of each tree
    • send the data via the Kobo-Collect form

The results show that stratification, based on satellite images, is validated by the reality on the ground. It can also be seen that the number of pre-existing trees per plot is reflected in the NDVI value during the dry season (NDVI measures vegetation health via satellite). NDVI is therefore a relatively robust indicator of pre-existing biomass.

Résultats PEB

On average, we will need to deduct 30 tonnes of biomass from existing trees from our subsequent measurements.

mesure de baseline à Sogboro - hauteur   mesure de baseline à Sogboro - circonférence

The project’s carbon footprint

Our reforestation project removes CO2 from the atmosphere, but what is the carbon footprint of arboRise’s activities? How much CO2 do the project’s activities emit into the atmosphere?

This carbon footprint is based on the Bilan Carbone™ methodology and lists all GHG emissions from arboRise and GUIDRE activities in Switzerland and Guinea for the two regions (Linko-Damaro-Konsankoro and Samana-Diassodou-Sokourala-Koumandou) during the 30-year and 20-year certification periods, respectively.

Summary of results:

Emissions de CO2 du projet arboRise

This carbon footprint of 1,100 t CO2e will enable the absorption of 2,400,000 t CO2e thanks to the reforestation activities carried out by arboRise and GUIDRE in two regions (Linko-Damaro-Konsankoro and Samana-Diassodou-Sokourala-Koumandou) over a period of 20 and 30 years respectively. The project’s emissions therefore represent only 0.5% of the CO2 that the project will remove from the atmosphere.

Comments and potential for improvement:

  • The travel of GUIDRE teams in the field is, of course, the main source of CO2 emissions. In the long term, the use of electric vehicles will need to be considered and tested.
  • Air travel (project leader, auditors, partners, business visitors) accounts for 18% of the total (196 t CO2e). If all non-employees (auditors, partners, business visitors) were represented by only one person instead of two, this would save 72 t CO2e. This requires a change in standards and practices. When the Transguinéen railway is available, we will be able to replace internal flights with train travel.
  • Half of the input footprint is made up of meals for GUIDRE teams in the field, which are difficult to reduce unless they become vegetarian (meat footprint: 123 t CO2e). Other inputs with a significant footprint are fencing and tarpaulins for seed families.

The detailed report is available here.: 251119_Bilan carbone arboRise