How do we calculate the amount of carbon bamboo can absorb?
To calculate the total amount of CO2 that is stored per hectare of bamboo grown on the plantation of Bamboo Village Uganda (BVU), a few steps need to be taken:
- Calculating the current amount of carbon stored in the vegetation of the land.
- Calculating the total amount of carbon to be stored in the future mature bamboo plantation.
- Calculating the amount of carbon stored in durable product produced by the bamboo plantation.
Total carbon sequestration on the land
The difference between the future amount of carbon on the land and the current amount of carbon on the land is the total extra amount of carbon that is stored. The future amount of carbon stored is 306.4 tonnes per ha and the current amount is 46.1 tonnes per ha. This is an increase of carbon storage of 260.3 tonnes per ha, or 955.4 tonnes of CO2.
Current amount of carbon on the land
The current situation can be categorised as predominantly tropical shrubland. African tropical shrubland has an above-ground biomass of 70 tonnes dry mass per ha, a root-shoot ratio of 0.4 and an average carbon fraction of 0.47 (Aalde, et al., 2006). This leads to a currently amount of stored carbon of 46.1 tonnes per ha. This equates to 169 tonnes of CO2 stored.
Future amount of carbon on the land
Bamboo of the species Bambusa Bambos will be planted on the land. This species was chosen because of its high potential in carbon storage, yearly yield and availability. Figures from other sources indicate the following carbon storage potential. All data from these sources is gathered in Southern India, with comparable or somewhat wetter and warmer conditions than in BVU (climate-data.org). On average, the total biomass is 260.4 tonnes per ha with 4250 culms per hectare. This is very low in comparison to studies done on other species (Nath, Lal, & Das, 2015).The sources report studies carried out in homegardens and small-scale operations.
The plan at BVU is to have a much denser and large-scale operation of 10,000 culms per ha. Using the numbers from the Indian studies, this would equate to a total biomass of 612.8 tonnes per ha. This equals 1124.4 tonnes of stored carbon dioxide.
Table 1: Literature review of biomass in Bambusa Bambos plantations.
|Above ground biomass (ton ha-1)||Belowground biomass (ton ha-1)||Culm density (ha-1)||Reference|
|287||–||4250||(Shanmughavel & Francis, 1996)|
|242||–||(Kumar & Rajesh, 2005)|
|162.2 *||10.6 *||(Yuen, Fung, & Ziegler, 2017)|
|306.9||11.2||4250||(Shanmughavel, Peddappaiah, & Muthukumar, 2001)|
*Calculated from carbon figures, assumed carbon fraction of 0.5.
Durable products pool
Durable products act as a carbon sink, as they still contain the amount of carbon stored by the bamboo. To estimate the durable products pool, a calculation is made for the yearly yield potential and the amount of biomass that will be used as building material at any given moment as the plantation matures.
Yearly yield potential
To calculate the emission reduction by substituting bamboo for other materials, the following assumptions are made:
- A culm is cut four years after it has started growing.
- 85% of the above ground biomass can be attributed to the culms ( (Shanmughavel, Peddappaiah, & Muthukumar, 2001).
- 50% of the biomass is C.
The total above ground biomass is 587.1 tonnes per ha. The culms weigh 85% of that: 499.1 tonnes. Every culm is cut after four year: 124.8 tonnes per ha per year: 62.4 tonnes C per ha per year, 228.9 tonnes CO2 per ha per year.
The plan is to use most of the production for building materials. Assumed is an efficiency of 50%. The waste from processing, like sawdust and cutting losses, will be processed into potting soils and fibrous products such as textiles and paper.
Only the building materials can be seen as a durable carbon sink. Assuming an average life span of 15 years for local bamboo building materials, half of the yearly yield will continue to act as a carbon sink for 15 years. So, 15 years after the first harvest, an equilibrium is reached. The total carbon sequestration is then increased with 15*0.5*yearly yield = 935.7 tonnes biomass, 467.9 tonnes carbon, 1717 tonnes CO2.
The total amount of carbon uptake by one hectare of land can now be calculated by subtracting the current amount of carbon stored on the land from the future amount of carbon on the plantation and adding the amount of carbon in the durable products pool. When the equilibrium is reached (mature plantation and 15 years of durable product in the pool) this is: -46.1 + 306.4 + 467.9 = 728.2 tonnes carbon per ha. This equals 267.2 kg CO2 uptake per m2.
Aalde, H., Gonzalez, P., Gytarsky, M., Krug, T., Kurz, W. A., Ogle, S., . . . Somogyi, Z. (2006). Volume 4: Agriculture, Forestry and Other Land Use. In IPCC, IPCC Guidelines for National Greenhouse Gas Inventories. Retrieved November 21, 2018, from https://www.ipcc-nggip.iges.or.jp/public/2006gl/vol4.html
Kumar, B., & Rajesh, G. (2005). Aboveground biomass production and nutrient uptake of thorny bamboo [ Bambusa bambos (L.) Voss] in the homegardens of Thrissur, Kerala. Journal of Tropical Agriculture, 43, 51-56.
Nath, A. J., Lal, R., & Das, A. K. (2015). Managing woody bamboos for carbon farming and carbon trading. Global Ecology and Conservation, 3, 654-663.
Shanmughavel, P., & Francis, K. (1996). Above ground biomass production and nutrient distribution in growing bamboo (Bambusa bambos (L.) Voss). Biomass & Bioenergy, 10, 383-391.
Shanmughavel, P., Peddappaiah, R. S., & Muthukumar, T. (2001). Biomass production in an age series of Bambusa Bambos plantations. Biomass and Bioenergy, 20, 113-117.
Yuen, J. Q., Fung, T., & Ziegler, A. D. (2017). Carbon stocks in bamboo ecosystems worldwide: Estimates and uncertainties. Forest Ecology and Management, 393, 113-138.