It is important to take into consideration that vetiver "plants" are in reality "clumps of plants". When you plant 8 plants per meter to form a hedge, over the growing season in a year, those original 8 plants grow into clumps of plants that grow together to form the hedgerow. Therefore the original 8 "plants" become a far greater number depending on the fertility of the soil and rainfall. Indeed a linear km of vetiver contains 8000 clumps of plants that are bunched solidly together. It is therefore possible to imagine that 8000 clumps could indeed even sequester more than the 2.5 kg per clump estimated here.
If you look at the pictures of the root biomass of a mature "clump" – (originally an individual plant), one sees a huge mass of roots that attain a depth of 2-4 meters after two years. Root derived soil carbon accumulation is being estimated by scientific studies across the globe under both grassland and forests, either in the tropics or in temperate areas. For carbon to truly be sequestered it must be transformed to mineralized carbon aided by the microbial activity in the soil associated with the root zones. One of the reasons for high vetiver plant vigor is a result of its mychoriza (type of soil microbiological organism) association. This association is one of the reasons vetiver hedgerows produce such high amounts of biomass on the one hand and such high amounts of carbon added to the sequestered soil carbon pool.
The Vetiver Network believes that we have a means of offsetting CO2 emissions by producing an equivalent carbon dioxide savings, that is, sequestering CO2 in the soil under vetiver hedges. Vetiver hedges also have many other benefits such as soil and water conservation, pollution control, erosion control, and poverty reduction especially in the tropics. It is especially useful at the community level to provide sustainable and affordable solutions to the variety of problems facing communities who are ill equipped to deal with these problems. When you combine the CO2 offset mechanism to these other benefits and considering its ease of planting and maintenance when compared with tree planting, the argument for using vetiver becomes even stronger.
Dale Rachmeler
If you look at the pictures of the root biomass of a mature "clump" – (originally an individual plant), one sees a huge mass of roots that attain a depth of 2-4 meters after two years. Root derived soil carbon accumulation is being estimated by scientific studies across the globe under both grassland and forests, either in the tropics or in temperate areas. For carbon to truly be sequestered it must be transformed to mineralized carbon aided by the microbial activity in the soil associated with the root zones. One of the reasons for high vetiver plant vigor is a result of its mychoriza (type of soil microbiological organism) association. This association is one of the reasons vetiver hedgerows produce such high amounts of biomass on the one hand and such high amounts of carbon added to the sequestered soil carbon pool.
The Vetiver Network believes that we have a means of offsetting CO2 emissions by producing an equivalent carbon dioxide savings, that is, sequestering CO2 in the soil under vetiver hedges. Vetiver hedges also have many other benefits such as soil and water conservation, pollution control, erosion control, and poverty reduction especially in the tropics. It is especially useful at the community level to provide sustainable and affordable solutions to the variety of problems facing communities who are ill equipped to deal with these problems. When you combine the CO2 offset mechanism to these other benefits and considering its ease of planting and maintenance when compared with tree planting, the argument for using vetiver becomes even stronger.
Dale Rachmeler
About vetiver and carbon sequestering.
ReplyDeleteI have tried to check your calculations and tried to find the data referred from CIAT. What I can find is that Fisher et all in Nature 2002, state that 100 -507 million Tons of Carbon probably is stored in grasslands with deep rooted grasses. I have another place found that they estimate that there is 35 million hectares of these grasslands in South America.
According to these data this gives 3-14 T of Carbon stored per ha. Consistent with what Fisher writes in 1998 on the CIAT website - up to 15 T C per ha.
Do you have other information than this, which justifies your calculations.
If we use 7 T of carbon stored per year, use 100,000 plants. This gives 70 g per plant and for 8000 plants per km of fence 560 kg C/year
Do you have other information, that justifies your calculations?
It would be very good if it was indeed much higher tha ½T C per km vetiver row per year.
You are quite right to question our calculations as they are decidely speculative.
ReplyDeleteThe data we used was attributed to some work by CIAT in 1995 indicating that Andropogon guyanus, a closely related species of vetiver (Vetiveria zizanioides) storing as as much as 53 tons of CO2 as organic matter per hectare per year, equivalent to about 5kg per square meter. It should be noted that Vetiver grass has a much more massive root structure than Andropogon guyanus. A mature vetiver plant would take up about half a square meter of land area, hence the 2.5 kg per plant.
At this stage I think that we need recognize that Vetiver grass has both high biomass below and above ground. There has been virtually no research work carried out to quantify how much carbon is sequestered and under what growth and climatic conditions.
It should be noted that there are many genotypes of Vetiveria zizanioides. Research in Taiwan by Yue-Wen Wang indicates differences as to where different genotypes store their carbon - some store more in the roots others in the leaves and stem. Plant mass varies too. Fresh weight of plants grown from individual seeds in one year varied from 77 to 8,300 gm per plant. Other results show that vetiver is an effective CO2 absorber in twice the CO2 concentration level.
Researchers are studying these and other aspects and we hope that within a few years that it will be possible to establish criteria for vetiver's carbon sequestering ability and its ability to be used as a biofuel feedstock
Our calculations are speculative, but we hope that research will prove that this ubiquitous plant will once again come up with trumps in this important area.