I am using InVEST model for my Thesis on the topic of Carbon Storage and Sequestration in relation to land-use change. However, Iβm facing some issues with
Understaing the economic model (viz attached), especially the π πππ’ππ π‘π₯. What does it stand for? I was assuming thatβs itβs a difference in carbon stored now and in the future, but why then this variable is called π πππ’ππ π‘π₯?
Welcome to the forum! For your first question, you are right that π πππ’ππ π‘π₯ in equation 1 in the userβs guide is the change in carbon stored in a parcel of land π₯ over time. Sequestration refers to change in the quantity of carbon stored, while storage refers to the absolute quantity at a specific time. From the userβs guide, βValuation is applied to sequestration, not storage, because market prices relate only to carbon sequestrationβ.
Regarding your second question: the βPrice/metric ton of carbonβ input is given in currency per metric ton of elemental carbon (not CO2) . Since the data you linked is given in β¬/ton CO2, you would need to convert to β¬/ton C by using the ratio of the masses of C and CO2 (12-ish/44-ish β 0.27), so 1 ton CO2 β 0.27 ton carbon in the form of CO2. The currency unit does not matter to the model, so you can leave it in β¬ and the output will be in β¬.
It looks like in the data you linked, the value of carbon is increasing with time. The βAnnual rate of change in price of carbonβ input can represent this with a small negative value. I did notice that your linked report states, βIn order to use cost rates for years for which no values are indicated in Table 1, we recommend interpolating linearly between the indicated cost rates.β The model only supports an exponential rate of change, so this wonβt be exactly possible. Maybe someone with more knowledge of the details of this model could advise how best to do this
Thank a lot for your reply, it is very-very helpful!
Regarding the equation, itβs all clear now and thatβs what I though Looking at the equation now again one more thing pops up in my head: why the second part is divided by 1? I am using InVEST softwear but I also managed to code the equation in exel, will have to explain every single part of it and, as my econ knowledges are not that strong, I am floating. (What I am basically trying to do is to recreate the whole process without using the software)
All clear now, that was my idea too, I was just wondering if I can actually do that and if it would make sense scientifically But that should be fine I guess.