Calibration of land area energy crop changes

[mxq517]

Hi Team,
After modifying the cropland area and crop production for China, the total cropland area expanded beyond its original size. But the future area of energy crops particularly biomass_tree has unexpectedly significantly increased, and the bioenergy provided by biomass far exceeds that from residues. Could you help me understand why this outcome occurs, and whether it is reasonable? Additionally, what steps could I take to reduce the competition posed by energy crops?

[pkyle]

From the information given there is no way to diagnose this problem, but you can see the dynamics responsible for these results within any land use region (basin), if you query the profit-rate of each land use type. Land allocations are anchored to base year shares, though changes to the relative profitability of the various land use types over time will cause changes in the land allocations.
To the question about how to reduce the land shares of biomass in particularly biomass treat in future periods, that is more or less controlled with an exogenous assumption found in input/gcamdata/inst/extdata/aglu/A_bio_ghost_share.csv, which assigns the percentage of a land node’s land that will be allocated to bioenergy production if the profit-rate of bioenergy production is equal to the dominant land use type in the node in 2015. However before just modifying that variable, I would suggest trying to figure out how the changes you have made have impacted the profit-rates of the various land use types that have led to the anomalous results that you see. If it helps:
profit-rate = (price – cost) * yield
where the profit rate is indicated per land area, prices and costs are indicated per unit of crop production, and costs consist of the sum of exogenous non land variable costs, water costs, and fertilizer costs.

[mxq517]

Thanks for your detailed reply. When I modified the crop production for the base year in 2015, it caused an imbalance in bioenergy supply and demand, leading to errors during the run. How can I resolve this issue and where do I make the supply and demand balance again？

[pkyle]

Modifying crop production quantities but nothing else should cause supply and demand imbalances, as all flows are calibrated, from primary production to end-use demand. The supply and demand imbalances from such a change should not be confined to bioenergy.
Introducing purpose grown bioenergy crop production in 2015 should also cause problems. As there was no such production in 2015, the various methods used to construct the full XML input file set do not accommodate such a scenario.
In general, the best place to revise supply and demand balances are in the input data to gcamdata, which for agriculture are found in the input/gcamdata/inst/extdata/aglu/FAO folder.
The gcamdata/R processing code is designed to create balanced data (for the model) out of imbalanced data (from the primary source). So in general if you do want to revise the data, it's best to do it upstream of the gcamdata processing code, so that all flows balance.