Documentation - Wood outside forest
Content
Inputs
The amount of wood outside forests (WOF) has to be preprocessed and is used in BEAST via the input file landscape_in.csv located in a .beast file. The csv table should contain growth and stock biomass potentials in tons dry mass for the entire research area in 10 year time intervalls. A method how to gain reasonable values of stock and growth of WOF can be found in Seidel et al. (2015) and Fehrmann et al. (2014). The following table shows the structure of landscape_in.csv.
| Column | Type | Unit | Description |
|---|---|---|---|
| year | Integer | a | Start year of harvesting interval |
| yield | Integer | tons (dry) | Growth within corresponding harvesting interval (10 yrs. by default) |
| stock | Integer | tons (dry) | Stock (without growth), should be reduced over periods |
Parameters
Following parameters from parameters.xml are used for the WOF submodel (section landscapeParams):
| Name | Unit | Description |
|---|---|---|
| startyear | a | Start year of period the parameters are valid for |
| periodLength | a | Length of simulation step |
| yieldPeriodLength | a | Length of yield period |
| interestRate | % | Imputed interest rate |
| tAtro2MWh | MWh/ton (dry) | Conversion factor from tons (dry) to MWh |
| percentAvailable | % | Percentage of biomass available for usage |
| basePrice | EUR/ton (dry) | Base price at start of simulation |
| priceChange | % | Annual price change percentage |
| baseCosts | EUR/ton (dry) | Base costs of harvesting at start of simulation |
| costChange | % | Annual cost change percentage |
Processes
Wood outside forests are simulated in 10 year periods by default. Growth and possibly stock usage is taken into account. Therefore, within a 20 year output interval two harvestings take place.
$potential_t = stock_t + yield_t$
with $t$ = year in the middle of yieldPeriod (started with 0 at the beginning of a simulation period and incremented over periodLength)
Typically, only a part of the total potential is availabe for harvesting, therefore, the total potential is reduced accordingly:
$potential_{available_t} = potential_t * {percentAvailable \over 100}$
For the conversion of the available biomass potential into energy a standard (averaged) conversion factor for wood is used:
$energyPotential_{available_t} = potential_{available_t} * tAtro2MWh$
For the simulation output the potentials of the yieldPeriods are aggregated over the periodLength.
It is assumed that harvesting takes place in the middle of the yieldPeriods. Therefore, the base prices and costs are prolongated accordingly:
$price_t = basePrice * (1+{priceChange \over 100})^t$
$costs_t = baseCosts * (1+{costChange \over 100})^t$
The contribution margin of a yieldPeriod is calculated as the difference of prices and costs multiplied with the available potential:
$cm_t = (price_t - costs_t) * potential_{available_t}$
Then, this contribution margin is discounted to the beginning of the simulation period:
$cm_{discount_e} = {cm_t \over {(1 + {interestRate \over 100})^t}} $
with $e$ = number of yieldPeriod $[1,({periodLength \over yieldPeriodLength})]$
This calculation is repeated for every yieldPeriod within the simulation period. The discounted contribution margins are summed up to the net present value:
$netPresentValue = \sum_{e=1}^{periodLength \over yieldPeriodLength} cm_{discount_e}$
Lastly, the total net present value is transformed into an annual annuity:
$annuity = \begin{cases} {netPresentValue * {{i^{(periodLength-1)} * (i - 1)} \over {i^{periodLength} - 1}}} & \quad \text{, if } interestRate > 0\\ {netPresentValue \over periodLength} & \quad \text{, else}\\ \end{cases} $
with $i = 1 + {interestRate \over 100}$
References
Seidel D, Busch G, Krause B, Bade C, Fessel C, Kleinn C (2015) Quantification of Biomass Production Potentials from Trees Outside Forests - A Case Study from Central Germany. BioEngery Research 8 (3): 1344-1351.
Fehrmann L, Seidel D, Krause B, Kleinn C (2014) Sampling for Landscape Elements - A Case Study from Lower Saxony, Germany. Environmental Monitoring and Assessment 168 (3): 1421-1430.