Documentation - Short rotation coppice
Content
Inputs
The field specific inputs regarding site conditions and yield are read from simulation period specific files src_in_2011.csv and src_in_2031.csv. These files contain values for each yield period within a simulation period. The files also contain the inputs for field crops which are used in this section. The results of the field crops calculations are reused here for comparisons of annuities. The spatial polygons from fields.geojson (with ETRS84-UTM32N projection) representing an arable field can be joined by the column beastid.
The csv tables should contain biomass yields in tons dry mass per harvesting interval, which have to be preprocessed. Busch & Thiele (2015) presented a method to develop and apply growth/yield simulation models for Lower Saxony, Germany.
The following table shows the structure of the input files (src_in_2011.csv and src_in_2031.csv).
| Column | Type | Unit | Description |
|---|---|---|---|
| beastid | Integer | - | ID of corresponding polygon |
| startyear | Integer | a | Start year of harvesting interval |
| area | Integer | ha | Spatial size of the field |
| slope | Integer | % | Slope of the field |
| adminId | Integer | - | ID of the administrative unit the field falls into |
| ecologicalId | Integer | - | ID of the ecological unit the field falls into |
| soilQualityIndex | Integer | - | Index value of the soil quality (German: Ackerkennzahl) |
| soilMoistureIndex | Integer | - | Index value of the soil moisture |
| rotation | Text | - | Field crop rotation (separated by "-", like: wheat-rape-barley) |
| birdProtectionArea | Boolean | - | Is the field located in a bird protection area |
| ffhArea | Boolean | - | Is the field located in a FFH (Natura 2000) protection area |
| floodingArea | Boolean | - | Is the field located in a flooding area |
| natureConservationArea | Boolean | - | Is the field located in a nature conservation area |
| regionSpecificProtectionArea | Boolean | - | Is the field located in a region specific protection area |
| waterProtectionArea | Boolean | - | Is the field located in a water protection area |
| bufferArea | Boolean | - | Is the field located in a buffer area |
| erosion | Integer | t/ha/a | Susceptibility to (water) erosion value |
| areaComplexity | Integer | h/ha * 10 | Index value of area complexity |
| percolationWater | Integer | mm/m^2/a | Rate of percolation water |
| landscapeDiversity | Integer | m/ha | Index value of landscape diversity |
| nitrateLeaching | Integer | t N/ha/a | Index value of nitrate leaching risk |
| wheat1 | Integer | dt/ha/a | Annual (potential) yield of wheat for the first decade of simulation period on the corresponding field |
| wheat2 | Integer | dt/ha/a | Annual (potential) yield of wheat for the second decade of simulation period on the corresponding field |
| sugarBeet1 | Integer | dt/ha/a | Annual (potential) yield of sugarbeet for the first decade of simulation period on the corresponding field |
| sugarBeet2 | Integer | dt/ha/a | Annual (potential) yield of sugarbeet for the second decade of simulation period on the corresponding field |
| barley1 | Integer | dt/ha/a | Annual (potential) yield of barley for the first decade of simulation period on the corresponding field |
| barley2 | Integer | dt/ha/a | Annual (potential) yield of barley for the second decade of simulation period on the corresponding field |
| rape1 | Integer | dt/ha/a | Annual (potential) yield of rape seed for the first decade of simulation period on the corresponding field |
| rape2 | Integer | dt/ha/a | Annual (potential) yield of rape seed for the second decade of simulation period on the corresponding field |
| maize1 | Integer | dt/ha/a | Annual (potential) yield of maize for the first decade of simulation period on the corresponding field |
| maize2 | Integer | dt/ha/a | Annual (potential) yield of maize for the second decade of simulation period on the corresponding field |
| src1 | Integer | dt/ha/a | Annual (potential) yield of short rotation coppice for the first 5-year harvesting interval of simulation period on the corresponding field |
| src2 | Integer | dt/ha/a | Annual (potential) yield of short rotation coppice for the second 5-year harvesting interval of simulation period on the corresponding field |
| src3 | Integer | dt/ha/a | Annual (potential) yield of short rotation coppice for the third 5-year harvesting interval of simulation period on the corresponding field |
| src4 | Integer | dt/ha/a | Annual (potential) yield of short rotation coppice for the fourth 5-year harvesting interval of simulation period on the corresponding field |
Parameters
Following parameters from parameters.xml are used for the SRC submodel (section srcParams; shared with field crops submodel):
| 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/tons (dry) | Conversion factor from tons (dry) to MWh |
Additional, following parameters are specified for SRC:
| Name | Unit | Description |
|---|---|---|
| areaPayment | EUR/ha/a | Annual payment per hectar |
| basePrice | EUR/dt | Basic price at the beginning of simulation period |
| priceChange | % | Annual price change in simulation period |
| baseVarCosts | EUR | Basic variable costs |
| baseVarCostsCreation | EUR/ha | Basic costs of initial plantation creation |
| baseVarCostsDismanteling | EUR/ha | Basic costs of dismanteling of plantation |
| baseLabourCosts | EUR | Basic labour costs |
| varCostsChange | % | Annual change of variable costs |
| varCostsChangeCreation | % | Annual change of costs of plantation creation |
| varCostsChangeDismanteling | % | Annual change of costs of plantation dismanteling |
| labourCostsChange | % | Annual change of labour costs in simulation period |
| varCostsYieldBeta1 | - | Parameter beta of variable costs equation |
| varCostsYieldReference | tons (dry)/a | Reference yield for basic variable costs |
| labourCostsYieldBeta1 | - | Parameter beta of labour costs equation |
| labourCostsYieldReference | tons (dry)/ha/a | Reference yield for basic labour costs |
| labourCostsSlopeFactor | - | Factor in slope correction term of labour costs |
| labourCostsSlopeExponent | - | Exponent in slope correction term of labour costs |
| labourCostsAreaBeta1 | - | Parameter beta in area correction term of labour costs |
| labourCostsAreaReference | ha | Reference area for basic labour costs |
| meanBaseYield | tons (dry)/a | Mean annual base yield |
| baseYieldPercent | % | Yield correction percentage |
| harvestingInterval | a | Time between harvesting events |
Busch & Thiele (2015) presented a method to derive parameter values for Lower Saxony, Germany.
Further parameters are defined for area selection restrictions:
| Name | Unit | Description |
|---|---|---|
| maxSrcArea | ha | Max. size of a single SRC field (only fields smaller than this threshold value) |
| maxSrcPercentagePerAdminUnit | % | Max. percentage of SRC per administration unit (by area) |
| maxSrcPercentagePerEcologicalUnit | % | Max. percentage of SRC per ecological unit (by area) |
| minSrcDistance | m | Min. distance between two SRC fields |
| noBirdProtectionAreas | - | Do not use bird protection areas for SRC plantations |
| noFFHAreas | - | Do not use FFH (Natura 2000) areas for SRC plantations |
| noFloodingAreas | - | Do not use flooding areas for SRC plantations |
| onlyFloodingAreas | - | Only use flooding areas for SRC plantations |
| noNatureConservationAreas | - | Do not use nature conservation areas for SRC plantations |
| noRegionSpecProtectionAreas | - | Do not use region specific protection areas for SRC plantations |
| noWaterProtectionAreas | - | Do not use water protection zones for SRC plantations |
| onlyWaterProtectionAreas | - | Only use water protection zones for SRC plantations |
| onlyBufferAreas | - | Only use buffer zones for SRC plantations |
| noBufferAreas | - | Do not use buffer zones for SRC plantations |
The criteria in the following two tables can be used to select fields for SRC that fulfill specific targets. These targets are separated into two groups: used as hard criteria with minimum and/or maximum values (like restrictions; next two tables) and targets used for selection optimization (only second table). For the first group, for each criterion the minimum (minTarget) and maximum values (maxTarget) can be defined as sub-parameters. Furthermore, the boolean parameters useMinTarget and useMaxTarget can be used to activate subsetting by minimum and/or maximum value.
| Name | Unit | Description |
|---|---|---|
| slope | % | Slope on area |
| soilQualityIndex | - | Index of soil quality (Ackerzahl) |
| soilMoistureIndex | - | Index soil moisture |
The judgement of the pairwise comparisons for the Analytical Hierarchy Process (AHP) is stored in a section pairwiseCriteriaComparison with a The numbers identify the criteria compared to each other with the following meaning:
| Number | Criterium |
|---|---|
| 1 | Difference between crop rotation annuity and SRC annuity |
| 2 | Susceptibility to (water) erosion |
| 3 | Index value of landscape diversity |
| 4 | Susceptibility to nitrate leaching |
| 5 | Rate of percolation water |
| 6 | Area complexity index |
E.g., erosion23 means importance comparison of "Susceptibility to (water) erosion" to "Index value of landscape diversity".
Targets used for optimization take additional sub-parameters for weightings and scalings. The weights of the target criterion is definied in criterionWeight (with values between 0 and 100) and gives the relative weight of this criterion to the other criteria. The scaling of the target is done using five support points of target value - scaling value pairs. Scaled values are always between 0 and 100.
| Name | Unit | Description |
|---|---|---|
| landscapeDiversity | m/ha | Index value of landscape diversity |
| erosion | t/ha/a | Susceptibility to (water) erosion |
| areaComplexity | ha/h*10 | Area complexity index |
| annuityDifference | EUR/ha/a | Difference between crop rotation annuity and SRC annuity |
| nitrateLeaching | t N/ha/a | Susceptibility to nitrate leaching |
| percolationWater | mm/m^2/a | Rate of percolation water |
Processes
Yield and Economy
Harvesting of SRC takes place in 5 year intervals with cumulative growth. Within a 20 years simulation period four harvestings are realized.
For the economic valuation intercepts of variable and labour costs for all fields are calculated:
$varCostsIntercept=baseVarCosts-varCostsYieldBeta1*varCostsYieldReference$
$labourCostsIntercept=baseLabourCosts-labourCostsYieldBeta1*$
$labourCostsYieldReference$
The following steps are processed within a loop over all fields.
It starts with the calculation of the adapted yield:
$yield_r = yield_r * {baseYieldPercent \over 100}$
with $r$=number of harvesting interval
Next, the slope and field size correction of labour costs is calculated:
$labourCostsSlopCorrection=1+(labourCostsSlopeFactor*e^{(labourCostsSlopeExponent*slope)})$
$labourCostsAreaCorrection={{area^{labourCostsAreaBeta1}} \over {labourCostsAreaReference^{labourCostsAreaBeta1}}}$
The following steps are processed in a loop for each harvesting interval.
First, the sum of yields for the corresponding harvesting intervall is processed:
$yieldSum_r=\sum_{y=1}^{5} yield_y$
The variable costs depend on the yield sum and are calculated as follows:
$varCosts_r=varCostsIntercept+varCostsYieldBeta1*yield_r$
Labour costs depend on yield sum, slope and field size:
$labourCosts_r=(labourCostsIntercept+labourCostsYieldBeta1*yield_r)*$
$labourCostsSlopCorrection*labourCostsAreaCorrection$
Next, the labour and variable costs as well as the prices are prolonged to the year of harvesting under consideration of annual costs and price changes:
$varCosts_r=varCosts_r*(1+{varCostsChange \over 100})^t$
$labourCosts_r=labourCosts_r*(1+{labourCostsChange \over 100})^t$
$price_r = basePrice * (1+{priceChange \over 100})^t$
with $t$=number of years from the beginning of the simulation period to the current harvesting.
Now, the contribution margin can be calculated:
$cm_r=price_r*yieldSum_r-varCosts_r-labourCosts_r$
Next, the contribution margins are discounted to the beginning of the simulation period. i.e. the net present values are calculated:
$cm_{discount_r}={{cm_r} \over {(1+{interestRate \over 100})^t}}$
Then, they are summed up to total net present value:
$netPresentValue = \sum_{r=0}^{3} cm_{discount_r}$
Now, the loop over the harvesting intervals ends.
Next, the annual area payments are discounted and added to the total net present value:
$netPresentValue=netPresentValue+ \sum_{j=0}^{periodLength-1} {areaPayment \over {(1+{interestRate \over 100})^j}}$
Afterwards, the costs of plantations and the discounted costs of dismanteling under consideration of annual cost change rate are subtracted from the total net present value:
$dismantelingCosts=baseVarCostsDismanteling*(1+{varCostsChangeDismanteling \over 100})^{periodLength}$
$netPresentValue=netPresentValue-{dismantelingCosts \over {(1+{interestRate \over 100})^{periodLength}}}$
$netPresentValue=netPresentValue-varCostsChangeCreation$
Now, the annual annuity can be calculated:
$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 $i = 1 + {interestRate \over 100}$
Using the annuity of field crop rotations (see here) the annuity difference can be calculated:
$annuityDifference=annuity_{src}-annutiy_{cropRotation}$
Additionally, the sum of yields over the simulation period are calculated:
$totalYield= \sum_{r=0}^{3} yieldSum_r$
and transformed into an energy sum:
$energySum=totalYield*tAtro2MWh$
Restrictions (I.)
If at least one of the following restrictions was set, it is applied in a loop over all polygons and the polygon attribute fulfillsRestrictions is set to true or false.
| max. field size |
| only buffer zones |
| no buffer zones |
| no bird protection areas |
| no FFH (Natura 2000) areas |
| no flooding areas |
| no nature conservation areas |
| no water protection areas |
| no region-specific protection areas |
The application of restrictions may reduce the number of prefered SRC fields.
Objectives
The fields are then iterated again to select those fields that support the objectives. For the following objectives minimum and/or maximum values can be set:
| annuity difference |
| susceptibility to (water) erosion |
| landscape diversity index |
| rate of percolation water |
| pot. nitrate leaching |
| area complexity index |
| slope |
| soil quality index |
| soil moisture index |
For each field the attribute fulfillsTargets is set to true or false, accordingly.
Criteria values
In another loop a scaled criterion value is calculated for the following criteria to be used for optimised area selection:
| annuity difference |
| susceptibility to (water) erosion |
| landscape diversity index |
| rate of percolation water |
| pot. nitrate leaching |
| area complexity index |
The scaling support points given by the user are used to apply the scaling function to the criteria values stored in the input table (or calculated in the above described processes for annuity difference). The scaling given by the user scales the criteria values to values between 0 and 100. These scaled criteria values are stored for each field for results output. Next, the scaled criteria values are multiplied with the weights derived from pairwise comparisons using the Analytical Hierarchy Process (AHP) (transformed to values between 0.0 to 1.0). These scaled and weighted criteria values are summed up over all criteria. Therefore, this criteria sum can have values between 0 and 100.
$scaledCriteriaSum= \sum_{c=1}^{\text{Number of criteria}} scaledCriterionValue_c*criterionWeight_c$
Area Selection and Restrictions (II.)
First, the area sum of administration (adminid) and ecological (ecologicalId) units are computed. Then, the area is calculated that can be used for SRC per unit without violating the restriction of maximum SRC area per administration and/or ecological unit. Now, the fields are sorted by descending scaled criteria sum. Then, the fields are iterated and the attribute src is set to true, if attributes fulfillsRestrictions and fulfillsTargets have value true and the maximum SRC area of the corresponding administration and/or ecological unit is not reached. If src is assigned to true the maximum SRC area of corresponding administration and ecological unit is reduced by the field size.
Clustering
The fields selected as prefered SRC areas, i.e. value of attribute src is true, are assigned to a SRC cluster. This clustering is based on the criteria sum of this field and represents a preference classification. The clusters are defined as follows:
| SRC class | scaledCriteriaSum |
|---|---|
| 5 | < 20 |
| 4 | < 50 |
| 3 | < 60 |
| 2 | < 80 |
| 1 | else |
References
Busch G., Thiele J.C. (2015) The Bioenergy Allocation and Scenario Tool (BEAST) to Assess Options for the Siting of Short Roation Coppice in Agricultural Landscapes: Tool Development and Case Study Results from the Göttingen District. In: D. Butler Manning, A. Bemmann, M. Bredemeier, N. Lamersdorf, C. Ammer (eds.): Bioenergy from Dendromass for the Sustainable Development of Rural Areas. Wiley-VCH, pp. 23-43.