The use of road-side LCMW biomass as the feedstock in Germany. Description of local biomass prunings and process of the fast pyrolysis.
The figure 1 shows the pruning potential per NUTS-3 in Germany originating from the EU-FP7-project EuroPruning supplied by CIRCE. In the case of Germany it shows considerable potentials e.g. 12,000 t/a of fruit prunings in a small area in the North (Stade, Hamburg) known as the “Altes Land” a centre of apple and cherry production and in larger areas in the South-West of Germany, which consist among others of the wine areas Baden and Pfalz. In all grey and dark blue areas the potentials are negligible.
Regarding the amount of prunings per hectare of land surface shown in the figure 2, high densities are observed in the broad wine producing areas as e.g. the Weinstrasse (wine street) in Rhineland-Palatinate with 200 to over 300 kg/ha*a. For comparison, the fruit production area ‚Altes Land‘, which covers a part of the Kreis Stade, achieves only about 75 kg/ha*a after normalisation over the whole area of the NUTS-3.
The model optimizing biofuel production via the catalytic pyrolysis pathway has been described in detail in the BioBoost project (www.bioboost.eu). The basic principle is a profit*amount-maximisation oriented approach of producing biofuel from biomass available in the NUTS-3 regions. The model optimizes the cost and fuel amounts with regard to the biomass sourcing, the logistics, the plant locations and their capacity.
The figure 3 shows the optimization result for biofuel production from prunings in Germany. The highlighted areas are the regions from where the model sources biomass and shows the utilisation ratio, which is nearly 100 % in these regions although cost per tonne of the feedstock increase to 200 % for 100 % utilization compared to lower costs for sourcing ratios below 50 % due to less competition. Due to the limited total amount (~270,000 t/a) and the low density of feedstock available, the cost optimum is one medium-sized catalytic pyrolysis plant for Germany located in Frankfurt. It sources about 250,000 t prunings (90 % of total potential) from all over Germany. On first glance this is surprising, because the long-distance feedstock transport from Hamburg or Saxony must be expensive. However, the potentials in these areas amount to several 100 tonnes per year, and the sourcing which has only a negligible impact on the total production cost and amount. However, shipping of 10,000 t/a over 500 km from Stade to Frankfurt makes a difference, which is why the algorithm eliminated this option.
The cost distribution of this optimization is displayed in figure 4.
The bars show the different components attributing to the costs of 2310 € per tonne of fuel. These production costs correspond to 1.73 €/l fuel from prunings without taxes and profit, whereas the cost of fuel produced from forest residues are in the order of 1.20 €/l.
The main reasons are the low density and wide distribution, the logistic cost related to the transport of the pruning feedstock to a pre-treatment plant. For the production of one tonne of transport fuel 7.25 tonnes of wood chips (40 % water content) are required, therefore transportation cost of low density pruning feedstock is very high (334 EUR/t fuel compared to 126 EUR/t with forest residues). Also the cost of the feedstock at source increases strongly as the model sources as much as possible -in general 100 %- which doubles the feedstock cost (673 EUR/t fuel at pruning, 290 EUR/t at forest residues). In both situations the economy of scale of the decentral conversion is stronger than the increase in the supply cost which leads to only one pruning-CP-plant built for whole Germany. Upgrading of the catalytic pyrolysis oil would yield 43,000 t transport fuel per year from prunings as feedstock. With forest residues as feedstock 11.8 million t/a (64 % of total technical potential), 21 catalytic pyrolysis plants would be fuelled in Germany depicted in figure 5, each plant with an average capacity of 70,000 t/a CP-oil; leading to an overall transport fuel production of over 1 million tonnes per year after upgrading in the 6 refineries.
The use of road-side LCMW biomass, a feedstock with low geographical density but twice the total amounts as feedstock compared to prunings for transport fuel production would result in production cost of 2301 EUR per tonne of fuel. This is 9 EUR/t less than for prunings but a considerably more than the 1606 EUR/t average production costs with forest residues. Taking combined woody biomass generated from forest residues, pruning and roadside LCMW, the production costs amounts to 1588 EUR/t, a drop of 18 EUR/t is due to slightly lower costs for feedstock purchase and logistics. The total amount of transport fuel remains unchanged, because the CP-oil upgrading in the existing refinery capacity is limited. Larger amounts would require construction of dedicated units, which would somewhat increase production costs.
This is also reflected in the average transportation distance of feedstock to the pre-treatment plant which is 229 km for road-side LCMW biomass, 192 km in the case of pruning and 65 km in the case of forest residues.
This result has been achieved with keeping cost for purchase and transport per tonne of forest residues, LCMW biomass and pruning feedstock at the same level.