Can LCMW biomass from fruit, wine and olive pruning make a substantial contribution to the economic production of biofuels on European scale?
To investigate this issue the cost optimization model has been fed with the EU-28 feedstock potential data on the resolution level NUTS-3. Potentials originate from the EuroPruning project and were supplied by CIRCE. All parameters for the feedstock (price, transport and conversion) have been assumed to be identical to those of forestry residues. This allows investigation of those supply chain parameters, which depend on the feedstock density. The overall technical available potentials of fruit pruning are compared to forestry residue potentials in the following table for EU-28, Germany and Spain.
Table 1: Technical feedstock potentials and their area-density (given as t/km²/a) for Europe, Germany and Spain
|Technical potential [t/a]||Relative amount [t/km²]||Technical potential [t/a]||Relative amount [t/km²]||Technical potential [t/a ]||Relative amount [t/km²]|
|Hedge- and tree row-, roadside-lignocellulosic LCMW biomass||3,169,000||0.73||545,223||1.53||316,000||0.64|
In the figure 1 the pruning potentials are shown. It is obvious that Spain, Italy and Greece have substantial potentials in the order of several 100,000 t/a in certain NUTS-3 regions whereas the potentials in Germany are relatively small.
These potentials have been used to optimize biofuel production using the catalytic pyrolysis pathway as one example.
From the total pruning potential the model identifies the most effective sites and sizes for biomass conversion to catalytic pyrolysis oil with respective feedstock supply regions and degree of sourcing. The figure 2 shows the feedstock cost in the supplying regions. Feedstock in southern Spain where the total potentials are high is sourced at around 50 % of the available potential with cost of about 70 €/t, whereas the feedstock cost in regions with less potential are around 100 €/t or even higher. This is due to a trade-off between plant capacity and feedstock costs. The conversion costs per unit decrease with increasing production capacity of a plant (scale-of-unit law). On the other side the feedstock price rises with increasing competition (at 100 % sourcing to more than twice the price at 50 % sourcing). A second trade-off exist between feedstock price increase due to higher competition in a region and lower purchase price but higher transport costs due to procurement in neighbouring regions. Overall, the general trend is towards large plants.
The figure 3 shows the best solution of this optimization. The blue arrows mark the feedstock transport from the sourcing regions to CP plants. The red arrows indicate the supply of CP-oil by train to existing mineral oil refineries for upgrading to transport fuel in the highlighted regions. The model optimizes cost*amount of produced transportation fuel by identifying best location and capacities of CP plants to deliver biocrude to existing oil refineries who have a spare capacity of 10 % of hydrogen production, and co-process the CP-oil. The number of feedstock-supplying regions depends on the available feedstock amount and supply costs and the CP-plant capacity. Similarly, smaller refineries (100 – 200 kt/a CP-transport fuel production capacity) are supplied by one or two CP-plants, the largest refinery in Rotterdam, The Netherlands (500 kt/a) is supplied by nine CP-plants from all over Europe. The four Spanish refineries are close to their maximum upgrading capacity and two Spanish CP-plants supply the Normandy-refinery in France. The two large Italian refineries are located on Sicily and Sardinia. However, ship transport is not implemented in the optimisation model and thus, the Italian CP-oil is upgraded in Karlsruhe (Germany) and Rotterdam. The only refinery in south-east Europe in Burgas (Bulgaria) is a 100 % of its upgrading capacity with supply from a Greek and a Romanian CP-plant. The other five CP-plants ship their products to Vienna (Austria), Ingolstadt (Germany) and Rotterdam. Several other refineries located in Belgium, France, Germany, Poland, Lithuania, Finland, Sweden and the United Kingdom are not supplied.
Figure 4 presents the results for the average, the most expensive, the least expensive and the case of the largest capacity and smallest capacity of the EU-28 optimisation run with prunings.
The most expensive (DE211 Ingolstadt) and the cheapest plant (ES612 Gibraltar) have a similar production capacity of 122 and 125 kt/a, respectively. The least expensive production is clearly there where the feedstock density is high and nearby.
The comparison of smallest (PT181, Sines refinery, Alentejo Litoral) and largest capacity (NL339, Rotterdam) demonstrates that in the case of pruning the smaller refineries can have a competitive production as they are only slightly more expensive than the cheapest one (1940 €/t compared to 1900 €/t). The largest refinery profits highly from economy of scale but has the disadvantage of long transport distance from the pruning-rich southern regions. This is different to results for forestry residues with high feedstock density closer by, which makes it typically one of the most cost-competitive plants.
The transportation fuel production capacity is 190 kt/a at cost of 2018 EUR/t for the EU-28 average. Under optimal conditions assuming that the first CP-plants would be build in the best region in southern Spain, 180 kt/a transport fuel could be produced at 1633 EUR/t at the Gibraltar refinery. Due to location in regions with high pruning potentials the feedstock costs free CP-plant are below 500 EUR/t transport fuel and contribute only 30 % to the total production costs. In the EU average, the cost for feedstock free plant gate amount to 788 EUR/t or 39 % of total costs. Cost of CP-oil production, transport to the refinery and upgrading are relatively similar for the average and the best plant. Fuel production from a pruning feedstock in best regions would be possible at a price level comparable to wood chip-based production in favourable regions. High production costs originate solely from increase in feedstock sourcing cost due to sourcing of more than 50 % of available potential or from the higher efforts for feedstock logistics; both due to low feedstock availability. A combination of all suitable biomass feedstocks (forest residues, prunings, LCMW biomass and land management material) would increase the potentials in more regions to favourable levels, further supporting the production of transport fuel.
The use of fruit pruning for biofuel production in Europe
The mostly lower feedstock density of pruning leads to an increase in average production cost of fuel by 500 €/t. In regions with high pruning potential the production cost are similar to those with forest residues.
The major cost is arising from the feedstock cost and feedstock logistic cost. For the sourcing cost the same parameter as for wood residues (cost 70 €/tdry at the place of harvest, at 0- 50 % utilization increasing to 140 € at 100 % utilisation) was chosen which led to average feedstock cost of 100 €. The feedstock logistic costs are also calculated with the same data as wood chips. A detailed analysis of the logistic properties of fruit pruning supply to the decentral plants would be needed to achieve more realistic results.
Conclusion – Chances and challenges of lignocellulosic biomass from LCMW of hedge- and tree rows on banks and road side maintenance
Lignocellulosic biomass from LCMW is a suitable fuel for biofuel production however in central Europe only in addition to larger amounts of forestry residues.
It could lead to a reduction of feedstock cost in the order of 100 €/t biofuel. Except for some areas with orchards and vineyards, LCMW biomass is too highly dispersed and as such not alone suitable to fulfil needs of biofuel production plants.
The potentials of LCMW biomass has been evaluated by greenGain partners in the model regions and compared with results achieved by other investigations in European projects BioBoost and S2Biom.
The often low geographic density of such feedstock (several kg per ha) leads to high logistic costs and therefore high fuel production costs. The small total amounts available and the demand of economy of scale in biofuel production leads in an optimisation of the overall fuel production costs to only one pyrolysis plant and upgrading in one refinery nearby for the whole of Germany. Production cost of fuel would be around 1000 €/t more expensive that with forest residues. However if the LCMW feedstock is utilized additionally to the forest residues the total feedstock potential is increased by approximately 10 % which leads to an overall cost reduction due to economy of scale effects of around 50-100 €/t of fuel. Similar investigations have been performed with fruit pruning biomass and show similar trends for Germany.
Countries like Spain and Italy with much higher LCMW biomass amounts from fruit pruning and less dense transportation infrastructure offer chance to build up de-central pyrolysis plants for utilisation as a biofuel.