The road to pure plant oil in diesel engines?

Harvesting rapeseed

Technology

The link between the field and the processor (or processing) includes the following activities:

• Transporting the seed from the field to the drying plant;
• Drying up to a moisture content whereby the seed can be kept for a long period;
• Storing the dried seed;
• Eventual transport from the storage facility to the processor/oil press.

Drying is required in order to prevent degradation and conversion of the oil in the seed caused by damp. In the Netherlands, after threshing the rapeseed has a moisture content of between 10% and 23% (usually between 14% and 18%) [Bernelot Moens, 2003], [Moers, 2003]. For long-term storage the moisture content should preferably be reduced to 7-9%.
It is assumed that the infrastructure between the field and the processor is the same in the Netherlands as in Germany. Based on German practice for PPO and biodiesel production, the following estimate can be made for setting up this infrastructure. The following differentiation is made:

A. Small-scale production (up to 5,000 ton seed processed per year), conform the current practice for PPO production in Germany;

B. Large-scale production (around 100,000 ton seed processed per year), conform the current practice for biodiesel in Germany.

The research team expect that for local agricultural systems coupled to small-scale oil presses, the seed will be transported direct from the field to the processor, and both dried and stored at the processor.
However, for large-scale systems, studies such as [Elsayed et al., 2003] and [FFE] have assumed an infrastructure whereby the seed is dried and stored at separate locations, before being transported to the oil press as and when required. The drying plant/storage facility is owned by a cooperation or by a commercial company. In the Netherlands farmers seldom do the drying themselves [Van der Mheen, 2003], [Kempenaar, 2003]. The research team therefore assumes that it is cheaper to perform such tasks using a central drying and storage plant.
It is also assumed that with small-scale oil presses, transport takes place by road, using a trailer. In Germany, this type of small-scale press is served by farmers within a radius of up to 100 km, with 70% of the farmers supplying within a radius of 50 km [Stotz, 2004]. This study has used a distance of 50 km when estimating the net environmental impact relating to PPO.
Large-scale biodiesel plants in Germany are often located along a waterway, and raw materials are often largely transported via water. The transport distance, according to [Elsayed et al., 2003] and [FFE] is generally around 200 km. Transport to a drying and storage facility generally occurs in trailers, via the road network. The distance is then several dozen kilometres.

Energy

The RIVM report [MV5, 2000] was used when calculating fuel consumption for road vehicles. A consumption of 36 litres/100 km was used, for a lorry carrying a 20 ton load. A total transport distance of around 50 km results in a fuel consumption of around 1 litre/ton seed.

Drying costs:
• Around 400 ± 100 MJ natural gas/ton seed9 ;
• Around 10 ± 2 kWhe/ton seed.
These consumptions are calculated on the basis of a moisture content of 14% - 18% before drying, and around 8% after drying10 .
The [MV5, 2000] report was also used for calculating transport by ship, with an average specific consumption of 0.02 litres diesel per tonUkm11 . For a total transport distance of around 200 km, the specific consumption is around 4 litres/ton dry seed.

Emissions

Table 4.1 provides estimates for the emissions related to road transport, drying and shipping transport. Transport emissions are based on [MV5, 2000]. Emissions for underfiring assume a specific NOx emission of 50 g/GJ and the CO2 emission factor of Gronings natural gas.

Costs

Drying, cleaning and storage of rapeseed by contracting companies costs (according to information from [Dekker, 2003], at a moisture content of 14-18%), around € 27 ± € 15 per ton of seed, including VAT (sales tax). These costs are also assumed to be valid for drying and storage.
As far as road transport is concerned, [Dekker, 2003] assumes an amount of€ 5 - € 8 per ton of seed, including VAT.

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