The road to pure plant oil in diesel engines?

Energy usage

Cold pressing
With respect to the energy consumption of a complete small-scale plant, excluding dryer, in practice values have been found ranging from 20 kWhe/ton dry seed to around 90 kWhe/ton dry seed [Widmann, 1998]. Energy consumption greatly depends on the design of the plant, particularly the engine driving the press. In practice, an average of around 45 kWhe/ton dry seed is used, which is comparable to the indication given in [Folkecenter, 2000a], of around 35 kWhe/ton.
Industrial plants
The literature [Elsayed et al., 2003] and [FFE], mentions the following energy usage per ton of dried seed for pressing/extracting:
• 700 – 850 MJ natural gas
• 30 – 35 kWhe
Refining
This same literature [Elsayed et al., 2003] and [FFE], mentions the following energy use per ton of raw oil:
• 350 - 580 MJ natural gas
• 6 - 10 kWhe
Fact sheets published on the Internet by manufacturers of plant-oil refining equipment (Lurgi, Cimbria Sket) quote similar figures.

Emissions

Cold pressing
As far as researchers currently know, cold pressing produces no direct emissions into the air or other forms of environmental impact.
Industrial plants, extraction and refining This form of production produces emissions to air and water. This primarily concerns emissions of organic substances to water, and fragrances to the air. However, there is no information available with respect to the extent of these emissions.
This production method also causes direct emissions from underfiring the natural gas. The related emissions are estimated, based on the natural gas consumptions given in the previous section and the following emissions factors:
• CO2 = 56 kg/GJ (Groningen gas).
• NOx = 50 g/GJ.

Costs

The research team has tried to produce an estimate of the basis production costs (for both small-scale and large-scale PPO production) per ton of PPO, excluding VAT, excluding purchasing of raw materials, and excluding the profit from selling these products. This information gives a better insight into the importance of production costs.
Cold pressing
Based on the research team’s own cost calculations, the process costs for an oil press capable of processing 750 kg of dry seed per hour15 is estimated at around € 30 - € 50 per ton dry seed, excluding the cost of the seed.

The annual costs have been estimated based on these parameters, using the Environmental Costing method [VROM, 1998]. This method was developed to determine the cost effectiveness of environmental measures and is thus a general method16 , so that further details are not given in this study.

The resulting build-up of the annual costs is shown in Table 5.4. Personnel and energy costs are derived by multiplying the annual time spent by personnel and the annual energy consumption with the hourly rate and electricity price respectively.

Industrial plants

Information on the costs of industrial plants is also extremely limited. It is only possible to determine (from the current prices for dry rapeseed, rapeseed scrap and rapeseed oil) that the process costs are around € 10/ton.

The price of dry rapeseed at the factory door is estimated at € 290/ton, based on the information from previous sections18 ;

The price for extracted scrap and refined oil are € 130/ton and € 600/ton ± € 100/ton respectively [Bergmans, 2004];

Dry seed with an average oil content of 43% and a moisture content of 8%, produces (at almost complete isolation of the oil) around 530 kg scrap and around 390 kg oil;

The balance for the process would thus be: (53%U130 + 39%U600) – 290 €10/ton dry seed.

Conclusions

The production costs are only a few tens of euro per ton of PPO (excluding VAT). Considering the costs of the rapeseed, the production costs cannot be characterised as an important cost element.

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