Biomassebaserade energibärare för transportsektorn

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There is a large potential for increasing the use of biomass for energy purposes in Sweden. Increasing the use of biomass can reduce emissions of carbon dioxide (CO2) from fossil-fuel combustion and dependence on imported fossil fuels. Furthermore, increased biomass use will affect emissions of other air pollutants than carbon dioxide as well as environmental impacts from land use.
The study deals mainly with the environmental impacts of an increase in the use of biomass-based energy carriers in the transportation sector. Comparisons of different alternatives for biomass use are made on a systems level, where the whole fuel cycle from land use to final use of biomass-based energy carriers is studied. The focus of the study is on using biomass-based energy carriers for reducing carbon dioxide emissions. The following indicators are used to evaluate how efficiently biomass can be used for reducing CO2 emissions:

* Yearly reduction of CO2 emissions per unit arable or forest land used for biomass production (kg CO2/ha, yr)
* Costs for CO2 emissions reduction (SEK/kg CO2)

All costs are expressed in SEK assuming 1993 price level, and an exchange rate of 1 USD = 7.4 SEK. All costs exclude domestic taxes, fees and subsidies. Investment costs are annualized using a real discount rate of 6%. All assumptions are based on large-scale production and use of the biomass-based energy carriers studied.

The following energy carriers and biomass resources are studied:
* rape methyl ester (RME) produced from rape seed oil and biomass-based methanol
* biogas from lucern
* ethanol from wheat
* ethanol from Salix (short rotation forest) and logging residues produced using acid
* ethanol from Salix and logging residues produced using enzymatic hydrolysis
* methanol from Salix and logging residues
* hydrogen from Salix and logging residues
* electricity from Salix and logging residues

Of the biomass-based fuels studied, those based on Salix provide the largest CO2 emission reduction per hectare of arable land. Lowest costs for CO2 emission reduction are achieved for methanol from Salix or logging residues (0.5-1.1 SEK/kg CO2 at current biomass costs, 0.4-0.9 SEK/kg CO2 at estimated biomass costs around 2015).
The technologies studied for ethanol production from cellulosic feedstocks, which are assumed to be commercially available in 5 to 10 years time, have an ethanol yield of 30 to 40%. The use of ethanol produced with these technologies will have significantly higher costs for CO2 reduction than methanol. If the ongoing development of new technologies for ethanol production from cellulosic materials with higher ethanol yields and lower costs will be succesful, ethanol from cellulosic materials could be economically competitive to methanol in the long term when used in internal combustion engine vehicles.
The costs for CO2 reduction are slightly higher for biogas from lucern than for methanol from Salix. The CO2 emission reduction per hectare is, however, significantly lower for biogas than for the fuels which are based on Salix.
Hydrogen from biomass has a potential for large CO2 reduction per hectare, but the costs are high as a result of high costs for fuel storage in the vehicle. Neither RME nor ethanol from wheat are economically competitive compared to methanol, even if there is a market for produced fodder by-products. The market for fodder by-products will, however, be limited with large-scale use of RME or ethanol from wheat. If the fodder by-products cannot be sold, the costs for RME and ethanol from wheat exceed the costs for all other fuels studied. Furthermore, large-scale utilization of RME will be restricted by the risk for crop rotation diseases resulting from increased rape seed cultivation.
It is assumed in the study that higher energy efficiencies can be achieved when methanol, ethanol or biogas are used instead of petrol in otto engines. Such advantages are not expected for methanol, ethanol or biogas used in diesel engines. These assumptions lead to higher CO2 emission reduction per quantity of biomass, and lower costs for CO2 reduction, if petrol is replaced with alcohols or biogas in light-duty vehicles than if diesel is substituted with these fuels in heavy-duty vehicles.
Other environmental advantages resulting from the use of bioamss-based fuels in heavy-duty vehicles can, however, motivate an earlier introduction in these vehicles. Emissions of nitrogen oxides and particulates will be significantly lower if biogas, methanol or ethanol are used instead of diesel in heavy-duty vehicles. Nitrogen oxides emissions cannot be expected to be lower if biogas or alcohol fuels are used instead of petrol in vehicles equipped with catalytic converters.
There is a large potential to increase biomass yields and reduce biomass costs. Within a couple of decades the net production of transportation fuels based on Salix and lucern per hectare of arable land could increase by 80-90%. The costs of the transportations fuels could decrease by 10-20% resulting from to lower biomass production costs.
The cultivation of Salix and ley crops instead conventional annual crops is expected to improve soil structure, increase the content of organic materials in the soils, and reduce nutrient leakage. Increased content of organic materials in soils will lead to improved production conditions and a withdrawal of CO2 from the atmosphere. Harvest of logging residues can cause nutrient imbalances and increased acidification. Compensation for these nutrient losses will be required to maintain long-term productivity. A fraction of the logging residues should also be left at the site.
The cost of using biomass-based methanol in a passenger car with an internal combustion engine will, at current biomass costs, be 0.1 to 0.2 SEK/km higher than the cost of using petrol at current fossil fuel prices. With biomass cost estimates for around the year 2015, total costs are estimated to be 0.08 to 0.15 SEK/km higher than for a petrol-fueled vehicle (1993 fossil-fuel prices). This corresponds to 3 to 6% increase in the total cost of using a passenger car. If carbon-dioxide emissions were valued to 0.32 SEK/kg CO2 (equal to the environmental fee 1993 in Sweden), the cost of using petrol would increase by some 0.07 SEK/km, thereby significantly decreasing the cost difference between using methanol and petrol.
Increased fossil-fuel prices would improve the competitiveness of biomass-based energy carriers. A 20% increase in the real price of petrol compared to 1993 would make methanol competitive with petrol in passenger cars with internal-combustion engines, assuming current biomass costs and that CO2 emissions are valued at 0.32 SEK/kg CO2.
The use of battery- or fuel-cell powered electric vehicles could result in efficient biomass use combined with very low air-pollutant emissions. Methanol and hydrogen are suitable energy carriers for fuel-cell electric vehicles, but using methanol reformed to hydrogen in such vehicles is expected to have lower costs. Building up a system for producing and using methanol from biomass in vehicles with internal-combustion engines could, due to the fuel's suitability for use in fuel-cell vehicles, be important in a strategy for creating a transportation system based on energy-efficient vehicles and energy carriers from renewable energy sources.
Original languageSwedish
Number of pages81
ISBN (Print)91-88370-94-1
Publication statusPublished - 1995

Publication series

ISSN (Print)1104-2621

Subject classification (UKÄ)

  • Energy Systems


  • biomass
  • carbon dioxide
  • biomassa
  • biofuel
  • kostnader
  • koldioxid
  • biodrivmedel
  • costs

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