Report: synthetic biofuels (BtL) and bioenergy efficient, competitive and sustainable in Germany

A new comprehensive report by Germany's Karlsruhe Institute of Technology (KIT) analyses the economic, environmental and technological aspects of biomass and its conversion into second-generation liquid fuels, electricity and heat. It concludes that both bioenergy (heat, electricity) and biomass-to-liquids (BtL) production from wood and agriculutral residues in Germany is (1) competitive with fossil fuels, (2) energy efficient and (3) offers a sustainable and cost-effective way to reduce greenhouse gas emissions. A consortium affiliated with the KIT has meanwhile begun construction on the specific BtL facilities discussed in the report (earlier post).

The researchers found that synthetic biofuels (gasified biomass liquefied via the Fischer-Tropsch process) are competitive when oil is priced above $65 per barrel and the synfuels are not taxed. Depending on the capacity of the plants, production of electricity from the particular biomass sources analysed (forestry residues, straw) is close to competitive with coal when co-fired with coal or used in highly efficient combined heat and power (CHP) plants. Heat from the same biomass is most competitive and does not require any subsidies or tax-exemptions today to compete with heating oil (biomass being 30% less costly).

The most cost-effective way to reduce CO2 emissions is by using these types of biomass directly for the production of heat, followed by combined heat and power generation (CHP), co-firing biomass with coal, and electricity from gasified biomass. Fischer-Tropsch fuels were not effective in this regard, but have economic benefits as replacements for oil products and petrochemicals.

The report titled 'Kraftstoff, Strom und Wärme aus Stroh und Waldrestholz – Eine systemanalytische Untersuchung' [*.pdf] (Fuels, Electricity and Heat from Straw and Forestry Residues), written by scientists from KIT's 'Institut für Technikfolgenabschätzung und Systemanalyse' (ITAS) says the new bioconversion technologies sharpen competition amongst renewable energy technologies (especially wind and solar) but also within the biomass sector itself. This is so because biomass can be used for a large range of end-products: heat, electricity, aternatives to petrochemicals and transport fuels. This battle for investments will have positive effects on the sector as a whole and will result in the gradual emergence of the most efficient conversion pathways.

The biomass-to-liquids system analysed by ITAS - the so called 'bioliq' concept currently being implemented by the Forschungszentrum Karlsruhe - involves a three step process:

1. decentralised pyrolysis plants are located close to the biomass source (forests, agricultural zones), where it undergoes fast-pyrolysis resulting in 'pyrolysis slurry', a mixture of bio-oil and pyrolysis coke. This first step turns the bulky biomass into a raw product with a higher energy density, so it can be transported more efficiently to a central location for further processing (the study analyses both decentralised and centralised concepts). The researchers analysed the efficiency of 7 different fast-pyrolysis reactor types
   
2. the pyrolysis products arrive at a gasification facility, where they are turned into a carbon monoxide and hydrogen-rich gas (syngas); 5 gasification technologies were compared
   
3. after cleaning and conditioning the syngas, it is liquefied via the Fischer-Tropsch (FT) process (synthesis of hydrogen and carbon monoxide) into synthetic biofuels which can be further refined into a range of very clean transport fuels (alternatives to gasoline, diesel, kerosene, and dimethyl-ether and methanol obtained from natural gas); three types of FT-reactors were compared
   

The researchers analysed the specific advantages of using the dominant biomass sources – straw and wood residues – as well as the disadvantages of the technology, and compared the concept to competing alternative uses for biomass (heat and electricity).

As a starting point, selected plant locations were chosen in the federal state of Baden-Württemberg (southwest Germany), on the basis of which the volume of straw and wood residues available for energy use was outlined, as well as the supply costs for these biomass sources. The technology analysis regarding liquid fuel production from biomass entailed a detailed description of the present status quo of fast pyrolysis, gasification, gas cleaning/conditioning, and Fischer Tropsch synthesis.

Energy balance
The energy balance of the synthetic biofuels based on the bioliq concept in the specified setting, was found to be strong. For fuels obtained from straw the final net balance - after pretreating, drying, pyrolysing, gasifying, upgrading, liquefying and refining the feedstock - was 34%; for synfuels based on forest residues the net balance was 29% (graph, click to enlarge). The energy inputs that go into harvesting and transporting the biomass and the pyrolysis slurry, are between 5 and 12% of the energy content of the FT-fuels, depending on the concept (decentralized/centralized):
energy :: sustainability :: biomass :: bioenergy :: biofuels :: pyrolysis :: gasification :: Fischer-Tropsch :: biomass-to-liquids :: synthetic biofuels :: Germany ::

Economics
Assuming the combined use of straw and wood residues, the economic estimates for energy self-sufficient plants reveal that bio-based FT-fuels can be produced at costs in a range from €0.90 to 1.00 per litre, depending on plant capacity. The biomass supply accounts for 50-65% to the production costs of FT-fuel, depending on the assumed plant capacity. The economics of two biorefineries were analysed: a small one with a conversion capacity of 0.2 million tonnes of biomass per year and one with a 1 million tonne capacity. Compare this with an oil refinery which requires at least a 10 million tonne capacity to be commercially feasible. If the synthetic biofuels produced in the analysed refineries are not additionally charged with a mineral oil tax, they compete with fossil diesel at crude oil prices of $65/bbl.

Depending on the capacity of the plants, production of electricity from forestry residues and straw is close to competitive with coal when co-fired with coal or used in highly efficient combined heat and power (CHP) plants. Large CHP plants (10-67MWin) burning biomass offer heat and electricity in a more competitive than the fossil baseline. Small CHP plants (1.5-13.4MWel) are far less cost-effective. The costs for eletcricity obtained from gasification of the two types of biomass range from €80 to 135 per MWh, compared to a baseline of €50 for coal in a 500MWel plant.

The study shows that the production of heat from wood residues is already outcompeting fossil heating oil. Because straw and forestry residues have a 30% cost advantage over heating oil, this type of bioenergy does not require subsidies by the state (graph, click to enlarge).

In conclusion, in comparison of the production of FT-fuel with heat and electricity production reveals that these alternatives are closer to competitiveness or have already reached competitiveness in Germany.

CO2 offsetting costs
The CO2 mitigation costs (graph, click to enlarge) are lowest when biomass is used directly for the production of heat, in which case they can even be negative (when waste streams and residues are used that would otherwise require disposal costs). When used in efficient combined heat and power plants, they range between a negative cost and around €50 per Mg CO2 equivalent. Co-firing biomass with coal results in a CO2 offsetting cost of around €40.

Carbon prices would have to fetch between €35-140 to make electricity production from gasified biomass a cost-effective CO2 mitigation technology. The wide range depends on the gasification technology.

For biobased FT-fuels the mitigation costs are above €200 per Mg CO2 equivalent. These results suggest not using the CO2 mitigation strategy as a central argument for the promotion of synthetic fuel production from biomass. But because the BtL concept opens up new ways to use biomass as carbon carrier for other chemical purposes, this technological path will be pursued in any case by the KIT.


The proposed BtL technology is already being implemented by the Forschungszentrum Karlsruhe (FZK) and Lurgi AG, who have been testing a fast-pyrolysis pilot plant for the past two years. Both organisations are now building the gasification and liquefaction plant needed to perform the FT-stage of the production. The work is being supported by the Fachagentur Nachwachsende Rohstoffe (Agency for Renewable Materials, of Germany's Ministry of Agriculture, Food and Consumer protection).

The Karlsruhe Instituts für Technologie is a cooperation between the Forschungszentrum Karlsruhe und der Universität Karlsruhe. The study was commissioned by the Ministry for Food and Agriculture of the state of Baden-Württemberg.

Image: the fast-pyrolis plant at the FZK in Karlsruhe. Courtesy: Forschungszentrum Karlsruhe.

References:
L. Leible, S. Kälber, G. Kappler, S. Lange, E. Nieke, P. Proplesch, D. Wintzer und B. Fürniß, "Kraftstoff, Strom und Wärme aus Stroh und Waldrestholz – Eine systemanalytische Untersuchung" [*.pdf], Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft, Wissenschaftliche Berichte, FZKA 7170, Institut für Technikfolgenabschätzung und Systemanalyse, Forschungszentrum Karlsruhe GmbH, Karlsruhe - [september] 2007

Biopact: German consortium starts production of ultra-clean synthetic biofuels - June 23, 2007