|Results of the Well-to-Tank lifecycle assessment of different BTL processes. The process with the lowest impact is set as reference (100%). Click to enlarge.|
The Integrated European Project “Renewable Fuels for Advanced Powertrains” (RENEW) has published its final scientific report on its four-year project studying different production routes for second-generation renewable biomass-to-liquid (BtL) fuels.
Of the concepts examined, the project concluded that the Chemrec process of black liquor gasification to produce dimethyl ether (DME) has the highest conversion efficiency, the lowest product cost and the highest greenhouse gas emission reductions on a well-to-tank basis. The Chemrec process is also one of two recommended for demonstration in industrial scale.
|Simplified flow of the Chemrec process. Click to enlarge.|
The evaluated Chemrec process, which is designed as an integral part of a pulp mill, reduces CO2 emissions by 95%. The efficiency is high due to a shift to more advanced technology in the energy and chemical recovery area of the pulp mill and the high efficiency achievable in DME and methanol synthesis. The process uses locally available biomass not competing with food production.
|Pathways for the production of BTL fuels. Click to enlarge.|
RENEW brought together 32 European partners in a four-year project to develop or improve several production routes for renewable biomass-to-liquid (BTL) fuels and to undertake a technical, economic and environmental assessment. The common interface was a synthesis gas (H2+CO) which was produced from ligno-cellulosic biomass (wood, straw, energy plants and black liquor) via gasification. BTL concepts studied in the project were:
Black liquor entrained flow gasification for dimethyl ether synthesis, BLEF-DME. Chemrec.
Centralized entrained flow gasification for diesel synthesis, cEF-D. Umwelt- und Energietechnik Freiberg (UET), CHOREN Industries
Circulating fluidized bed gasification for diesel synthesis, CFB-D. Clausthaler Umwelttechnik Institut (CUTEC).
Circulating fluidized bed gasification for ethanol synthesis, CFB-E. Abengoa Bioenergy (Abengoa) & AICIA (Asociación de investigación y cooperación industrial de Andalucía).
Decentralised pyrolysis and central entrained flow gasification for diesel synthesis, dEF-D. Forschungszentrum Karlsruhe (FZK).
Entrained flow gasification for ethanol synthesis, EF-E. Abengoa Bioenerggy (Abengoa) & AICIA (Asociación de investigación y cooperación industrial de Andalucía).
Internal circulation fluidized bed gasification for diesel synthesis, ICFB-D. Technische Universität Wien (TUV), Repotec (RPT) & Biomassekraftwerk Güssing (BKG).
Generally the challenge in BtL technology is to modify well developed synthesis technologies like FT- or DME synthesis to be based on biomass. Present processes utilise synthesis gas which is produced from coal or natural gas. The precise challenge of biomass in terms of gasification is its structured, inhomogeneous nature and the high share of accompanying compounds. Hence, the research focussed mainly on the mechanism to introduce the biomass into the gasifier and on the removal of ash and various impurities from the synthesis gas.
Overall, the study concluded that there are multiple opportunities for BTL production in Europe, but that the best regions for first industrial scale BTL plants of the Chemrec type would be West Poland and Sweden.
For the future, it can be expected that highly efficient ligno-cellulosic biomass utilization systems like in Sweden and Finland will be established all over Europe, leading to diminishing differences in biomass supply costs of 3.5 to 4 €/GJ, This will increase the potential number of suitable locations for BtL production in 2020. However, site-specific studies of biomass availability and respective prices are required as well as studies for integration possibilities to e.g. refineries, pulp & paper mills and heating grids prior to any decision on the BTL plant locations.
Besides the recommendations for the first large-scale commercial BtL plants, RENEW identified other key areas where more R&D work needs to be done:
Local studies on biomass production, supply and respective costs.
Studies on the socio-economic effects of new biomass plantations.
Technology-related R&D work in terms of integration of BtL plants to refineries, pulp&paper mills, heating grids.
For less mature production concepts, research on gas conditioning and—as long as FT-catalysts are not commercially available—on synthesis.
BTL specification. The project also developed a recommendation for a future Fischer-Tropsch BTL fuel specification.
The fuels’ properties were classified either as parameters or characteristics. Parameters are fuel properties, which are directly influenced by the production process. E.g. the high content of normal paraffins is a characteristic of the FT process. Characteristics are properties which are an indirect consequence of the parameters. The high cetane number is a consequence of the high normal paraffin content. Some of the characteristics may be improved by additives.
|Draft specifications for BTL fuels. Click to enlarge.|
Renewable Fuels for Advanced Powertrains Final Report