Techno-economic assessments are important for identifying more promising process routes, and for identifying major areas of uncertainty where further R&D would have a significant impact on technical feasibility and commercial viability. The technical and economic viability of liquid fuels production that include catalytic processing has been investigated by a number of researchers and research groups as summarised in Tables 6.10 and 6.11.

Many individual cost estimates and economic evaluations have been carried out which are difficult to compare as the bases are rarely published in sufficient detail for valid comparisons to be made. The IEA Bioenergy Agreement has also been sponsoring process, technical and economic assessments for over 10 years, beginning with the conceptual design of a biomass test liquefaction plant (167) and progressing through direct liquefaction, flash pyrolysis and upgrading (117, 159, 168 — 170) to the current examination of electricity generation systems. Some dedicated computer packages have been developed by Aston University which include process simulations and a common approach to cost estimation to provide a consistent comparison of alternative routes (176 — 181). This enables the user to examine alternative technologies, process conditions, routes, feedstocks and products.

Typical estimates of transport fuel costs from direct liquefaction processes are summarised in Figure 4 (296). In both cases the current pre-tax cost of fossil fuel derived products is shown. The conclusions agree well with those carried out by the IEA Bioenergy Agreement over the last few years (117).

For gasification derived synfuels, Table 13 summarises the ratio of costs of biomass derived liquid fuels to conventionally produced fuels as an example of analysis of results from cost estimates (177).

Basis: Capacity 1000 t/d d. a.f. feed,

Feedstock costed at 50 ECU/dry t (US$40/dry t)

The overall conclusion from all these assessments is that transport fuels cannot currently be produced economically from purpose grown biomass or energy crops without some economic support. For site specific wastes, there are opportunities for fuel gas and liquid fuels for heat and electricity production. The short term prognosis is, however, very hopeful as the more promising products only require modest improvements in process performance or cost to be competitive with fossil fuels (159). Catalyst development is likely to play a key role in meeting these objectives.

2.5 CONCLUSIONS

The use of catalysts to improve either the yield or quality of gas and liquid fuels from thermochemical biomass conversion processes is still in its infancy. While there is extensive fundamental work underway, considerably more research is necessary to explore the wide range of conventional and unconventional catalysts. Of particular potential significance is the integration of catalytic processes into the thermal conversion process to improve efficiency and reduce costs.

For fast pyrolysis processes, there are considerable opportunities for production of conventional and unconventional fuels for both electricity generation and fuel and chemical synthesis. The R&D requirements here are for more fundamental research into catalyst selection and evaluation for higher product specificity and/or higher yields of marketable products, since the products from these processes are much more complex than from gasification. Chemicals are always of greater potential interest due to their higher value compared to fuels. Here also catalysis has a significant role to play, and is more likely to justify more intensive R&D. Integrated fuel and chemicals production is the most likely scenario.