This is carried out with a hydrogen-providing solvent in the presence of catalysts (Co-Mo, Ni-Mo) at high temperatures and pressures.

Catalytic cracking

Oxygen can be removed from bio-oils by catalytic decomposition in the presence of cata­lysts. Although this is cheaper than hydrodeoxgenation, it suffers from high coking.

Steam reformation for hydrogen production

The production of hydrogen from the reforming of bio-oils has been investigated and shows some promise.

Emulsification

Bio-oils have been combined directly with diesel to form a fuel, but a surfactant is required as the bio-oil is immiscible with diesel. Chiaramonti et al. (2003) showed that the optimum level of bio-oil addition was between 0.5 and 2%, but above these values the viscosity was too high. Light fractions of bio-oil have been obtained by centrifugation and used at 10-30% in emulsions with diesel (Ikura et al., 2003). The viscosity of the mixture was lower than the bio-oil and the cetane number was reduced by 0.4 for each 10% addition. In both cases, the long-term effect on the engine needs to be determined. The cost of bio-oil based on 2000 prices has been determined (Brammer et al., 2006) at a value of €32/MWth which was not competi­tive with conventional energy sources.

Application Product

Heat

Electricity

Combined heat and power (CHP) Electricity

Combined heat and power (CHP) Electricity

Combined heat and power (CHP) Combined heat and power Emulsion use for transport

Some of the applications of bio-oil as a heating fuel, diesel fuel and gas turbine fuel are listed in Table 7.4 (Brammer et al., 2006). In six European countries, one application of bio-oil was competitive due to low biomass costs.