Biorefineries are often seen as analogous to oil refineries, but in reality they will probably have a quite different scope as they will produce a narrower range of liquid fuels but a much broader range of chemicals and solid products.
Further, whereas oil is taken from the ground and then all taken to oil refineries for processing, the logistics of moving ligno-cellulose from its point of growth to the bio refinery will be much more complicated.
To this must be added difficulties such as competition for land use and conservation issues.
This paper will discuss how these factors might be addresses and how integration might be achieved at all levels in the chain from forests to finished products.
Keywords Biorefining, Bio processing, Process Integration
There is increasing interest in the topic of biorefineries, that is facilities analogous to oil refineries but which convert biomass into a range of fuels and chemicals.
In many ways, the concept of the biorefinery is rather restrictive. As will be shown below, the real issue is the use of biomass as a starting material for fuels in particular and chemicals to a lesser extent. In many cases, the fuel needs can be provided by means that do not require the complexity of a refinery with its implications of multiple products. Notwithstanding any issues relating to the nature of the processing of biomass employed , the large scale use of biomass as a raw material will require careful integration at several levels:
- Integration with other land use. In particular compatibility with food production and with conservation values.
- Integr ation of logistics. The volumes of raw materials and/or finished products to be transported will be as great or greater than that of the fossil fuel that is replaced. Also the materials will generally have their own special characteristics that will affect how they are handled and transported.
- Process integration within the biorefinery to maximise production efficiency
Before considering specifics of integration, it is necessary to consider the reasons for developing biorefineries and the scale at which they would need to operate to make a significant contribution to global energy supplies . The main reasons given for considering the manufacture of biofuels are:
- Depletion of reserves and increasing cost of certain fossil fuels. The class of fuels with the smallest reserve to consumption ratio is liquids (crude oil etc). Thus if this is the objective, the biorefinery would be concerned with making liquid fuels and petrochemical substitutes. According to the EIA, the oil reserves to production ratio is 25 40 years 1 and reserves are still increasing 2 . There is a tendency for more oil to be discovered (e.g. the large finds in Brazil and Argentina in late 2 007 3 ) so there is no short term risk of oil not being available. This gives time for the development of biorefineries to be done in an orderly manner.
- Reduction of green house gas emissions. To meet this objective, it would be desirable to concentrate on replacement of coal, and this could be achieved by the production of solid fuels from biomass . The most re cent estimate of reserves to production for coal is 143 years 2 and this ratio is falling, but mainly because some reserves are no longer considered economic. There is comparatively little exploration for coal and there are probably very large deposits whi ch have not yet been located or evaluated. Therefore reduction in green house emissions is the main reason for considering the replacement of coal.
- To exploit available biological wastes. This is of course an opportunistic scenario and the product to be made will depend on the particular economic situation.
Thus the focus is most likely to be for solid and liquid fuels. There may be some local demand for gaseous fuels, but the technology for this is already fairly well established.