Marine Cropping
A possible solution to large-scale biomass production in an environmentally acceptable manner could be plantations of salt-water organisms in desert areas,
|
Table 4-18 |
|
|
Typical Properties of Bio-Oil |
|
|
Property |
Typical Values |
|
Moisture content |
20-30% |
|
pH |
2-3 |
|
Density |
1200 kg/m3 |
|
c |
56 wt% |
|
H |
7wt% |
|
О |
37 wt% |
|
N |
0.1 wt% |
|
Ash |
0-0.2 wt% |
|
Viscosity (40°C, |
|
|
20% H20) |
40-100cP |
|
Particulates |
< 0.3-1 wt% |
|
Heating value |
16-18 MJ/kg |
|
Source: Meier 2002 |
which are located close to the sea. The advantage of this approach is that problems associated with fertilizers, irrigation, and so on are virtually absent. Moreover, aquatic crops are probably easier and safer to harvest.
Such farms should of course be located where there is a lot of sunshine. These are also locations where solar power is available and hence hydrogen can also be generated by electrolysis of water. This in turn enables the conversion of the biomass into true hydrocarbons for transport fuels or organic chemicals to be carried out close to the biomass production, thus grossly diminishing the transport problems. In addition, the option of first converting the biomass into bio-oil by flash pyrolysis could have advantages.
For countries in the Middle East and North Africa, which are now heavily dependent on crude oil exports for their income, this would suggest that they could continue to supply the world with hydrocarbon fuels. But other countries, such as Australia, also offer opportunities for such schemes.
Before considering biomass as a fuel it must be stressed that its primary function in a renewables-based world is that it is the only source of concentrated carbon. This aspect is often overlooked. It is important to remember, however, because when biomass is our only make-up source for concentrated carbon, it must be made possible to convert biomass into a material that can be an intermediate for all organic chemicals and transport fuels. The solution is then to have a process available that can convert biomass into synthesis gas efficiently. This can provide an alternative to ethylene as the main source of organic bulk chemicals as well as of Fischer-Tropsch products. This provides an opportunity for gasification (van der Burgt 1997).
