Biomass plantations

Still another possibiUty is a marine biomass plantation such as that envisaged for giant brown kelp grown off the California coast and conversion of the kelp to methane in a system similar to that shown in Figure 19. The location of the SNG plant could be either on a floating platform near the kelp growth area or located on shore, in which case the biomass or fuel transport requirements would be different. 

For the total integrated biomass production—conversion system, the arithmetic product of the efficiencies of biomass production and conversion is the efficiency of the overall system. An overall conversion efficiency near 45% would thus be produced by integrating the biomass plantation illustrated in Table 30 with a conversion process that operated at an overall efficiency of 50%. Every operation in the series is thus equally important. 

In 2002, a prominent collection of scientists wrote, Biomass plantations can produce carbon-neutral fuels for power plants or transportation, but photosynthesis has too low a power density ( 6 W/m2) for biofuels to contribute significantly to climate stabilization. These researchers find the scale of our growing energy demand so daunting that they conclude that none of today s current options for renewable energy or energy efficiency are up to the... 

According to Blix (1997), so-called renewable sources total a little more than 2% of world commercial energy. The bulk of that total comes from geothermal installations, new wind and solar technologies, and biomass plantations. This share could increase, but only to a limited extent. The estimate made by the World Energy Council for new renewable supplies in the medium term is that with adequate support, the share of new renewable energy supplies, currently only 2%, could reach 5% to 8% of increased world energy supply by 2020. 

Let us consider the effect of C02 reduction in power generation with biomass produced by sustainable biomass plantation. Table 4 summarizes the results. The C02 emission in plantation is a value estimated according to the assun tion described previously. Surely the construction of a power plant is necessary for biomass power generation, and the energy required in the building of a power plant and the accompanying C02 emission should be calculated. 

Basic stoichiometry teaches that for every 100 kg of polyolefin (polyethylene, PE polypropylene, PP) manufactured, a net 314 kg of CO2 is released into the environment at its end of life (100 kg of PE contains 85.7 kg carbon and upon combustion will yield (44/12) x 85.7 = 314 kg of CO2). Similarly, PET contains 62.5% carbon, which results in 229 kg of CO2 released into the environment at end of life. However, if the carbon in the polyester or polyolefin comes from biomass feedstock, the net release of CO2 into the environment is zero, because the CO2 released is sequestered in a short time period by the next crop or biomass plantation (Eigure 14.2). Thus, the fundamental value proposition for bio-based plastics arises from this intrinsic zero material carbon footprint and not necessarily from the process carbon footprint, which may be equal to or slightly better than current processes. 

Several studies estimate the potential of available virgin and waste biomass as energy resources (Table 4) (10). In Table 4, the projected potential of the recoverable materials is about 25% of the theoretical maximum woody biomass is about 70% of the total recoverable potential. These estimates of biomass energy potential are based on existing, sustainable biomass production and do not iaclude new, dedicated biomass energy plantations that might be developed. 

Gross heating value of biomass or methane. Conversion of biomass or methane to another biofuel requires that the process conversion efficiency be used to reduce the potential energy available. These figures do not include additional biomass from dedicated energy plantations. 

Hansen EA (1993) Soil carbon sequestration beneath hybrid poplar plantations in the north central United States. Biomass Bioenergy 6 431-436... 

A large portion of the overall GHG emissions from the supply of biomass based fuels results from the formation of N20 in fertilised soils. To calculate N20 emissions, the European Soil Model is typically applied, developed by the European Joint Research Centre in Ispra (Italy). The data in Table 7.5 represent the average N20 emissions from the plantation of rapeseed in EU25 (R. Edwards, personal communication, Joint Research Centre (JRC), Ispra, August 2005). 

Large-scale biomass production will come at a considerable cost to the society. We have already given an order of magnitude estimate for wood plantations. When biomass raw material is processed that competes with the food chain, as vegetable oils and sugars, the situation is even worse. For instance Smil [4] mentions that if the US vehicles were to run solely on corn derived ethanol the country would have to plant corn on an area 20% larger than is currently cropland . 

Figure 1.3 A growth curve showing the increase of biomass in forestry plantation over a 100-year period.

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