Biomass global estimate

There are two types of data necessary to obtain accurate global estimates of vegetation carbon pools or biomass. First, it is important to have accurate data on the areal extent of major ecosystems. Matthews (29) found that calculations of global biomass were significantly influenced by the land cover data set used. Second, there must be accurate estimates of biomass density for terrestrial ecosystems. There is a wide range of estimates published for the same ecosystem, each derived by different methods (29), and none having statistical reliability (7). 

Petroleum, coal and natural gas are globally limited, and they will be exhausted in the future. On the other hand, biomass resources are renewable and can be produced continuously by photosynthesis. Therefore, biomass resources can be utilized as renewable energy without disturbing carbon balance of ecosystem on the earth. The amount of biomass is estimated about 830 billion tons as carbon. It accounts for the total amount of petroleum, coal and natural gas, and 80 times as much as the amount of the energy consumed in a year in the world. 

Table 3 Global estimates of annual amounts of biomass burning and of the resulting release of carbon to the atmosphere.

There are no global estimates of the production and biomass of aquatic phanerogams, but rough estimates of estuarine primary production (in which submerged phanerogams mainly share) do exist 1 X 10 t C yr" (Woodwell et al., 1978), which is 4% of the total global marine primary production. 

Quantitative estimates of the global distribution and biomass of zooplankton are extremely difficult. The routine net sampling techniques probably fail to collect a considerable proportion of the microzooplankton which could itself equal the biomass of the net zooplankton (Pomeroy, 1974). Zooplankton biomass data were summarised for various oceanic and coastal waters by Raymont (1966). It is striking that Mullin (1969) in his survey of the production of zooplankton in the ocean does not himself venture any global estimate. 

Menzies et al. (1973) have reviewed global estimates of macrozoobenthos biomass expressed in terms of wet weight, which are recalculated by Whittle (1977) as dry weight and organic carbon (Table V). The biomass value of... 

Menzies et al. (1973) of 0.5 X 10 t C is about three times lower than the global estimate of Bogorov (in Moiseev, 1969) 1.67 X 10 t C. Table V supports the statement that there is an inverse relationship between benthic biomass and depth, but the often stated view that there is a direct relationship between surface productivity and benthic biomass holds primarily at depths above the thermocline (Menzies et al., 1973). 

Table 2.18 Global estimates of NPP and biomass (standing crop) A Townsend et al. (2007), B Nieder and Bebin (2008).

Table 2.43 Global estimates of burned biomass and released carbon into the atmosphere.

Ito, A. and J. E. Penner (2004) Global estimates of biomass burning emissions based on satellite imagery for the year 2000. Journal of Geophysical Research 109, D14S05, doi 10.1029/2003JD004423. 

Distribution of Carbon. Estimation of the amount of biomass carbon on the earth s surface is a problem in global statistical analysis. Although reasonable projections have been made using the best available data, maps, surveys, and a host of assumptions, the vaHdity of the results is impossible to support with hard data because of the nature of the problem. Nevertheless, such analyses must be performed to assess the feasibiHty of biomass energy systems and the gross types of biomass available for energy appHcations. 

Several studies, based on models, examined the effects of land-use change on the global carbon cycle and conclude that there is a net release of carbon due to land clearing. However, the results and conclusions of these studies are based on assumed sizes of vegetation carbon pools which are inputs to the models. For example, Melillo et al. 24) concluded that boreal and temperate deciduous forests of the northern hemisphere are net sources of atmospheric carbon. Their analysis used values for carbon density derived by Whittaker and Likens 19) from work by Rodin and Bazilevich (27). Rodin and Bazilevich extrapolated results of small, unrelated studies in Europe and the USSR to estimate total biomass of Eurasian boreal and temperate deciduous forests. Their estimates have since been extrapolated to forests worldwide and are used often today. 

Most vegetation maps are derived from a variety of sources using different methods and made at different times. This can lead to an overlap between adjacent areas of interest, the exclusion of some areas, and the improper extrapolation of carbon densities, thus resulting in inaccurate estimates of reservoir size. We found that the biomass density of the southern North American boreal forest was over 2.5 times larger than the biomass density of the northern part of the boreal forest (55). Past estimates of boreal forest biomass density extrapolated southern biomass density values to the entire boreal forest, which in part accounts for the large overestimation (7). It is important that a consistent method be developed to map vegetation globally. 

Most estimates of global vegetation biomass densities are extrapolations from studies never intended to represent large areas (e.g. 79, 36) or they were derived from questionnaires sent to botanists (57). These estimates are still used commonly in the examination and modeling of the global carbon cycle. Some of the earliest estimates were made when almost no quantitative data were available and the data or the estimates were largely speculative. Other estimates are... 

Global atmospheric CO2 has increased by approximately 25% since the industrial revolution (circa 1850). The primary source is the combustion of fossil fuels (72). However, recent estimates indicate that biomass burning may comprise 40% of... 

The Renewables-Intensive Global Energy Scenario (RIGES) predicts a primary energy potential from biomass resources for Western Europe to be 14160 PJ/year by 2025 and 14 170 PJ/year by 2050 (Johansson et al., 1993). Thereby the biomass potential comprises resources from wood, energy crops, agricultural residues and industrial biomass residues. The estimates are based on the biomass production at that time in combination with assumptions of future growth rates. 

The potential of biomass to make a large contribution towards replacing conventional fuels is constrained by land availability and competition with other end-use sectors. In particular, the potential for oil seeds to generate FAME is limited. Generally, yields of biofuels from purpose-grown crops depend on the species, soil type and climate.22 At a global level, it is estimated that biofuels could substitute up... 

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