Helmut Haberl from the Institute of Social Ecology, at Klagenfurt University in Vienna, who does interesting work on human appropriation of ecological production, has a paper The global socioeconomic energetic metabolism as a sustainability problem in a special issue of Energy 31 (2006) 87–99. In the paper, Haberl some interesting figures that estimate total human energy use over the last 1,000,000 years and since the widespread use of fossil fuel.

Haberl writes:

conventional energy balances and statistics only account for energy carriers used in technical energy conversions as, for example, combustion in furnaces, steam engines or internal combustion engines, production and use of electricity or district heat, etc. That is, energy statistics neglect, among others, biomass used as a raw material as well as all sorts of human or animal nutrition. These are very important energy conversions in hunter-gatherer and agricultural societies, but are still significant even in industrial society.

Global socioeconomic energy metabolism in the last 1 Million years. The increase in socioeconomic energy flows encompasses six orders of magnitude, from 0.001 Exajoule per year (EJ/yr) about 1 million years ago to nearly 1,000 EJ/yr today.

According to this rough estimate biomass accounts for more than 50% of all global socioeconomic energy input—compared to about only 9%, according to conventional energy statistics

The paper concludes by providing perspective on humanity’s energy future, raising concerns about the use of biomass fuels and pointing out the value of using energy more efficiently.

The calculations presented in this paper indicate that it would be flawed to regard biomass as an abundant resource that should be used instead of fossil fuels to the maximum possible extent—as is sometimes the case, at least in Europe. This is so because substituting biomass for a significant proportion of the fossil fuels currently used could lead to a surge in HANPP and cause the destruction of many valuable ecosystems around the globe. If biomass should contribute (to some extent) to a sustainable energy scenario, this would be possible within a strategy of ‘cascade utilization’ of biomass; that is, through a strategy of re-use, recycling, use of biomass by-products or residues, etc.—in order words, by increasing the efficiency of biomass use. In contrast to technologies that use biomass grown only for energy production such a strategy would focus on energy production from biomass that has before been used for other socioeconomic purposes and does, therefore, not contribute to HANPP.

This indicates that strategies aiming at a more sustainable development should focus on energy conservation and renewable energy options such as wind power, direct use of solar energy, etc. that require much less area than biomass energy.