Traditional Biomass is a generic term referring to a variety of more or less direct products of photosynthesis: firewood, agricultural residues and dung. While it has been used by mankind without interruption for the last 400 000 years, traditional biomass is often forgotten in energy statistics because it is not a commercial commodity. However, in the turn of this century, it supplies about 10% of the world primary energy consumption: more than 1.5 billion people – one fourth of the world population – must rely on it alone for cooking and some kind of heating.

But the rudimentary combustion of traditional biomass in open fireplaces can be very polluting, with a severe impact on human health. Furthermore, overexploitation of fuelwood leads to deforestation which contributes significantly to global warming.

All along its history, Man has employed available vegetal and animal resources for non-food uses: clothing, defence, heat, cooking, agriculture, housing, furniture and so on. Starting from the mid 19th century, fossil fuels and their derivatives replaced biomass for many such uses. Firewood remains nevertheless the staple resource for heat and cooking in many countries where it is available and among those who cannot afford to buy fossil fuels, despite the risks of biomass depletion.

The combustion of traditional biomass supplies roughly 1 Gtoe per year, i.e. about 10% of the world primary energy consumption, but locally, in large regions of Africa for instance, it supplies more than 90% of the domestic energy consumption. In France, endowed with many well groomed forests, firewood produces 9.4 Mtoe/y i.e. 3.4% of the primary energy consumption. This makes France number one within the European Union (EU 15) for firewood consumption, but far behind Finland, Sweden and Austria on a per capita basis.

On should notice that the efficiency of photosynthesis is very low, but solar energy is so plentiful...

A slightly more optimistic view comes from Marc Cantegril:
“Under our latitudes, 1 hectare of forest receives annually 3500 MWh of solar energy and produces 10 tons of dry biomass, i;e; slightly under 50 MWh” Efficiency = 1.4%

 

People believe that biomass is automatically renewable, but it depends widely on the rate of exploitation. Mankind’s development came along with massive clearing of the primeval forests for firewood supply but mostly for agriculture. Nowadays, deforestation proceeds on a large scale in Latin America, Africa and Indonesia but Europe and – more recently – Asia are reforesting. The global balance remains widely negative, even though one can detect a slowing down in the process:
Between 1990 and 2000, net deforestation amounted to 89 000 km2 per year, from 2000 to 2005, the rate went down to 73 000 km2 per year (still about 200 km2 per day!). Deforestation has caused the desertification of entire regions like Sahel

 

In rural areas of the Third World, two and a half billion people use firewood, charcoal, dung and agricultural residues for cooking, which constitutes often 90% of their domestic energy consumption.

In addition to deforestation, consequences to public health are disastrous: around 1.3 million people, mostly women and children, die prematurely every year from air pollution in houses, a pollution caused by biomass combustion. It is more than malaria (1,2M) and hardly less than tuberculosis (1,6M) ! Furthermore, the time spent collecting firewood and agricultural residues is not spent in education or earning money.

 

Burning wood just sends back to the atmosphere the carbon dioxide that biomass had absorbed from the atmosphere through photosynthesis. As far as greenhouse effect is concerned, and as long as the total mass remains constant, biomass is globally neutral. But, because of deforestation, the mass is not constant and the clearing of forests causes every year the emission in the atmosphere of 2 billion tons of carbon, which is quite significant. Furthermore, when biomass rots under water, it produces methane which is 25 times more potent a greenhouse gas than CO2.