[LUM#19] Forever Wood
From the domestication of fire in prehistoric times to the wood-pellet stoves that are now a common sight in our living rooms, wood remains an indispensable source of energy. It is, by its very nature, an energy source with a promising future, thanks in particular to research aimed at optimizing its use to better preserve both the resource and the environment.
One-third of the world’s population—2.4 billion people worldwide—relies on wood as their primary energy source, whether for cooking, heating, or even generating electricity. “Wood is the primary energy resource in the Global South, ” explains Bruno Clair, a CNRS researcher at the Montpellier Laboratory of Mechanics and Civil Engineering (LMGC)* and co-director of the Master’s program in Wood Sciences
But its use is widespread in both hemispheres, as evidenced by the 88.5 million people who rely on wood fuels as their primary source of heat, mainly in North America and Europe. “In fact, the University of Montpellier’s buildings are themselves heated by a wood-fired boiler, ” the researcher notes.
Tight market
And wood is on the rise everywhere: “It’s the leading source of renewable energy in France, ahead of solar and wind power. And in a tight market where gas and oil prices are skyrocketing, more and more people want to heat their homes with wood, ” notes Bruno Clair.
How can we preserve our timber resources in the face of this ever-growing demand? “By its very nature, wood is a renewable energy source because when a tree is cut down, another one grows in its place if the forest is managed sustainably, ” explains the researcher. In fact, France’s forest area is expanding, having grown from 9 million hectares in 1840 to 14 million in 1985 and 17 million hectares in 2021.
The situation is even more concerning on a global scale: according to the Food and Agriculture Organization of the United Nations, global forest loss since 1990 is estimated at 420 million hectares. “But this deforestation has little to do with using wood as an energy source or building material! For the most part, these trees are cut down to create new farmland, ” explains Bruno Clair. “It’s important to understand that a significant portion of the population in Africa farms to produce its own food, and since these food crops are more productive on recently deforested plots, this remains the most widespread practice even today,” adds François Pinta, a researcher at the BioWooEB (Biomass, Wood, Energy, and Bioproducts) laboratory**.
Best option
According to the LMGC researcher, wood heating is often the best option. “There is a balance between the CO₂ emissions generated by burning wood and the amount of CO₂ absorbed as trees grow, but we must also take into account the energy required to harvest and transport the wood. “For wood energy to be truly sustainable, it must be a final-stage utilization after the highest-quality wood has been used for applications where carbon will be stored over the long term, such as in construction, ” Bruno Clair clarifies.
While wood heating has an excellent carbon footprint, this does not mean it is pollution-free. “When combustion is carried out properly, wood can be considered to emit virtually no greenhouse gases, but for that to happen, the combustion process must take place under the right conditions,” explain François Pinta and Kevin Candelier, who also teach in the Master’s program in Wood Science, without mincing words.
Cleaning up exhaust fumes
Optimizing these processes is precisely one of the areas being explored by the two researchers and their colleagues at the BioWooEB laboratory. “ “Certain wood-to-energy processes, such as wood pyrolysis, release a wide variety of gaseous molecules—not only carbon dioxide, but also carbon monoxide, fine particles, and other volatile compounds, such as acetic acid, for example,” explains Kevin Candelier . “We analyze the composition of these fumes produced under different conditions to better understand them and explore ways to utilize them.”
This is because some of the chemical compounds emitted can be highly polluting to the environment and toxic to human health. “Our research aims to reduce pollution associated with the use of wood as an energy source, particularly by focusing on reducing emissions from the charcoal production process, ” explains François Pinta.
And while optimizing wood-energy processes helps protect the environment and public health, the benefits of this research extend far beyond that. “If the fuel is used properly, we reduce the amount of wood needed, which in turn lowers costs and eases the pressure on natural resources; the research creates a true virtuous cycle of improvement, ” concludes François Pinta.
A safe gas
When it comes to generating energy from biomass, researchers at BioWooEB are exploring every possible avenue. Biomass can thus be subjected to various conversion processes: combustion, carbonization, torrefaction, flash pyrolysis, and even gasification. “Gasification is a thermochemical process that involves breaking down a solid carbonaceous fuel under the effect of heat in the presence of a gaseous reactant, ” explains François Pinta. The end result is a gas that can be used as fuel. Its nickname? Syngas, short for synthetic gas. Once purified, it can be used to power an internal combustion engine to generate electricity or in an industrial burner to produce heat. In both cases, the goal is to effectively replace fossil-based gas and drastically reduce greenhouse gas emissions. “Syngas is very useful when you need to control the heat, for example, to fire clay bricks at very high temperatures. Our team is currently monitoring new applications being implemented by companies in France and Occitanie, ” explains the researcher.
Listen to
* LMGC (UM, CNRS)
**BioWooEB (CIRAD)
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