Wood energy
Wood energy corresponds to the use of wood for energy purposes, mainly to produce heat and electricity. The wood used for energy production can come from Silviculture, Agroforestry, hedges, etc.
It is a renewable energy despite the significant emissions it releases into the atmosphere.
Local renewable energy resource
Wood energy is the leading source of renewable energy in France (about 33% of renewable energy production). Indeed, it is an energy whose use does not result in the irreversible disappearance of the resource, and which regenerates within a human lifetime.
Wood produced in agroforestry is transported and then stored in local supply structures. It is then sold and used by communities, individuals, or companies.
Actors in the wood energy sector
- The wood producers[1] : farmers who produce the fuel, who cut down the trees and chip them using the chippers of the departmental Cuma.
- The departmental Cuma : they provide the chippers and support farmers in managing trees and hedges.
- The local supply structures : they buy wood from producers to resell it to consumers.
Forms of wood energy
Wood energy can take different forms [2]:
- The log : intended for fireplace fires and coming from hardwood species (oak, beech, etc.), softwood (birch, plane tree, etc.) or conifers (spruce, pine, etc.).
- The forest chip : which corresponds to wood that has been shredded.
- The pellet : it is a cylinder made from compacted wood sawdust.
Benefits
- Additional income[3] : the purchase price is about €15/hour of logging work in 2020.
- Sustainable hedgerow management : through the Sustainable Hedgerow Management Plan (PGDH), which allows planning maintenance work and enhancing hedges.
Wood energy production
Wood production
There are different ways to produce wood energy:
- Hedges or agroforestry : branches or trunks from pruning can be used for wood energy
- Coppices [4]: bundles of fine branches, logs with large diameter branches or chipping to make chips
- Silviculture : the stems that hinder the development of better trees are cut and valorized as wood energy
However, be careful to choose a local supply chain for wood sales to ensure good profitability.
Calorific value
The calorific value (measured in kWh/kg) corresponds to the amount of heat released during the combustion of one kilogram of wood. The higher it is, the more the wood will produce energy during combustion.
| Moisture | Hardwoods (kWh/kg) | Conifers (kWh/kg) |
|---|---|---|
| 0 | 5.1 | 5.3 |
| 25 | 3.7 | 3.8 |
| 50 | 2.2 | 2.3 |
| 75 | 0.8 | 0.8 |
The calorific value is similar between species, but varies greatly with moisture ; dry wood has a much higher calorific value than wet wood. Wood can be dried naturally (duration of 6 months to 1 year) or by artificial drying, faster but more expensive.
However, note that the calorific value does not take into account wood density; some species therefore have a higher calorific value at equal volume: this is the case of beech (€60/t of logs in 2015)[5], oak (€30/t in 2015), and hornbeam.
Sources
- ↑ Hedge'nergy Normandy, 2018 : Agricultural wood energy sector in Normandy http://www.haienergienormandie.cuma.fr/content/filiere-bois-energie-agricole-en-normandie
- ↑ ONF, 2018 : What is wood energy? https://www.onf-energie-bois.com/qu-est-ce-que-le-bois-energie/
- ↑ Mayenne wood energy, 2020 : Local wood of agricultural origin. https://www.mayenne-bois-energie.fr/les-origines-du-bois/bois-local-dorigine-agricole/
- ↑ Coppices: Uses of coppices https://trognes.fr/usages/
- ↑ Mixed Syndicate Pays de Lourdes et des Vallées des Gaves, 2015: Sustainable mobilization plan of forest resources of Pays de Lourdes et des Vallées des Gaves https://www.valleesdesgaves.com/components/comp_ckfinder/ckfinder/userfiles/files/d%C3%83%C2%A9veloppement%20%C3%83%C2%A9co/Phase%203%20Annexe%201a%20Fiche%20Filiere%20Bois%20energie.pdf
