Last Updated on December 17, 2021 by admin
Wood is used as fuel, for construction, but also for paper and packaging, textiles and more. Research is being conducted to find new application areas constantly. Politicians and timber industry representatives cheer for the new “bioeconomy” that is to succeed the fossil-based one, but do forest resources suffice to replace fossil fuels and oil-based products? We should also consider whether forest resources are used economically in the context of the ecosystem boundaries. To start of with, we investigate how Swedish forest resources are being used today.
Growth and Harvest
|Living tree biomass in the Swedish forest, outside protected areas. Source: Riksskogstaxeringen.|
- Tree trunks increase their volume by approximately 128 million m3 per annum (2011-2015) corresponding to 97 tons of dry biomass1 if we include stumps and branches (source: Swedish Forest statistics).
- Total above-ground biomass plus stump increases by approximately 16.3 million tonnes annually (Figure).
- The amount of dead wood in forests increases by 4.8 million tonnes each year by natural causes but also due to forestry.
- Approximately 76 million tonnes (97-16.3-4.8), corresponding to about 75% of the growth is cut down2 but a significant amount is left in the forest (for instance branches and stumps). The amount that is left varies a lot between cuts (see Myth 1 for an image of a “vacuum-cleaned” cut).
- 16 million m3 forest is turned into construction wood (number from 2013) corresponding to 6.4 million tonnes of dry biomass3. Average value over a longer period is 4.3 million tonnes (Source: Swedish EPA).
- The remainder of the annual production, 69 million tonnes of dry biomass, is used for short-lived products and bioenergy.
What impact do Swedish forests and forestry have on the carbon balance? 1 ton of wood yields 1.83 tonnes of CO2 when combusted, (and the inverse in photosynthesis). Thus, the Swedish forests sequester approximately 178 million tonnes of CO2 each year.
We assume (somewhat optimistically) that construction wood is taken out of the carbon cycle for good, but that in contrast (somewhat pessimistically) all paper and pulp products disappear into the atmosphere rapidly. Permanent sequestration is 33 million tonnes of CO2 in living trees, 9 million tonnes of CO2 in dead wood and 8 million tons CO2 in wood products. The remainder, 125 million tonnes of CO2 per year is emitted through biofuels and paper and pulp products (or because it is left in the forest). This implies the emission due to forestry and forestry products is almost two times larger than that of the other sectors of the Swedish economy combined. These emissions are compensated for by the annual growth but it is doubtful whether harvesting almost all growth is the best use of resources from a climate perspective. The Swedish Environmental Protection Agency, that register greenhouse gas emissions for Sweden, do not included the emissions due to forestry and forestry products at all which makes it difficult for interested parties to get this information. To further complicate matters, Sweden imports (!) a significant amount of biofuel and household garbage for combustion in district heating systems, while simultaneously exporting a large amount of forestry products. Part of the exported products may end up on landfills and therefore will not contribute to CO2 emissions immediately.
The pulp and paper industry, together with wood product industry use over half of all the energy in Swedish industry, (81.5 of 155.2 TWh). According to the Swedish Energy Agency about 23% of energy in the whole country was based on biofuels (130 out of 555 TWh). The forestry sector contributes 90% of these biofuels. Other biofuels derive from household trash and oils of vegetable as well as animal origin. The total energy contribution due to the forestry sector therefore was 117 TWh, leading to a net energy production of 35.5 TWh (or 6.5% of the total energy in the country). This yield an EROI (Energy Return on Investment) of 1.43 which is very low compared to what would be possible if the forest were used just for producing pellets, in which case an EROI of 20 could be achieved. In this light the forestry sector is an inefficient energy source.
- A stem volume of 1 m3 corresponds to a dry biomass weight of about 0.756 tonnes (source: Swedish Forest statistics).
- This number is higher than what is reported by the Swedish Forest Agency, namely 91 million m3 timber (2015, preliminary), corresponding to 69 million tonnes dry biomass.
- The density of construction wood is approximately 400 kg/m3.