Forest residues to reuse

Limbs, sawdust and treetops are some of the components so called forest residues. Unwanted by products from wood processing industries and forest harvesting have in my opinion a large potential in the field of bioenergy.

The largest biomass potential on the earth calculated per unit area are from forests, which covers approximately one third of the earth´s surface (Biomassa, 2020). Woody biomass in general is today the most common used biomass, and using the forest as material and energy source is not something new. But the increasing problem with deforestation is critical and contribute to loss of biodiversity and decreased carbon uptake capacity (FAO & UNEP, 2020).

I think that we must become better at taking care of the unwanted by products that arise along the process chain in a more sustainable way. Felling in the form of thinning is something that is needed to maintain the forests and ensure that all other vegetation thrives and can be used as biomass in conversion to energy (FAO & UNEP, 2020). There is a potential to increase harvest of biomass without increasing the harvest area by using forest residues. In Figure 1 below the energy use from residues 2015 and an estimation of potential energy use from residues are shown. In the high case the estimation is based on a sustainable enhanced residue collection, without compromising ecosystems (IRENA, 2019).  

Figure 1. Actual and enhanced residue collection in Sweden 2015.

Forest residues is categorized as a second generation biomass as well as an second generation biofuel (Cheng, 2017). The residues can either be processed towards an end-product as biofuel in forms of biodiesel or electricity/heat generation as pellets or biogas. The advantages of using forest residues in energy conversion are the use and optimization of residues along process chains that operate regardless and the potential in supply is large. Slash, stumps and treetops are used instead of rotten in the forest. However, forest residues have a few disadvantages that is important to keep in mind (Cambero, Sowlati, Marinescu & Röser, 2015). The residues have a low energy density and heating values, there is high costs in the supply chain mostly regarding transport. Mixed characteristics in the forest residues is also a disadvantage when it comes to the technical conversion process in energy recovery (Belyakov, 2020).

Biomassa.(2020, September 17). In Nationalencyklopedin. Retrieved September 17, 2020, fromång/biomassa 

Belyakov, N. (2020). Sustainable Power Generation – Current Status, Future Challenges, and Perspectives. (1. ed.) Elsevier Inc. DOI:10.1016/c2018-0-01215-3.

Cheng, Jay (2017). North Carolina State University: Biomass to renewable energy processes (2. ed) Taylor & Francis Inc.

Cambero, C., Sowlati, T., Marinescu, M., & Röser, D. (2015).
Strategic optimization of forest residues to bioenergy and biofuel supply chain. INTERNATIONAL JOURNAL OF ENERGY RESEARCH Int. J. Energy Res. Wiley Online Library, 39, 439–452. DOI: 10.1002/er.3233

FAO and UNEP. (2020). The State of the World’s Forests 2020. Forests, biodiversity and people. Rome.

IRENA (2019), Bioenergy from boreal forests: Swedish approach to sustainable wood use, International Renewable Energy Agency, Abu Dhabi.

2 Comments on “Forest residues to reuse

  1. Hi, thank you for a great post. I agree with you that there is a lot of potential in the forests. From an economical perspective, is it worth to make use of the residues from forestry with the equipment and technology available today? I was also thinking that there might be an environmental (CO2 binding) benefit of preserving the residues in the forest, or will it just stop other vegetation from binding CO2?


  2. This is a very interesting blog post that presents the value of forest residue as a 2nd generation biofuel. I fully agree, we need to make use of the residue from the forest, and limit the consumption of healthy living trees to sustainable levels. We need as many trees as possible in our forest to optimize the CO2 uptake. The change from a fossil based energy system to one depending on biomass is great, but we need to be careful that we harvest our forest resources sustainably, allowing for optimal CO2 uptake, otherwise the benefits of burning wood instead of coal might be less obvious. How much residue do we generate from the Swedish forests per year, and how much of the biomass combusted is from residue, and how much is from trees cut down, just for the purpose of being fed into a boiler?


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