Bioenergy production from forest harvest residues can reduce the carbon stock of forests and as such the process may negate greenhouse gas savings obtained by using bioenergy, according to research published in the journal GCB Bioenergy.
As harvesting from forest residues increases it decreases the amount of forest litter – the detritus shed from plants – that exists in a forest and adds nutrients and carbon into the soil, according to Sustainability of forest bioenergy in Europe: land-use-related carbon dioxide emissions of forest harvest residues.
The study used a model that assumed a sustainable amount of forest litter was being used across Europe from 2016 to 2100. The researchers found that the forest harvest residue removal reduced the carbon stocks of litter and soil on average by 3 percent over the period in the modeling area. The reduction was small compared to the size of the carbon stocks but “significant” in comparison to the amount of energy produced from the litter, the study says.
As a result, bioenergy production from forest harvest residues would need to be continued for 60–to-80 years to achieve a 60 percent carbon dioxide emission reduction in heat and power generation compared to the fossil fuels it replaces in most European countries – a threshold crucial for such fuel to pass a mooted EU sustainable fuel regulation, according to the Finnish Environment Institute.
The EU is planning to extend its specific sustainability criteria based on greenhouse gas emissions for biofuels to renewable energy produced from solid biomass. These criteria are expected to require a 60 percent reduction in greenhouse gas emissions compared to an alternative fossil fuel, the FEI says.
The gap between the emission reductions and the EU requirement could decrease interest in this “considerable source” of renewable energy in many European countries, the FEI says.
In November, the US Department of Agriculture awarded almost $10 million to a consortium of academic, industry and government organizations led by Colorado State University to research using insect-killed trees in the Rockies as a sustainable feedstock for biofuel.
The project began work at the end of 2013, assessing beetle-kill feedstock availability and how to harvest and process the material in an environmentally and economically sustainable manner, while producing high quality renewable fuels and biochar.
Picture credit: Pine forest floor via Shutterstock.