As an avid fan of the “heavier” music genres, it is difficult to resist alluding to a 1980s album title track from Australian hard rock legends, AC/DC with all the associative puns and witticisms that spring to mind when pondering over carbon dioxide removal (CDR) and negative emission technologies (NETs). In short, NETs remove carbon dioxide from the atmosphere and transition it from the fast carbon cycle to the slow carbon cycle, also known as the "rock cycle", indefinitely.
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Rapidly reducing anthropogenic greenhouse gas (GHG) emissions is unequivocally a top priority. Bioenergy systems operate within the fast biogenic carbon cycle.
This implies a fundamentally different influence on atmospheric carbon dioxide (CO2) concentrations over time compared to fossil fuel emissions which transfer carbon out of the slow rock cycle into the atmosphere, causing the net accumulation of atmospheric CO2.
The faster we reign in on fossil fuel emissions, the better, and the fewer NETs will be required to remove this excess.
However, there is no getting away from having to deploy NETs, even if all fossil fuel emissions ceased overnight. Natural Climate Solutions (NCS) like afforestation, reforestation, and rewilding are one such considered NETs.
While they can deliver negative emissions with biological storage at scale quickly, at low cost, and could provide extensive co-benefits such as biodiversity, NCS as the standalone NET, as the “leave forests as forests” folks would like, is insufficient.
Why? Because there is a limit to how much carbon an existing forest or a planted one left alone to “rewild” will absorb before reaching carbon saturation, that is the rate of carbon uptake from growth will no longer be larger than the rate of carbon release from mortality.
Some new research findings from a soon-to-be-published study called “CO2-Balance of Selected Forest Management Scenarios in Europe” and presented by Dr Hubert Röder during the Central European Biomass Conference (CEBC) in Graz, Austria suggests that in all four climate change scenarios applied by the study, the total carbon stock of unmanaged forests in Europe will become saturated by 2050-2060. In contrast, the total carbon stock of managed forests and harvested woody biomass in Europe will further increase in all studied scenarios.
Carbon-centered forestry and material use of wood and other biomass is another NET. Yet, although part of the fast biogenic carbon cycle, bioenergy should not be assumed to be carbon-neutral purely by default.
AsUSIPA points out, a precondition to deliver emissions reductions through the use of woody biomass requires procuring it without depleting the carbon stocks of source forests and this is why there are sustainability criteria and certification systems in place.
According to Dr Röder, a holistic approach is needed to assess the full GHG effects of forest management, including the storage of bio-based carbon and the substitution of fossil fuels.
Forests managed according to sustainable forest management principles and practices can make really significant contributions to climate change mitigation by replacing GHG-intensive materials and fossil fuels and by storing carbon in the forest and in long-lived forest products.
One such GHG-intensive material is steel and substituting a share of fossil coal and coke with biocoal and biocarbon goes a long way as a recent MUSIC workshop on the topic revealed.
Illustrating the benefit of a holistic approach, an IEA Bioenergy Task 48 paper “Alternative sustainable carbon sources as substitutes for metallurgical coal” notes that if 10 percent of the world’s gasoline demand were replaced with ethanol produced from lignocellulosic sources, approximately 20 percent of fossil coke consumption could be replaced by renewable lignin.
And if the ethanol is produced using carbon capture and storage (CCS) for its process emissions – asseveral producers in the United States are planning– the benefits become greater.
Bioenergy lends itself exceptionally well to integration with NETs, for instance, bioenergy with carbon capture and storage (BECCS), and pyrogenic carbon capture and storage (PyCCS).
These open a myriad of opportunities for both existing- and new biomass heat- and/or power plants across almost the entire range of plant sizes. In the latter, biochar is the storage format and features in this issue with numerous inspirational and concrete examples such asEnergieWerk Ilg in Dornbirn, Austriashowcased on the cover.
AsIEA Bioenergy put it“rather than choosing between different options, a complementary approach is needed—tapping into biomass for renewable carbon, moving further towards a circular economy to maximize the use of a limited resource, and helping mitigate climate change/reduce GHG emissions. Biomass use has to be targeted at where it creates the highest value, not only economically, but also in terms of reducing net carbon emissions, while also respecting other Sustainable development Goals (SDGs).”
Black is the new green, bioenergy is back in black.
