Why sustainable biomass actually is a good idea
Martin Junginger is Professor of Bio-Based Economy (UU), Gert-Jan Nabuurs is Professor of European Forest Resources (Wageningen) and involved in IPCC reports, André Faaij is University Professor of Energy System Analysis (RUG) and Director of Science at ECN part of TNO, Johan Sanders is emeritus professor of Biobased Commodity Chemicals (Wageningen) and Patricia Osseweijer is Professor of Biotechnology & Society (TU Delft)
This article (ref 1) was originally published on Thursday 22 November 2018 in the Dutch newspaper NRC as a response to the opinion-article of Martijn Katan cum suis (ref 2).
In their article Biomass firing is a disaster for the climate (ref 2) Martijn Katan and colleagues argues that it is absurd to use wood for the large-scale generation of bio-energy. However, their arguments are not correct.
Bio-energy from wood is, in principle, climate neutral. When trees grow they absorb CO2; if they then die and decay, the majority of this CO2 is released, and the balance is zero – this is called the short carbon cycle. If mankind burns wood to generate energy, this same CO2 is released. In other words, it is true that this CO2would also have been released in nature. By burning biomass rather than fossil fuels, we avoid emissions from fossil-derived CO2. As such, it is irrelevant that a little more CO2 is released during the combustion of biomass per unit of energy than burning coal: the emissions produced by the combustion of coal are a net addition of CO2 to the atmosphere, CO2 from biomass is not.
Katan et al. believe that it will typically take 50-100 years before biomass generates climate benefits, due to the slow growth of new forests. But certainly for the southeast of the US this timescale is considerably shorter – between 0 and 50 years (ref 3). In fact, when using sawdust or wood thinnings (trees cut down to give other trees more space to grow) this timescale can be 0 to 10 years (ref 4). Within these timeframes, bioenergy can make a meaningful contribution to combating climate change. Of course, shipping biomass requires energy and therefore emissions, but these are limited as a result of tough reduction requirements (ref 5) : for example, from 2021 onwards, energy production supply chains will need to show at least 70 percent lower life-cycle GHG emissions than those from fossil fuels (this is already achieved today). From 2026, 80 percent reduction will be required.
How much wood?
Elsewhere, Katan and his colleagues write that we burn more fossil fuels every day than we can compensate for with biomass growth in 1000 years. This is simply not true: when taking into account the growth of algae, trees and plants, about four thousand times more CO2 is recorded than the value used by the authors. And do we need to cut down forests on a massive scale? There are no concrete policy plans anywhere in the world to convert hundreds of coal-fired plants to biomass. The Dutch Energy Agreement of 2013 shows that approximately 3.5 million tons of biomass is needed per year (the subsidies for ‘co-firing’ of biomass will stop after 2024). Is that a lot? In the southeast of the US, where most wood pellets for industrial use come from, a production value of 3 million tons of wood pellets equals 3 percent of the total wood harvest, equivalent to 0.1 percent of the existing forest. What is more, for many decades now, there has been a net increase in standing stock – for every tonne of harvested wood in this region; about 1.65 tonnes has been added, as documented by the USDA Forest Service.
Moreover, this supply chain capitalises on the fact that there is a huge surplus of cheaply available, wood (ref 6). But given the currently low prices for wood, forest owners will think twice after harvesting whether they will plant trees again, or rather higher value crops such as cotton or corn. As such, demand for wood can be directly responsible for reforestation and productive forest management. A market for forest residues and wood thinning acts as a stimulus, rejuvenating the forest and thus maintaining the carbon sequestration capacity of the forest. Combining the use of wood for construction, furniture, paper and energy is a climate-friendly way to utilise sustainably managed forests.
Strict sustainability requirements
The authors also state that a greater demand for certified timber encourages fraud. On the contrary: it is precisely because of the fact that the Netherlands (ref 7) and the EU (ref 5) put up strict sustainability demands that pellet producers are forced to provide insights about their feedstock sourcing. For example, Enviva, the largest pellet producer in the world – after heavy criticism in the past on the wood used by them – has set up a track & trace system (ref 8) with which the origin of their wood can be traced down to a given hectare; a fairly unique level of transparency in the forestry sector.
Relatedly, the authors claim that less stringent sustainability requirements for pellets produced from sawdust would lead to an increase in sawdust production from saw logs. In light of the enormous price difference between sawdust and wood pellets (a factor of 7 without a subsidy for wood pellets, an estimated factor of 4 with subsidies), we think this is extremely unlikely. Sawdust is a waste product of the wood processing industry and is often cited by scientists and environmental organizations as a prominent example of sustainable biomass. Why should this feedstock now suddenly be regarded as unsustainable?
Finally, they confuse life cycle analysis and accounting rules from the IPCC for the measurement of CO2 emissions per country. Yes, in the country of combustion, the emission of biomass is not counted, but that is because the timber harvest already counts as an emission. All countries (including the US and Russia) report annually to the UN convention on their entire forests; both the stock increase (i.e. carbon sequestration) and the emissions from harvesting trees. It is not correct to state that countries do not report this. The IPCC deliberately chose to count the emissions at the time of wood harvesting. If one were to count the combustion of wood as an emission, then the harvest could not be counted as an emission. And exactly that would be a license for unsustainable deforestation. It is true that the US does not report obligations related to the Kyoto-protocol (reporting to what extent emission targets have been reached), because they do not (or no longer) endorse the Kyoto and Paris treaties. This is a possible loophole in terms of achieving goals; however, by burning wood from the US in the Netherlands, no emissions will disappear from the UN accounting system.
Sustainable biomass use on a large scale is also indispensable to achieve our climate targets, according to the latest ‘1.5 degree’ IPCC report. This is possible in combination with good forest management, better farming methods and, for example, reforestation of marginal and degraded land. Building a biomass market is therefore essential to steadily increasing the availability of sustainable biomass, which will then supply food; energy and materials; and yield environmental benefits through more efficient agriculture and associated benefits to soil health.