Questions and answers on biomass

On 8 May 2020, PBL Netherlands Environmental Assessment Agency published a study into the availability and applications of sustainable biomass. It triggered a large number of responses from engaged citizens, civil society organisations, scientists and other stakeholders. In this document, PBL provides answers to several frequently recurring questions that are being asked in the debate following the publication of our study.

What is true about claims that 'whole trees' end up in power plants?

Let's start with a few figures (in Dutch) : in 2018, over 60% of our renewable electricity and heat was produced from biomass. To do this, 1.65 million tons of woody biomass were used. The largest part (1.15 million tons) consisted of wood chips and wood clippings, and a small part (0.17 million tonnes) was made up of wood pellets for auxiliary firing and co-firing in power plants. The rest (0.33 million tons) included matter such as sewage sludge and paper sludge. More than three quarters of all biomass (1.27 million tons) came from the Netherlands and the rest was sourced from Europe, particularly from Germany and Belgium. Around 37% of the biomass came from forest, nature and landscape management and from the management and execution of structural projects, infrastructural projects and activities related to urban green areas. The other 63% consisted mainly of waste wood from construction.

As for the 37% mentioned above, most of the branches and pieces of top wood that become available are left behind in the forest to improve biodiversity and soil fertility. Roundwood harvested in the Netherlands goes to saw mills to be processed into planks. However, part of the harvest consists of 'whole trees' which are not suitable for sawnwood, because they are too crooked, too thin or rotten, but they can still be used for other applications, such as wood pellets. Therefore, strictly speaking, it is possible that in 2018 on occasion 'whole trees' from Dutch or other European forests were burned in power plants, but these were certainly not of sawnwood quality.

In the coming years, the use of wood pellets will increase to about 3.5 million tons per year, mainly due to auxiliary firing and co-firing of biomass in power plants. Most of these pellets will be imported from the Baltic states and other foreign countries. However, wood pellets are generally not the main forestry product, representing only a small part of total output. The primary impulse for forestry, most certainly in the USA and Europe, almost always comes from the production of high quality sawnwood, which is worth up to ten times more than wood pellets. For this reason, pellets are not produced from precious 'whole trees' of sawnwood quality. In terms of volume, the most important output of forestry is pulpwood and other types of small roundwood. This is the part of the harvest mentioned above (including treetops which can be up to ten metres long), which is not suitable for sawnwood, but can be used for paper or as a raw material for fibreboard and wood pellets. Technically, this can also involve cases of 'whole trees' being processed into wood pellets, but, once again, these are not of sawnwood quality. However, for economic reasons, forestry companies will direct their efforts towards processing as much wood as possible into sawnwood, and therefore not transform good quality trees into much less valuable wood pellets.

Why has PBL asserted that there is anecdotal evidence of abusive practices in wood pellet production?

In the past few decades, the forestry sector, particularly that of Europe and North America, has shown that it is possible for increasing wood production to go hand in hand with rising levels of carbon sequestration and the expansion of forest cover. All wood pellets used in the Netherlands must fulfil stringent sustainability criteria. Nevertheless, several NGOs such as NRDC and Dogwood Alliance claim that natural forests in the southeast of the USA are being felled for pellet production, particularly the deciduous bottomland forests that exist at the transition between marshland and drier areas. It should be noted that the harvest from this type of forest is only a very small part of the total harvest in that region, but according to NGOs, there are plans to increase the number of pellet plants in these areas, which are vulnerable and insufficiently protected. In Europe, the British NGO BiofuelWatch has made the claim that forests in Estonia are being over-exploited for pellet production, and that felling activity is taking place in Natura 2000 areas. But these claims do not constitute proof of systematic and structural felling of forests for the production of wood pellets.

PBL does, however, believe that more careful investigations should be conducted, preferably by an independent party, into the abusive practices identified by NGOs, such as the felling of natural forests and the pelletisation of 'whole trees'. The question is to uncover to what degree such practices are actually taking place in a structural way, or are threatening to become more frequent due to the expansion of pellet production in vulnerable and insufficiently protected areas. If investigations show that those practices are taking place on a structural basis, they must be combated. After all, no upright party has an interest in such practices. They contravene European and Dutch legislation, and the certification schemes used by the producers themselves.

Is it true that PBL recommends that the Netherlands should continue to import large quantities of wood pellets under the proviso that they are made from trees of pulp quality?

In a recent publication by Tim Searchinger and three other authors, it is claimed that this would be the most important recommendation in the PBL biomass report. This is not correct. The report limits itself to describing current practice in forestry and where wood pellets will be sourced from in the coming years (see above). The report states, for example, that the primary production in forestry includes not only sawnwood, but also pulpwood, which is used to make paper, cardboard, fibreboard and also wood pellets.

In addition, the report covers much more than just wood pellets and also deals with the availability and the applications of all types of biomass flows from agriculture and forestry. The report is the result of an extensive stakeholder process which involved verifying arguments and points of view against the literature. This led to the drawing up of tentative conclusions and recommendations as a contribution to a more nuanced social and political debate and as input for the advisory report by the Social and Economic Council of the Netherlands (SER) on the sustainability framework for biomass. With regard to natural forests and forestry activity, the report concludes, among other things, that:

  • biodiversity loss stemming from large-scale production of biomass is a real risk (see below for additional details);
  • an important task to be taken on is determining how European and Dutch forests can be more properly managed and protected, and how forestry can be coupled to multiple functions;
  • forestry can go hand in hand with net CO2 sequestration, but active policies are required to maintain levels of sequestration.

Isn't PBL far too optimistic about the carbon debt of woody biomass? After all, when a tree is felled, it takes years for a newly planted tree to store the same amount of CO2 as the felled tree releases.

In its study, PBL does not make a choice for one or another method of calculating carbon debt. The report maps out the different ways there are to calculate carbon debt, payback time and carbon parity. Carbon debt refers to the amount of CO2 that is released as forest resources are harvested and utilised. Payback time is the time it takes for the growth of vegetation to capture those CO2 emissions minus the avoided CO2 emissions due to decreased consumption of fossil fuels. Carbon parity occurs at the moment all the CO2 is captured that would have been captured by the forest, had it not been harvested.

To be able to calculate these quantities properly, there must first be agreement on the counterfactual: what would have happened in the forest and during energy generation if the biomass in question had not been harvested and used. In that light, it appears to be virtually impossible to base policies on a concrete maximum payback time. PBL therefore concludes, for the sake of caution, that restrictions may be imposed to minimise the risk of carbon debt becoming (too) high or payback times becoming (too) long. An example is the restrictions on permitted flows for a specific end use. The European Renewable Energy Directive (RED II), which has recently been tightened on the issue of sustainability of woody biomass, in part thanks to input from the Netherlands, also has many stipulations which reduce the risk of excessive carbon debt and payback times.

Some people argue that it is better to use natural gas than biomass in the transition to sustainable forms of energy. How does PBL look upon this question?

The biomass study does not make any comparisons between biomass and other forms of energy, but PBL makes calculations, for the Netherlands and for the world as a whole, for many future scenarios in which biomass and natural gas both play a role. In these efforts, PBL does not take a principled position on how much 'better' natural gas is than biomass, or vice versa, but it examines an optimal mix of sustainable energy sources to achieve the goal, set by the government, of a carbon-neutral economy in 2050. Natural gas does not play a role in this final vision, unless its CO2 emissions are captured and stored underground (Carbon Capture and Storage, CCS). Along the path towards 2050, natural gas will certainly have a role to play, whether or not in combination with CCS, not least because natural gas produces low levels of fossil CO2 emissions per unit of energy, compared with sources such as coal.

A point that was also brought up in the stakeholder process was that biomass emits more CO2 per unit of energy than coal, and much more than natural gas, and therefore is bad for the climate. While the first part of this assertion is factually correct, this does not automatically lead to the conclusion that biomass is therefore worse than the alternatives.

To be able to assess if biomass brings CO2 gains relative to fossil energy carriers, it is necessary to not only consider the CO2 emissions at the chimney or the exhaust pipe, but to also include in the calculations the effects over a previously set time span of the entire production chain (cultivation, harvesting, processing, conversion, transport) and the counterfactual — that is, what would have occurred if the biomass had not been harvested for energy or feedstock (see comment above). The comparison should also take into account the entire production chain of coal or gas, including methane that is released during extraction and transport.

Do biomass power plants lead to poorer air quality? Are the requirements for air quality being violated?

Provided they meet the emission requirements, larger modern biomass power plants can cause a slight or only very slight deterioration in air quality compared to gas-fired plants. Of course, if the number of biomass power plants continues to rise, there could be a negative effect on air quality.

It is important to not only consider large power plants, but also boilers, stoves and fireplaces in dwellings. In its report, PBL states that modern biomass boilers, pellet stoves and modern wood-burning stoves (DIN+) with heat outputs up to 5 MW have a relatively small effect on air quality compared to older conventional wood-burning stoves and fireplaces. Moreover, the toxicity of the particulate matter from a properly functioning boiler or pellet stove is much lower than that from an older wood-burning stove. It is possible to achieve a significant reduction in emissions, and improvement in efficiency, by replacing older stoves and fireplaces with modern ones. In addition, as announced in the Dutch Climate Agreement, the emission standards for smaller boilers will be made stricter as of 2022, a move that is supported by the sector.

It is important that concerns and warning signs about failure to comply with emission requirements are taken seriously and that maximum transparency is exercised. It would be beneficial if an independent party such as the National Institute for Public Health and the Environment (RIVM) carried out further research into these issues, particularly into the effect of use of smaller boilers by businesses and in the built environment.

Does PBL take the impact of biomass on biodiversity seriously?

Biodiversity loss caused by large-scale production of biomass for energy and materials is a serious concern in the biomass debate. This mainly involves direct and indirect changes in land use and the question of the degree to which biomass production can be compatible with the conservation of nature and biodiversity. It is clear that biodiversity loss is significant if the expansion of biomass cultivation takes place in natural ecosystems. On the other hand, intensification of agriculture can free up agricultural land for the benefit of biomass cultivation, so that it does not need to be practiced at the expense of natural ecosystems. This is a way to avoid or limit biodiversity loss. Much of the widely available literature shows that there may be negative impacts on biodiversity stemming from cultivation of biomass crops and large-scale harvesting of wood for energy purposes and other applications. The global assessment report on biodiversity and ecosystems services and the IPCC report on land use point out the risk that large-scale cultivation of biomass could result in monocultures replacing natural forest, agriculture or subsistence farming, and thereby produce negative effects on biodiversity and other ecosystem services, such as food security and water availability.

Another important question is the degree to which the remedy may be worse than the disease. That is, to what extent does biodiversity loss due to the use of biomass outweigh biodiversity gains from reduced climate change? The answer to this general question is not clear-cut, and depends greatly on how the biomass is produced and on the changes in land use that it brings about. The long-term effects of climate change on biodiversity are also highly uncertain. Given this complexity, it is pertinent to state the importance of analysing and closely monitoring the impacts of increased biomass use on land use changes and biodiversity. As policies are elaborated in further detail, the trade-off between climate change and biodiversity conservation must be considered carefully. This has already partly been tied into Dutch policies, because biomass that is used and subsidised in the Netherlands under the SDE++ scheme needs to fulfil five biodiversity requirements that have to  guarantee that biodiversity is conserved and, where possible, enhanced.