Sustainability of biomass

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Within the right boundary conditions, biomass can play an important role in the energy transition

The public debate on the use of biomass for energy applications is heated, especially when it concerns co-firing wood in coal-fired power stations.

A subject of much discussion recently has been whether or not the use of biomass for energy applications (also referred to as bio-energy) can contribute in a sustainable way to the energy transition. Proponents argue that bio-energy across the entire chain can greatly reduce CO2 emissions, and that this is possible without negative side-effects for the environment and food supply. They also argue that without biomass it will be difficult to realize an energy supply with negative greenhouse gas (GHG) emissions. Net negative CO2 emissions will be necessary to keep the temperature rise within agreed upon limits in the longer term, and for that purpose capturing and storing the CO2 that is released during biomass combustion (bio-energy with carbon capture and storage, or BECCS) is a possibility. Opponents, on the other hand, criticize the application of biomass, in particular wood co-firing in coal-fired power stations. They argue that wood co-firing results in nature  being lost and that it creates unwanted competition with agriculture. Furthermore, they argue that co-firing is being used as an excuse to sustain coal-fired power plants and that on balance CO2 is released by the burning of biomass. In order to form an opinion on this, it is good to delve deeper into the different types of biomass that are used and their sustainability requirements.

In addition to wood, many other types of biomass are used as an energy source.

There is a wide range of types of biomass that are used for energy; it does not just concern wood as the discussion seems to suggest. With wood, it is often a matter of residual flows from forestry, of which the main products are beams, planks and raw material for the paper industry. Forestry does not concern nature but can actually be seen as a form of agriculture. Other woody biomass comes from pruning and thinning wood from parks and nature reserves in, for example, the Netherlands. Vegetable and animal residual streams from the food industry, the biogenic part of household waste, animal manure and sewage treatment sludge are also sources of biomass. Types of biomass are not limited to these. For example in the future, seaweed from the North Sea could make a substantial contribution.  

The relative shares in the end use of energy for different applications in the Netherlands can be seen in the graph below. The total share of biomass in final energy use in the Netherlands in 2018 was 4.5%. The total contribution of all forms of renewable energy in 2018, including wind and sun, among other things, amounted to 7.4% of the final consumption. Biofuels were therefore responsible for more than half of the Netherlands’ renewable energy. The table shows that the import of wood pellets had fallen to zero in 2015. In recent years, the use of biomass in coal-fired power stations has declined following the expiry of earlier subsidy schemes, which were halted. From 2016 there was again a subsidy in the scheme up to a maximum of 25 PJ of produced energy, and this has been used. That is why an increase in the use of biomass in coal-fired power stations is expected again in the coming years.

Figure 1. Share of biofuels in the final energy consumption in the Netherlands (Source: CBS)

 

Table 1. Solid biomass for energy, 2013-2017 (Source: CBS)
Biomass can be considered climate neutral if the CO₂ that is emitted into the atmosphere from its combustion is the same as the CO₂ that is removed from growing the biomass.

Everyone agrees with the undesirability of using certain types of biomass for energy applications, certainly since the publication of the IPBES Global Assessment Report (https://www.ipbes.net/global-assessment-report-biodiversity-ecosystem-services ). Jungle logging to make way for palm oil production (for producing liquid biofuel; the EU has decided to phase out palm oil imports) or sugar cane (for the production of the bio-ethanol motor fuel) is very harmful to biodiversity. Jungle logging is a term used in relation to forms of (rain)forest degradation and destruction. It also affects GHG emissions as a direct consequence of deforestation. The climate neutrality of other crops is less clear-cut. Although more CO2 is released during the combustion of biomass than during the combustion of coal for the same amount of heat production, CO2 is captured during the growth of biomass. This leads to a relatively short cycle of carbon. Whether this reasoning makes sense depends on whether the growth of biomass keeps pace with consumption. This is only possible when applying the right boundary requirements.

 

There are strict requirements for biomass that is used as energy.

Part of the discussion concerns the desirability of importing wood pellets, particularly in view of the risk of shortage arising if more and more countries would like to import wood pellets. Due to its small surface area and high population density and relatively energy-intensive industry, the Netherlands has limited opportunities to generate sufficient renewable energy to cover its energy demand. There are not many countries that need as much import of biomass as the Netherlands, so the availability of biomass exported by other countries combined with the share needed for use in the Netherlands could be less problematic than expected. The Netherlands has also set strict requirements for subsidies for the use of biomass for co-firing. European requirements for biomass have been set in EU directives on the promotion of renewable energy. As can be seen in the table, a limited proportion of the total biomass used in the Netherlands  consists of imported wood.

Advantages of biomass use include possibilities for application with intermittent renewable energy, that it is carbon neutral and can contribute to a bio-based economy.

A frequently mentioned disadvantage of wind and solar energy is that they are not always available to meet demand. This does not apply to the other two renewable energy forms with great potential in the Netherlands, namely geothermal energy and biomass. Biomass can be used for CO2-free dispatchable power. Another interesting aspect of the use of biomass is that the CO2 released during incineration can be captured and stored. This counts as negative CO2 emissions (which is justified in the case of carbon neutral biomass, where the same amount is grown as is burnt). Setting up a market for sustainable biomass for energy use can go hand-in-hand with setting up a circular economy based on biological materials that can help make petrochemicals more sustainable. The trick is to combine the benefits of using biomass with the preservation of nature and sufficient agricultural land. Taking into account the aforementioned preconditions, this should be possible.

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