It is true that biomass from plants, trees and other organic matter has the ability to regrow after being cut and harvested. However, whereas solar, wind or wave power can’t be depleted or over-exploited by human actions, biomass resources can. For example, over-exploitation could mean that forests are being cut to the extent that it harms their capability to produce other ecosystem services and to maintain biodiversity or that soil is cultivated so intensively its capacity to grow plants lowers.
The sustainability of biomass use for energy requires much more careful consideration than the use of non-depletable sources. In Europe, as well as globally, our ecological footprint is already bigger than the global biocapacity, which refers to the capacity of ecosystems to produce useful biological materials (vital for humankind) and to absorb waste and emissions generated by humans. This means that already today our use of biomass resources is not on a sustainable basis and there’s too much pressure on land and forests from different human needs.
It is widely assumed that biomass combustion would be “carbon neutral” and produce no greenhouse gas emissions. It is nevertheless obvious that when burning biomass, in other words organic matter, carbon is released from exhaust pipes or chimneys. So how come bioenergy is not supposed to be producing carbon emissions?
The first basic error in the carbon accounting of bioenergy is the failure to account for the production and uses generated by biomass and land if not used for bioenergy. Reduction of greenhouse gas is usually compared to baseline level of emissions (in international policies the emission level of 1990 is an often used baseline.) With plants and trees, the baseline situation is that they keep on growing and absorbing carbon. However, when the biomass is harvested and burned for energy instead, the carbon benefit of continued growth will be lost.
Alternatively, the baseline situation can be that the biomass or land is used for other human needs e.g. wood is used for construction and land for food production. If the biomass or land is used for energy instead, construction material and food will need to be produced elsewhere. To evaluate the carbon balance of bioenergy use correctly, the baseline or the so-called counterfactual scenario needs to be taken into account.
For example, if land is used to produce crops for energy rather than food, the food typically needs to be grown somewhere else as the food demand remains or even rises following an increasing world population. If this leads to additional land clearing for agriculture, carbon will be released from the cleared ecosystems, such as forests (phenomenon also called indirect land use change (ILUC). In the case of forests and other slow growing biomass, the carbon neutrality assumption also falsely suggests that all the biomass harvested will grow back with time. In the case of an old-growth forest replaced by a commercial forest, this is not usually the case. There is also a time lag in the re-absorption of carbon released in combustion since the regrowth of trees can take several decades (phenomenon known as carbon debt).
All of these impacts and their emissions are ignored in the current energy policies which mostly wrongly assign bioenergy a zero-carbon factor. If the use of bioenergy replaces the use of fossil fuels, more carbon will be left stored underground in the form of fossil fuels. However, this benefit comes at the expense of less carbon stored by plants and soils. Bioenergy reduces CO2 emissions only to the extent the first effect is larger than the second.
International standards for the accounting of greenhouse gas emissions have been developed for the purposes of the international climate convention (United Nations Framework – Convention on Climate Change). The UNFCCC is supported by the International Panel on Climate Change, a scientific intergovernmental body which also develops guidance on greenhouse gas accounting.
Under accounting for the international climate convention, countries separately report their emissions from energy use and from land-use. For example, if a hectare of forest is cleared and the wood is used for bioenergy, the carbon lost from the forest is counted as a land-use emission. To avoid double-counting, the rules therefore allow countries to ignore the same carbon when it is released from a chimney. This accounting principle does not assume that biomass is carbon neutral, but rather that emissions can be reported in the land-use sector. As the IPCC has clearly stated, it “does not automatically consider biomass used for energy as “carbon neutral”, even if the biomass is thought to be produced sustainably”.
Europe is already using significant amounts of biomass for energy. It’s estimated that roughly one half of the wood harvested in Europe is actually used for energy, either directly or as part of an industrial process where the main output is material such as paper or pulp (Mantau, 2010). Wood from forests and land to grow crops are the most crucial and needed resources when it comes to producing biomass. Several studies (examples here and here) already indicate that the potential in Europe to increase forest loggings or to cultivate more land is very limited.
The EU’s planned demand for wood by 2030, assuming that current growing use of wood for energy continues, will probably outstrip the amount that can be safely and sustainably extracted from European forests. This means that Europe will rely more on imported wood or see degradation of its own forests. The amount of land that can be used for energy crops without displacing food or damaging valuable habitats has been estimated to be a maximum of 1.3 million hectares. In 2010, land roughly three times more than that was already used for biofuels production in the EU.
There are several ways in which bioenergy differs from other renewable energy sources such wind, solar or wave power. Firstly, even though renewable, biomass resources can be depleted and over-exploited by human actiona and their capacity to renew hampered. Other renewable energy sources are hardly affected by humans.
Secondly, energy production from biomass is based on its combustion, like in the case of fossil fuels such as coal or oil. This means that biomass burning directly creates heat unlike other renewables. It also means that much of the energy infrastructure needed for bioenergy is similar to fossil fuels. With a few modifications, biomass can often be burned in the same power plants as coal or processed into fuels that can be used in the same tanks as gasoline in transportation. Reliance on biomass therefore is not a strong driver for the changes needed for an ‘energy transition’ or changes in infrastructure such as decentralised energy production, electrification of transport or closure of inefficient old power plants. In other words, biomass co-firing with coal allows the fossil fuel-based business model to continue.
For example, as a result of the EU’s efforts to increase the use of bioenergy, more power plants have started to co-fire biomass with coal in coal power plants. This results in very low efficient energy production and can prolong the life of old coal power plants that otherwise would have reached the end of their life.
Finally, since bioenergy always requires combustion, there are several other emissions apart from CO2 related to it, just like with coal or other fossil fuels. Biomass combustion typically produces a lot of small particulate matter (PM) emissions which can affect the heart and lungs and cause serious health effects.
Energy companies often declare that they only use biomass resources not needed by other industries, particularly in the case of wood. They claim that they only use the leftover residues.
The paper and pulp and wood working sectors have already clearly recognised the energy sector as a competitor over the same wood resources, which already indicates that the energy sector isn’t only using leftovers of others. The competition has grown due to the renewable energy policies that have resulted in subsidies for the use of wood for energy, without any limitations or constraints.
There’s also direct evidence, particularly from the Southern US which is currently the biggest importer of wood for energy use in Europe, that whole trees are harvested for energy and that harvesting for energy has been carried out in biodiversity rich forests.
In an effort to move away from fossil fuel use towards more sustainable, renewable energy sources and a low carbon future, bioenergy can have a role to play. Practically all scenarios and models of energy use in the next decades – assuming we take the fight against climate change seriously – assume that a certain amount of energy will be produced with bioenergy. This applies both to scenarios of international institutions such as the International Energy Agency (IEA) and of environmental NGOs such as Greenpeace or WWF.
The share of bioenergy and its role in the energy sector nevertheless varies significantly between different scenarios, meaning there are many alternatives to choose from. Scenarios advocating for high levels of bioenergy use tend to focus more on the energy sector only, with less consideration for impacts on ecosystems and raw material markets, availability of land and with less precaution in general.
Other scenarios show that moving to a renewable energy future is also possible if we limit bioenergy use to the sustainable availability of waste and residue-based resources and to a very limited availability of land for energy crops, with bigger overall environmental benefits from biomass use. Such scenarios usually highlight the use of biomass in the heating sector and for specific uses in transportation where alternatives to combustion engines are harder to find. They also assume increased efforts in the efficiency of biomass burning.
Increased use of bioenergy today is mostly driven by policies that aim to tackle climate change and reduce greenhouse gas emissions. With these policy aims, comparison of the emission levels of bioenergy and fossil fuel energy should be a priority.
Several studies have already shown that if the full carbon emission impacts (including those resulting from indirect impacts and carbon stock changes in ecosystems due to bioenergy use) are considered, bioenergy does not always reduce emissions compared to fossil fuels. This is particularly the case with biodiesels made from soy, palm oil or rapeseed that require land to be grown and can lead to indirect land use change (e.g. clearing of forests for agricultural land elsewhere) and with wood pellets if they have, for example, lead to increasing harvests in the forests and are used to produce electricity only.