When it comes to renewables, woody biomass (the energy industry term for fuel created from wood) has recently gained a bad reputation.
Despite being considered a cheap and flexible way to supply renewable energy, burning wood for biomass power isn’t carbon-neutral and could be contributing to global warming.
According to a new report by Chatham House, it can release more greenhouse gas emissions into the atmosphere than the fossil fuels it replaces and threatens the maintenance of natural forests and the biodiversity that depends on them.
As a result, there needs to be less emphasis placed on the importance of wood biomass in policy-making, in favour of other renewable sources of energy.
Wood, particularly wood pellets, are the dominant solid biomass commodity on world markets — which means it is likely the biomass fuel of choice for some time. For instance, the European Union is the world’s biggest consumer of biomass power and heat, driven by its 2020 renewable energy targets which aims to have 20 percent of EU energy coming from renewables.
Within the EU the UK is the largest importer of wood pellets for heat and power and biomass power generation has been increasing over the past few years.
What is going on with biomass then?
Biomass is classified as a source of renewable energy in national policy frameworks. It is considered to be a carbon-neutral energy source, meaning that though it does create some carbon dioxide when it is burned, this is considered to be part of the natural cycle in which forest growth absorbs the carbon emitted by burning wood for energy.
However, this assumption is not always correct. Wood biomass is considered to be less dense than fossil fuels and contains higher quantities of moistures and less hydrogen. At the point of combustion, burning for wood usually emits more greenhouse gases per unit of energy than those produced from burning fossil fuels like coal.
The technology used to burn the fuel can also impact the carbon-negative aspect of biomass. Dedicated biomass plants tend to have lower efficiencies than fossil fuel plants, depending on size and age of the unit.
And there is the supply chain emission aspect to consider – from harvesting and collecting the wood, to processing and transporting the fuel.
The report makes the point that these factors can vary but in general “the use of woody biomass for energy will release higher levels of emissions than coal, and considerably higher levels than gas.”
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Offsetting these emissions with new forest growth will require decades, and with global climate change the world does not have decades.
Duncan Brack, associate fellow of the energy, environment and resources department at Chatham House, said:
“Current policies that treat biomass as carbon-neutral do not reflect their real impacts on the climate. Public money should only be used to subsidise technologies that genuinely reduce carbon emissions. As the biggest consumer of biomass in the world, the EU should take the opportunity of its current revision of energy policies to address this problem.”
If the EU alone, if it wants to achieve its aim of providing 27 percent of its energy consumption from renewable energy sources by 2030, the amount of biomass it would need from wood is huge. It’s estimated this would be the equivalent to the total EU wood harvest, for all purposes, in 2015.
Due to the falling costs of other forms of renewable energy, such as solar photovoltaic and wind, renewable energy policy should focus on alternative renewables. However, biomass energy has an advantage over solar and wind in that it is ‘dispatchable’ – the electricity it generates can be dispatched at the request of power grid operators or of the plant owner. Solar and wind energy can be present or not present depending on the conditions.
The paper advises that further analysis of the impact on the climate of using woody biomass for energy. What is clear though, is that if the EU wants to continue its devotion to renewable energy to offset global climate change, biomass isn’t the right fuel to continue using.