Study decries biomass: ‘renewable, not carbon neutral’ (updated)

A report from the Cary Institute of Ecosystem Studies adds to the growing criticism of biomass' ability to curb carbon dioxide emissions. It also highlights the negative effects that artificial forests have on biodiversity.

While providing more analysis of the balance between carbon sequestration in forest growth and carbon emissions in burning, the study looks at the effect that artificial forests (which are typically made up of a single species) have on biodiversity.

“It makes no sense to have Europeans embracing wood pellets as carbon neutral, while overlooking the carbon dioxide emitted during shipment and the losses of carbon storage from forests in the United States,” said William Schlesinger, president emeritus of the Institute and author of the study.

“Ultimately, the question is what kinds of forests are most desirable for the future. Recent research indicates that unless forests are guaranteed to regrow to carbon parity, production of wood pellets for fuel is likely to put more carbon dioxide into the atmosphere and preserve fewer species on the landscape during the next several decades.”

The study also claims that cleared forests are more prone to development, although the biomass industry has previously countered that by creating a market for wood it is ensuring the continued existence and growth of forested areas.

James Court, the head of policy and external affairs at the Renewable Energy Association is critical of the study’s conclusions: “Biomass is a crucial technology if we are going to decarbonise the electricity sector. It provides around 22% of the UK’s renewable power capacity and offers a way to replace coal without compromising on our stable energy supply.

“Sustainable biomass supports forest growth and coal-to-biomass conversion offers very significant carbon emissions reductions. Replacing coal directly can cut emissions up to 90%, but all biomass must cut lifecycle emissions by at least 60% compared to fossil fuels. Supplier forests in the USA have more than doubled their inventories since the 1950s and EU working forests have seen net growth of 38% since 1990.”

Court did not offer comment on concerns about biodiversity. In response, Schlesinger said that Court’s comments only were true if biomass is defined as a carbon-neutral fuel, which up to now has only been done on the political rather than the scientific level: “If one looks at the underlying carbon balance of the forest, it is not carbon neutral.   Before harvest, there is a lot of carbon in trees.  After the harvest, there is not. Where is the rest? In the atmosphere for decades, if and until the forest is allowed to grow back to carbon parity.”

Benedict McAleenan, head of the industry group Biomass UK, had more direct criticism for the study: “This paper almost completely ignores the real-world regulations and market practices that are involved in biomass sourcing. As a result, it comes to the wrong conclusions.

“In reality, our need for low-grade wood fibres (things like thinnings, small branches and off-cuts) is tiny in comparison to the surplus available in existing working forests, so there’s no market need to convert additional land. As an extra protection though, UK generators are prevented from sourcing from native forest land by UK regulations. And finally, the few ‘old growth’ forests in the Southern USA are protected by US law.”

Schlesinger responded: “Interesting that the UK sees fit to protect its native forests by regulation, apparently casting a blind-eye to what is happening on the other side of the puddle.

“And, I am sorry, but I live in North Carolina, and I know that not all old growth forests are protected by US law.”

There has been a growing body of research criticising biomass’ place as a renewable source of energy, with MIT releasing a study in January denouncing the mechanisms through which the biomass industry and some politicians perform carbon accounting.


This article was updated 16:30 27/03 with comments from Benedict McAleenan and William Schlesinger.

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