In November, 2015, a report was put in front of The Scottish Parliament’s infrastructure and capital investment committee showing a bioheat plant intended to help St Andrews university achieve carbon neutrality was at least as likely to increase emissions as it was to reduce them. Just over a year later, flanked by smiling primary school children, university principal Sally Mapstone ceremonially lit the completed biomass boiler – paid for with £10 million in public funds and a subsidised loan of £11 million.
For those unfamiliar with bioenergy, this investment may appear as an exceptional act of folly. Others with experience of this means of climate change mitigation will be less surprised, given the same kind of questionable faith is put in biomass at the national scale – only with vastly greater sums at stake.
In December last year, the Government guaranteed Drax power station £100 per MWh for electricity from a new biomass unit – making its power more expensive than that from the notoriously pricey Hinkley Point C. In total, in 2015, £817million in public money was handed to energy companies to generate 9% of the UK’s electricity by burning solid biomass.
The money is being spent, as with the university’s bioheat plant, both in the belief that biomass helps mitigate emissions and in the face of criticism of this claim. A report last October by the Natural Resources Defence Council drew upon recent science when it stated that in many cases bioenergy produced more carbon emissions than using coal or natural gas. A paper by Chatham House in February this year went further, saying public subsidies for biomass should largely be withdrawn. The scepticism has even infected Government, with the now defunct DECC commissioning a report into whether biomass is worse than coal in terms of warming the planet.
The criticisms of the St Andrews plant and of biomass in general are essentially the same. The combustion part of the biomass lifecycle (as opposed to, say, processing or transport) is assumed by supporters to be carbon neutral as, since trees absorb carbon when they grow, forest growth will balance the carbon emitted by burning wood for energy. However, this assumption fails to take into account all the consequences of using biomass. For example without a demand for biomass, the wood may not have been burnt and therefore continued to sequester rather than emit carbon. Or it may have been used for another purpose, such as wood products, in which embodied carbon is not released into the atmosphere. In their consequential analysis of the St Andrews plant, the report authors identified thirteen scenarios which may unfold if the plant were set up. In seven of them the lifecycle emissions from producing the same amount of energy were greater from the bioheat plant than they were from the original gas boiler. Similarly, the Chatham house paper argued that mill residues and post-consumer waste are the only biomass feedstocks which lead to a genuine reduction of emissions.
Unfortunately the idea that biomass is carbon neutral is enshrined in both policy and carbon accounting. Advocates of theSt Andrews project and Drax argue that, because of the source of their biomass, their bioenergy produces less emissions vis a vis fossil fuels even according a more rigorous consequential perspective. Because of the assumed neutrality of biomass, they’re not required to prove this however. In the case of St Andrews, the plant was greenlit on the basis of a corporate accounting methodology which does not require bioenergy emissions to be counted. Likewise, at the national level, biomass emissions are not included in inventories, making bioenergy an attractive way to hit emissions reductions targets.
It’s true that biomass emissions seem set to become more visible. Recent product lifecycle assessment guidance requires the explicit quantification of both biogenic emissions and removals, the IPCC plan a new technical note on the burning of imported biomass and the UK Government have developed a (purely advisory) model to assess biomass’s mitigation potential, including against “counterfactuals” in which it is not burnt. But even if bioenergy is pared back to genuinely carbon neutral processes, doubts remain.
Biomass burning can have a long carbon payback period whatever its ultimate net emissions are. In other words it may take a long time for the emissions at the point of combustion to be compensated for by new plant growth. As climate tipping points could be crossed in the short-term, increasing the amount of carbon in the atmosphere for even a few decades could be dangerous.
In their concluding remarks, the authors of the St Andrews analysis – which was commissioned to help decide whether to proceed with the scheme – offered three notes of caution. Firstly, they cited a 66-year-old work of political philosophy which argued that decisions should be based on an understanding of all the possible consequences. Secondly, they admitted the consequences of the plant were uncertain, but submitted that this uncertainty itself was a finding. Thirdly, they argued that if there is so much uncertainty surrounding biomass, why not plump for another technology which offered guaranteed emissions mitigation.
Sound advice which, as we have seen, went unheeded. Meanwhile, the UK has become the world’s largest importer of wood pellets, burning 42% of total global imports in 2015. Pleas for a rethink generally, it seems, are also set to be ignored.