It seems that Geoffrey Glover (PE online 17 May) is determined to miss the point regarding biomass and CO2 production.
If the biomass is produced sustainably, then over the production cycle the biomass absorbs carbon equivalent to that released during its combustion. On this basis, over the cycle period, the use of biomass is carbon neutral. For short rotation coppice the cycle period is one to five years.
As fossil fuels were laid down tens to hundreds of millions of years ago, the carbon released is effectively new carbon that cannot be mopped up by planting biomass. Indeed, as we have burnt several millions years worth of fossil fuel biomass since the start of the industrial revolution, we would need several planets worth of space to provide a sustainable system.
If carbon capture develops as a viable technology, its introduction will further enhance the benefits of sustainable biomass.
I entirely agree with Martin Kressman (PE online 30 April) that any biomass has to be produced sustainably to be carbon neutral. However, I am not sure how the quoted upper limit of 50 MW for UK production was derived; an article in ‘Bioresource Technology’ (June 2010) suggests that short rotation coppice willow and miscanthus biomass could produce 75 TWh per year from UK sources; sufficient for a 2.5 GW power station at 30% efficiency. To put that in perspective, for 2009 the UK consumption of primary energy was 2,300 TWh and electricity consumption was about 340 TWh; so, on its own biomass is never going to wean us off fossil fuels.
Glover claims that no climate scientist has satisfactorily explained the lack of global warming over the last fifteen years. The reason for this is probably that the global temperature records continue to show an increase in the global average temperature anomaly. Data from the UK’s Meteorological Office (HadCRUT3 – based on surface station measurements) shows an increase in the 11-year moving average global temperature anomaly of 0.26 K over the period April 1997 to April 2012. Data from the University of Alabama, Huntsville (UAH – based on satellite monitoring) shows an increase of 0.27 K over the same period. I have used an 11-year moving average to eliminate any bias resulting from cyclic weather patterns. Shorter averaging periods also indicate that the average global temperature anomaly is continuing to increase.
Glover’s final point concerning the merits of the UK developing sustainable energy systems is complex. There are moral, political and economic arguments for the UK leading the way with sustainable energy development. Morally, we started the industrial revolution and grew very wealthy on the back of the early CO2 emissions. Politically, it is unlikely that low per capita CO2 emitters in the developing world will do much until the rich west start the ball rolling. Economically, we rely on trade and need products to export, sustainable energy technology might provide a viable alternative to financial services!
Robin Trow, Snodland, Kent