Some thoughts about current Bio issues.
Whilst there are some good reasons to produce biogas from wood when you analyse the process on an exergy basis it is inferior to the combustion of the wood in large scale CHP as practiced in Copenhagen.
The reason the work done by the Carbon Trust signalled that AD is an effective route for biomaterials was that the work followed rules set down by the climate change committee for the analysis of biomass.
These rules were based on the assumption that the emissions from bio-based materials when burnt or converted to other forms of energy are close to zero.
This is what is termed a cradle to grate assumption.
The committees most recent report however has recommended a change in the method of analysis for biomaterials emphasising that it must be based on cradle to final use.
When this method of analysis is used then use of biomaterials in large scale CHP tops the list.
Given such plants can then be economically fitted with CCS then you get the added benefit of use of biomaterials as well as being sustainable also actually reduce CO2 emissions.
The rules of the game are changing and wise investors will be backing away from biomass boilers, understanding that their products of combustion emit more CO2 than coal and the by products of the combustion from wood may present as great or greater problems for the environment than smokeless coal. Or even some coals such as anthracite.
Coal after all is bio product processed into an excellent fuel over the millennia.
So use the wood in buildings and burn the coal gives greater CO2 savings than burning wood.
Counter intuitive certainly, but sound engineering!