As a vaguely environmentally-minded person I have been aware of some time about the apparent benefits of burning biomass for energy.
Cultivating quick growing vegetation which can then be burnt is a relatively carbon-neutral way of generating energy, and so would seem to be attractive from a renewable energy perspective. As a result the UK Government has set targets for generating energy from burning biomass.
Ah, targets. One of the things you learn when studying systems is that targets have a funny way of distorting what happens. In order to meet the targets people will do all sorts of crazy things, and in the case of biomass they have started importing timber from the United States (http://www.bbc.co.uk/news/science-environment-22630815). So the timber is transported within the USA to a port, is then put on a ship which burns diesel fuel to cross the Atlantic, and is then transported from the docks to a power station.
Now, I don't know what the energy cost for doing this is, but I wouldn't mind betting that the whole biomass system is far from carbon-neutral.
Again, yesterday morning I heard a news item which said that subsidies for producing biomass were diverted land from food production, which was pushing up prices. Unfortunately the radio item did not go into detail and I have not been able to explore this further in order to fully understand the problem. But again, we see systemic issues kicking in.