Some comment on a few things on this thread (I have just come back from Colombia where I presented in the biomass conversion session of the BERSTIC 2020 renewable energy conference).
Firstly, why burning wet wood is 'bad'. The problem is that it takes a lot of energy to boil off the water and it can't burn hotter until the water has gone. This is exactly the same as boiling a kettle - energy is going in continuously to produce steam at a fixed temperature. The total energy produced is no lower, however you do have less radiant heat and more goes up the chimney in the steam. The real problem, in a domestic setting, is that the lower temperature of the smoke/steam means less of a temperature gradient so the fire draws less well and, more significantly, being colder to start with it is more likely that the smoke will cool enough in the chimney for the tars to drop out onto the chimney wall, sooting up the chimney and ultimately resulting in a chimney fire. Coincidentally, this is exactly the same issue as happens when people fit log burners into fireplaces without adding a double-walled, insulated liner. The tar can also seep through brickwork and if ignited can very slowly smoulder right through, leading to house fires, particularly if the other side of the brickwork the chimney passes through thatch - this is the root cause of a lot of the fires in thatched houses in the early 2000s with the rise in popularity of log burners.
Secondly, whilst using woodchip imported from Canada and the southern states is not as energy efficient as using home-grown would be, we would need to properly re-start the forestry industry. That is an enormous challenge for many reasons. The chip is at least dry, not wet. Do not get the idea this is like some tree surgeon chucking it through his chipper and the next day it is at the power plant! Wood dries to 20% moisture content at about 1" thickness every 6 months, however that is when water is only being lost across the grain. Losing water through the end grain is a lot quicker and wood chip can be dried in tumblers on mesh using the waste heat from the power station so tends to be very dry.
Yes, carbon capture and storage results in the only release being water, however the carbon dioxide is still produced, just stuck down old oil wells. It is not very energy efficient to do this. I haven't run a project on this for some years but from memory I think it takes 20-30% of the energy produced to compress and pump the CO2.
Many renewable sources are weather dependent and the cycle does not match well with demand - inconveniently people tend to want the lights on when it is dark, and solar panels are not working... If you have surplus electricity at certain times, e.g. at night, to make use of it you need storage which is expensive. Conveniently, if lots of people buy electric cars and charge them at night then you don't have to install as much storage, since your customers will still take the electricity.
There is no one simple solution. Wood and other hydrocarbon based fuels will remain part of the mix for a long time to come, both for transport and domestic heating. Gas is not going anywhere soon.
Alec
Oh and Alan - you would be amazed at the number of surviving elms around here, which is rather nice. I am running trial on disease resistance in native strains at the moment
http://www.futuretrees.org/files/uploads/Future-Trees-Trust-Where-we-are-with-elm-December-2019.pdf
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Topic: The banning of coal and wet wood for domestic heating ... (Read 28236 times)
