Hi. Sorry for the late reply (Twix), but I wanted to group together replies, rather than replying to everyone individually.
Twix and Allan J
I did consider buying/making a wooden boat, but the kits that I found were a bit out of my price. I've no experience building boats, but after doing a bit of research, I'm inclined to agree with Allan that plastic has good recycling options (DesMes offer a recycling service, and
www.Recoup.org (recovery of unused plastic) list all the plastic reprocessing plants in the UK), but the source of it isn't (uh oh, here's that word again) sustainable, whereas wood is in some cases. Not sure about how some methods of construction of plastic boats using 3 different layers would work, but I'm sure it'd be fine for recycling.
It's pointless to try and state anything to be accurate unless it's really been properly looked at though. Something I've been getting into for work is Carbon Footprinting, which in short, defines processes and products in terms of their associated lifetime carbon dioxide emissions. So it could be used to come up with a measurement of each different boat's friendliness!
Jim
Good, I'm glad you think I'm part way there. In that case, I'm satisified. I'd rather things were questioned, than not. Maybe that gets us closer to the truth?
CeeGee
Interesting also! In answer to your post, I'll be doing both to varying degrees, where I can. I will be catching as much as possible, and buying things locally (I will have emergency food also). And according to the IMO definitions you gave - I have surprisingly never managed to get down to Mingulay (!) or ever seen the W coast of Lewis, so am very excited about that!
Just a thought
Just thought of environmental reason for expeditioning...when we're on expeditions, camping trips, whatever you want to call it, we are using a lot less energy (no PC, no fridge, no heaters, no TV, etc). So, no quantitative backing (yet), but I bet if you're away long enough, the reduction in energy consumption will outweigh the energy consumed to travel to the destination.
Cheers