I've also read that recycling glass uses four times as much energy as producing a new bottle and that the old system of milkman (milkperson now?) collecting empties was far more beneficial.
Simply not true - glass is one of the most worthwhile items to recycle. Regarding the collecting empties issue, there is something in that - but given that very few, proportionally, of the glass receptacles constituting waste are actually of Irish origin or have a suitable collection network, it's just not practical [who's going to take all those wine bottles back to Australia, the beer bottles back to Germany, the Dolmio jars back to Italy
? ].
The recycling abroad is an issue, but not one about which we always have a choice - for example, the Irish Glass Bottle Company closed down because the site was so valuable, and private industry is sitting on its hands and hoping the Government will grant assist a new one, even though it would almost certainly be a profitable venture from the get-go. However, it's worth considering that a great deal of the time, the recyclables are transported as ballast in cargo ships which would otherwise just be travelling back empty - the carbon implications of the long distance transport are therefore negligible, as the ships would be making the journey, or a very similar journey, irrespective of whether the recyclables were being transported.
But there are lots of people who think that if you just segregate some of your waste, without doing anything at all to reduce / reuse (re-think), they've done the environment a huge favour for which they should be patted on the back. The "recyclers" who annoy me most are the ones who drive to the recycling centre / bottle bank, with a dozen or so bottles, and who
leave the engine running while they "nip out" to recycle. Grrrr!
... Envelopes: gummed bit is generally only a problem if it's that really heavy duty gum you occasionally get on large envelopes, in which case you should probably cut off the flap.