In other countries (USA,Canada at least!) you can buy milk and other liquids in bags. Then simply put bag in a purpose made jug, snip off the corner, and pour (then store jug in fridge). For detergents, buy in bags, refill large heavy plastic bottle and all you have to dispose of is bags. Not ideal, but much better. Only downside is possibility of leakage during transit between home and shops, but that could be overcome with care and decent strength bags. Simple but not being done here!