Let's see ... quite a lot of environmentally friendly things.
Planted over 200 trees and shrubs a few years ago to turn an area into a wild wood, that also provides some shelter from the north and east winds [which helps protect the house from wind chill].
[Some of the faster growing trees have shaded out others, which - having seasoned standing - will provide firewood this winter. Some thinning may take place this winter]
Recycle or reuse what glass, plastic containers and cardboard that I can.
Home compost as much as I can - then spread the results on my garden.
I don't normally use commercial fertilisers & pesticides - also grow bee & butterfly friendly native plants.
Have put up over 50 nest-boxes, I must replace most of the first batch, so need to build over 30 and "service" the rest.
Have barely used the car for months ... I don't have access to local public transport in winter [In summer there is a tourist route nearby] ... used to use rail for longer distances when possible. Last time I flew anywhere was more than two decades ago, I even went to Poland by train in 2009. Basically semi-retired now, which means the long commute has ceased (2 x 80 mile / day) and has been replaced by one of less than 2 miles to my local workshop. In any case, I mostly WFH on admin ...
Covid precautions have made us have food etc delivered, which had made us more economical by reducing food waste, stopping frequent journeys to the shops and we now have started a small winter weather stockpile.
Changed windows to reduce drafts [& fitted double glazing]. New(-ish) doors ditto. Upgraded loft insulation and will need to do something with the cavity & underfloor insulation [would help if there was a suitable grant].
Tried to get solar panels, but the roof angle was too flat for both of the installations companies I tried. Without the grants, I can't afford it atm. Thinking about a wind mini-turbine. Problem with these two is planning permission as I live in a national park & world heritage site !
Unfortunately, I have tanked LPG for cooking & heating. The boiler is a condensing combi, relatively new & efficient.
The hot water tank has solid insulation, but it's getting an additional (thin) jacket next month.
We also have two 90gal cold water tanks [long story, due to supply problems] and they'll get more insulation if needed
Have just changed the shower for a more efficient model - it takes the HW from the combi-boiler, I rarely use the bath.
Not on mains drainage so have to be environmentally friendly otherwise it is expensive to "re-start" the septic tank - actually, the tank is so old that the description is a bit optimistic. The outflow system was "serviced" this year and now works. The inflow pipes were repaired & cased from the inside three years ago - the farmer drove a tractor over it and the weight partially crushed the pipe. In the fullness of time, I would like a digester, but the tank isn't on my land and is in a field across a quite busy road.