patio progress

Waiting to get a call back from Scottish Power to send in my first Feed-in Tariff (FIT) reading. The 10 kw of solar panels have had an excellent summer and the inverter tells me they have created energy that is equivalent to 4439 kg of CO2. That seems a whopping amount to me!
But before I get too virtuous I need to add a note of caution. Blog reader alert - self beat-up, hairshirt moment arriving!!!
Our patio (terrace) is being laid and phase 1 should be finished this week. Looks great. There are buts -big ones too.
First, we chose imported natural stone rather than
manufactured stone. Both have an environmental cost - the natural stone quarrying causes environmental degradation and there's the cost on CO2 in bringing it here. We were told that it was ethically sourced.
Manufactured stone contains 'embodied energy' incurred during its manufacture although there is a shorter distance for it to travel.
But the other cost is the considerable amount of carbon released into the environment during the laying process. Each 25kg bag of cement releases 20kg of carbon. I guess our patio will cause the release of over a tonne of carbon through the use of cement. I feel sick just thinking about it but no other solutions presented themselves.
My hope is that zero carbon living that the house will bestow will compensate for this contribution to environmental damage over the life of the building.
And 'The Terrace' as mum likes to call it, is already looking great, is quite relaxed about its antecedence and is looking forward with eager anticipation to welcoming family and friends.