When I was in Beira, Mozambique, in the 80s, I saw:
1. a mass of poverty-stricken unemployed people
2. lots of people with malaria
3. lots of puddles
4. lots of mosquitoes breeding in the puddles
5. lots of sand
The screamingly obvious solution to these 5 problems is to pay 1 to put 5 in 3, thus mitigating 4 and 2.
But they couldn't do this, as they had no money (meanwhile, military helicopters flew hither and yon).
Now a wise Government could create the money to roll out the solution.
It makes perfect economic sense: less hospital bills, less family and economic disruption as families have less disruption, a fitter workforce, and more money circulating in the local economy. Winners all round.
This is Green Keynesianism in action. If it is physically possible, it is financially possible. If it is good for environment and people, then it is good for the economy, and money can safely be spent into existence.