Go to the C:\Users\user_name\Documents\X-Morph Defense\config" (or C:\Program Files\X-Morph Defense\conf). Open config.cfg file and replace the number in the line:
set money_from_debris "0.1"
You can use Notepad, Notepad++, etc on windows to open this file.
You can substitute 0.1 with another value. e.g. If you replace 0.1 with 5, you can receive 50 times as many points for picking up trash. Then the line will be:
set money_from_debris "5.0"