Although related, Apple recycling program and Trade-in program are slightly different.
Apple recycling program primarily concerns with providing an avenue to recycle used hardware in an environmentally responsible way. It also gives Apple the opportunity to reuse certain components again.
You are generally not paid when you recycle old/used products. It's more about an ethically appropriate way to give away unusable hardware.
Apple trade-in program on the other hand lets you receive store-credit in eligible countries in exchange for a working hardware.
As you have a working Mac, you should go ahead with trade-in by visiting the trade-in homepage here:
You'll be presented with a questionnaire that lets Apple verity the eligibility for trade-in. You start by providing your Mac's serial number which will help Apple determine the system type and configuration.
Based on your responses, Apple will either show you an estimate of the store credit that can be availed, or suggest you to recycle the device.
You can locate the Apple trade-in or recycling webpage for your specific country by visiting the Apple Recycling Programs homepage.