You can bring a maximum (they will weigh it) of 5kg back with an ePermit as hand luggage on your flight back.what is involved in getting greens back into Oz?
Even then you will sometimes hit an AQIS agent that will charge you a second time, typically that doesnt happpen as hand luggage but will if you post them back.
1. An Import Permit is required and must be valid at the time the goods are imported into Australia. Permit applications may be sent to AQIS Plant Programs, Canberra office for assessment.
2. All packaging used with the consignment must be clean and new.
3. Each consignment may be subject to an inspection to verify that the beans are free of live insects and other quarantine risk material.
4. If the consignment does not meet the above conditions it will require treatment as detailed in the Commercial conditions below.
5. If the above conditions are met, the consignment can be released for processing.
Import Conditions Database - ICON - AQIS
The permit will cost you $130(ish currently) and is good for 12 months. You will need to have the import permit on you at the airport with the beans (they won't look it up on the computer)
To land any more than the 5kg you need to do a lot of homework and have deep pockets.
Sounds like a fun trip though!