Biology is natural. Technology is artificial.
So when Biology becomes technology, artificial processes are built to imitate nature.
How does our body fight diseases, how to replace an amputated leg with Prosthetics, how to replace blood with artificial blood, how to artificially create Haemoglobin for patients, how to replace petrol/diesel with Biofuel, how to clean waste water with Bio-remediation strategies.
As you can see, the possibilities are limitless when you try to apply technology to imitate biology. Take a biological problem and see how you can replicate it using technology.