How can I trade in them ?
Commodities that are expected to become major trading instruments over the next few years are called 'Emerging commodities'.
For example - Electricity is a major commodity that gets traded in the Nord Pool Spot. However even before the Nord Pool Spot could introduce the official electricity contracts, electricity was actually being traded over the counter by few select players. So what was then an emerging commodity transitioned into a major commodity with the official electricty trading contract kicking in.
You cant really trade an Emerging Commodity because there is no liquid and official market for it.