The model would be deployed to study the link between environmental behaviour/intentions and likely socio-psychological drivers of such behaviour/intentions.
many distinct models are employed in environmental behaviour research. Jackson's review (see link) provides an accessible overview.
I have based my own work on farmer environmental behaviour on Triandi's Theory of Interpersonal Behaviour, albeit modified as discussed in Feola and Binder (2010) (see also Feola et al 2015). However there is no one-fit-all model and different models have been shown to explain some types of behaviours (e.g. planned vs non-planned; or mobility vs recycling behaviour), or behaviours in particular social contexts. So I don't think there is one single answer to your question, I am afraid. A good look at the literature for the specific behaviour you want to investigate should help you identify a range of possible models to use.
Finally, as an interesting critique of behavioural modelling approaches, I suggest Shove's "Beyond the ABC: climate change policy and theories of social change" (see link).
You can integrate 2 or more theories together to get a plausible explanation of the environmental behaviour you're investigating. No model/theory is perfect and sadly you may discover that some of the available models/theories are more or less built on the premise of TRA/TPB.