This life cycle assessment is just required by ISO 14001 during the identification of the environmental aspects and impacts. This is not required by either ISO 9001 or ISO 45001.
What you need to consider are all the environmental aspects of the activities, products and services from a life cycle perspective that your company can either control or influence. Life cycle stages include the acquisition of raw materials, design and development of a product, production, transportation and delivery, use, end of life treatment, and final disposal. Basically, your organization needs to be aware of all environmental impacts in each every stage of a product’s or service's life to manage the impacts in the best way possible.
Sometimes you won´t be able to control the environmental aspect or impact, for instance when your product is already delivered and will be disposed by the user. In this case you can opt by writing some instructions indicating how to best manage the disposal of the product by the consumer.