To combat severe climate change, several governments around the world have set ambitious targets to reach net-zero emissions in the coming decades. To this end, policymakers will need decarbonisation planning tools, such that a decarbonisation pathway optimised to local constraints is selected and implemented. There are several policymaking planning tools available for macro-scale planning and operations at region-wide level, however tools and research on smaller, enterprise-level scale remain limited, despite commitments being made by several large companies to become net-zero carbon emitters. This work presents an optimisation-based decarbonisation planning tool for use by industrial companies to plan for carbon emission reduction by implementing a variety of different technologies. The model can consider feedstock changes and alternative energy sources and, given a set of demands and constraints, can suggest the optimal technology selection of carbon, capture and storage (CCS), low emission energy and feedstocks, and negative emissions technologies to achieve emissions targets. Unlike previous models, the model accounts for price changes across decades and provides a plan on how companies can invest in the right technologies, either constrained by a budget or given an emissions target, while still delivering products to satisfy demands. The model is demonstrated on a case study based on ExxonMobil’s Baytown refinery complex which consists of an oil refinery, a plastics plant, an olefins plant and a chemical plant, where a net-zero emission limit is set within six 5-year periods. The pathway created by the model is able to suggest a full reduction of emissions in the chemical, plastics and olefins plant respectively within a 10-year implementation of biogas and negative emissions technologies and is able to reduce the oil refinery from 44 Mt/y of CO2 emissions to 4.5 Mt/y after 25 years by phasing out oil in favour of renewable biogas refining.