Resource efficiency and chemicals: energy, emissions and material flows

Industrial chemicals and their derivatives are all-pervasive. Plastic, rubber and synthetic textiles adorn our buildings, vehicles and countless other elements of the modern built environment. Modern agricultural systems could not function at their current level of output without synthetic fertilisers and other agrochemicals, and the pharmaceutical sector as we know it would not exist. We are dependent on chemicals. According to statistics compiled by the International Energy Agency, the chemical sector is the largest industrial energy consumer. Paradoxically though, the chemical sector is responsible for fewer direct greenhouse gas emissions than either the steel or cement industries. This apparent mismatch arises mainly from the consumption of more than half its energy inputs as feedstock; fuels used as raw material inputs. This factor, combined with the sector’s overall complexity, makes it a challenging area in which to mitigate emissions, especially given the increases in demand projected for many of its products. The core aims of this research are to identify, compare and prioritise mitigation options for the chemical sector. By adopting the concept of resource efficiency, a broader range of mitigation options can be explored, including supply-side and demand-side options. The former concerns efforts to reduce the emissions that take place during the production-phase of chemical products’ life cycles (e.g. increasing process energy efficiency), whilst the latter includes options that reduce emissions at multiple points in the life cycle by reducing demand for chemical products (e.g. increasing the efficiency of fertiliser application). Supply-side options are compared using optimisation modelling, leading to a set of priorities. In the medium-term, process energy improvements and reducing the use of coal (as a fuel and feedstock) contribute most to emissions reductions. In the longer-term (and overall), carbon capture utilisation and storage (CCUS) makes the largest contribution. If electricity prices are low, electrolytic process routes provide an attractive alternative to CCUS. A major impediment to examining demand-side options is the lack of information on the sector’s material flows. A material flow analysis of the chemical sector is provided, from fossil fuel feedstocks to chemical products. This analysis is used as the foundation to construct a framework that translates changes in demand for chemical products to impacts on emissions levels. Using the framework, a series of “What if…?” analyses reveals that substantial mitigation potential – similar to that of the priorities identified on the supply-side – is available via technically feasible demand-side interventions, particularly measures that result in reduced fertiliser demand. The core contribution of this thesis is to provide a consistent basis for examining a comprehensive portfolio of mitigation options for the chemical sector, avoiding the current tendency to focus on the supply-side. While a re-balancing of emphasis on the demand-side is shown to yield considerable benefits, supply-side options will continue to be integral to securing a more sustainable supply of chemical products, especially in the long-term