Adds section on reducing emissions

docs/user-guide/energy.md

@@ -194,6 +194,20 @@ In this section we provide a brief overview of greenhouse gas (GHG) emissions so
 we have estimated the emissions associated with the service and describe how users can estimate
 emissions associated with their use of ARCHER2.
 
+### Impact on reducing emissions
+
+As well as a producer of GHG emissions, HPC systems like ARCHER2 also contribute to reducing emissions. The main source of reduced emissions from services such as ARCHER2 is in the research that leads to new technology, policies and approaches to reducing emissions. Some examples include:
+
+- HPC services run the climate models that are used to provide evidence for setting emissions reductions policies and targets across the world.
+- Research and modelling on HPC services leads to development of improved zero emission energy generation by, for example, modelling new wind turbine and wind farm designs.
+- Modelling to support the development of new energy storage technologies such as improved batteries.
+The emissions reductions from such activities are extremely difficult to quantify for a number of reasons so, at the moment, these are not factored in to the emissions estimates for ARCHER2.
+
+As well as the research activities on the service leading to reductions in emissions, there are other activities that HPC services can potentially take. For example:
+
+- Using the waste heat generated by large scale HPC services as a heat source for homes, businesses or farming. For the ACF data centre where ARCHER2 is hosted we are looking for options on how to do this.
+- Incorporating environmental and biodiversity improvements into the service. For the ACF data centre (which is in a rural location) we have been working to improve the site biodiversity and improve habitats. Responsible carbon offset schemes could also potentially be used to reduce emissions if they were undertaken as part of the service.
+
 ### Emission sources
 
 The emissions from ARCHER2 potentially fall into two categories (wording inspired by the Green Software Practitioner course linked below):