Optimisation of energy usage and carbon emissions monitoring using MILP for an advanced anaerobic digester plant

This paper proposes a realistic model for energy and carbon management of an advanced municipal wastewater treatment works. Through minimisation of total cost of operations, it provides operators with a visual daily operational schedule based on varying tariffs. This site is the first in the UK with a mixed operational strategy for biomethane produced on site: to burn in CHP (Combined Heat and Power) engines to create electricity, burn in Steam Boilers for onsite steam use or inject the biomethane into the gas distribution network - Natural Gas can be imported to make up shortfalls in biomethane if required. Implemented using a novel mixed integer linear programming (MILP) approach, results indicate that biomethane injection should be maximised for the highest financial gain - the driving force for optimising the remaining operations being the site electricity imports and whether the electricity imported ‘generates’ carbon emissions. Based on the source of electricity and the new carbon emissions performance criteria, under the current operational strategy importing electricity from carbon-based sources has no tangible impact on site revenues (but does impact CO2 emissions), however carbon free (renewable) electricity sources could see shift in operations leading a revenue increase of 12% [Display omitted] •Optimisation of biogas and energy distribution and carbon emissions monitoring using MILP.•Changes to current operations are needed to meet emissions pledges.•Changes to operational strategy could also see revenues increase by up to 12%.•Biomethane Injection primary driver of revenues.