(135d) A techno-economic analysis of energy efficiency and CO2 emissions in bioethanol production due to fouling

Maximizing the energy efficiency and minimising GHG emissions of production processes is paramount for biofuels to become a viable economic and environmentally friendly alternative to fossil fuels, particularly in the transportation sector.

One of the main performance issues faced by these processes is the deposition of unwanted material in process equipment (fouling), especially in the beer column, evaporators and heat exchangers. This is a well know problem but its impact not well quantified in the literature. Periodic cleaning and maintenance are required to minimise shutdown time, avoid off-spec products and maintain energy consumption and CO2 emissions to levels that make the whole process economically viable (Wisconsin, 2020). However, maintenance is typically performed based on experience and simple heuristics with the main goal of ensuring production. The question arising is whether further optimisation of such maintenance activities could help further improve the average performance of production plants (by minimising water use, energy consumption, and CO2 emissions). This could be relevant to contribute to the sustainability of biofuels production and, together with other improvements, enable a true transition from conventional fuels to biofuels. However, the information available on the subject is rather dispersed (and scarce) and it is difficult to find quantitative information on the impact that fouling actually has.

In this work, after presenting information gathered in the existing literature, we aim to quantify the impact of fouling for key units in the dry-grind process based on simulations for a typical plant. The assessment indicates that fouling can easily cost in the order of several millions of dollars per year in an average size bioethanol production plant as a result of increased fuel and water consumption and extra CO2 emissions. In this context, advanced monitoring and predictive maintenance tools, which have been proven to provide significant savings to other industries, are proposed as a part of the solution to improve the management of fouling and optimise maintenance decisions.