The formation of deposits in energy conversion and utilisation processes has long been recognised as deleterious to the efficient and safe operation of those processes. Many of the deposits have a biological component, so that proper control of biofouling is essential. The biocides used for this control are recognised as having a potential negative impact on the environment, and there is therefore pressure to reduce or discontinue their use. The negative impacts of this course of action are not generally considered. Major contributions would come from the increased emissions of greenhouse gases and acid rain precursors from the burning of extra fuel that would be required to maintain the same industrial output. These would be caused principally by the reduction in heat transfer efficiency, particularly in the electricity industry, the requirement for increased pumping power, and the emissions associated with the extraction, production and fabrication of larger or additional capital plant. Estimates of the environmental impact of not using biocides in the energy conversion and utilisation industries are made with the assistance of data previously collected m the study of the costs of biofouling and other deposit forming processes to industry, the recently published Pilot United Kingdom Environmental Accounts, and data published by Eurostat for the European Union.