A risk-aware assessment for buffer recycling across unit operations for monoclonal antibody purification and its potential

Abstract

Water for injection (WFI) for biopharmaceuticals is coming into focus considering the sustainability goals of society. WFI production consumes excessive amounts of water and energy. Strategies to reduce WFI energy cost include cold WFI production or reduction of buffer volumes used in the process. A suggested alternative with proposed saving of up to 90 % was the recycling of buffers, potentially across multiple unit operations. In this work a risk-based assessment of the idea is made to quantify the potential savings. All streams of an antibody purification were classified according to their potential risk. This analysis showed that the process does not produce sufficient recyclable outlet streams to cover all replaceable inlet streams. From a potentially replaceable 42 % of inlet buffers only a total of 23 % can be replaced, even if cross-batch recycling is allowed. If this is not allowed, the savings drop down to 14 %. While this saves some water and energy, it shows that making full use of the theoretical potential is impossible, and 90 % reduction is never achievable when risk-aware design of recycling across unit operations is used. A universal risk-based assessment is important and can build the rationale to convince regulatory authorities in case of implementation of such a strategy.