Design algorithms are sets of equations for the construction (e.g., equipment sizing, material selection) or end-of-life (e.g., disposal, salvage) stages of unit processes within the system. These algorithms can vary in complexity. For example, a simple design algorithm can scale the dimensions or number of fermenters based on the required volume, but a more complex model may include the specification of fermenter height, wall thickness, and weight, which are calculated using factors such as aspect ratio, fractional weld efficiency, reactor pressure, and material properties. Compared to construction, the relative importance of the end-of-life stage can be minor and is often excluded from the analysis (e.g., for wastewater treatment facilities ).