What is often a limitation of using solely the tonnage method to evaluate recycling programs?

Using solely the tonnage method to evaluate recycling programs has significant limitations, especially in that it overlooks material type and quality. When focusing exclusively on the weight of materials recycled, this method fails to differentiate between the various types of recyclables. For instance, recycling a ton of low-quality materials may not have the same environmental or economic benefit as recycling a ton of high-quality materials. Different materials have varying impacts on sustainability, economic value, and energy requirements during the recycling process. Therefore, evaluating recycling success based only on tonnage can lead to an incomplete picture of a program's effectiveness, as it ignores critical factors such as the overall quality of the materials processed and the potential benefits or detriments associated with the types of recyclables collected.

In contrast, the other options touch on relevant considerations but do not directly address this fundamental limitation of the tonnage method. For example, requiring extensive public participation does not inherently apply to the tonnage method itself but rather to the broader context of recycling program effectiveness. Similarly, concerns about data manipulation and the influence of new technologies are valid but are secondary to the more immediate issue of not assessing the intrinsic value of the materials involved.