A number of barriers may thwart the impetus of the drivers mentioned above. Barriers that can emerge during consideration of commercial AD projects include (1) uncertainty about the feasibility or reliability of the technology (both AD and energy production), (2) uncertainty about the economic and business outcome of the project, (3) uncertainty about public policy that might impact AD (e. g., incentive pricing or lack thereof for renewable energy, environmental rules and regulations and compliance therewith), (4) uncertainty about selling the renewable electricity to the main grid and standby fees, and (5) uncertainty about or fear of liability or penal­ties (from the complexity of compliance with environmental or safety regulations), and damage to corporate or product image from suboptimal or failed AD projects. The barriers to AD implementation are complex and vary in type and importance for each candidate site or enterprise. They can also be iterative whereby resolution of one concern may reveal a subsequent concern that also discourages implementation of an AD project (e. g., concern over disposal of digestate, or potential impact on material flow or heat recovery of the core operations of the business).

Among the major barriers is the concern over the capability and reliability of the AD system to digest the available feedstock(s) and the inability to validate the biogas yields predicted from the feedstock(s) because biogas and energy yield primarily dictates the economic viability of any commercial AD implementation. Although observation of a similar AD system operating elsewhere can alleviate this concern, concerns often exist over possible unpredictable digester failure that can potentially disrupt the core operation of the factory or farm. Such fear is a strong deterrent to AD implementation and can be difficult to overcome. Additionally, con­cerns can arise from the distraction from core business operations brought by the implementation of an “alien” technology (i. e., AD). Another barrier is the lack of supportive public policy that can provide assured markets for methane biogas and incentive pricing based on its fair value for not only the renewable energy, but also the environmental and social benefits. Uncertain long-term value of a feedstock or its value for alternative use (e. g., bioethanol production) can also further discourages commercial implementation of AD.