Accelerating and Stabilizing Anaerobic Digestion by Promoting Direct Interspecies Electron Transfer

Investigators: University of Massachusetts

Start Date:
Feb 2015

Award Amount:
$125,000

The overall goal of this project is to develop a new strategy for the anaerobic digestion of solid waste that will make solid waste conversion to methane faster and more reliable. This goal fits the EREF’s strategic research plan to “generate sustainable, efficient and environmentally responsible technologies and solid waste management strategies” and the stated interest in anaerobic biological treatment as a solid waste treatment option. Anaerobic digestion is an attractive solution for the treatment of solid waste because it can efficiently convert solid waste to a high quality energy source and can effectively harvest energy from solid waste with high moisture content. However, anaerobic digestion is often ruled out as treatment option because this process can be slow and somewhat unreliable due to frequent digester failures.

Our recent research has established a new paradigm for microbial interactions within anaerobic digesters, known as direct interspecies electron transfer (DIET). In DIET methaneproducing microorganisms (i.e. methanogens) make biological electrical connections with other microbial species, which feed electrons to methanogens for the reduction of carbon dioxide to methane. We have clearly documented DIET in upflow anaerobic sludge blanket digesters treating high-strength brewery wastes. However, in the current design of solid waste anaerobic digesters the methanogens are more likely to receive their electrons via interspecies H2 transfer, an inefficient and unstable process in which H2, rather than direct electrical connections, serves as the electron carrier. Thus, our goal is to provide inexpensive and durable electrically conductive materials that can serve as electrical connections to promote DIET in solid waste digesters. The DIET-based system is expected to more rapidly convert solid waste to methane and be less susceptible to the environmental stresses that often upset traditional digesters.

The primary research tasks/objectives required to reach the overall goal are:

  1. Determine an optimal strategy for promoting DIET in anaerobic solid waste.
  2. Determine whether anaerobic solid waste digestion via DIET is faster and more resilient to upsets than traditional anaerobic solid waste digestion.