Economic Perspectives of Biogas Production via Anaerobic Digestion

Abstract

As the demand for utilizing environment-friendly and sustainable energy sources is increasing, the adoption of waste-to-energy technologies has started gaining attention. Producing biogas via anaerobic digestion (AD) is promising and well-established; however, this process in many circumstances is unable to be cost competitive with natural gas. In this research, we provide a technical assessment of current process challenges and compare the cost of biogas production via the AD process from the literature, Aspen Plus process modeling, and CapdetWorks software. We also provide insights on critical factors affecting the AD process and recommendations on optimizing the process. We utilize four types of wet wastes, including wastewater sludge, food waste, swine manure, and fat, oil, and grease, to provide a quantitative assessment of theoretical energy yields of biogas production and its economic potential at different plant scales. Our results show that the cost of biogas production from process and economic models are in line with the literature with a potential to go even lower for small-scale plants with technological advancements. This research illuminates potential cost savings for biogas production using different wastes and guide investors to make informed decisions, while achieving waste management goals.

Keywords: anaerobic digestion; bioenergy; biogas; techno-economic analysis; waste-to-energy; wet waste.

Figure 1

(a) Availability of wet wastes in the U.S.; (b) Wet waste energy potential in the U.S. [6]. 1 kg = 0.0011 U.S. tons; 1 L = 0.264 U.S. liquid gallons.

Figure 2

Steps in the Anaerobic Digestion Process.

Figure 3

Process Flow Diagram for Modeling AD using Aspen Plus.

Figure 4

Process Flow Diagram of a WWT Facility as Modeled in CapdetWorks.

Figure 5

Process Flow Diagram of an AD Facility Converting Food Waste or Manure as Modeled in CapdetWorks.

Figure 6

Biogas Energy Yield (%) from Wet Waste Feedstocks. The bar chart shows the theoretical values of energy yield from different wastes while the line chart shows the range of energy yields from the literature.

Figure 7

Total Biogas Production Costs in USD/GJ for AD Processing (a) Wastewater Treatment Sludge, (b) Food Waste, (c) Swine Manure, and (d) Fat, Oil, and Grease. Please note that that y-axis on Figure 7a is plotted on a log-scale.