Anaerobic digestion of food waste and organics has a long history. While the first known anaerobic digester was built in 1859 in Bombay, India, the technology goes back as far as 10 BC, where biogas was collected and used to heat bath water.
Returning to the present day, I was recently at the Waste Conversion Technology Conference (WCTC) in Atlantic City, New Jersey. The conference, which focuses on methods in which waste can be converted into alternative fuel and energy, is the largest waste conversion conference in the country, drawing scientists and waste professionals from around the world who are working on new ways to get the most out of our waste.
During the conference, I presented on trends in anaerobic digestion of food waste, and what these trends mean for the future of food waste recycling. With a number of gasification and anaerobic digestion professionals in the audience, I highlighted the differences between on-farm and stand-alone anaerobic digestion facilities, and I touched on supplemental and competing technologies.
What is Anaerobic Digestion?
Anaerobic digestion is a process in which food waste and organics are mixed together in a container known as an anaerobic digester. In the absence of oxygen, microorganisms break down this organic matter and transform it into biogas. Once this biogas has been purified at a biogas plant, the natural gas can be turned into electricity, fuel, and thermal energy.
Anaerobic Digester System © Copyright Tennessee Department of Environment & Conservation
While food waste is joined by yard trimmings, biomass, and other organics in an anaerobic digester, a study by the East Bay Municipal Utility District in Oakland, California found that food waste has over three times as much energy potential in the form of biogas produced per ton of materials as biosolids, and 15 times as much energy potential as manure from cattle.
With between 34-40 percent of the food produced in the United States going uneaten annually, and a current landfill rate of over 76 percent, our growing mountain of food waste presents an enormous opportunity for businesses looking to do their part for the environment by reducing food waste in the landfill and creating renewable clean energy.
On-Farm Anaerobic Digestion Facilities
There are approximately 282 on-farm anaerobic digestion facilities across the United States currently, with roughly 58 of these processing food waste. There is the potential for the number of on-farm digesters to increase to 8,200 facilities, according to the American Biogas Council, representing a large potential growth in this sector.
The main benefits of on-farm anaerobic digestion facilities are:
- Co-digestion opportunities to manage both manure, food waste, and other organics
- Additional income to farmers
- The closed-loop system means all outputs can be used on farm
The disadvantages of on-farm facilities are:
- Transportation; the need to bridge the gap between most of the country’s waste being concentrated in metropolitan areas and most of the country’s farms being in rural areas
- The need for additional processes which are not core farming functions
Here at Rubicon we work with on-farm anaerobic digestion facilities across the United States to manage food waste reduction for our clients.
Stand-Alone Anaerobic Digestion Facilities
There are approximately 60 stand-alone anaerobic digestion facilities (processing food waste) in the United States, which are split into two categories: dedicated facilities and merchant facilities.
Dedicated facilities are located at an organization’s manufacturing plant, processing plant, or distribution center. They don’t take in outside materials; they only process their own waste streams. Merchant facilities, on the other hand, accept inputs from off-site locations, and they require these outside sources for feedstock with which to operate.
The main benefits of dedicated facilities are:
- There is no transportation required
- Gas, electricity, and heat can be utilized on-site
The disadvantages of dedicated facilities are:
- Anaerobic digestion is not the facility’s core function
- They generally do not help the surrounding community with organics recycling
- Spatial constraints
The main benefits of merchant facilities are:
- They can be located closer to urban sources of organics compared to composting facilities
- They are equipped to handle a variety of organic waste streams, as anaerobic digestion is their core function
The disadvantages of merchant facilities are:
- Anaerobic digestion is the facility’s core function, creating a high risk for the sizable investment
- It is competing with other technologies and facilities
In truth, anaerobic digestion of food waste and other organics still has a long way to go in order to realize it’s full potential. Once we get there, however, the full benefits of this ancient technology will be unmistakable.
If you want to talk about how you can implement an anaerobic digestion program and move toward a path to converting waste into valuable resources for your business, please reach out to me any time at firstname.lastname@example.org.
Ryan Cooper is a Waste Diversion Manager and the Organics Recycling Lead at Rubicon. To stay ahead of Rubicon’s announcements of new partnerships and collaborations around the world, be sure to follow us on LinkedIn, Facebook, and Twitter, or contact us today.