The true cost of anaerobic biodigesters: Is biogas worth it?

2022-07-26

4 minutes, 11 seconds read

The true cost of anaerobic biodigesters: Is biogas worth it?

In the last few years, anaerobic digestion facilities have become a target of investor interest. These massive facilities offer a unique opportunity to generate revenue both from the input of organic waste and the output of biogas that is converted into heat.

Today, millions of dollars are being poured into the construction of anaerobic digestion facilities. This allows food producing organizations to comply with regulations that prohibit sending organic waste to landfills by simply switching which waste hauler they pay. 

But are these facilities truly living up to their sustainability promise? Or is anaerobic digestion a feel-good solution for the disposal of organic waste? 

Organic food waste with leaves, peppers, and and other vegetable clippings.

The future of anaerobic digestion

During the process of anaerobic digestion bacteria break down biomass in an oxygen-free environment. The resulting byproducts include a solid bio-digestate, often treated and used as fertilizer, and biogas, a mix of methane as well as carbon dioxide, hydrogen sulfide, and trace amounts of other compounds. In anaerobic digestion facilities, this gas is captured and cleaned. The methane is used to generate electricity, provide heat, or compressed for use as vehicle fuel, among other uses. 

According to the American Biogas Council, the United States operates approximately 2,200 biogas systems at landfills across all 50 states, with the potential to add an additional 13,500 more systems. Through grants and other funding mechanisms, farms are also encouraged to invest in these costly on-premise solutions for disposing of agricultural and livestock waste. Across the U.S., the number of anaerobic digestion facilities is growing

There’s a reason that these solutions are being subsidized. At present, the production of biogas energy is not economically attractive. The technology remains inefficient, making it difficult to deploy on a wide scale. What’s more, research continues to emerge that biogas energy is not the environmentally friendly solution it proposes to be. 

Overstated benefits 

In areas such as the United Kingdom where anaerobic digestion technology has already scaled, negative feedback continues to emerge. These facilities have been subject to complaints about odors, toxic spills, and other issues. In addition, critics have pointed out that the combustion of biogas into usable electricity or heat generates additional greenhouse gas (GHG) emissions.

In 2020, Feedback Global, an investigative research organization focused on food waste, published Bad Energy, a report on biogas’ impact on a net-zero future. The report examined evidence demonstrating that the benefits of aerobic digestion have been overstated and, in fact, have crowded out more environmentally sound food waste disposal alternatives. The report challenges anaerobic digestion industry claims that biogas is cutting UK emissions by 1% annually, with the potential to reduce GHG emissions by 6%. 

The basis of the report is a life cycle assessment (LCA) conducted in collaboration with researchers at Bangor University. The LCA compares two scenarios. In the first scenario, the team modeled the volume of feedstocks processed by anaerobic digestion in line with the industry’s growth targets. The second scenario modeled the results of sending fewer feedstocks to digesters while prioritizing more sustainable alternatives such as scaling up food waste prevention in concert with other efforts. The results found that the second scenario would achieve roughly twice the emissions mitigation of the first anaerobic digestion-focused scenario. 

The point, the researchers said, was grants and other funds earmarked for anaerobic digestion facilities could make a significantly bigger impact if spent on solutions that limit waste disposal at landfills while also helping reduce excessive food production. 

“This report finds that far from only dealing with ‘unavoidable waste’ … [anaerobic digestion] can actively hinder waste prevention, particularly when paired with a lack of regulation and funding for the better alternatives. Companies and redistribution charities have reported that edible food can be diverted down the food waste hierarchy to [anaerobic digestion] when incentives are skewed towards [anaerobic digestion], hindering prevention efforts.”

A healthier alternative 

This is an area where onsite aerobic digesters hold significant promise. Unlike anaerobic digesters, onsite aerobic biodigesters use microbes to break down organic material in an oxygen-rich process. The result is that the equipment does not emit the damaging levels of methane that result from anaerobic digestion. In fact, biodigesters’ byproducts include only carbon dioxide and grey water that has been rendered safe to enter the sewage system or irrigate surrounding land. According to an independent study conducted by Brunel University London, a community’s aerobic digestion, using LFC biodigesters, produced 73% fewer emissions than anaerobic digestion. 

More importantly, units such as the LFC biodigester collect data about the types of waste broken processed. Through Power Knot’s LFC Cloud, organizations are able to track data on the amount of waste food being digested and the type or source of the waste. This is data that can help organizations with intensive food preparation to take steps to reduce or otherwise adjust their purchasing. It’s a solution that can help manage waste at every stage of the waste hierarchy pyramid

To learn more about how an LFC biodigester can provide the data you need to reduce your carbon footprint, contact Power Knot.