Should biodigesters be used as septic tanks?

November 22, 2022

4 minutes, 37 seconds read

Should biodigesters be used as septic tanks?

As biodigesters increase in popularity, organizations are increasingly looking to maximize the value that they can achieve from their equipment. However, this desire can lead to challenges if there’s not a clear understanding of how the two very different types of biodigesters operate. For example, an online search of biodigester uses might lead end users to wonder if their equipment is suitable for use as an environmentally friendly septic alternative. 

The short answer is that a sealed, above ground aerobic biodigester is no replacement for a traditional septic tank. And while anaerobic biodigesters—a distinctly different type of equipment—are in some cases being given this role, there are some drawbacks to these units which may encourage organizations to rethink their use of anaerobic biodigesters altogether. 

Aerobic versus anaerobic processes 

Biodigesters of all types are meant to break down organic waste by putting naturally occurring bacteria to work in replicating the decomposition processes that occur in nature. However, the presence or absence of oxygen in this process can dictate the type of output that is created—and the potential for dangerous emissions. 

Anaerobic decomposition 

An anaerobic decomposition process does not include oxygen. Once microbes break down organic waste within sealed anaerobic biodigesters, the equipment emits digestate—a residual solid and liquid end product that requires further disposal—as well as biogas.

About 50% to 75% of this biogas is composed of the greenhouse gas methane, according to the U.S. EPA, with the remainder made up of carbon dioxide, hydrogen sulfide, and trace amounts of other gases. This is a problem as methane is more than 87 times as effective as carbon dioxide at trapping heat within the atmosphere, making it a significant contributor of climate change. 

Traditional septic tanks share much in common with anaerobic biodigesters, and have in recent years been linked to methane emissions. The perceived advantage of anaerobic biodigesters is that they provide an opportunity for capturing these biogas emissions for use as heat, electricity or to be purified for use as a renewable natural gas.

While promising, these end uses require significant investments in additional infrastructure to capture the full benefit of biogas. While biogas today is a more sustainable solution than traditional natural gas, we should consider it as an important transition fuel on the road to completely decarbonizing our energy supply.

Aerobic decomposition 

On the other end of this spectrum are aerobic biodigesters. This sealed equipment involves oxygen in the decomposition of organic waste, alongside naturally occurring microbes. The result of this process is a harmless grey water that can be disposed of through the sewer system and small amounts of carbon dioxide. 

To spur this decomposition process, LFC biodigesters use Powerzyme, a special mix of microbes that includes naturally occurring bacteria, fungi, and enzymes. These microorganisms are capable of rapidly digesting grease and fat, reducing key wastewater parameters, eliminating unpleasant odors, and degrading a wide range of complex chemicals. 

Select the right equipment for long-term durability 

Anaerobic biodigesters have been used on an industrial scale at a number of waste management sites worldwide. As communities, businesses, and now homeowners evaluate the use of an emerging array of smaller-scale anaerobic biodigesters, it may help to understand some of the issues now facing landfills. These industrial facilities are frequently subjects of complaints about odors, toxic spills, overstated benefits, and other issues. Many of these complaints, however, stem from improper installation or maintenance. 

As unwanted emissions are a chief complaint, it is important that anaerobic biodigesters used as septic tanks must be placed underground due to the strong smells they can emit. The container must also be sealed to prevent water and gas leakage. Manufacturers of small-scale anaerobic biodigesters advise selecting a tank with a solid, corrosion-resistant structure to ensure long-term stability. They also advise that the tank has sufficient insulation to maintain a consistent chamber temperature throughout the year, as this facilitates the decomposition process. 

LFC biodigesters, on the other hand, have been installed in numerous locations around the globe with no reports of emitting odors. In fact, these units are often used not only above ground but inside kitchens and other food production organizations because they eliminate odors while minimizing time spent on food waste management. 

These systems also operate on different ends of piping infrastructure. Above ground aerobic biodigesters make use of existing sewage infrastructure, disposing of output safely into sewage systems. Underground anaerobic biodigesters are an end unto themselves, which makes installation and maintenance of any associated piping the responsibility of the facility owner. 

A more environmentally friendly solution

For organizations in search of an environmentally friendly septic alternative, an aerobic biodigester is not the answer. Aerobic biodigesters are best used in commercial kitchens, manufacturing sites, or other facilities where much organic waste is generated. LFC biodigesters provide an easy to use and environmentally friendly solution for reducing the time and cost of managing organic waste. 

If you’re looking for an environmentally friendly septic alternative, it’s important to do your research before deciding that an anaerobic biodigester is the answer. This equipment comes with a range of challenges that could exacerbate environmental problems while adding significant capital costs. 

To learn more about environmentally friendly options for organic waste management, we invite you to visit Power Knot’s Center of Sustainability, your resource for best practices for improving corporate sustainability and lowering your carbon offset. Or, for insight into how an aerobic biodigester can transform your operations, contact Power Knot today.