Global concern is growing over natural resource consumption and climate change. Many governments, companies, and industries are taking action to reduce the environmental footprint associated with material and product manufacture and processing. Both natural resource consumption and greenhouse gas emissions are being monitored closely as resource shortages and emissions continue to rise globally.
Onsite wastewater treatment systems have historically been composed of concrete septic tanks and stone/pipe drainfields. However, the processes and materials used to manufacture conventional systems consume a large amount of resources (aggregate, water, fuel, electricity) and emit a large amount of carbon dioxide. Alternatively, other materials have been increasingly substituted for conventional materials, including recycled thermoplastic septic tanks and chambers. These materials have qualitatively been considered more environmentally friendly, but no quantitative comparison has been evaluated in regards to resource consumption and carbon emissions.
Therefore, the environmental impacts of both conventional septic systems and systems using recycled thermoplastics were evaluated. A conventional septic system was defined as a precast concrete septic tank and gravel/pipe drainfield. This was compared to the equivalent recycled thermoplastic system, consisting of a septic tank and chambers. Water consumption, electricity consumption, fuel consumption, and carbon emissions were evaluated through raw material production, product manufacturing and transportation for both systems. Installation of the system was not included in this study, as the method and ease of installation varies greatly among sites.
It was concluded that there is a significant difference in the environmental impact associated with each system type. When transporting a recycled thermoplastic system 1000 miles and a conventional system only 30 miles, the recycled system reduced electricity consumption by 85% (5468 kWh saved), fuel consumption by 67% (4480 kBtu saved), water consumption by 97% (950 gal saved), and carbon emissions by 34% (148 kg C saved). When compared to the total number of septic systems installed each year (estimated at 400,000 installed septic systems in 2013), this could amount to a total yearly savings of 2.2 billion kWh of electricity, 1.8 billion kBtu of fuel, 380 million gallons of water, and 59 kilotons of carbon if every septic system was composed of recycled thermoplastics rather than conventional materials.