The New England Waste System’s VSB or Vegetated Sand Field (VSF) can reduce CO2 emissions from sewage to near zero while contributing significant quantities of oxygen to the atmosphere.
A hypothetical 4,100 m2 VSF produces 17,117 kg/yr of dry matter in year and it removed 24,990 kg of CO2 from the atmosphere, which will almost completely offset the 26,767 kg of CO2 that is released from the wastewater being treated. And that only includes the above ground biomass produced by the plants. When root biomass production is added in, the CO2 offset is greater than 100%. A VSF not only provides a 100% carbon offset, but each year it also produces 18,258 kg of oxygen that is added to the atmosphere.
By comparison, mechanical treatment systems are net CO2 producers because they rely exclusively on fossil fuels for operation. As a rule, mechanical treatment with different operating efficiencies, approximately 2.65 kWh of electricity for every kg of BOD that is treated. For each kWh of electricity consumed – 0.97 kg of CO2 are released from the power generating plant. This of course doesn’t include the CO2 produced from the sewage breakdown itself.
Human populations presents a global environmental threat that precipitated a classification of CO2 as an atmospheric pollutant by the US Environmental Protection Agency and a call for both an international carbon tax on fossil fuels and a carbon credit system for technologies that are CO2 neutral.
Municipalities and developers with an eye on the future can permanently decouple the cost of operating their wastewater treatment systems from the volatile and continually rising fossil fuel market by utilizing natural treatment technologies. In doing so they are also positioning their natural treatment system to benefit from an income revenue stream derived from the carbon credit system once it is in place.
300 million people in the USA, with 75% of them connected to municipal wastewater treatment plants, the tons of CO2 being produced each day is staggering.
To make matters worse, the practice of chlorinating the partially treated effluent discharge produces trihalomethanes that are recognized cancer producers in people, to say nothing of what they do to the ecology of the rivers and lakes that they dump into. Then rivers quickly transport that same water into the nearest sea or ocean.
According to US EPA, the household, municipal, and institutional potable water consumption in the USA is about 100 gallons per capita per day. Multiply that by 300 million people and it represents more than 30 billion gallons of wastewater effluent each day that gets “flushed to the sea”. If we add in another 1400 gallons per capita per day for agricultural and industrial consumption the numbers become staggering.
Of course this technology comparison would not be complete without pointing out that VSFs are typically designed as “green space” or “eco park” areas where the water can be recycled onto the land, and where the plant product can typically be used as animal food. If the nations wastewater effluent went to corn production we might even be able to convert sewage to ethanol. Feces to fuel! Now that’s a novel idea!!
download the PDF here TheCarbonFootprintofWastewaterTreatment
About the authors:
Dr. Ronald Lavigne holds graduate degrees in Plant and Soil Sciences, Public Health, Environmental Sciences and Environmental Engineering. He has more than 35 years of Environmental Technology Research and writes regularly for Boating on the Hudson. Your comments can be directed to newswet (at) aol.com. All comments will be responded to.
Kelly Gloger holds graduate degrees in architecture and fisheries and wildlife. He is based in the US Virgin Islands, works as an environmental consultant throughout the Caribbean, and manages a solar technology company.