Fitting Sewage Sludge Treatment into Our 'Planetary Boundaries'

Inspired by our original post: "Biosolids and the Care for Our Common Home", we further explore our Planetary Boundaries.

The Earth is a system limited by planetary boundaries.  In 2009, scientists from the Stockholm Resilience Centre and the Australian National University developed this conceptual framework of planetary boundaries. Since then, groups around the world have begun to reference this concept when addressing environmental issues.

The High-level Panel on Global Sustainability and the United Nations Environmental Programme have incorporated planetary boundaries into their dialogue on global environmental and developmental challenges. In the report from the High-Level Panel on Global Sustainability titled Resilient People Resilient Plant A Future Worth Choosing, the group encourages using the concept of planetary boundaries or similar concepts, such as planetary limits or tipping points, as a way to strengthen the link between science and policy. NGOs and government agencies in Ireland (Environmental Pillar) and the legal think tank group Planetary Boundaries Initiative are part of a list of organizations encouraging local and global levels of governance that focus on principles underpinning the planetary boundaries framework.  

The boundaries defined in the 2009 framework are:

  • Climate Change

  • Introduction of Novel Entities

  • Stratospheric Ozone Depletion

  • Atmospheric Aerosol Loading

  • Ocean Acidification

  • Biochemical Flows

  • Freshwater Use

  • Land-System Change

  • Change in Biosphere Integrity

As stated on the Stockholm resilience website, in the article Planetary Boundaries 2.0 new and improved, “The science shows that these nine processes and systems regulate the stability and resiliency of the Earth System – the interactions of land, ocean, atmosphere and life that together provide conditions upon which our societies depend.”

There are skeptics. Some UN members believe the planetary boundaries framework focuses on the planet’s wellbeing rather than humanity’s wellbeing. Developed countries may use the framework as a way to reprimand developing countries who are trying to progress using the same environmentally detrimental pathways that developed countries used to become developed. Those doubts have disrupted any movement towards the framework being used by governments as a guideline for future sustainable development.

Research for the framework has continued, and in the most recent report in January of 2015 a team of 18 international researchers updated the framework. They found that four of the boundaries have been crossed because of human activity. These boundaries are climate change, loss of biosphere integrity, biodiversity loss and the biogeochemical flow. Crossing these boundaries could push the Earth System into a new state leading to greater challenges in addressing poverty and human wellbeing around the world.

The science behind the framework can inform everyone’s decisions on how to live sustainably. How can we change our actions so we do not cross additional boundaries? How can we put an end to our movement beyond the boundaries we have already crossed?

Change requires action and awareness from every part of society.

The wastewater industry can be an important player in changing society. It has already made important moves in the way it manages human excreta. As recently as fifty years ago cities in the USA were dumping raw sewage into water channels. The wastewater industry has greatly decreased the flow of untreated sewage waste entering the environment.

Using the planetary boundaries framework, the wastewater industry is aligned with action necessary to reduce or pull back humanity’s detrimental impacts on freshwater use, climate change, biochemical flows and land-system change.

It starts with water. Water discharged from plants is used by other industries. Some cities are now considering using treated water as a water source for people. One beer enthusiast even used treated wastewater to brew beer. NPR has more on that in their story Why Dump Treated Wastewater When You Could Make Beer with It?

The remaining dewatered sewage sludge is treated to make biosolids, which is primarily made of organic material and contains various essential nutrients. It is similar in many ways to elements found in the soil that benefit plants.

To make biosolids, sewage is processed in a number of different ways, often by using aerobic or anaerobic digestion, in order to kill harmful bacteria and further stabilize the material to reduce nuisance odors.  Biosolids is a material high in nutrients such as phosphate and nitrogen, both essential components in soil needed for plant growth, and it contains a full suite of micronutrients, which are often depleted in farm soils after generations of cultivation. The biosolids can build soil organic matter when land applied, improving moisture holding capacity and water infiltration.

When biosolids is digested anaerobically, methane gas is produced. If released to the air, methane would become a greenhouse gas, but instead methane is often used onsite as a renewable energy source for the treatment plants. Some plants have been able to produce enough electricity and heat to have a net zero energy demand for treatment processes. Further, in those wastewater plants that use incinerators, heat from combustion can be recovered for use in the facility.

Managing is sewage a global issue. Its importance will continue to increase as the human population grows and puts additional stresses on natural systems. Although sewage sludge enters wastewater facilities as a waste, through proper treatment it is separated into various valuable resources. Using these resources helps prevent humanity from further stepping beyond the planetary boundaries and helps to reverse the damage that has already been done.