While the primary concern of the Knowledge Hub is the problem of ocean wastewater pollution, as one digs deeper, it becomes clear that the solutions can create other benefits that are just as valuable; both from an environmental and economic perspective. To put it simply, by flushing away human waste, we not only pollute the environment, but we also miss an opportunity to address other environmental problems and needs, such as climate change, water scarcity, and sustainable agriculture. Recycling our human excretions is the ultimate recycling. Seeing waste management as a closed loop to support a circular economy; where our human waste is seen as a resource rather than waste; capturing the value of the resource, while avoiding environmental degradation, is the way of the future. With limited resources such as water, phosphorus, and fuel becoming scarcer, and more expensive, and even damaging to procure, it makes sense to focus future solutions on capturing the value of human excretions. See Appendix for great examples that already exist.
According to Heal the Ocean, 1.1 billion gallons of treated water a day are discarded into the ocean and estuaries in California alone (Hawkins et al., 2018). Instead of releasing this water, some communities are treating it to meet US standards and reusing it as drinking water. Orange County, in Southern California, has been operating the world’s largest waste- water-to-drinking-water plant for the past 40 years. It provides reclaimed water to its customers through an indirect system, and is projected to supply 130 million gallons of drinking water to 1 million customers by 2023. Similar large-scale systems are in places with dense populations such as Singapore (Leslie, 2018). With only 2.5% of the world’s water resources being freshwater, and only 0.49% of that accessible for use (Shiklomanov, 1993), freshwater is just too rare to be throwing it away.
The value of human feces alone is estimated to be $10 billion (USD 2020) per year, with the poop of 1 billion people producing $400 million in methane gas annually (Kluger, 2015). That is enough gas to provide power to 10-18 million households. Additionally, given how important phosphorus is for increasing crop yields, and generating food for billions of people, not capturing this limited resource and reusing it contributes to more problems than just pollution. Releasing phosphorus into the ocean stimulates growth of nuisance algae in tropical systems, and can lead to death and overgrowth of highly valuable seagrass systems by leafy algae. The potential for mining phosphorus from human waste is tremendous, with each human producing close to 1 pound of phosphorus annually. The world supply of phosphorus — which is essential for both animal and plant life, as it forms the basis of our energy compounds, or ATP — is often considered finite, and only available through mining of phosphate rock; as the phosphorus cycle does not have a gas phase, like the nitrogen cycle, that would result in recirculation. For this reason, phosphorus supply is often, like oil, considered a nonrenewable resource. Harvesting it from human waste could change that. In addition, phosphorus mining creates its own environmental hazards, so recycling, rather than allowing it to pollute, has multiple environmental benefits.
There are a range of ways to capture resources from human waste, and more technological solutions are in development. This is a huge growth area and opportunity for innovation and new business. Below we include several general types of technologies as examples.