Space exploration has always pushed the boundaries of human ingenuity, testing our capabilities in environments that are vastly different from Earth. As humanity looks toward long-term missions to the Moon, Mars, and beyond, sustainable living in space becomes a pressing concern. One innovative solution to this challenge is the use of biodigesters—systems that convert organic waste into valuable resources. We explore how biodigesters could revolutionize life in space, drawing lessons from current missions and highlighting potential future technologies.
An unexpected trip extension
What was originally planned as an eight-day mission has turned into an eight-month journey around Earth for two NASA astronauts, Sunita Williams and Barry Wilmore. On June 5th, they arrived on the International Space Station (ISS) aboard Boeing’s Starliner, which encountered several technical problems on its way, including helium leaks that impacted the propulsion system and control thrusters. Through thorough reviews and the development of contingency plans, NASA determined that Boeing’s spacecraft did not meet the safety and performance requirements for human spaceflight. This decision underscores the unpredictable nature of space missions and the need for reliable systems that support long-duration stays.
What does this mean for our stranded astronauts and what challenges will they face?
Living on the ISS presents unique challenges. The station, which is 356 feet (109 meters) long—just shy of the length of an American football field—circles Earth at a speed of 17,500 miles per hour, completing approximately 16 orbits each day. This rapid orbit means that astronauts experience frequent day and night cycles, which can disrupt circadian rhythms and impact overall health.
Moreover, the ISS lacks a laundry system, so astronauts dispose of their dirty clothes, which eventually burn up upon reentry into Earth’s atmosphere. This practice, while necessary, is not sustainable for longer missions where resupply missions are not feasible. Efficient waste management becomes crucial, not only for clothing but also for food and other organic materials.
Meals on the ISS are meticulously planned and prepared at NASA’s Space Food Systems Laboratory in Houston. To save on weight and simplify preparation, most foods are dehydrated. However, this process generates significant waste in the form of packaging and uneaten food.
Current waste disposal aboard the ISS
Minimizing waste in a zero-gravity environment like space presents a set of unique challenges that are vastly different from those faced on Earth. In space, every resource is precious, and the inability to easily dispose of waste makes waste management an essential part of mission planning and daily life. Here’s a closer look at the specific challenges astronauts face in managing waste in a zero-gravity environment and how these solutions could inspire innovative waste reduction strategies on Earth.
Containment and segregation of waste
In a zero-gravity environment, waste management begins with the basic challenge of containment. Without gravity, even the smallest particles of waste can float freely around the spacecraft, posing contamination risks to both the equipment and the crew. This risk is especially significant with organic waste, which can decompose and produce gasses or harmful pathogens.
To address this, astronauts on the ISS must meticulously segregate waste into wet and dry categories and store it in tightly sealed bags. This careful separation prevents cross-contamination and allows for more efficient waste handling. The process is manual and labor-intensive, requiring astronauts to dedicate a portion of their daily routine to managing waste. However, this level of precision ensures that waste does not compromise the health of the crew or the functionality of the spacecraft.
Earth Application: On Earth, similar principles of containment and segregation could be used to enhance waste management systems. By promoting meticulous sorting of organic and inorganic waste at the source—such as in homes, restaurants, and food production facilities—we can reduce contamination and increase the efficiency of recycling processes. Innovative packaging designs that are easy to separate and degrade could further reduce waste.
Limited space for waste storage
The confined quarters of spacecraft like the ISS present another challenge: limited space for waste storage. Unlike on Earth, where waste can be taken away regularly, space missions do not have the luxury of frequent disposal. Every bit of waste generated must be stored until it can be disposed of safely, often upon re-entry into Earth’s atmosphere, where it burns up. This constraint requires highly efficient storage solutions that minimize space while maximizing safety and hygiene.
One solution currently employed is compacting waste to reduce its volume. On the ISS, a compactor beneath the shuttle’s floor crushes food waste and packaging, and astronauts manually segregate trash into wet and dry bags.
Depending on the type of spacecraft, this trash either returns to Earth or burns up in the atmosphere. While this system works for shorter missions, it is not a sustainable solution for extended stays on other planets.
Earth Application: On Earth, compacting technologies could be further developed and implemented in urban environments and industries to reduce the volume of waste. This can lead to fewer trips for waste collection services, reduced fuel consumption, and lower greenhouse gas emissions. Additionally, compacted organic waste could be more easily transported to central facilities for composting or biogas production, enhancing the overall efficiency of waste management systems.
Preventing decomposition and odor in a closed environment
In a spacecraft, where air circulation is limited, preventing the decomposition of organic waste and managing odors is critical. The decomposition process can release gasses such as methane, which could be hazardous in a closed environment. Furthermore, unpleasant odors can affect the morale and well-being of the crew, making effective odor management a priority.
To manage these challenges, space missions use tightly sealed bags and containers to store waste and incorporate chemical treatments to neutralize odors. Some systems also employ advanced filtration technologies to remove any gasses released before they can affect the cabin atmosphere.
Earth Application: Learning from space missions, Earth-based waste management systems could implement more effective strategies for preventing decomposition and managing odors.
Research suggests that food waste and other organic discards, such as peels and pits, could be repurposed to grow new food and optimize nutrients through processes like fermentation. This idea led to the proposal of the Biodigester Feasibility & Design for Space & Earth Project in 2016. Biodigesters use a technology that converts waste into valuable byproducts such as fertilizer, making them a promising tool for creating closed-loop systems essential for deep space missions.
Biodigesters on Mars, to infinity and beyond
On Mars or even at the Johnson Space Center (JSC) on Earth, biodigesters could help grow food more sustainably by recycling waste into nutrients. However, implementing these systems in space requires managing the odors of effluents, and ensuring the nutrient viability of the outputs. By improving the efficiency of biodigesters and relying on renewable energy sources, deep space missions could become more feasible and sustainable.
One potential future solution is Power Knot’s LFC biodigester, an aerobic digester. Unlike anaerobic digesters, which do not require oxygen and are well-suited to certain conditions in space, aerobic digesters could play a crucial role if space travel and planetary atmospheres can support the use of oxygen. Aerobic digesters break down organic material using oxygen, creating a cycle that not only reduces waste but also produces water and carbon dioxide. This carbon dioxide could potentially be used to build an atmosphere on other planets, aiding in the creation of habitable environments.
The LFC biodigester, which operates efficiently in environments with oxygen, could be adapted for use in space habitats where controlled environments mimic Earth-like conditions. By integrating such technologies, future space missions could achieve a new level of sustainability, reducing reliance on Earth for resupply and making long-term extraterrestrial living a reality.
As humanity ventures further into the cosmos, the need for sustainable life-support systems becomes increasingly critical. Biodigesters, both anaerobic and aerobic, offer a promising solution for waste management and resource recycling in space. By harnessing these technologies, we can create closed-loop systems that minimize waste and maximize resource efficiency, paving the way for longer, more sustainable missions on the ISS, Mars, and beyond. The future of space exploration may well depend on our ability to turn waste into resources, ensuring that nothing is wasted as we reach for the stars.